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In Press articles are edited and published online ahead of issue. When the final article is assigned to volumes/issues, the Article in Press version will be removed and the final version will appear in the associated published volumes/issues.
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Effects of 1 MeV electron radiation on the AlGaN/GaN high electron mobility transistors
Shijie Pan, Shiwei Feng, Xuan Li, Zixuan Feng, Xiaozhuang Lu, Kun Bai, Yamin Zhang
, Available online  
doi: 10.1088/1674-4926/24020020

In this study, the effects of 1 MeV electron radiation on the D-mode GaN-based high electron mobility transistors (HEMTs) were investigated after different radiation doses. The changes in electrical properties of the device were obtained, and the related physical mechanisms were analyzed. It indicated that under the radiation dose of 5 × 1014 cm−2, the channel current cannot be completely pinched off even if the negative gate voltage was lower than the threshold voltage, and the gate leakage current increased significantly. The emission microscopy and scanning electron microscopy were used to determine the damage location. Besides, the radiation dose was adjusted ranging from 5 × 1012 to 1 × 1014 cm−2, and we noticed that the drain−source current increased and the threshold voltage presented slightly negative shift. By calculations, it suggested that the carrier density and electron mobility gradually increased. It provided a reference for the development of device radiation reinforcement technology.

In this study, the effects of 1 MeV electron radiation on the D-mode GaN-based high electron mobility transistors (HEMTs) were investigated after different radiation doses. The changes in electrical properties of the device were obtained, and the related physical mechanisms were analyzed. It indicated that under the radiation dose of 5 × 1014 cm−2, the channel current cannot be completely pinched off even if the negative gate voltage was lower than the threshold voltage, and the gate leakage current increased significantly. The emission microscopy and scanning electron microscopy were used to determine the damage location. Besides, the radiation dose was adjusted ranging from 5 × 1012 to 1 × 1014 cm−2, and we noticed that the drain−source current increased and the threshold voltage presented slightly negative shift. By calculations, it suggested that the carrier density and electron mobility gradually increased. It provided a reference for the development of device radiation reinforcement technology.
High-performance GaSb planar PN junction detector
Yuanzhi Cui, Hongyue Hao, Shihao Zhang, Shuo Wang, Jing Zhang, Yifan Shan, Ruoyu Xie, Xiaoyu Wang, Chuang Wang, Mengchen Liu, Dongwei Jiang, Yingqiang Xu, Guowei Wang, Donghai Wu, Zhichuan Niu, Derang Cao
, Available online  
doi: 10.1088/1674-4926/24040024

This paper examines GaSb short-wavelength infrared detectors employing planar PN junctions. The fabrication was based on the Zn diffusion process and the diffusion temperature was optimized. Characterization revealed a 50% cut-off wavelength of 1.73 μm, a maximum detectivity of 8.73 × 1010 cm·Hz1/2/W, and a minimum dark current density of 1.02 × 10−5 A/cm2. Additionally, a maximum quantum efficiency of 60.3% was achieved. Subsequent optimization of fabrication enabled the realization of a 320 × 256 focal plane array that exhibited satisfactory imaging results. Remarkably, the GaSb planar detectors demonstrated potential in low-cost short wavelength infrared imaging, without requiring material epitaxy or deposition.

This paper examines GaSb short-wavelength infrared detectors employing planar PN junctions. The fabrication was based on the Zn diffusion process and the diffusion temperature was optimized. Characterization revealed a 50% cut-off wavelength of 1.73 μm, a maximum detectivity of 8.73 × 1010 cm·Hz1/2/W, and a minimum dark current density of 1.02 × 10−5 A/cm2. Additionally, a maximum quantum efficiency of 60.3% was achieved. Subsequent optimization of fabrication enabled the realization of a 320 × 256 focal plane array that exhibited satisfactory imaging results. Remarkably, the GaSb planar detectors demonstrated potential in low-cost short wavelength infrared imaging, without requiring material epitaxy or deposition.
10 × 10 Ga2O3-based solar-blind UV detector array and imaging characteristic
Haifeng Chen, Zhanhang Liu, Yixin Zhang, Feilong Jia, Chenlu Wu, Qin Lu, Xiangtai Liu, Shaoqing Wang
, Available online  
doi: 10.1088/1674-4926/24030005

A 10 × 10 solar-blind ultraviolet (UV) imaging array with double-layer wire structure was prepared based on Ga2O3 film grown by atomic layer deposition. These single detection units in the array exhibit excellent performance at 3 V: photo-to-dark current ratio (PDCR) of 5.5 × 105, responsivity (R) of 4.28 A/W, external quantum efficiency (EQE) of 2.1 × 103%, detectivity (D*) of 1.5 × 1014 Jones, and fast response time. The photodetector array shows high uniformity under different light intensity and low operating bias. The array also has good temperature stability. Under 300 °C, it still presents clear imaging and keeps high R of 34.4 and 6.45 A/W at 5 and 1 V, respectively. This work provides a new insight for the large-scale array of Ga2O3 solar-blind UV detectors.

A 10 × 10 solar-blind ultraviolet (UV) imaging array with double-layer wire structure was prepared based on Ga2O3 film grown by atomic layer deposition. These single detection units in the array exhibit excellent performance at 3 V: photo-to-dark current ratio (PDCR) of 5.5 × 105, responsivity (R) of 4.28 A/W, external quantum efficiency (EQE) of 2.1 × 103%, detectivity (D*) of 1.5 × 1014 Jones, and fast response time. The photodetector array shows high uniformity under different light intensity and low operating bias. The array also has good temperature stability. Under 300 °C, it still presents clear imaging and keeps high R of 34.4 and 6.45 A/W at 5 and 1 V, respectively. This work provides a new insight for the large-scale array of Ga2O3 solar-blind UV detectors.
Heterojunction-engineered carrier transport in elevated-metal metal-oxide thin-film transistors
Xiao Li, Zhikang Ma, Jinxiong Li, Wengao Pan, Congwei Liao, Shengdong Zhang, Zhuo Gao, Dong Fu, Lei Lu
, Available online  
doi: 10.1088/1674-4926/24040016

This study investigates the carrier transport of heterojunction channel in oxide semiconductor thin-film transistor (TFT) using the elevated-metal metal-oxide (EMMO) architecture and indium−zinc oxide (InZnO). The heterojunction band diagram of InZnO bilayer was modified by the cation composition to form the two-dimensional electron gas (2DEG) at the interface quantum well, as verified using a metal−insulator−semiconductor (MIS) device. Although the 2DEG indeed contributes to a higher mobility than the monolayer channel, the competition and cooperation between the gate field and the built-in field strongly affect such mobility-boosting effect, originating from the carrier inelastic collision at the heterojunction interface and the gate field-induced suppression of quantum well. Benefited from the proper energy-band engineering, a high mobility of 84.3 cm2·V−1·s−1, a decent threshold voltage (Vth) of −6.5 V, and a steep subthreshold swing (SS) of 0.29 V/dec were obtained in InZnO-based heterojunction TFT.

This study investigates the carrier transport of heterojunction channel in oxide semiconductor thin-film transistor (TFT) using the elevated-metal metal-oxide (EMMO) architecture and indium−zinc oxide (InZnO). The heterojunction band diagram of InZnO bilayer was modified by the cation composition to form the two-dimensional electron gas (2DEG) at the interface quantum well, as verified using a metal−insulator−semiconductor (MIS) device. Although the 2DEG indeed contributes to a higher mobility than the monolayer channel, the competition and cooperation between the gate field and the built-in field strongly affect such mobility-boosting effect, originating from the carrier inelastic collision at the heterojunction interface and the gate field-induced suppression of quantum well. Benefited from the proper energy-band engineering, a high mobility of 84.3 cm2·V−1·s−1, a decent threshold voltage (Vth) of −6.5 V, and a steep subthreshold swing (SS) of 0.29 V/dec were obtained in InZnO-based heterojunction TFT.
Growth of two-inch free-standing heteroepitaxial diamond on Ir/YSZ/Si (001) substrates via laser-patterned templates
Pengfei Qu, Peng Jin, Guangdi Zhou, Zhen Wang, Zhanguo Wang
, Available online  
doi: 10.1088/1674-4926/24060003

Effects of gallium surfactant on AlN thin films by microwave plasma chemical vapor deposition
Lu Wang, Xulei Qin, Li Zhang, Kun Xu, Feng Yang, Shaoqian Lu, Yifei Li, Bosen Liu, Guohao Yu, Zhongming Zeng, Baoshun Zhang
, Available online  
doi: 10.1088/1674-4926/24020017

In this work, AlN films were grown using gallium (Ga) as surfactant on 4° off-axis 4H-SiC substrates via microwave plasma chemical vapor deposition (MPCVD). We have found that AlN growth rate can be greatly improved due to the catalytic effect of trimethyl-gallium (TMGa), but AlN crystal structure and composition are not affected. When the proportion of TMGa in gas phase was low, crystal quality of AlN can be improved and three-dimensional growth mode of AlN was enhanced with the increase of Ga source. When the proportion of TMGa in gas phase was high, two-dimensional growth mode of AlN was presented, with the increase of Ga source results in the deterioration of AlN crystal quality. Finally, employing a two-step growth approach, involving the initial growth of Ga-free AlN nucleation layer followed by Ga-assisted AlN growth, high quality of AlN film with flat surface was obtained and the full width at half maximum (FWHM) values of 415 nm AlN (002) and (102) planes were 465 and 597 arcsec.

In this work, AlN films were grown using gallium (Ga) as surfactant on 4° off-axis 4H-SiC substrates via microwave plasma chemical vapor deposition (MPCVD). We have found that AlN growth rate can be greatly improved due to the catalytic effect of trimethyl-gallium (TMGa), but AlN crystal structure and composition are not affected. When the proportion of TMGa in gas phase was low, crystal quality of AlN can be improved and three-dimensional growth mode of AlN was enhanced with the increase of Ga source. When the proportion of TMGa in gas phase was high, two-dimensional growth mode of AlN was presented, with the increase of Ga source results in the deterioration of AlN crystal quality. Finally, employing a two-step growth approach, involving the initial growth of Ga-free AlN nucleation layer followed by Ga-assisted AlN growth, high quality of AlN film with flat surface was obtained and the full width at half maximum (FWHM) values of 415 nm AlN (002) and (102) planes were 465 and 597 arcsec.
Multiframe-integrated, in-sensor computing using persistent photoconductivity
Xiaoyong Jiang, Minrui Ye, Yunhai Li, Xiao Fu, Tangxin Li, Qixiao Zhao, Jinjin Wang, Tao Zhang, Jinshui Miao, Zengguang Cheng
, Available online  
doi: 10.1088/1674-4926/24040002

The utilization of processing capabilities within the detector holds significant promise in addressing energy consumption and latency challenges. Especially in the context of dynamic motion recognition tasks, where substantial data transfers are necessitated by the generation of extensive information and the need for frame-by-frame analysis. Herein, we present a novel approach for dynamic motion recognition, leveraging a spatial-temporal in-sensor computing system rooted in multiframe integration by employing photodetector. Our approach introduced a retinomorphic MoS2 photodetector device for motion detection and analysis. The device enables the generation of informative final states, nonlinearly embedding both past and present frames. Subsequent multiply-accumulate (MAC) calculations are efficiently performed as the classifier. When evaluating our devices for target detection and direction classification, we achieved an impressive recognition accuracy of 93.5%. By eliminating the need for frame-by-frame analysis, our system not only achieves high precision but also facilitates energy-efficient in-sensor computing.

The utilization of processing capabilities within the detector holds significant promise in addressing energy consumption and latency challenges. Especially in the context of dynamic motion recognition tasks, where substantial data transfers are necessitated by the generation of extensive information and the need for frame-by-frame analysis. Herein, we present a novel approach for dynamic motion recognition, leveraging a spatial-temporal in-sensor computing system rooted in multiframe integration by employing photodetector. Our approach introduced a retinomorphic MoS2 photodetector device for motion detection and analysis. The device enables the generation of informative final states, nonlinearly embedding both past and present frames. Subsequent multiply-accumulate (MAC) calculations are efficiently performed as the classifier. When evaluating our devices for target detection and direction classification, we achieved an impressive recognition accuracy of 93.5%. By eliminating the need for frame-by-frame analysis, our system not only achieves high precision but also facilitates energy-efficient in-sensor computing.
Localized-states quantum confinement induced by roughness in CdMnTe/CdTe heterostructures grown on Si(111) substrates
Leonarde N. Rodrigues, Wesley F. Inoch, Marcos L. F. Gomes, Odilon D. D. Couto Jr., Bráulio S. Archanjo, Sukarno O. Ferreira
, Available online  
doi: 10.1088/1674-4926/24030022

This work shows that despite a lattice mismatch of almost 20%, CdMnTe/CdTe/CdMnTe heterostructures grown directly on Si(111) have surprisingly good optical emission properties. The investigated structures were grown by molecular beam epitaxy and characterized by scanning transmission electron microscopy, macro- and micro-photoluminescence. Low temperature macro-photoluminescence experiments indicate three emission bands which depend on the CdTe layer thickness and have different confinement characteristics. Temperature measurements reveal that the lower energy emission band (at 1.48 eV) is associated to defects and bound exciton states, while the main emission at 1.61 eV has a weak 2D character and the higher energy one at 1.71 eV has a well-defined (zero-dimensional, 0D) 0D nature. Micro-photoluminescence measurements show the existence of sharp and strongly circularly polarized (up to 40%) emission lines which can be related to the presence of Mn in the heterostructure. This result opens the possibility of producing photon sources with the typical spin control of the diluted magnetic semiconductors using the low-cost silicon technology.

This work shows that despite a lattice mismatch of almost 20%, CdMnTe/CdTe/CdMnTe heterostructures grown directly on Si(111) have surprisingly good optical emission properties. The investigated structures were grown by molecular beam epitaxy and characterized by scanning transmission electron microscopy, macro- and micro-photoluminescence. Low temperature macro-photoluminescence experiments indicate three emission bands which depend on the CdTe layer thickness and have different confinement characteristics. Temperature measurements reveal that the lower energy emission band (at 1.48 eV) is associated to defects and bound exciton states, while the main emission at 1.61 eV has a weak 2D character and the higher energy one at 1.71 eV has a well-defined (zero-dimensional, 0D) 0D nature. Micro-photoluminescence measurements show the existence of sharp and strongly circularly polarized (up to 40%) emission lines which can be related to the presence of Mn in the heterostructure. This result opens the possibility of producing photon sources with the typical spin control of the diluted magnetic semiconductors using the low-cost silicon technology.
Recent progress on fabrication, spectroscopy properties, and device applications in Sn-doped CdS micro-nano structures
Bo Cao, Ye Tian, Huan Fei Wen, Hao Guo, Xiaoyu Wu, Liangjie Li, Zhenrong Zhang, Lai Liu, Qiang Zhu, Jun Tang, Jun Liu
, Available online  
doi: 10.1088/1674-4926/24040041

One-dimensional semiconductor materials possess excellent photoelectric properties and potential for the construction of integrated nanodevices. Among them, Sn-doped CdS has different micro-nano structures, including nanoribbons, nanowires, comb-like structures, and superlattices, with rich optical microcavity modes, excellent optical properties, and a wide range of application fields. This article reviews the research progress of various micrometer structures of Sn-doped CdS, systematically elaborates the effects of different growth conditions on the preparation of Sn-doped CdS micro-nano structures, as well as the spectral characteristics of these structures and their potential applications in certain fields. With the continuous progress of nanotechnology, it is expected that Sn-doped CdS micro-nano structures will achieve more breakthroughs in the field of optoelectronics and form cross-integration with other fields, jointly promoting scientific, technological, and social development.

One-dimensional semiconductor materials possess excellent photoelectric properties and potential for the construction of integrated nanodevices. Among them, Sn-doped CdS has different micro-nano structures, including nanoribbons, nanowires, comb-like structures, and superlattices, with rich optical microcavity modes, excellent optical properties, and a wide range of application fields. This article reviews the research progress of various micrometer structures of Sn-doped CdS, systematically elaborates the effects of different growth conditions on the preparation of Sn-doped CdS micro-nano structures, as well as the spectral characteristics of these structures and their potential applications in certain fields. With the continuous progress of nanotechnology, it is expected that Sn-doped CdS micro-nano structures will achieve more breakthroughs in the field of optoelectronics and form cross-integration with other fields, jointly promoting scientific, technological, and social development.
Achievable hole concentration at room temperature as a function of Mg concentration for MOCVD-grown p-GaN after sufficient annealing
Siyi Huang, Masao Ikeda, Feng Zhang, Minglong Zhang, Jianjun Zhu, Shuming Zhang, Jianping Liu
, Available online  
doi: 10.1088/1674-4926/24010017

Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper. Different annealing conditions were applied to obtain sufficient activation for p-GaN samples with different Mg doping ranges. Hole concentration, resistivity and mobility were characterized by room-temperature Hall measurements. The Mg doping concentration and the residual impurities such as H, C, O and Si were measured by secondary ion mass spectroscopy, confirming negligible compensations by the impurities. The hole concentration, resistivity and mobility data are presented as a function of Mg concentration, and are compared with literature data. The appropriate curve relating the Mg doping concentration to the hole concentration is derived using a charge neutrality equation and the ionized-acceptor-density [$N_{\mathrm{A}}^- $] (cm−3) dependent ionization energy of Mg acceptor was determined as $E_{\mathrm{A}}^{{\mathrm{Mg}}} $ = 184 − 2.66 × 10−5 × [$N_{\mathrm{A}}^- $]1/3 meV.

Relationship between the hole concentration at room temperature and the Mg doping concentration in p-GaN grown by MOCVD after sufficient annealing was studied in this paper. Different annealing conditions were applied to obtain sufficient activation for p-GaN samples with different Mg doping ranges. Hole concentration, resistivity and mobility were characterized by room-temperature Hall measurements. The Mg doping concentration and the residual impurities such as H, C, O and Si were measured by secondary ion mass spectroscopy, confirming negligible compensations by the impurities. The hole concentration, resistivity and mobility data are presented as a function of Mg concentration, and are compared with literature data. The appropriate curve relating the Mg doping concentration to the hole concentration is derived using a charge neutrality equation and the ionized-acceptor-density [$N_{\mathrm{A}}^- $] (cm−3) dependent ionization energy of Mg acceptor was determined as $E_{\mathrm{A}}^{{\mathrm{Mg}}} $ = 184 − 2.66 × 10−5 × [$N_{\mathrm{A}}^- $]1/3 meV.
A mechanically coupled MEMS filter with high-Q width extensional mode resonators
Wei Wang, Wenli Liu, Junyuan Zhao, Bo Niu, Zeyu Wu, Yinfang Zhu, Jinling Yang, Fuhua Yang
, Available online  
doi: 10.1088/1674-4926/24050007

This work presents a novel radio frequency (RF) narrowband Si micro-electro-mechanical systems (MEMS) filter based on capacitively transduced slotted width extensional mode (WEM) resonators. The flexibility of the plate leads to multiple modes near the target frequency. The high Q-factor resonators of around 100 000 enable narrow bandwidth filters with small size and simplified design. The 1-wavelength and 2-wavelength WEMs were first developed as a pair of coupled modes to form a passband. To reduce bandwidth, two plates are coupled with a λ-length coupling beam. The 79.69 MHz coupled plate filter (CPF) achieved a narrow bandwidth of 8.8 kHz, corresponding to a tiny 0.011%. The CPF exhibits an impressive 34.84 dB stopband rejection and 7.82 dB insertion loss with near-zero passband ripple. In summary, the RF MEMS filter presented in this work shows promising potential for application in RF transceiver front-ends.

This work presents a novel radio frequency (RF) narrowband Si micro-electro-mechanical systems (MEMS) filter based on capacitively transduced slotted width extensional mode (WEM) resonators. The flexibility of the plate leads to multiple modes near the target frequency. The high Q-factor resonators of around 100 000 enable narrow bandwidth filters with small size and simplified design. The 1-wavelength and 2-wavelength WEMs were first developed as a pair of coupled modes to form a passband. To reduce bandwidth, two plates are coupled with a λ-length coupling beam. The 79.69 MHz coupled plate filter (CPF) achieved a narrow bandwidth of 8.8 kHz, corresponding to a tiny 0.011%. The CPF exhibits an impressive 34.84 dB stopband rejection and 7.82 dB insertion loss with near-zero passband ripple. In summary, the RF MEMS filter presented in this work shows promising potential for application in RF transceiver front-ends.
A 128 × 128 SPAD LiDAR sensor with column-parallel 25 ps resolution TA-ADCs
Na Tian, Zhe Wang, Kai Ma, Xu Yang, Nan Qi, Jian Liu, Nanjian Wu, Runjiang Dou, Liyuan Liu
, Available online  
doi: 10.1088/1674-4926/24030019

This paper presents a design of single photon avalanche diode (SPAD) light detection and ranging (LiDAR) sensor with 128 × 128 pixels and 128 column-parallel time-to-analog-merged-analog-to-digital converts (TA-ADCs). Unlike the conventional TAC-based SPAD LiDAR sensor, in which the TAC and ADC are separately implemented, we propose to merge the TAC and ADC by sharing their capacitors, thus avoiding the analog readout noise of TAC’s output buffer, improving the conversion rate, and reducing chip area. The reverse start-stop logic is employed to reduce the power of the TA-ADC. Fabricated in a 180 nm CMOS process, our prototype sensor exhibits a timing resolution of 25 ps, a DNL of +0.30/−0.77 LSB, an INL of +1.41/−2.20 LSB, and a total power consumption of 190 mW. A flash LiDAR system based on this sensor demonstrates the function of 2D/3D imaging with 128 × 128 resolution, 25 kHz inter-frame rate, and sub-centimeter ranging precision.

This paper presents a design of single photon avalanche diode (SPAD) light detection and ranging (LiDAR) sensor with 128 × 128 pixels and 128 column-parallel time-to-analog-merged-analog-to-digital converts (TA-ADCs). Unlike the conventional TAC-based SPAD LiDAR sensor, in which the TAC and ADC are separately implemented, we propose to merge the TAC and ADC by sharing their capacitors, thus avoiding the analog readout noise of TAC’s output buffer, improving the conversion rate, and reducing chip area. The reverse start-stop logic is employed to reduce the power of the TA-ADC. Fabricated in a 180 nm CMOS process, our prototype sensor exhibits a timing resolution of 25 ps, a DNL of +0.30/−0.77 LSB, an INL of +1.41/−2.20 LSB, and a total power consumption of 190 mW. A flash LiDAR system based on this sensor demonstrates the function of 2D/3D imaging with 128 × 128 resolution, 25 kHz inter-frame rate, and sub-centimeter ranging precision.
Review of the SiC LDMOS power device
Ziwei Hu, Jiafei Yao, Ang Li, Qi Sun, Man Li, Kemeng Yang, Jun Zhang, Jing Chen, Maolin Zhang, Yufeng Guo
, Available online  
doi: 10.1088/1674-4926/24010029

Silicon carbide (SiC), as a third-generation semiconductor material, possesses exceptional material properties that significantly enhance the performance of power devices. The SiC lateral double-diffused metal–oxide–semiconductor (LDMOS) power devices have undergone continuous optimization, resulting in an increase in breakdown voltage (BV) and ultra-low specific on-resistance (Ron,sp). This paper has summarized the structural optimizations and experimental progress of SiC LDMOS power devices, including the trench-gate technology, reduced surface field (RESURF) technology, doping technology, junction termination techniques and so on. The paper is aimed at enhancing the understanding of the operational mechanisms and providing guidelines for the further development of SiC LDMOS power devices.

Silicon carbide (SiC), as a third-generation semiconductor material, possesses exceptional material properties that significantly enhance the performance of power devices. The SiC lateral double-diffused metal–oxide–semiconductor (LDMOS) power devices have undergone continuous optimization, resulting in an increase in breakdown voltage (BV) and ultra-low specific on-resistance (Ron,sp). This paper has summarized the structural optimizations and experimental progress of SiC LDMOS power devices, including the trench-gate technology, reduced surface field (RESURF) technology, doping technology, junction termination techniques and so on. The paper is aimed at enhancing the understanding of the operational mechanisms and providing guidelines for the further development of SiC LDMOS power devices.
The surface electron transfer strategy promotes the hole of PDI release and enhances emerging organic pollutant degradation
Yunchuan Yang, Dongyu Wang, Jisheng Geng, Jun Liu, Jun Wang
, Available online  
doi: 10.1088/1674-4926/24050005

In semiconductor photocatalysts, the easy recombination of photogenerated carriers seriously affects the application of photocatalytic materials in water treatment. To solve the serious problem of electron−hole pair recombination in perylene diimide (PDI) organic semiconductors, we loaded ferric hydroxyl oxide (FeOOH) on PDI materials, successfully prepared novel FeOOH@PDI photocatalytic materials, and constructed a photo-Fenton system. The system was able to achieve highly efficient degradation of BPA under visible light, with a degradation rate of 0.112 min−1 that was 20 times higher than the PDI system, and it also showed universal degradation performances for a variety of emerging organic pollutants and anti-interference ability. The mechanism research revealed that the FeOOH has the electron trapping property, which can capture the photogenerated electrons on the surface of PDI, effectively reducing the compounding rate of photogenerated carriers of PDI and accelerating the iron cycling and H2O2 activation on the surface of FeOOH at the same time. This work provides new insights and methods for solving the problem of easy recombination of carriers in semiconductor photocatalysts and degrading emerging organic pollutants.

In semiconductor photocatalysts, the easy recombination of photogenerated carriers seriously affects the application of photocatalytic materials in water treatment. To solve the serious problem of electron−hole pair recombination in perylene diimide (PDI) organic semiconductors, we loaded ferric hydroxyl oxide (FeOOH) on PDI materials, successfully prepared novel FeOOH@PDI photocatalytic materials, and constructed a photo-Fenton system. The system was able to achieve highly efficient degradation of BPA under visible light, with a degradation rate of 0.112 min−1 that was 20 times higher than the PDI system, and it also showed universal degradation performances for a variety of emerging organic pollutants and anti-interference ability. The mechanism research revealed that the FeOOH has the electron trapping property, which can capture the photogenerated electrons on the surface of PDI, effectively reducing the compounding rate of photogenerated carriers of PDI and accelerating the iron cycling and H2O2 activation on the surface of FeOOH at the same time. This work provides new insights and methods for solving the problem of easy recombination of carriers in semiconductor photocatalysts and degrading emerging organic pollutants.
Improved efficiency and stability of inverse perovskite solar cells via passivation cleaning
Kunyang Ge, Chunjun Liang
, Available online  
doi: 10.1088/1674-4926/24040033

Amidst the global energy and environmental crisis, the quest for efficient solar energy utilization intensifies. Perovskite solar cells, with efficiencies over 26% and cost-effective production, are at the forefront of research. Yet, their stability remains a barrier to industrial application. This study introduces innovative strategies to enhance the stability of inverted perovskite solar cells. By bulk and surface passivation, defect density is reduced, followed by a "passivation cleaning" using Apacl amino acid salt and isopropyl alcohol to refine film surface quality. Employing X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic force microscopy (AFM), we confirmed that this process effectively neutralizes surface defects and curbs non-radiative recombination, achieving 22.6% efficiency for perovskite solar cells with the composition Cs0.15FA0.85PbI3. Crucially, the stability of treated cells in long-term tests has been markedly enhanced, laying groundwork for industrial viability.

Amidst the global energy and environmental crisis, the quest for efficient solar energy utilization intensifies. Perovskite solar cells, with efficiencies over 26% and cost-effective production, are at the forefront of research. Yet, their stability remains a barrier to industrial application. This study introduces innovative strategies to enhance the stability of inverted perovskite solar cells. By bulk and surface passivation, defect density is reduced, followed by a "passivation cleaning" using Apacl amino acid salt and isopropyl alcohol to refine film surface quality. Employing X-ray diffraction (XRD), scanning electron microscope (SEM), and atomic force microscopy (AFM), we confirmed that this process effectively neutralizes surface defects and curbs non-radiative recombination, achieving 22.6% efficiency for perovskite solar cells with the composition Cs0.15FA0.85PbI3. Crucially, the stability of treated cells in long-term tests has been markedly enhanced, laying groundwork for industrial viability.
Structure and electrical properties of polysilicon films doped with ammonium tetraborate tetrahydrate
Yehua Tang, Yuchao Wang, Chunlan Zhou, Kefan Wang
, Available online  
doi: 10.1088/1674-4926/24030032

Here, p-type polysilicon films are fabricated by ex-situ doping method with ammonium tetraborate tetrahydrate (ATT) as the boron source, named ATT-pPoly. The effects of ATT on the properties of polysilicon films are comprehensively analyzed. The Raman spectra reveal that the ATT-pPoly film is composed of grain boundary and crystalline regions. The preferred orientation is the (111) direction. The grain size increases from 16−23 nm to 21−47 nm, by ~70% on average. Comparing with other reported films, Hall measurements reveal that the ATT-pPoly film has a higher carrier concentration (>1020 cm−3) and higher carrier mobility (>30 cm2/(V·s)). The superior properties of the ATT-pPoly film are attributed to the heavy doping and improved grain size. Heavy doping property is proved by the mean sheet resistance (Rsheet,m) and distribution profile. The Rsheet,m decreases by more than 30%, and it can be further decreased by 90% if the annealing temperature or duration is increased. The boron concentration of ATT-pPoly film annealed at 950 °C for 45 min is ~3 × 1020 cm−3, and the distribution is nearly the same, except near the surface. Besides, the standard deviation coefficient (σ) of Rsheet,m is less than 5.0%, which verifies the excellent uniformity of ATT-pPoly film.

Here, p-type polysilicon films are fabricated by ex-situ doping method with ammonium tetraborate tetrahydrate (ATT) as the boron source, named ATT-pPoly. The effects of ATT on the properties of polysilicon films are comprehensively analyzed. The Raman spectra reveal that the ATT-pPoly film is composed of grain boundary and crystalline regions. The preferred orientation is the (111) direction. The grain size increases from 16−23 nm to 21−47 nm, by ~70% on average. Comparing with other reported films, Hall measurements reveal that the ATT-pPoly film has a higher carrier concentration (>1020 cm−3) and higher carrier mobility (>30 cm2/(V·s)). The superior properties of the ATT-pPoly film are attributed to the heavy doping and improved grain size. Heavy doping property is proved by the mean sheet resistance (Rsheet,m) and distribution profile. The Rsheet,m decreases by more than 30%, and it can be further decreased by 90% if the annealing temperature or duration is increased. The boron concentration of ATT-pPoly film annealed at 950 °C for 45 min is ~3 × 1020 cm−3, and the distribution is nearly the same, except near the surface. Besides, the standard deviation coefficient (σ) of Rsheet,m is less than 5.0%, which verifies the excellent uniformity of ATT-pPoly film.
Impact of strain relaxation on the growth rate of heteroepitaxial germanium tin binary alloy
Pedram Jahandar, Maksym Myronov
, Available online  
doi: 10.1088/1674-4926/24030002

The growth of high-quality germanium tin (Ge1–ySny) binary alloys on a Si substrate using chemical vapor deposition (CVD) techniques holds immense potential for advancing electronics and optoelectronics applications, including the development of efficient and low-cost mid-infrared detectors and light sources. However, achieving precise control over the Sn concentration and strain relaxation of the Ge1–ySny epilayer, which directly influence its optical and electrical properties, remain a significant challenge. In this research, the effect of strain relaxation on the growth rate of Ge1–ySny epilayers, with Sn concentration >11 at.%, is investigated. It is successfully demonstrated that the growth rate slows down by ~55 % due to strain relaxation after passing its critical thickness, which suggests a reduction in the incorporation of Ge into Ge1–ySny growing layers. Despite the increase in Sn concentration as a result of the decrease in the growth rate, it has been found that the Sn incorporation rate into Ge1–ySny growing layers has also decreased due to strain relaxation. Such valuable insights could offer a foundation for the development of innovative growth techniques aimed at achieving high-quality Ge1–ySny epilayers with tuned Sn concentration and strain relaxation.

The growth of high-quality germanium tin (Ge1–ySny) binary alloys on a Si substrate using chemical vapor deposition (CVD) techniques holds immense potential for advancing electronics and optoelectronics applications, including the development of efficient and low-cost mid-infrared detectors and light sources. However, achieving precise control over the Sn concentration and strain relaxation of the Ge1–ySny epilayer, which directly influence its optical and electrical properties, remain a significant challenge. In this research, the effect of strain relaxation on the growth rate of Ge1–ySny epilayers, with Sn concentration >11 at.%, is investigated. It is successfully demonstrated that the growth rate slows down by ~55 % due to strain relaxation after passing its critical thickness, which suggests a reduction in the incorporation of Ge into Ge1–ySny growing layers. Despite the increase in Sn concentration as a result of the decrease in the growth rate, it has been found that the Sn incorporation rate into Ge1–ySny growing layers has also decreased due to strain relaxation. Such valuable insights could offer a foundation for the development of innovative growth techniques aimed at achieving high-quality Ge1–ySny epilayers with tuned Sn concentration and strain relaxation.
A review of ToF-based LiDAR
Jie Ma, Shenglong Zhuo, Lei Qiu, Yuzhu Gao, Yifan Wu, Ming Zhong, Rui Bai, Miao Sun, Patrick Yin Chiang
, Available online  
doi: 10.1088/1674-4926/24040015

In recent years, propelled by the rapid iterative advancements in digital imaging technology and the semiconductor industry, encompassing microelectronic design, manufacturing, packaging, and testing, time-of-flight (ToF)-based imaging systems for acquiring depth information have garnered considerable attention from both academia and industry. This technology has emerged as a focal point of research within the realm of 3D imaging. Owing to its relatively straightforward principles and exceptional performance, ToF technology finds extensive applications across various domains including human−computer interaction, autonomous driving, industrial inspection, medical and healthcare, augmented reality, smart homes, and 3D reconstruction, among others. Notably, the increasing maturity of ToF-based LiDAR systems is evident in current developments. This paper comprehensively reviews the fundamental principles of ToF technology and LiDAR systems, alongside recent research advancements. It elucidates the innovative aspects and technical challenges encountered in both transmitter (TX) and receiver (RX), providing detailed discussions on corresponding solutions. Furthermore, the paper explores prospective avenues for future research, offering valuable insights for subsequent investigations.

In recent years, propelled by the rapid iterative advancements in digital imaging technology and the semiconductor industry, encompassing microelectronic design, manufacturing, packaging, and testing, time-of-flight (ToF)-based imaging systems for acquiring depth information have garnered considerable attention from both academia and industry. This technology has emerged as a focal point of research within the realm of 3D imaging. Owing to its relatively straightforward principles and exceptional performance, ToF technology finds extensive applications across various domains including human−computer interaction, autonomous driving, industrial inspection, medical and healthcare, augmented reality, smart homes, and 3D reconstruction, among others. Notably, the increasing maturity of ToF-based LiDAR systems is evident in current developments. This paper comprehensively reviews the fundamental principles of ToF technology and LiDAR systems, alongside recent research advancements. It elucidates the innovative aspects and technical challenges encountered in both transmitter (TX) and receiver (RX), providing detailed discussions on corresponding solutions. Furthermore, the paper explores prospective avenues for future research, offering valuable insights for subsequent investigations.
Colloidal synthesis of lead chalcogenide/lead chalcohalide core/shell nanostructures and structural evolution
Yang Liu, Kunyuan Lu, Yujie Zhu, Xudong Hu, Yusheng Li, Guozheng Shi, Xingyu Zhou, Lin Yuan, Xiang Sun, Xiaobo Ding, Irfan Ullah Muhammad, Qing Shen, Zeke Liu, Wanli Ma
, Available online  
doi: 10.1088/1674-4926/24050026

Lead chalcohalides (PbYX, X = Cl, Br, I; Y = S, Se) is an extension of the classic Pb chalcogenides (PbY). Constructing the heterogeneous integration with PbYX and PbY material systems makes it possible to achieve significantly improved optoelectronic performance. In this work, we studied the effect of introducing halogen precursors on the structure of classical PbS nanocrystals (NCs) during the synthesis process and realized the preparation of PbS/Pb3S2X2 core/shell structure for the first time. The core/shell structure can effectively improve their optical properties. Furthermore, our approach enables the synthesis of Pb3S2Br2 that had not yet been reported. Our results not only provide valuable insights into the heterogeneous integration of PbYX and PbY materials to elevate material properties but also provide an effective method for further expanding the preparation of PbYX material systems.

Lead chalcohalides (PbYX, X = Cl, Br, I; Y = S, Se) is an extension of the classic Pb chalcogenides (PbY). Constructing the heterogeneous integration with PbYX and PbY material systems makes it possible to achieve significantly improved optoelectronic performance. In this work, we studied the effect of introducing halogen precursors on the structure of classical PbS nanocrystals (NCs) during the synthesis process and realized the preparation of PbS/Pb3S2X2 core/shell structure for the first time. The core/shell structure can effectively improve their optical properties. Furthermore, our approach enables the synthesis of Pb3S2Br2 that had not yet been reported. Our results not only provide valuable insights into the heterogeneous integration of PbYX and PbY materials to elevate material properties but also provide an effective method for further expanding the preparation of PbYX material systems.
Physico−mathematical model of the voltage−current characteristics of light-emitting diodes with quantum wells based on the Sah−Noyce−Shockley recombination mechanism
Fedor I. Manyakhin, Dmitry O. Varlamov, Vladimir P. Krylov, Lyudmila O. Morketsova, Arkady A. Skvortsov, Vladimir K. Nikolaev
, Available online  
doi: 10.1088/1674-4926/23120044

Herein, a physical and mathematical model of the voltage−current characteristics of a p−n heterostructure with quantum wells (QWs) is prepared using the Sah−Noyce−Shockley (SNS) recombination mechanism to show the SNS recombination rate of the correction function of the distribution of QWs in the space charge region of diode configuration. A comparison of the model voltage−current characteristics (VCCs) with the experimental ones reveals their adequacy. The technological parameters of the structure of the VCC model are determined experimentally using a nondestructive capacitive approach for determining the impurity distribution profile in the active region of the diode structure with a profile depth resolution of up to 10 Å. The correction function in the expression of the recombination rate shows the possibility of determining the derivative of the VCCs of structures with QWs with a nonideality factor of up to 4.

Herein, a physical and mathematical model of the voltage−current characteristics of a p−n heterostructure with quantum wells (QWs) is prepared using the Sah−Noyce−Shockley (SNS) recombination mechanism to show the SNS recombination rate of the correction function of the distribution of QWs in the space charge region of diode configuration. A comparison of the model voltage−current characteristics (VCCs) with the experimental ones reveals their adequacy. The technological parameters of the structure of the VCC model are determined experimentally using a nondestructive capacitive approach for determining the impurity distribution profile in the active region of the diode structure with a profile depth resolution of up to 10 Å. The correction function in the expression of the recombination rate shows the possibility of determining the derivative of the VCCs of structures with QWs with a nonideality factor of up to 4.
Self-powered UVC detectors based on α-Ga2O3 with enchanted speed performance
Aleksei Almaev, Alexander Tsymbalov, Bogdan Kushnarev, Vladimir Nikolaev, Alexei Pechnikov, Mikhail Scheglov, Andrei Chikiryaka
, Available online  
doi: 10.1088/1674-4926/24020001

Detectors were developed for detecting irradiation in the short-wavelength ultraviolet (UVC) interval using high-quality single-crystalline α-Ga2O3 films with Pt interdigital contacts. The films of α-Ga2O3 were grown on planar sapphire substrates with c-plane orientation using halide vapor phase epitaxy. The spectral dependencies of the photo to dark current ratio, responsivity, external quantum efficiency and detectivity of the structures were investigated in the wavelength interval of 200−370 nm. The maximum of photo to dark current ratio, responsivity, external quantum efficiency, and detectivity of the structures were 1.16 × 104 arb. un., 30.6 A/W, 1.65 × 104%, and 6.95 × 1015 Hz0.5·cm/W at a wavelength of 230 nm and an applied voltage of 1 V. The high values of photoelectric properties were due to the internal enhancement of the photoresponse associated with strong hole trapping. The α-Ga2O3 film-based UVC detectors can function in self-powered operation mode due to the built-in electric field at the Pt/α-Ga2O3 interfaces. At a wavelength of 254 nm and zero applied voltage, the structures exhibit a responsivity of 0.13 mA/W and an external quantum efficiency of 6.2 × 10−2%. The UVC detectors based on the α-Ga2O3 films demonstrate high-speed performance with a rise time of 18 ms in self-powered mode.

Detectors were developed for detecting irradiation in the short-wavelength ultraviolet (UVC) interval using high-quality single-crystalline α-Ga2O3 films with Pt interdigital contacts. The films of α-Ga2O3 were grown on planar sapphire substrates with c-plane orientation using halide vapor phase epitaxy. The spectral dependencies of the photo to dark current ratio, responsivity, external quantum efficiency and detectivity of the structures were investigated in the wavelength interval of 200−370 nm. The maximum of photo to dark current ratio, responsivity, external quantum efficiency, and detectivity of the structures were 1.16 × 104 arb. un., 30.6 A/W, 1.65 × 104%, and 6.95 × 1015 Hz0.5·cm/W at a wavelength of 230 nm and an applied voltage of 1 V. The high values of photoelectric properties were due to the internal enhancement of the photoresponse associated with strong hole trapping. The α-Ga2O3 film-based UVC detectors can function in self-powered operation mode due to the built-in electric field at the Pt/α-Ga2O3 interfaces. At a wavelength of 254 nm and zero applied voltage, the structures exhibit a responsivity of 0.13 mA/W and an external quantum efficiency of 6.2 × 10−2%. The UVC detectors based on the α-Ga2O3 films demonstrate high-speed performance with a rise time of 18 ms in self-powered mode.
A highly sensitive ratiometric near-infrared nanosensor based on erbium-hyperdoped silicon quantum dots for iron(Ⅲ) detection
Kun Wang, Wenxuan Lai, Zhenyi Ni, Deren Yang, Xiaodong Pi
, Available online  
doi: 10.1088/1674-4926/24020018

Ratiometric fluorescent detection of iron(Ⅲ) (Fe3+) offers inherent self-calibration and contactless analytic capabilities. However, realizing a dual-emission near-infrared (NIR) nanosensor with a low limit of detection (LOD) is rather challenging. In this work, we report the synthesis of water-dispersible erbium-hyperdoped silicon quantum dots (Si QDs:Er), which emit NIR light at the wavelengths of 810 and 1540 nm. A dual-emission NIR nanosensor based on water-dispersible Si QDs:Er enables ratiometric Fe3+ detection with a very low LOD (0.06 μM). The effects of pH, recyclability, and the interplay between static and dynamic quenching mechanisms for Fe3+ detection have been systematically studied. In addition, we demonstrate that the nanosensor may be used to construct a sequential logic circuit with memory functions.

Ratiometric fluorescent detection of iron(Ⅲ) (Fe3+) offers inherent self-calibration and contactless analytic capabilities. However, realizing a dual-emission near-infrared (NIR) nanosensor with a low limit of detection (LOD) is rather challenging. In this work, we report the synthesis of water-dispersible erbium-hyperdoped silicon quantum dots (Si QDs:Er), which emit NIR light at the wavelengths of 810 and 1540 nm. A dual-emission NIR nanosensor based on water-dispersible Si QDs:Er enables ratiometric Fe3+ detection with a very low LOD (0.06 μM). The effects of pH, recyclability, and the interplay between static and dynamic quenching mechanisms for Fe3+ detection have been systematically studied. In addition, we demonstrate that the nanosensor may be used to construct a sequential logic circuit with memory functions.
Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off
Danrui Wan, Jianping Zhou, Guoyun Meng, Ning Su, Dongdong Zhang, Lian Duan, Junqiao Ding
, Available online  
doi: 10.1088/1674-4926/24040008

Boron-nitrogen doped multiple resonance (BN-MR) emitters, characterized by B−N covalent bonds, offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high efficiency. However, there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR emitters. Herein, we present the synthesis of a BN-MR emitter, tCz[B−N]N, through a one-pot borylation reaction directed by the amine group, achieving an impressive yield of 94%. The emitter is decorated by incorporating two 3,6-di-t-butylcarbazole (tCz) units into a B−N covalent bond doped BN-MR parent molecule via para-C−π−D and para-N−π−D conjugations. This peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region, peaking at 526 nm with a narrowband full-width at half maximum (FWHM) of 41 nm. Consequently, organic light emitting diodes (OLEDs) employing this emitter achieved a maximum external quantum efficiency (EQEmax) value of 27.7%, with minimal efficiency roll-off. Even at a practical luminance of 1000 cd∙m−2, the device maintains a high EQE value of 24.6%.

Boron-nitrogen doped multiple resonance (BN-MR) emitters, characterized by B−N covalent bonds, offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high efficiency. However, there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR emitters. Herein, we present the synthesis of a BN-MR emitter, tCz[B−N]N, through a one-pot borylation reaction directed by the amine group, achieving an impressive yield of 94%. The emitter is decorated by incorporating two 3,6-di-t-butylcarbazole (tCz) units into a B−N covalent bond doped BN-MR parent molecule via para-C−π−D and para-N−π−D conjugations. This peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region, peaking at 526 nm with a narrowband full-width at half maximum (FWHM) of 41 nm. Consequently, organic light emitting diodes (OLEDs) employing this emitter achieved a maximum external quantum efficiency (EQEmax) value of 27.7%, with minimal efficiency roll-off. Even at a practical luminance of 1000 cd∙m−2, the device maintains a high EQE value of 24.6%.
InGaZnO-based photoelectric synaptic devices for neuromorphic computing
Jieru Song, Jialin Meng, Tianyu Wang, Changjin Wan, Hao Zhu, Qingqing Sun, David Wei Zhang, Lin Chen
, Available online  
doi: 10.1088/1674-4926/24040038

Photoelectric synaptic devices could emulate synaptic behaviors utilizing photoelectric effects and offer promising prospects with their high-speed operation and low crosstalk. In this study, we introduced a novel InGaZnO-based photoelectric memristor. Under both electrical and optical stimulation, the device successfully emulated synaptic characteristics including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), long-term potentiation (LTP), and long-term depression (LTD). Furthermore, we demonstrated the practical application of our synaptic devices through the recognition of handwritten digits. The devices have successfully shown their ability to modulate synaptic weights effectively through light pulse stimulation, resulting in a recognition accuracy of up to 93.4%. The results illustrated the potential of IGZO-based memristors in neuromorphic computing, particularly their ability to simulate synaptic functionalities and contribute to image recognition tasks.

Photoelectric synaptic devices could emulate synaptic behaviors utilizing photoelectric effects and offer promising prospects with their high-speed operation and low crosstalk. In this study, we introduced a novel InGaZnO-based photoelectric memristor. Under both electrical and optical stimulation, the device successfully emulated synaptic characteristics including excitatory postsynaptic current (EPSC), paired-pulse facilitation (PPF), long-term potentiation (LTP), and long-term depression (LTD). Furthermore, we demonstrated the practical application of our synaptic devices through the recognition of handwritten digits. The devices have successfully shown their ability to modulate synaptic weights effectively through light pulse stimulation, resulting in a recognition accuracy of up to 93.4%. The results illustrated the potential of IGZO-based memristors in neuromorphic computing, particularly their ability to simulate synaptic functionalities and contribute to image recognition tasks.
Artificial hawk-eye camera for foveated, tetrachromatic, and dynamic vision
Wenhao Ran, Zhuoran Wang, Guozhen Shen
, Available online  
doi: 10.1088/1674-4926/24060010

Embedded high-quality ternary GaAs1−xSbx quantum dots in GaAs nanowires by molecular-beam epitaxy
Xiyu Hou, Lianjun Wen, Fengyue He, Ran Zhuo, Lei Liu, Hailong Wang, Qing Zhong, Dong Pan, Jianhua Zhao
, Available online  
doi: 10.1088/1674-4926/24030038

Semiconductor quantum dots are promising candidates for preparing high-performance single photon sources. A basic requirement for this application is realizing the controlled growth of high-quality semiconductor quantum dots. Here, we report the growth of embedded GaAs1−xSbx quantum dots in GaAs nanowires by molecular-beam epitaxy. It is found that the size of the GaAs1−xSbx quantum dot can be well-defined by the GaAs nanowire. Energy dispersive spectroscopy analyses show that the antimony content x can be up to 0.36 by tuning the growth temperature. All GaAs1−xSbx quantum dots exhibit a pure zinc-blende phase. In addition, we have developed a new technology to grow GaAs passivation layers on the sidewalls of the GaAs1−xSbx quantum dots. Different from the traditional growth process of the passivation layer, GaAs passivation layers can be grown simultaneously with the growth of the embedded GaAs1−xSbx quantum dots. The spontaneous GaAs passivation layer shows a pure zinc-blende phase due to the strict epitaxial relationship between the quantum dot and the passivation layer. The successful fabrication of embedded high-quality GaAs1−xSbx quantum dots lays the foundation for the realization of GaAs1−xSbx-based single photon sources.

Semiconductor quantum dots are promising candidates for preparing high-performance single photon sources. A basic requirement for this application is realizing the controlled growth of high-quality semiconductor quantum dots. Here, we report the growth of embedded GaAs1−xSbx quantum dots in GaAs nanowires by molecular-beam epitaxy. It is found that the size of the GaAs1−xSbx quantum dot can be well-defined by the GaAs nanowire. Energy dispersive spectroscopy analyses show that the antimony content x can be up to 0.36 by tuning the growth temperature. All GaAs1−xSbx quantum dots exhibit a pure zinc-blende phase. In addition, we have developed a new technology to grow GaAs passivation layers on the sidewalls of the GaAs1−xSbx quantum dots. Different from the traditional growth process of the passivation layer, GaAs passivation layers can be grown simultaneously with the growth of the embedded GaAs1−xSbx quantum dots. The spontaneous GaAs passivation layer shows a pure zinc-blende phase due to the strict epitaxial relationship between the quantum dot and the passivation layer. The successful fabrication of embedded high-quality GaAs1−xSbx quantum dots lays the foundation for the realization of GaAs1−xSbx-based single photon sources.
Flexible ultrasound arrays with embossed polymer structures for medical imaging
Zhongming Chen, Qilin Hua, Guozhen Shen
, Available online  
doi: 10.1088/1674-4926/24050042