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2019年JOS入选“中国科技期刊卓越行动计划”
In Press
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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  • Designer substrates and devices for mechanobiology study

    Wang Xi, Delphine Delacour, Benoit Ladoux

    , Available online

    doi: 10.1088/1674-4926/41/4/041607

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    Both biological and engineering approaches have contributed significantly to the recent advance in the field of mechanobiology. Collaborating with biologists, bio-engineers and materials scientists have employed the techniques stemming from the conventional semiconductor industry to rebuild cellular milieus that mimic critical aspects of in vivo conditions and elicit cell/tissue responses in vitro. Such reductionist approaches have help to unveil important mechanosensing mechanism in both cellular and tissue level, including stem cell differentiation and proliferation, tissue expansion, wound healing, and cancer metastasis. In this mini-review, we discuss various microfabrication methods that have been applied to generate specific properties and functions of designer substrates/devices, which disclose cell-microenvironment interactions and the underlying biological mechanisms. In brief, we emphasize on the studies of cell/tissue mechanical responses to substrate adhesiveness, stiffness, topography, and shear flow. Moreover, we comment on the new concepts of measurement and paradigms for investigations of biological mechanotransductions that are yet to emerge due to on-going interdisciplinary efforts in the fields of mechanobiology and microengineering.

  • A brief review of formation energies calculation of surfaces and edges in semiconductors

    Chuen-Keung Sin, Jingzhao Zhang, Kinfai Tse, Junyi Zhu

    , Available online

    Abstract Full Text PDF

    To have a high quality experimental growth of crystals, understanding the equilibrium crystal shape (ECS) in different thermodynamic growth conditions is important. The factor governing the ECS is usually the absolute surface formation energies for surfaces (or edges in 2D) in different orientations. Therefore, it is necessary to obtain an accurate value of these energies in order to give a good explanation for the observation in growth experiment. Historically, there have been different approaches proposed to solve this problem. This paper is going to review these representative literatures and discuss the pitfalls and advantages of different methods.

  • HI hydrolysis-derived intermediate as booster for CsPbI3 perovskite: from crystal structure, film fabrication to device performance

    Zhizai Li, Zhiwen Jin

    , Available online

    Abstract Full Text PDF

    Nowadays, inorganic CsPbI3 perovskite solar cells (PSCs) have become one of the most attractive research hotspots in photovoltaic field for its superior chemical stability and excellent photo-electronic properties. Since the first independent report in 2015, the power conversion efficiency (PCE) of CsPbI3 based PSCs has sharply increased from 3.9% to 19.06%. Importantly, during the developing process of CsPbI3 PSCs, HI hydrolysis-derived intermediate plays an important role: from stabilizing the crystal structure, optimizing the fabricated film to boosting the device performance. In this review, the different crystal and electronic structures of CsPbI3 are introduced. We then trace the history and disputes of HI hydrolysis-derived intermediate to make this review more logical. Meanwhile, we highlight the functions of HI hydrolysis-derived intermediate, and systematically summarize the advanced works on CsPbI3 PSCs. Finally, the bottlenecks and prospects are revealed to further increase the CsPbI3 PSCs performance.

  • Two-dimensional transition metal dichalcogenides for lead halide perovskites-based photodetectors: band alignment investigation for the case of CsPbBr3/MoSe2

    Le Huang, Nengjie Huo, Zhaoqiang Zheng, Huafeng Dong, Jingbo Li

    , Available online

    Abstract Full Text PDF

    The distinguished electronic and optical properties of lead halide perovskites (LHPs) make them good candidates for active layer in optoelectronic devices. Integrating LHPs and two-dimensional (2D) transition metal dichalcogenides (TMDs) provides opportunities for achieving increased performance in heterostructured LHPs/TMDs based optoelectronic devices. The electronic structures of LHPs/TMDs heterostructures, such as the band offsets and interfacial interaction, are of fundamental and technological interest. Here CsPbBr3 and MoSe2 are taken as prototypes of LHPs and 2D TMDs to investigate the band alignment and interfacial coupling between them. Our GGA-PBE and HSE06 calculations reveal an intrinsic type-II band alignment between CsPbBr3 and MoSe2. This type-II band alignment suggests that the performance of CsPbBr3-based photodetectors can be improved by incorporating MoSe2 monolayer. Furthermore, the absence of deep defect states at CsPbBr3/MoSe2 interfaces is also beneficial to the better performance of photodetectors based on CsPbBr3/MoSe2 heterostructure. This work not only offers insights into the improved performance of photodetectors based on LHPs/TMDs heterostructures but it also provides guidelines for designing high-efficiency optoelectronic devices based on LHPs/TMDs heterostructures.

  • Growth of aligned SnS nanowire arrays for near infrared photodetectors

    Guozhen Shen, Haoran Chen, Zheng Lou

    , Available online

    doi: 10.1088/1674-4926/41/4/042602

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    Aligned SnS nanowires arrays were grown via a simple chemical vapor deposition method. As-synthesized SnS nanowires are single crystals grown along the [111] direction. The single SnS nanowire based device showed excellent response to near infrared lights with good responsivity of 267.9 A/W, high external quantum efficiency of 3.12 × 104 % and fast response time. Photodetectors were built on the aligned SnS nanowire arrays, exhibiting a light on/off ratio of 3.6, and the response and decay time of 4.5 and 0.7 s, respectively, to 1064 nm light illumination.

  • Nanofiber/nanowires-based flexible and stretchable sensors

    Dongyi Wang, Lili Wang, Guozhen Shen

    , Available online

    doi: 10.1088/1674-4926/41/4/041605

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    Nanofibers/nanowires with one-dimension (1D) nanostructure or well-patterned microstructure have shown distinctly advantages in flexible and stretchable sensor fields, owing to their remarkable tolerance against mechanical bending or stretching, outstanding electronic/optoelectronic properties, good transparency, and excellent geometry. Herein, latest summaries in the unique structure and properties of nanofiber/nanowire function materials and their applications for flexible and stretchable sensor are highlighted. Several types of high-performance nanofiber/nanowire-based flexible pressure and stretchable sensors are also reviewed. Finally, a conclusion and prospect for 1D nanofiber/nanowires-based flexible and stretchable sensors are also intensively discussed. This summary offers new insights for the development of flexible and stretchable sensor based 1D nanostructure in next-generation flexible electronics.

  • Characteristics and techniques of GaN-based micro-LEDs for application in next-generation display

    Zhou Wang, Xinyi Shan, Xugao Cui, Pengfei Tian

    , Available online

    doi: 10.1088/1674-4926/41/4/041606

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    Due to the excellent optoelectronic properties, fast response time, outstanding power efficiency and high stability, micro-LED plays an increasingly important role in the new generation of display technology compared with LCD and OLED display. This paper mainly introduces the preparation methods of the GaN-based micro-LED array, the optoelectronic characteristics, and several key technologies to achieve full-color display, such as transfer printing, color conversion by quantum dot and local strain engineering.

  • A review of flexible halide perovskite solar cells towards scalable manufacturing and environmental sustainability

    Melissa Davis, Zhibin Yu

    , Available online

    doi: 10.1088/1674-4926/41/4/041603

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    The perovskite material has many superb qualities which allow for its remarkable success as solar cells; flexibility is an emerging field for this technology. To encourage commercialization of flexible perovskite solar cells, two main areas are of focus: mitigation of stability issues and adaptation of production to flexible substrates. An in-depth report on stability concerns and solutions follows with a focus on Ruddlesden-Popper perovskites. Roll to roll processing of devices is desired to further reduce costs, so a review of flexible devices and their production methods follows as well. The final focus is on the sustainability of perovskite solar cell devices where recycling methods and holistic environmental impacts of devices are done.

  • Flexible inorganic oxide thin-film electronics enabled by advanced strategies

    Tianyao Zhang, Guang Yao, Taisong Pan, Qingjian Lu, Yuan Lin

    , Available online

    doi: 10.1088/1674-4926/41/4/041602

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    With the advent of human-friendly intelligent life, as well as increasing demands for natural and seamless human-machine interactions, flexibility and wearability are among the inevitable development trends for electronic devices in the future. Due to the advantages of rich physicochemical properties, flexible and stretchable inorganic oxide thin-film electronics play an increasingly important role in the emerging and exciting flexible electronic field, and they will act as a critical player in next-generation electronics. However, a stable strategy to render flexibility while maintaining excellent performance of oxide thin films is the most demanding and challenging problem, both for academic and industrial communities. Thus, this review focuses on the latest advanced strategies to achieve flexible inorganic oxide thin-film electronics. This review emphasizes the physical transferring strategies that are based on mechanical peeling and the chemical transferring strategies that are based on sacrificial layer etching. Finally, this review evaluates and summarizes the merits and demerits of these strategies toward actual applications, concluding with a future perspective into the challenges and opportunities for the next-generation of flexible inorganic oxide thin-film electronics.

  • Skin-inspired electronics: emerging semiconductor devices and systems

    Zhong Ma, Desheng Kong, Lijia Pan, Zhenan Bao

    , Available online

    doi: 10.1088/1674-4926/41/4/041601

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    Current electronics are driven by advanced microfabrication for fast and efficient information processing. In spite of high performance, these wafer-based devices are rigid, non-degradable, and unable to autonomous repair. Skin-inspired electronics have emerged as a new class of devices and systems for next-generation flexible and wearable electronics. The technology gains inspiration from the structures, properties, and sensing mechanisms of the skin, which may find a broad range of applications in cutting-edge fields such as healthcare monitoring, human-machine interface, and soft robotics/prostheses. Practical demands have fueled the development of electronic materials with skin-like properties in terms of stretchability, self-healing capability, and biodegradability. These materials provide the basis for functional sensors with innovative and biomimetic designs. Further system-level integrations and optimizations enable new forms of electronics for real-world applications. This review summarizes recent advancements in this active area and speculates on future directions.

  • Recent progress of morphable 3D mesostructures in advanced materials

    Haoran Fu, Ke Bai, Yonggang Huang, Yihui Zhang

    , Available online

    doi: 10.1088/1674-4926/41/4/041604

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    Soft robots complement the existing efforts of miniaturizing conventional, rigid robots, and have the potential to revolutionize areas such as military equipment and biomedical devices. This type of system can accomplish tasks in complex and time-varying environments through geometric reconfiguration induced by diverse external stimuli, such as heat, solvent, light, electric field, magnetic field, and mechanical field. Approaches to achieve reconfigurable mesostructures are essential to the design and fabrication of soft robots. Existing studies mainly focus on four key aspects: reconfiguration mechanisms, fabrication schemes, deformation control principles, and practical applications. This review presents a detailed survey of methodologies for morphable mesostructures triggered by a wide range of stimuli, with a number of impressive examples, demonstrating high degrees of deformation complexities and varied multi-functionalities. The latest progress based on the development of new materials and unique design concepts is highlighted. An outlook on the remaining challenges and open opportunities is provided.

  • Tubular/helical architecture construction based on rolled-up AlN nanomembranes and resonance as optical microcavity

    Jinyu Yang, Yang Wang, Lu Wang, Ziao Tian, Zengfeng Di, Yongfeng Mei

    , Available online

    doi: 10.1088/1674-4926/41/4/042601

    Abstract Full Text PDF Get Citation

    Aluminum nitride (AlN) has attracted a great amount of interest due to the fact that these group III–V semiconductors present direct band gap behavior and are compatible with current micro-electro-mechanical systems. In this work, three dimensional (3D) AlN architectures including tubes and helices were constructed by rolling up AlN nanomembranes grown on a silicon-on-insulator wafer via magnetron sputtering. The properties of the AlN membrane were characterized through transmission electron microscopy and X-ray diffraction. The thickness of AlN nanomembranes could be tuned via the RIE thinning method, and thus micro-tubes with different diameters were fabricated. The intrinsic strain in AlN membranes was investigated via micro-Raman spectroscopy, which agrees well with theory prediction. Whispering gallery mode was observed in AlN tubular optical microcavity in photoluminescence spectrum. A postprocess involving atomic layer deposition and R6G immersion were employed on as-fabricated AlN tubes to promote the Q-factor. The AlN tubular micro-resonators could offer a novel design route for Si-based integrated light sources. In addition, the rolled-up technology paves a new way for AlN 3D structure fabrication, which is promising for AlN application in MEMS and photonics fields.

  • Preface to the Special Issue on Flexible Materials and Structures for Bioengineering, Sensing, and Energy Applications

    Yongfeng Mei, Wei Gao, Hui Fang, Yuan Lin, Guozhen Shen

    , Available online

    doi: 10.1088/1674-4926/41/4/040101

    Abstract Full Text PDF Get Citation

  • Recent advancements in flexible humidity sensors

    Yan Wang, Jia Huang

    , Available online

    doi: 10.1088/1674-4926/41/4/040401

    Abstract Full Text PDF Get Citation

  • Variation tolerance for high-speed negative capacitance FinFET SRAM bit cell

    Yaqian Qian, Shushan Qiao, Rongqiang Yang

    , Available online

    Abstract Full Text PDF

    Negative capacitance FinFET (NC-FinFET) has a promising developmental prospect due to its superior performance in SS < 60 mV/dec (subthreshold swing), especially in SRAM. Noise margin is an important metric to evaluate the performance for SRAM, together with static leakage, read speed, etc. In this paper, we study the effects of the variation of ferroelectric material (thickness, polarization), FinFET critical physical parameters (fin number, channel length) and some ambient factors (working temperature, supply voltage) on the performance of NC-FinFET SRAM within the reasonable fluctuation tolerance range. The SRAM bit cell is analyzed with a basic 6T structure. The impact of fin number and channel length for NC-FinFET SRAM is different from that of conventional FinFETs. Additionally, the ferroelectric material and some other factors are assessed in detail.

  • Low on-resistance 1.2 kV 4H-SiC power MOSFET with Ron, sp of 3.4 mΩ·cm2

    Qiang Liu, Qian Wang, Hao Liu, Chenxi Fei, Shiyan Li, Runhua Huang, Song Bai

    , Available online

    Abstract Full Text PDF

    A 4H-SiC power MOSFET with specific on-resistance of 3.4 mΩ·cm2 and breakdown voltage exceeding 1.5 kV is designed and fabricated. Numerical simulations are carried out to optimize the electric field strength in gate oxide and at the surface of the semiconductor material in the edge termination region. Additional n-type implantation in JFET region is implemented to reduce the specific on-resistance. The typical leakage current is less than 1 μA at VDS = 1.4 kV. Drain-source current reaches 50 A at VDS = 0.75 V and VGS = 20 V corresponding to an on-resistance of 15 mΩ. The typical gate threshold voltage is 2.6 V.

  • 4H-SiC trench MOSFET with an integrated Schottky barrier diode and L-shaped P+ shielding region

    Xiaorong Luo, Ke Zhang, Xu Song, Jian Fang, Fei Yang, Bo Zhang

    , Available online

    Abstract Full Text PDF

    A novel 4H-SiC trench MOSFET is presented and investigated by simulation in this paper. The device features an integrated Schottky barrier diode and an L-shaped P+ shielding region beneath the gate trench and aside one wall of the gate trench (S-TMOS). The integrated Schottky barrier diode works as a free-wheeling diode in reverse recovery and reverse conduction, which significantly reduces reverse recovery charge (Qrr) and reverse turn-on voltage (VF). The L-shaped P+ region effectively shields the coupling of gate and drain, resulting in a lower gate–drain capacitance (Cgd) and date–drain charge (Qgd). Compared with that of conventional SiC trench MOSFET (C-TMOS), the VF and Qrr of S-TMOS has reduced by 44% and 75%, respectively, with almost the same forward output current and reverse breakdown voltage. Moreover, the S-TMOS reduces Qgd and Cgd by 32% and 22%, respectively, in comparison with C-TMOS.

  • An 18-bit sigma–delta switched-capacitor modulator using 4-order single-loop CIFB architecture

    Guiping Cao, Ning Dong

    , Available online

    Abstract Full Text PDF

    Oversampling sigma–delta (Σ–Δ) analog-to-digital converters (ADCs) are currently one of the most widely used architectures for high-resolution ADCs. The rapid development of integrated circuit manufacturing processes has allowed the realization of a high resolution in exchange for speed. Structurally, the Σ–Δ ADC is divided into two parts: a front-end analog modulator and a back-end digital filter. The performance of the front-end analog modulator has a marked influence on the entire Σ–Δ ADC system. In this paper, a 4-order single-loop switched-capacitor modulator with a CIFB (cascade-of-integrators feed-back) structure is proposed. Based on the chosen modulator architecture, the ASIC circuit is implemented using a chartered 0.35 μm CMOS process with a chip area of 1.72 × 0.75 mm2. The chip operates with a 3.3-V power supply and a power dissipation of 22 mW. According to the results, the performance of the designed modulator has been improved compared with a mature industrial chip and the effective number of bits (ENOB) was almost 18-bit.

  • Defect levels in d-electron containing systems: comparative study of CdTe using LDA and LDA + U

    Yuan Yin, Yu Wang, Guangde Chen, Yelong Wu

    , Available online

    Abstract Full Text PDF

    The defect properties in d-electron containing materials will be strongly influenced by the non-negligible on-site Coulomb interactions. However, this has been omitted in the current widely adopted standard first-principles calculations, such as LDA, leading to a large deviation of calculated results. Therefore, as a comparative case study, in this paper the defects of CdTe are investigated by first-principles calculations including standard LDA and LDA + U, and we find that LDA + U gives more accurate formation energies of the neutral point defects than the standard LDA. The same trend can be found in transition energies of the charged state defects as well. These comparative analyses show that LDA + U gives better results for the defects of CdTe than the standard LDA and requires less computing resource than LAPW, indicating it should have huge potential to model supercells with large number of atoms and strong electron interactions. Moreover, a new anion interstitial defect structure is found to be more stable than the well-known tetrahedron central anion interstitial defect structure \begin{document}${\rm{Te}}_i^a$\end{document}.

  • First principles study of the electronic structure and photovoltaic properties of β-CuGaO2 with MBJ + U approach

    Guoping Luo, Yingmei Bian, Ruifeng Wu, Guoxia Lai, Xiangfu Xu, Weiwei Zhang, Xingyuan Chen

    , Available online

    Abstract Full Text PDF

    Based on the density functional theory, the energy band and electronic structure of β-CuGaO2 are calculated by the modified Becke-Johnson plus an on-site Coulomb U (MBJ + U) approach in this paper. The calculated results show that the band gap value of β-CuGaO2 obtained by the MBJ + U approach is close to the experimental value. The calculated results of electronic structure indicate that the main properties of the material are determined by the bond between Cu-3d and O-2p energy levels near the valence band of β-CuGaO2, while a weak anti-bond combination is formed mainly by the O-2p energy level and Ga-4s energy level near the bottom of the conduction band of β-CuGaO2. The β-CuGaO2 thin film is predicted to hold excellent photovoltaic performance by analysis of the spectroscopic limited maximum efficiency (SLME) method. At the same time, the calculated maximum photoelectric conversion efficiency of the ideal CuGaO2 solar cell is 32.4%. Relevant conclusions can expand β-CuGaO2 photovoltaic applications.

  • A high performance adaptive on-time controlled valley-current-mode DC–DC buck converter

    Chanrong Jiang, Changchun Chai, Chenxi Han, Yintang Yang

    , Available online

    Abstract Full Text PDF

    This paper presents an AOT-controlled (adaptive-on-time, AOT) valley-current-mode buck converter for portable application. The buck converter with synchronous rectifier not only uses valley-current-mode control but also possesses hybrid-mode control functions at the same time. Due to the presence of the zero-current detection circuit, the converter can switch freely between the two operating modes without the need for an external mode selection circuit, which further reduces the design difficulty and chip area. The converter for the application of high power efficiency and wide current range is used to generate the voltage of 0.6–3.0 V with a battery source of 3.3–5.0 V, while the load current range is 0.05–2 A. The circuit can work in continuous conduction mode with constant frequency in high load current range. In addition, a stable output voltage can be obtained with small voltage ripple. In pace with the load current decreases to a critical value, the converter transforms into the discontinuous conduction mode smoothly. As the switching period increases, the switching loss decreases, which can significantly improve the conversion efficiency. The proposed AOT controlled valley current mode buck converter is integrated with standard 0.18 μm process and the simulation results show that the converter provides well-loaded regulations with power efficiency over 95%. When the circuit switches between the two conduction modes drastically, the response time can be controlled within 30 μs. The undershoot voltage is controlled within 25 mV under a large current hopping range.

  • Strain-induced the dark current characteristics in InAs/GaSb type-II superlattice for mid-wave detector

    H. J. Lee, S. Y. Ko, Y. H. Kim, J. Nah

    , Available online

    Abstract Full Text PDF

    Type-II superlattice (T2SL) materials are a key element for infrared (IR) detectors. However, it is well known that the characteristics of the detectors with the T2SL layer are greatly affected by the strain developed during the growth process, which determines the performance of IR detectors. Therefore, great efforts have been made to properly control the strain effect and develop relevant analysis methods to evaluate the strain-induced dark current characteristics. In this work, we report the strain-induced dark current characteristics in InAs/GaSb T2SL MWIR photodetector. The overall strain of InAs/GaSb T2SL layer was analyzed by both high-resolution X-ray diffraction (HRXRD) and the dark current measured from the absorber layer at the elevated temperature (≥ 110 K), where the major leakage current component is originated from the reduced minority carrier lifetime in the absorber layer. Our findings indicate that minority carrier lifetime increases as the tensile strain on the InAs/GaSb T2SL is more compensated by the compressive strain through ‘InSb-like’ interface, which reduces the dark current density of the device. Specifically, tensile strain compensated devices exhibited the dark current density of less than 2 × 10–5 A/cm2 at 120 K, which is more than one order of magnitude lower value compared to that of the device without tensile strain relaxation.

  • 1064 nm InGaAsP multi-junction laser power converters

    Jiajing Yin, Yurun Sun, Shuzhen Yu, Yongming Zhao, Rongwei Li, Jianrong Dong

    , Available online

    Abstract Full Text PDF

    Laser photovoltaic devices converting 1064 nm light energy into electric energy present a promising prospect in wireless energy transmission due to the commercial availability of high power 1064 nm lasers with very small divergence. Besides their high conversion efficiency, a high output voltage is also expected in a laser energy transmission system. Meanwhile, 1064 nm InGaAsP multi-junction laser power converters have been developed using p+-InGaAs/n+-InGaAs tunnel junctions to connect sub-cells in series to obtain a high output voltage. The triple-junction laser power converter structures are grown on p-type InP substrates by metal-organic chemical vapor deposition (MOCVD), and InGaAsP laser power converters are fabricated by conventional photovoltaic device processing. The room-temperature IV measurements show that the 1 × 1 cm2 triple-junction InGaAsP laser power converters demonstrate a conversion efficiency of 32.6% at a power density of 1.1 W/cm2, with an open-circuit voltage of 2.16 V and a fill factor of 0.74. In this paper, the characteristics of the laser power converters are analyzed and ways to improve the conversion efficiency are discussed.

  • Numerical study of mono-crystalline silicon solar cells with passivated emitter and rear contact configuration for the efficiency beyond 24% based on mass production technology

    Peng Wang, Gaofei Li, Miao Wang, Hong Li, Jing Zheng, Liyou Yang, Yigang Chen, Dongdong Li, Linfeng Lu

    , Available online

    Abstract Full Text PDF

    Mono-crystalline silicon solar cells with a passivated emitter rear contact (PERC) configuration have attracted extensive attention from both industry and scientific communities. A record efficiency of 24.06% on p-type silicon wafer and mass production efficiency around 22% have been demonstrated, mainly due to its superior rear side passivation. In this work, the PERC solar cells with a p-type silicon wafer were numerically studied in terms of the surface passivation, quality of silicon wafer and metal electrodes. A rational way to achieve a 24% mass-production efficiency was proposed. Free energy loss analyses were adopted to address the loss sources with respect to the limit efficiency of 29%, which provides a guideline for the design and manufacture of a high-efficiency PERC solar cell.

  • Modelling and optical response of a compressive-strained AlGaN/GaN quantum well laser diode

    A. Menani, L. Dehimi, F. Pezzimenti, S. Dehimi

    , Available online

    Abstract Full Text PDF

    The effects of the quantum well (QW) width, carrier density, and aluminium (Al) concentration in the barrier layers on the optical characteristics of a gallium nitride (GaN)-based QW laser diode are investigated by means of a careful modelling analysis in a wide range of temperatures. The device’s optical gain is calculated by using two different band energy models. The first is based on the simple band-to-band model that accounts for carrier transitions between the first levels of the conduction band and valence band, whereas the second assumes the perturbation theory (k.p model) for considering the valence intersubband transitions and the relative absorption losses in the QW. The results reveal that the optical gain increases with increasing the n-type doping density as well as the Al molar fraction of the AlxGa1–xN layers, which originate the GaN compressive-strained QW. In particular, a significant optical gain on the order of 5000 cm–1 is calculated for a QW width of 40 Å at room temperature. In addition, the laser threshold current density is of few tens of A/cm2 at low temperatures.

  • A review on performance comparison of advanced MOSFET structures below 45 nm technology node

    Namrata Mendiratta, Suman Lata Tripathi

    , Available online

    Abstract Full Text PDF

    CMOS technology is one of the most frequently used technologies in the semiconductor industry as it can be successfully integrated with ICs. Every two years the number of MOS transistors doubles because the size of the MOSFET is reduced. Reducing the size of the MOSFET reduces the size of the channel length which causes short channel effects and it increases the leakage current. To reduce the short channel effects new designs and technologies are implemented. Double gate MOSFET design has shown improvement in performance as amplifiers over a single MOSFET. Silicon-based MOSFET design can be used in a harsh environment. It has been used in various applications such as in detecting biomolecules. The increase in number of gates increases the current drive capability of transistors. GAA MOSFET is an example of a quadruple gate around the four sides of channel that increases gate control over the channel region. It also increases effective channel width that improves drain current and reduces leakage current keeping short channel effects under limit. Junctionless MOSFET operates faster and uses less power with increase in ON-state current leading to a good value of ION/IOFF ratio. In this paper, several gate and channel engineered MOSFET structures are analyzed and compared for sub 45 nm technology node. A comparison among different MOSFET structures has been made for subthreshold performance parameters in terms of IOFF, subthreshold slope and DIBL values. The analog/RF performance is analyzed for transconductance, effective transistor capacitances, stability factor and critical frequency. The paper also covers different applications of advance MOSFET structures in analog/digital or IoT/ biomedical applications.

  • A 0.1–1.5 GHz multi-octave quadruple-stacked CMOS power amplifier

    Shizhe Wei, Haifeng Wu, Qian Lin, Mingzhe Zhang

    , Available online

    Abstract Full Text PDF

    In this letter, we design and analyze 0.1–1.5 GHz multi-octave quadruple-stacked CMOS power amplifier (PA) in 0.18 μm CMOS technology. By using two-stage quadruple-stacked topology and feedback technology, the proposed PA realizes an ultra-wideband CMOS PA in a small chip area. Wideband impedance matching is achieved with smaller chip dimension. The effects of feedback resistors on the RF performance are also discussed for this stacked-FET PA. The PA shows measured input return loss (< –10.8 dB) and output return loss (< –9.6 dB) in the entire bandwidth. A saturated output power of 22 dBm with maximum 20% power added efficiency (PAE) is also measured with the drain voltage at 5 V. The chip size is 0.44 mm2 including all pads.

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