In this study, we present an in-depth exploration of charge transport phenomena and variable photo-switching characteristics in a novel double-perovskite-based three-terminal device. The Cs₂AgBiBr₆ thin film (TF) was synthesized through a three-step thermal evaporation process followed by precise open-air annealing, ensuring superior film quality as confirmed by structural and morphological characterizations. Photoluminescence spectroscopy revealed distinct emissions at 2.28 and 2.07 eV, indicative of both direct and indirect electronic transitions. Our device exhibited space-charge limited current (SCLC) behaviour beyond 0.35 V, aligning with the relationship $ {\text{Current}\left(I\right)\propto\text{Voltage\ }\left(V\right)^m }$, where the exponent m transitioned from ≤1 to >1. Detailed analysis of Schottky parameters within the trap-filled limit (TFL) regime was conducted, accounting for variations in temperature and optical power. Significantly, the self-powered photodetector demonstrated outstanding performance under illumination. The sensitivity of the device was finely tunable via the applied bias voltages at the third terminal. Notably, an optimal bias voltage of ±100 μV yielded maximum responsivity (R) of 0.48 A/W and an impressive detectivity (D*) of 1.07 × 10⁹ Jones, highlighting the potential of this double-perovskite-based device for advanced optoelectronic applications.

This paper introduces a pioneering application of secondary ion mass spectrometry (SIMS) for estimating the electronic properties of Pb_1−xSn_xTe, a compound categorized as a topological crystalline insulator. The proposed approach marks the first application of SIMS for such estimations and focuses on investigating variations in ionization probabilities and shifts in the energy distribution of secondary ions. The ionization probabilities are influenced by pivotal parameters such as the material's work function and electron affinity. The derivation of these parameters hinges upon the energy gap's positioning relative to the vacuum level for varying values of $ x $ within the Pb_1−xSn_xTe compound. The findings elucidate noteworthy alterations in SIMS signals, particularly near the critical point of band-gap closing.

4H silicon carbide (4H-SiC) has gained a great success in high-power electronics, owing to its advantages of wide bandgap, high breakdown electric field strength, high carrier mobility, and high thermal conductivity. Considering the high carrier mobility and high stability of 4H-SiC, 4H-SiC has great potential in the field of photoelectrochemical (PEC) water splitting. In this work, we demonstrate the irradiation-resistant PEC water splitting based on nanoporous 4H-SiC arrays. A new two-step anodizing approach is adopted to prepare 4H-SiC nanoporous arrays with different porosity, that is, a constant low-voltage etching followed by a pulsed high-voltage etching. The constant-voltage etching and pulsed-voltage etching are adopted to control the diameter of the nanopores and the depth of the nanoporous arrays, respectively. It is found that the nanoporous arrays with medium porosity has the highest PEC current, because of the enhanced light absorption and the optimized transportation of charge carriers along the walls of the nanoporous arrays. The performance of the PEC water splitting of the nanoporous arrays is stable after the electron irradiation with the dose of 800 and 1600 kGy, which indicates that 4H-SiC nanoporous arrays has great potential in the PEC water splitting under harsh environments.

In this study, we present the development of self-aligned p-channel GaN back gate injection transistors (SA-BGITs) that exhibit a high ON-state current. This achievement is primarily attributed to the conductivity modulation effect of the 2-D electron gas (2DEG, the back gate) beneath the 2-D hole gas (2DHG) channel. SA-BGITs with a gate length of 1 μm have achieved an impressive peak drain current (I_D,MAX) of 9.9 mA/mm. The fabricated SA-BGITs also possess a threshold voltage of 0.15 V, an exceptionally minimal threshold hysteresis of 0.2 V, a high switching ratio of 10⁷, and a reduced ON-resistance (R_ON) of 548 Ω·mm. Additionally, the SA-BGITs exhibit a steep sub-threshold swing (SS) of 173 mV/dec, further highlighting their suitability for integration into GaN logic circuits.

Superjunction (SJ) is one of the most innovative concepts in the field of power semiconductor devices and is often referred to as a "milestone" in power MOS. Its balanced charge field modulation mechanism breaks through the strong dependency between the doping concentration in the drift region and the breakdown voltage V_B in conventional devices. This results in a reduction of the trade-off relationship between specific on-resistance R_on,sp and V_B from the conventional R_on,sp∝V_B^2.5 to R_on,sp∝W∙V_B^1.32, and even to R_on,sp∝W·V_B^1.03. As the exponential term coefficient decreases, R_on,sp decreases with the cell width W, exhibiting a development pattern reminiscent of "Moore’s Law". This paper provides an overview of the latest research developments in SJ power semiconductor devices. Firstly, it introduces the minimum specific on-resistance R_on,min theory of SJ devices, along with its combination with special effects like 3-D depletion and tunneling, discussing the development of R_on,min theory in the wide bandgap SJ field. Subsequently, it discusses the latest advancements in silicon-based and wide bandgap SJ power devices. Finally, it introduces the homogenization field (HOF) and high-K voltage-sustaining layers derived from the concept of SJ charge balance. SJ has made significant progress in device performance, reliability, and integration, and in the future, it will continue to evolve through deeper integration with different materials, processes, and packaging technologies, enhancing the overall performance of semiconductor power devices.

Low-resistance Ohmic contact is critical for the high efficiency GaN-based laser diodes. This study investigates the introduction of the In_0.15Ga_0.85N contact layer on the specific contact resistance. Experimental results reveal that adopting the In_0.15Ga_0.85N contact layer yields a minimized specific contact resistance of 2.57 × 10⁻⁵ Ω·cm² which is two orders of magnitude lower than the GaN contact layer (7.61 × 10⁻³ Ω·cm²). A decrease in the specific contact resistance arises from the reduction of the barrier between the metal and p-type In_0.15Ga_0.85N. To develop an optimal metal electrode combination on the In_0.15Ga_0.85N contact layer, the Pd/Au and Ni/Au electrode stacks which are most commonly used in the formation of Ohmic contact with p-GaN are investigated. Metal stack of 10/30 nm Pd/Au is demonstrated effective in reducing the specific contact resistance to 10⁻⁵ Ω·cm² level. The mechanism of the variation of the specific contact resistance under different annealing atmospheres is explained by auger electron spectroscopy.

In this work, a PEDOT:PSS/Sn:α-Ga₂O₃ hybrid heterojunction diode (HJD) photodetector was fabricated by spin-coating highly conductive PEDOT:PSS aqueous solution on the mist chemical vapor deposition (Mist-CVD) grown Sn:α-Ga₂O₃ film. This approach provides a facile and low-cost p-PEDOT:PSS/n-Sn:α-Ga₂O₃ spin-coating method that facilitates self-powering performance through p−n junction formation. A typical type-Ⅰ heterojunction is formed at the interface of Sn:α-Ga₂O₃ film and PEDOT:PSS, and contributes to a significant photovoltaic effect with an open-circuit voltage (V_oc) of 0.4 V under the 254 nm ultraviolet (UV) light. When operating in self-powered mode, the HJD exhibits excellent photo-response performance including an outstanding photo-current of 10.9 nA, a rapid rise/decay time of 0.38/0.28 s, and a large on/off ratio of 91.2. Additionally, the HJD also possesses excellent photo-detection performance with a high responsivity of 5.61 mA/W and a good detectivity of 1.15 × 10¹¹ Jones at 0 V bias under 254 nm UV light illumination. Overall, this work may explore the potential range of self-powered and high-performance UV photodetectors.

Pre-ohmic-annealing (POA) treatment of P-GaN/AlN/AlGaN epitaxy under N₂ atmosphere was demonstrated to effectively achieve good p-type ohmic contact as well as decreased epitaxy sheet resistance. Ohmic contact resistance (R_c) extracted by transfer length method reduced from 38 to 23 Ω·mm with alleviated contact barrier height from 0.55 to 0.51 eV after POA treatment. X-ray photoelectron spectroscopy and Hall measurement confirmed that POA treatment was able to reduce surface state density and improve the hole concentration of p-GaN. Due to the decreased R_c and improved two-dimensional hole gas (2DHG) density, an outstanding-performance GaN E-mode p-channel MOSFET was successfully realized.

Metal oxide mesocrystals are the alignment of metal oxide nanoparticles building blocks into the ordered superstructure, which have potentially tunable optical, electronic, and electrical properties suitable for practical applications. Herein, we report an effective method for synthesizing mesocrystal zinc oxide nanorods (ZnONRs). The crystal, surface, and internal structures of the zinc oxide mesocrystals were fully characterized. Mesocrystal zinc oxide nanorods/reduced graphene oxide (ZnONRs/rGO) nanocomposite superstructure were synthesized also using the hydrothermal method. The crystal, surface, chemical, and internal structures of the ZnONRs/rGO nanocomposite superstructure were also fully characterized. The optical absorption coefficient, bandgap energy, band structure, and electrical conductivity of the ZnONRs/rGO nanocomposite superstructure were investigated to understand its optoelectronic and electrical properties. Finally, the photoconductivity of the ZnONRs/rGO nanocomposite superstructure was explored to find the possibilities of using this nanocomposite superstructure for ultraviolet (UV) photodetection applications. Finally, we concluded that the ZnONRs/rGO nanocomposite superstructure has high UV sensitivity and is suitable for UV detector applications.

The choices of proper dopants and doping sites significantly influence the doping efficiency. In this work, using doping in AlN as an example, we discuss how to choose dopants and doping sites in semiconductors to create shallow defect levels. By comparing the defect properties of C_N, O_N, Mg_Al, and Si_Al in AlN and analyzing the pros and cons of different doping approaches from the aspects of size mismatch between dopant and host elements, electronegativity difference and perturbation to the band edge states after the substitution, we propose that Mg_Al and Si_Al should be the best dopants and doping sites for p-type and n-type doping, respectively. Further first-principles calculations verify our predictions as these defects present lower formation energies and shallower defect levels. The defect charge distributions also show that the band edge states, which mainly consist of N- s and p orbitals, are less perturbed when Al is substituted, therefore, the derived defect states turn out to be delocalized, opposite to the situation when N is substituted. This approach of analyzing the band structure of the host material and choosing dopants and doping sites to minimize the perturbation on the host band structure is general and can provide reliable estimations for finding shallow defect levels in semiconductors.

This paper presents the design, fabrication, packaging, and characterization of a high-performance CMUT array. The array, which features rectangular cells fabricated using a sacrificial release process, achieves a receiving sensitivity of −231.44 dB (re: 1 V/μPa) with a 40 dB gain. Notably, the CMUT array exhibits a minimal sensitivity variation of just 0.87 dB across a temperature range of 0 to 60 °C. Furthermore, the output voltage non-linearity at 1 kHz is approximately 0.44%. These test results demonstrate that the reception performance of the 67-element CMUT array is superior to that of commercial transducers. The high performance and compact design of this CMUT array underscore its significant commercial potential for hydrophone applications.

Perovskites dominate the photovoltaic research community over the last two decades due to its very high absorption coefficient, electron and hole mobility. However, most of the reported solar cells constitute organic perovskites which offer very high efficiency but are highly unstable. Chalcogenide perovskites like BaZrS₃, CaZrS₃, etc. promise to be a perfect alternate owing to its high stability and mobilities. But, till now no stable photovoltaic device has been successfully fabricated using these materials and the existing challenges present in the synthesis of such perovskites are discussed. Also, the basic thermodynamic aspects that are essential for formation of BaZrS₃ are discussed. An extensive review on the precedent literatures and the future direction in the BaZrS₃ photovoltaic device research is clearly given.

Frequency combs with equally spaced frequency lines show great potentials for applications in spectroscopy, imaging, communications, and so on. In the terahertz frequency region, the quantum cascade laser (QCL) is an ideal radiation source for frequency comb and dual-comb operation. The systematic evaluation of phase noise characteristics of terahertz QCL frequency comb and dual-comb sources is of great importance for high precision measurements. In this work, we present detailed measurements and analysis of the phase noise characteristics of terahertz QCL frequency comb and dual-comb sources emitting around 4.2 THz with repetition frequencies of ~6.2 GHz. The measurement results for the current noise of the direct current (DC) sources (that are used to electrically pump the terahertz QCLs) indicate that at 100 Hz, the current noise for DC-1 and DC-2 is 0.3895 and 0.0982 nA/Hz^1/2, respectively. Such levels of current noise can be safely disregarded. The phase noise of radio frequency (RF) generators (that are employed for injection locking and phase locking), intermode beatnotes, and dual-comb signals with and without phase-locked loop (PLL) are all measured and compared. The experimental results show that in the free-running mode, the phase noise of the intermode beatnote signals is always lower than that of the dual-comb signals across all frequencies. Additionally, the phase noise induced by the radio frequency generators is negligible. By employing the phase locking technique, the phase noise of the intermode beatnote and dual-comb signals in the low offset frequency band can be significantly suppressed. At an offset frequency of 100 Hz, the measured phase noise values of the dual-comb line without and with phase locking are 15.026 and −64.801 dBc/Hz, respectively.

Sharing the advantages of high optical power, high efficiency and design flexibility in a compact size, quantum cascade lasers (QCLs) are excellent mid-to-far infrared laser sources for gas sensing, infrared spectroscopic, medical diagnosis, and defense applications. Metalorganic chemical vapor deposition (MOCVD) is an important technology for growing high quality semiconductor materials, and has achieved great success in the semiconductor industry due to its advantages of high efficiency, short maintenance cycles, and high stability and repeatability. The utilization of MOCVD for the growth of QCL materials holds a significant meaning for promoting the large batch production and industrial application of QCL devices. This review summarizes the recent progress of QCLs grown by MOCVD. Material quality and the structure design together determine the device performance. Research progress on the performance improvement of MOCVD-grown QCLs based on the optimization of material quality and active region structure are mainly reviewed.

Flexible photodetectors have garnered significant attention by virtue of their potential applications in environmental monitoring, wearable healthcare, imaging sensing, and portable optical communications. Perovskites stand out as particularly promising materials for photodetectors, offering exceptional optoelectronic properties, tunable band gaps, low-temperature solution processing, and notable mechanical flexibility. In this review, we explore the latest progress in flexible perovskite photodetectors, emphasizing the strategies developed for photoactive materials and device structures to enhance optoelectronic performance and stability. Additionally, we discuss typical applications of these devices and offer insights into future directions and potential applications.

In the era of Metaverse and virtual reality (VR)/augmented reality (AR), capturing finger motion and force interactions is crucial for immersive human-machine interfaces. This study introduces a flexible electronic skin for the index finger, addressing coupled perception of both state and process in dynamic tactile sensing. The device integrates resistive and giant magnetoelastic sensors, enabling detection of surface pressure and finger joint bending. This e-skin identifies three phases of finger action: bending state, dynamic normal force and tangential force (sweeping). The system comprises resistive carbon nanotubes (CNT)/polydimethylsiloxane (PDMS) films for bending sensing and magnetoelastic sensors (NdFeB particles, EcoFlex, and flexible coils) for pressure detection. The inward bending resistive sensor, based on self-assembled microstructures, exhibits directional specificity with a response time under 120 ms and bending sensitivity from 0° to 120°. The magnetoelastic sensors demonstrate specific responses to frequency and deformation magnitude, as well as sensitivity to surface roughness during sliding and material hardness. The system’s capability is demonstrated through tactile-based bread type and condition recognition, achieving 92% accuracy. This intelligent patch shows broad potential in enhancing interactions across various fields, from VR/AR interfaces and medical diagnostics to smart manufacturing and industrial automation.

The hierarchical and coordinated processing of visual information by the brain demonstrates its superior ability to minimize energy consumption and maximize signal transmission efficiency. Therefore, it is crucial to develop artificial visual synapses that integrate optical sensing and synaptic functions. This study fully leverages the excellent photoresponsivity properties of the PM6 : Y6 system to construct a vertical photo-tunable organic memristor and conducts in-depth research on its resistive switching performance, photodetection capability, and simulation of photo-synaptic behavior, showcasing its excellent performance in processing visual information and simulating neuromorphic behaviors. The device achieves stable and gradual resistance change, successfully simulating voltage-controlled long-term potentiation/depression (LTP/LTD), and exhibits various photo-electric synergistic regulation of synaptic plasticity. Moreover, the device has successfully simulated the image perception and recognition functions of the human visual nervous system. The non-volatile Au/PM6 : Y6/ITO memristor is used as an artificial synapse and neuron modeling, building a hierarchical coordinated processing SLP-CNN cascade neural network for visual image recognition training, its linear tunable photoconductivity characteristic serves as the weight update of the network, achieving a recognition accuracy of up to 93.4%. Compared with the single-layer visual target recognition model, this scheme has improved the recognition accuracy by 19.2%.

Synaptic nano-devices have powerful capabilities in logic, memory and learning, making them essential components for constructing brain-like neuromorphic computing systems. Here, we have successfully developed and demonstrated a synaptic nano-device based on Ga₂O₃ nanowires with low energy consumption. Under 255 nm light stimulation, the biomimetic synaptic nano-device can stimulate various functionalities of biological synapses, including pulse facilitation, peak time-dependent plasticity and memory learning ability. It is found that the artificial synaptic device based on Ga₂O₃ nanowires can achieve an excellent "learning−forgetting−relearning" functionality. The transition from short-term memory to long-term memory and retention of the memory level after the stepwise learning can attribute to the great relearning functionality of Ga₂O₃ nanowires. Furthermore, the energy consumption of the synaptic nano-device can be lower than 2.39 × 10^‒11 J for a synaptic event. Moreover, our device demonstrates exceptional stability in long-term stimulation and storage. In the application of neural morphological computation, the accuracy of digit recognition exceeds 90% after 12 training sessions, indicating the strong learning capability of the cognitive system composed of this synaptic nano-device. Therefore, our work paves an effective way for advancing hardware-based neural morphological computation and artificial intelligence systems requiring low power consumption.

Memristors have a synapse-like two-terminal structure and electrical properties, which are widely used in the construction of artificial synapses. However, compared to inorganic materials, organic materials are rarely used for artificial spiking synapses due to their relatively poor memrisitve performance. Here, for the first time, we present an organic memristor based on an electropolymerized dopamine-based memristive layer. This polydopamine-based memristor demonstrates the improvements in key performance, including a low threshold voltage of 0.3 V, a thin thickness of 16 nm, and a high parasitic capacitance of about 1 μF∙mm⁻². By leveraging these properties in combination with its stable threshold switching behavior, we construct a capacitor-free and low-power artificial spiking neuron capable of outputting the oscillation voltage, whose spiking frequency increases with the increase of current stimulation analogous to a biological neuron. The experimental results indicate that our artificial spiking neuron holds potential for applications in neuromorphic computing and 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.