Qianyu Hou

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 μm 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.

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.

The ultraviolet (UV) response of a floating-base 4H-SiC n–p–n phototransistor is characterized before and after 10 MeV electron irradiation. The pristine device demonstrates visible-blind UV detection at 275 nm, achieving a UV/dark current ratio of ∼106, a specific detectivity of 1.37 × 1012 Jones, and a responsivity of 1.36 A/W. Responsivity monotonically increases with incident optical power density. After 500 kGy irradiation, responsivity degrades by 80%, with dose dependence following a double-exponential decay. Vacuum annealing at 800 K restores 79% of the pre-irradiation optical gain, confirming a partial reversibility of irradiation-induced defects. Deep level transient spectroscopy reveals defect evolution post-annealing, identifying corresponding energy levels, identities, and annihilation dynamics. High-temperature annealing primarily annihilates irradiation-induced point defects, enabling significant recovery, while thermally stable defect complexes prevent full restoration.

This work presents a novel enhancement-mode hybrid p-type gate AlGaN/GaN high electron mobility transistor (HEMT) with a double barrier structure. The double barrier hybrid-gate (DBHG) HEMT yields better performance than the traditional p-GaN gate HEMTs in terms of threshold voltage and breakdown voltage, which can be attributed to the regulation of the interface electric field in the AlGaN barrier layers. Moreover, the simulated results indicate that the DBHG HEMT exhibits a high threshold voltage of 1.8 V and a breakdown voltage of 995 V. In addition, we discussed the influence of the thickness of each layer in the double barrier layer structure on device performance. This work provides valuable insights for future innovations in the structure design of HEMTs.

Normally off AlGaN/GaN high electron mobility transistors (HEMTs) with p-type gates are attracting increasing attention due to their high safety and low power loss in the field of power switching. In this work, to solve the Mg difficult activating problem of the conventional p-GaN gate AlGaN/GaN HEMTs, we propose an advanced design for the normally off AlGaN/GaN HEMT with a p-type hexagonal boron nitride (h-BN) gate cap layer to effectively manipulate the channel transport of the device. The simulation results demonstrate that the p-hBN gate cap HEMTs yield superior performance over conventional p-GaN gate HEMTs in terms of output current and breakdown voltage, which can be attributed to the deeper potential well formation at the AlGaN/GaN interface and more accumulation of holes located at the p-hBN/AlGaN interface. Moreover, we investigate the effect of bandgap variation on device performance, taking into account that the exact bandgap of h-BN remains under debate. Herein, valuable insights into h-BN cap-gate E-mode AlGaN/GaN HEMT devices are provided, which could serve as a useful reference for the future development of robust III-nitride material power electronic devices.

Radiation-hardened semiconductor GaN has drawn considerable attention owing to its excellent properties such as large displacement energy. Many studies have focused on evaluating the degradation of GaN-based power device performance by proton beam or particle irradiation, while quantitative analysis of the energy transfer process of particles inside the material and the mechanisms involved in inducing degradation of electrical properties are rare. Here, on the basis of the fabricated alpha-particle detector, a device model validated by basic electrical experiments is established to simulate the influence of alpha-particle irradiation on the leakage current of the device. We observe that the current does not change significantly with increasing radiation fluence at low bias, while it shows a descending trend with increasing radiation fluence at higher bias. However, increasing the energy of the radiation particles at the same radiation fluence directly leads to a monotonically elevated leakage current. Such a series of phenomena is associated with radiation-induced changes in the density of trapped states within the active layers of the device.