We report Al0.1Ga0.9N visible-blind ultraviolet (UV) single-photon avalanche diodes (SPADs) for 355 nm photon detection. By employing free-standing GaN (FS-GaN) substrates, the threading dislocation density in the Al0.1Ga0.9N layers was reduced by more than two orders of magnitude. The devices exhibit low dark current densities below 2 × 10−4 A/cm2 at breakdown, positive temperature coefficient of 0.019 V/K, and robust avalanche characteristics with the avalanche current increasing by more than five orders of magnitude within a 2 V bias range. Additionally, the variable-range hopping (VRH) conduction that dominates the leakage current under high reverse bias was significantly suppressed. Furthermore, the device exhibits an ultrafast response time of 1.40/1.88 ns and an ultrahigh avalanche gain exceeding 2 × 107, enabling Geiger-mode operation. Consequently, single-photon detection was achieved with a photon count rate exceeding 1 MHz and a single-photon detection efficiency above 2%.

Bipolar all-solid-state photodiodes, based on the photoelectric effect, are heralding a new dawn for the development of ultraviolet photonic integrated circuits. Here, we present a self-powered ultraviolet bipolar switching photodetector (SUBS-PD) based on a β-Ga2O3/GaN heterojunction. By introducing a heterojunction dual electric field to bidirectionally modulate carrier transport, the device achieves wavelength-selective photocurrent polarity reversal. It generates a positive photocurrent at 365 nm and a negative photocurrent at 270 nm, enabling intrinsic dual-band spectral discrimination without external power. By precisely engineering the thickness and doping concentration of the Ga2O3 layer, the optical absorption, internal electric-field distribution, and carrier transport dynamics are optimized, resulting in enhanced device performance. Furthermore, a simulated ultraviolet signal receiver incorporating the SUBS-PD demonstrates accurate American Standard Code for Information Interchange (ASCII) decoding. These results establish a compact and energy-efficient platform for programmable photonic circuits and secure ultraviolet optical communication.

In this paper, a 2.5 nm thick Al2O3 interlayer deposited by atomic layer deposition was inserted between AlGaN/GaN HEMT structure and SiNx passivation layer to reduce interface damage of the semiconductor/dielectric introduced directly by plasma-enhanced chemical vapor deposition. It is found that this ultra-thin Al2O3 interlayer can not only obviously increase the output current and extrinsic transconductance by reducing the access-region resistance, but also effectively suppress current collapse and the threshold voltage drift due to fewer interface defects in the access region between the gate and drain. More importantly, dynamic on-resistance degradation of devices with an Al2O3 interlayer is significantly improved in comparison with the only Si3N4-passivated HEMTs without an Al2O3 interlayer.

GaN current aperture vertical electron transistors (CAVETs) face critical bottlenecks, including low threshold voltage (Vth), poor forward gate robustness, and severe current crowding. To overcome these limitations, this paper proposes a novel enhancement-mode dual N–I–P junction GaN CAVET (DNIPJ-CAVET) based on a superjunction architecture. Simulation results indicate that the Vth increases from 1.65 V in conventional devices to 3.5 V in the DNIPJ-CAVET. This increase corresponds to a 112% enhancement. The forward gate breakdown voltage is elevated from 9 V to 28.94 V. These improvements are primarily attributed to the built-in electric field modulation of the N–I–P gate stack and the enhanced lateral depletion effect induced by the dual-island structure. Additionally, the absence of vertical electrostatic confinement in the aperture region effectively alleviates current crowding, resulting in a maximum saturation current (Idmax) of 136 mA/mm. Moreover, the source–drain breakdown voltage (BV) of the DNIPJ-CAVET remains as high as 2210 V. This work provides a viable design paradigm for high-performance GaN vertical power switches targeting electric vehicles and industrial power supply systems.

We report a deep-ultraviolet (DUV) metal-semiconductor-metal (MSM) photodetector based on a β-Ga2O3 thin film deposited by chemical vapor deposition (CVD) on a patterned sapphire substrate (PSS), compared with a control device using a film grown on flat sapphire. To the best of our knowledge, this is the first demonstration of β-Ga2O3 films with a preferred (510) orientation. The film grown on PSS exhibited high defect densities, including structural disorders, oxygen vacancies, and dangling bonds, which enabled exceptional responsivity (106.5 A/W) and specific detectivity (1.36 × 1013 Jones) through strong internal gain and extrinsic transitions, despite a relatively large dark current. A UV/visible rejection ratio (R255/R400) above 104 further confirmed the device's sensitivity. A comprehensive analysis was performed on the impact of defects on the increased dark current and slower response. These findings offer important insights into the growth mechanism of β-Ga2O3 on PSS and highlight its potential for scalable, cost-effective solar-blind photodetectors.

Driven by the rapid development of augmented reality (AR) and virtual reality (VR) displays, micro light-emitting diode (μLED) technology is evolving toward high brightness, high refresh rate, and high pixel density, which conventional driving and driving integration schemes can hardly meet. GaN-based monolithic drive-display integration is promising, yet existing schemes are limited by Mg doping-induced issues, poor process compatibility and high fabrication complexity. This work proposed and realized monolithically integrated Mg-free trench-gate metal-oxide-semiconductor field-effect transistors (MOSFETs) and μLEDs, which deliver a specific on-resistance of ~15.4 mΩ·cm² and an on/off current ratio of ~5×10⁶, alongside turn-on/off delays of 300 ns/30 ns measured at 100 kHz. By replacing conventional Mg doping with polarization-induced doping, this approach offers high process compatibility and low fabrication complexity, paving a novel route for monolithic integration of GaN transistors and μLEDs.

High-Al-content AlGaN microrods represent an effective platform for engineering deep-ultraviolet (DUV) emission. Here, we fabricated AlGaN microrods with varying diameters (2, 3, and 4 μm) via a top-down approach involving inductively coupled plasma dry etching followed by a KOH wet chemical modification. Their crystallographic facets and size-dependent optical properties were systematically investigated using scanning electron microscopy (SEM), cathodoluminescence (CL) spectroscopy, and CL mapping. We found that the KOH treatment selectively forms a-plane-dominated sidewalls on the high-Al-content portion of the microrods, whereas the etch pit bottoms stabilize as m-plane facets. Notably, the CL spectra show that the band-edge emission intensity of the 2 μm microrods is enhanced by a factor of 3.76 compared to the 4 μm structures. CL mapping further unveils the competitive dynamics between radiative recombination within the quantum wells and non-radiative recombination at surface states. These findings pinpoint 2 μm as the optimal diameter among the investigated range for maximizing spontaneous emission from these high-Al-content AlGaN microrods.

Creating a MXene-based NO2 gas sensor with high sensitivity, selectivity, rapid response/recovery speeds, longterm stability and low detection limit at room temperature remains great challenges. In this work, the uniform V2CTx nanosheets modified with WO3 nanoparticles (V2CTx/WO3) are prepared via a low-cost hydrothermal method combined with a thermal treatment. A wireless gas sensor based on the as-prepared V2CTx/WO3 nanocomposites is applied to detect ppb-level NO2 in practical scenarios at room temperature. Specifically, the response of VW-30 sensor (288.39%) to 100 ppm NO2 is 18.99 times higher than that of pure V2CTx sensor (15.19%), and it also displays good linearity in the NO2 concentration ranging from 100 to 1000 ppb, low detection limit (6.65 ppb), and fast average response/recovery speed (10.5/12.4 s), indicating more excellent reliability than other reported V2CTx-based NO2 sensors at room temperature. The WO3 modified V2CTx nanosheets significantly exposes more active basal, edge sites and high specific surface area, as well as strong interfacial interactions between V2CTx nanosheets and WO3 nanoparticles compared to pure V2CTx nanosheets. Density functional theory calculations reveal that the adsorption energies of V2CTx/WO3 for NO2 at different sites are stronger than those on pure V2CTx, leading to outstanding NO2 sensing performance. Finally, a developed wireless detection system based on VW-30 sensor proves that our sensor can provide accurate feedback in a timely manner in respiratory environment. This work will provide a simple and effective route for fabricating gas sensor based on the combination of two-dimensional carbides and metal oxides to effectively detect ppb-level NO2 at room temperature.

Power electronic devices exposed to the space environment face severe threats from high-energy space heavy-ion irradiation. This work demonstrates that p-GaN HEMTs fabricated on low-cost 6-inch sapphire substrates exhibit robust single-event irradiation hardness under 1.3 GeV heavy ion bombardment. The enhanced hardness is primarily attributed to the drastically reduced ion deposition energy in the thin AlN buffer coupled with the insulating properties of the sapphire substrate. Resultantly, the irradiation-hardened HEMTs achieve a remarkable single-event burnout voltage exceeding 700V, substantially surpassing that of the conventional GaN-on-Si HEMTs. Furthermore, the irradiated devices maintain fast switching performance, with turn-ON and turn-OFF times in the nanosecond range. These superior irradiation performances, achieved by simple, cost-effective GaN-on-sapphire technology, offer a promising pathway toward high-voltage, irradiation-hardened power devices for aerospace applications.

Polarization detection in shortwave spectrum using wurtzite wide-bandgap semiconductors remains challenging due to the isotropic limitations of conventional polar crystal planes. Nonpolar planes offer a promising route, yet the underlying physical mechanism is unclear. Here, we establish a direct correlation between crystallographic polarity and anisotropic photoresponse on nonpolar a-plane GaN, demonstrating an intrinsic polarization-sensitive photodetection scheme. Crystal-field-induced valence band splitting yields distinct transition dipole moments from heavy-hole and crystal field split-off bands to the conduction band minimum, enabling selective absorption for light polarized perpendicular or parallel to the c-axis. Using the nonpolar plane of GaN, electron transition probability between the heavy-hole band and conduction band minimum for polarization perpendicular to the c-axis is selectively enhanced, governing polarization-angle-dependent absorption. Our device achieves a high dichroic ratio of 3.79 (318% higher than c-plane) and an ultrafast response speed of 1.7 µs at 10 V, surpassing conventional polar-plane architectures and prior polarization-sensitive detectors. Furthermore, by introducing an oxygen injection layer to strategically break lattice symmetry, anisotropic charge density distribution around oxygen atoms further enhances the dichroic ratio. Exceptional polarization discrimination is validated in single-pixel polarized imaging and intensity/polarization binary-channel optical communication encryption. This work establishes a material-intrinsic paradigm for high-sensitivity polarization detection, offering new perspectives for multidimensional optoelectronics.

Mastering interfacial electronic structure at the atomic scale is key to breaking performance bottlenecks in solid-state gas sensors. Herein, we demonstrate that precise d-band engineering of a Pd/Ag-alloy gate, achieved by alloying Pd with 24.7 at% Ag, downshifts the d-band center by 0.15 eV relative to pure Pd. This atomic-level tuning reduces hydrogen adsorption energy by 44% and enhances capacity by 12.5-fold, as validated by DFT. Coupled with an ultrathin AlGaN barrier that enables efficient transduction of surface potential changes into channel conductance under zero gate bias, the resulting AlGaN/GaN HEMT sensor exhibits an exceptionally high response of 16,269% to 200 ppm H₂ at 200 °C—among the highest for self-biased devices—along with rapid kinetics (<30 s), excellent selectivity, and >30-day stability. In situ XRD and XPS provide direct evidence of the reversible lattice expansion and Pd–H bond formation underlying this enhancement. This work establishes d-band center modulation as a powerful and generalizable lever for optimizing metal/semiconductor interfaces in next-generation sensing and catalytic systems.

We report a p-NiO gate-engineered AlGaN/ GaN ultraviolet phototransistor (UVPT) that achieves high-sensitivity, visible-blind UV detection with ultralow dark current and strong photogating. The device employs an ultrathin in-situ SiNx interlayer beneath the p-NiO gate, which preserves an intact 2DEG transport interface while enabling gate-side charge storage. The large vertical band bending under reverse gate bias creates a strong electric field across the gate stack, which efficiently separates photogenerated carriers and drives holes toward the gate dielectric. Under 365 nm illumination (V-GS/V-DS = -8/10 V), the UVPT achieves a photo-to-dark current ratio (PDCR) exceeding 4 & times; 10(9), responsivity (R) up to 1 & times; 10(6) A/W, and UV-to-visible rejection ratio (UVRR) surpassing 1 & times; 10(10). A significant negative threshold-voltage shift is observed and intensifies with photon injection, indicating a photo-gating mechanism associated with gate-side hole retention at the p-NiO/SiNx interface. The accumulated Qphoto partially offsets the reverse gate bias, shifts Vth negatively, and thereby gives rise to the large current contrast. The device further exhibits fast dynamics (200-ns-rise/ 34.2-mu s-decay) and a flicker-noise-limited specific detectivity (D & lowast;) of 5.52 & times;10(16) cm & centerdot;Hz(1/ 2)& centerdot;W-1. These results highlight p-NiO/SiNx gate engineering as an effective design paradigm for high-sensitivity and visible-blind UV photodetection in wide-bandgap semiconductor platforms.

Charge-sensitive amplification is critical for processing ultra-weak signals, necessitating a nearly isolated terminal with superior leakage blocking and stable operation point maintenance. This work demonstrates a monolithic chip based on a 4H-SiC p-n-p junction that integrates three key functions: charge coupling via a feedback capacitor, voltage signal transfer through a transistor, and charge dissipation via a diode to maintain a near-zero operation point. The implemented feedback capacitor of 0.15 pF enables charge analysis at the femto-coulomb (fC) level. The transistor achieves an output conductance as low as 1×10-5 S, ensuring low-noise signal transfer, while the diode exhibits a specific on-resistance of 16.7 Ω·mm² and a charge dissipation time within 1 μs. Leveraging these integrated capabilities, the chip achieves precise charge counting and transient tracking performance for a minute charge of 240 fC with a standard error of 1.5% and a processing time of 5 μs.

This work presents a nanosecond time resolution strategy for SiC soft X-ray single photon detection based on charge integration, active reset and time to digital conversion electronics. Enabled by a 100 μm thick lightly doped epitaxial layer, 4H-SiC single photon detector (SPD) achieves 0.1 pA leakage current at 200 V reverse bias, which critically enhances signal-to-noise ratio (SNR). A charge sensitive amplifier (CSA) with transmission gate (TG) reset is developed to suppress the thermal noise in traditional resistance based reset CSA and eliminate charge injection effect in single MOS switch. Additionally, hysteresis comparator is adopted to mitigate false triggering from noise, while delay-line based time-to-digital conversion (TDC) configuration records single photon timing resolution with 1.045 ns for the statistical photon time of arrival (TOA) analysis, as measured at 5.89 keV X-ray photons. Ultimately, systematic correlations between photon energy and time resolution have been established through multi-energy source experiments, providing a series of performance levels in the 4H-SiC based system for X-ray sensing.

Space power electronics systems are regarded as a critical emerging application domain for wide-bandgap GaN power devices, where space radiation involving high-energy heavy ions (e.g. krypton, Kr) remains the biggest threat, leading to susceptible AlGaN/GaN heterojunctions. This work comprehensively investigates the stress and strain in heterojunction as well as latent tracks and defect characteristics in devices under Kr irradiation fluences up to 1 & times; 1010 ion cm-2. Through Raman spectroscopy, the enhanced compressive stress in AlGaN is revealed and quantitatively correlated with strain-induced polarization effects, thus providing insights into the dominant mechanism underlying heterojunction performance degradation, and establishing a numerical derivation involving stress, strain and polarization effects under irradiation. Meanwhile, the discontinuities and sub-nanometer diameter latent tracks revealed in the transmission electron microscopy experiments suggest that the device suffers minimal damage under heavy ion Kr irradiation, primarily due to the low electronic energy loss. Furthermore, the intensity ratio between yellow luminescence and near band edge signals in the 80 K low-temperature photoluminescence spectrum increases evidently with elevating irradiation fluence, indicating an increase in defects caused by irradiation. These findings offer critical insights into the behavior and performance of AlGaN/GaN power devices in satellite applications under Kr ion irradiation conditions.

Alpha-particle detectors face several fundamental challenges, including the difficulty in achieving thick, high-quality depletion regions essential for efficient charge collection, high leakage currents caused by material defects, and severe energy loss in conventional electrode configurations. To address these limitations, we developed a GaN p-i-n alpha-particle detector on a free-standing substrate with a 20 mu m thick intrinsic layer. A grid-shaped front electrode is introduced to minimize dead-layer energy loss. The device achieves full depletion at a low bias of -40 V and maintains leakage currents below several tens of picoampere up to -100 V. Notably, it exhibits an energy resolution of 1.5% at just -10 V, as well as a charge collection efficiency of 83.6%, which increases to 98.1% at -70 V. Theoretical modeling further reveals the underlying mechanism behind the anomalous energy resolution trend. These advances are attributed to the high crystalline quality of the thick i-GaN layer and the grid-shaped electrode design, which collectively suppress dislocation-induced leakage and dead-layer effects. This work provides a practical pathway to low-voltage, high-performance GaN alpha-particle detectors.

This paper proposes a back-illuminated separated absorption and multiplication (SAM) structure photodiode based on ferroelectric scandium gallium nitride (ScGaN), which improves the problems of low gain and high operating voltage in conventional gallium nitride (GaN)-based ultraviolet avalanche photodiodes (APDs). Upon introducing an n-type ScGaN interlayer into the device, the strong polarization effect contributes to the enhancement of the built-in electric field. In comparison with conventional p-i-n-i-n GaN-based APDs, the designed back-illuminated device shows a 56% enhancement in avalanche gain to 9.2 × 104 and a decrease in avalanche breakdown voltage from 72 V to 64 V. According to analysis of the internal electric field and band structure, this paper explains the physical mechanism behind the performance enhancement and further optimizes the thickness and doping concentration parameters of the n-ScGaN interlayer. The proper utilization of results will greatly advance ScGaN's potential for future applications in optoelectronic devices.

Abstract This work presents a GaN based p-channel heterostructure field effect transistor featuring an embedded Ga 2 O 3 layer within the AlGaN barrier. Electrical simulations demonstrate that the incorporation of the Ga 2 O 3 layer enables enhancement-mode operation, due to valence band depression at the GaN/AlGaN heterojunction under zero bias induced by its wide bandgap. However, this improvement in transfer characteristics is accompanied by a reduction in output current and an increase in on-resistance ( R on ), resulting from the decreased hole concentration in the channel under on-state conditions. Through systematic optimization of the Ga 2 O 3 layer dimensions, an optimal length of 2 μm and thickness of 27 nm are chosen, achieving a threshold voltage ( V th ) of −2.93 V and a saturation drain current ( I D_sat ) of 3.92 mA mm −1 .

This letter presents a new method for real-time in-situ temperature measurement and thermal resistance extraction of AlGaN/GaN high electron mobility transistors (HEMTs) based on Schottky diode integrated sensors for the first time. Through an innovative structure design, the independent Schottky diode sensor is integrated near the gate of the HEMT, and the fabrication process is fully compatible with the standard electrode manufacturing process. Experimental results show that the sensor has a temperature sensitivity of 4.192 mV/degrees C. (testing current = 1.0 mu A) and a time resolution of microsecond is achieved, which can realize transient temperature monitoring without affecting the operation state of the device. It shows high temperature sensitivity without measurement delay time caused by circuit switching. Meanwhile, it does not require the damage to package which is necessary in the optical methods. It can accurately capture the transient temperature change of the hot spot near the gate and construct the structure function, so as to extract the thermal resistance of each layer of the package device. The integrated sensor provides an effective characterization method for the thermal management optimization of power devices, and shows an important application value in the field of reliability analysis and heat dissipation design. This method can also serve as a benchmark for evaluating alternative temperature-measurement techniques.

In this work, a tetralateral GaN position sensitive detector (PSD) with a 4 mm x 4 mm effective area is demonstrated for visible-blind ultraviolet (UV) detection. By utilizing an epitaxially grown thin p-GaN layer as the lateral resistive channel, the PSD exhibits a low interelectrode resistance of 41 k Omega and a low terminal capacitance of 35 pF, enabling a fast response time of 0.271 mu s. The device presents a peak external quantum efficiency over 67% under zero bias, a high UV-to-visible rejection ratio exceeding 3000, and a broad spectral response covering 200-360 nm range. With these characteristics, the device also demonstrates a low position nonlinearity of 2.3% and a high position resolution of 1.32 mu m, enabling reliable real-time tracking of moving UV light sources. These results highlight the potential of GaN-based PSDs for high-speed visible-blind UV position detection.