Based on the Non-Ionizing Energy Loss (NIEL) theory and the Boltzmann transport equation, this study systematically examines the damage behavior of InxGa1-xAs material under neutron irradiation, considering variations in layer thickness, indium mole fraction (x), and incident neutron energy. The findings reveal that in micron-scale thin targets, the NIEL values remain nearly composition-independent, whereas in thick targets, a pronounced attenuation of NIEL with depth is observed. The total number of Primary Knock-on Atoms (PKA) decreases noticeably with increasing neutron energy and indium content. In the low-energy region (<0.1 MeV), the damage primarily arises from elastic scattering, resulting in a relatively smaller number of displaced atoms. As neutron energy increases, inelastic scattering begins to play a significant role. In the high-energy region (>1 MeV), both scattering mechanisms act synergistically, with a single reaction capable of producing up to thousands of displaced atoms, leading to cascade damage. The non-ionizing energy deposition (T-dam) under thin-target conditions shows differences among alloys of varying compositions mainly in magnitude, while under thick-target conditions, it demonstrates an exponential decay trend with depth.

In this work, a recessed T-gated AlN/GaN-HEMT with a β-Ga2O3 buffer is proposed and compared with conventional buffer configurations, including Fe-doped GaN/AlGaN structures with and without back-barriers (BBs), to evaluate their influence on direct-current (DC) and radiofrequency (RF) performance. The electrostatic analysis of HEMT with β-Ga2O3-buffer reveals a peak gm of 431.5 mS/mm, an Id_peak of 1.90 A/mm, an Ids_sat of 2.42 A/mm, and an fT of 197.1 GHz owing to better carrier confinement, reduced parasitic effects, minimal buffer leakage, and the high crystalline quality of the β-Ga2O3/GaN interface. We investigated the impact of barrier material selection and observed that an AlN barrier offered better performance, attributed to stronger polarization-induced charge, followed by Al0.83In0.17N, and Alx​Ga1−xN, with a gradual decline as the Al composition decreased. The AlN/GaN/β-Ga2O3/β-Ga2O3-HEMT with Lg = 40 nm delivered a maximum gm of 538.5 mS/mm, an Id_peak of 3.22 A/mm, and an fT of 469.6 GHz, along with an Ids_sat of 3.49 A/mm, benefiting from improved lattice compatibility. Notably, this structure eliminates the need for additional BB layers and AlN nucleation, offering both performance and fabrication advantages. The AlN/GaN/β-Ga2O3/SiC-HEMT also delivered competitive performance, providing a compelling combination of thermal conductivity, material stability, and integration feasibility, while remaining cost-effective. These results offer valuable design insights for AlN/GaN-HEMT development and contribute to ongoing efforts toward enhancing GaN-HEMT performance through the integration of ultrawide bandgap (UWBG) β-Ga2O3 buffers, making it highly suitable for next-generation 5G/6G wireless infrastructure, sub-THz high-speed communication systems, and advanced radar applications.

The paper is a systematic study of the effect of various back barrier materials-AlGaN, InGaN, InAlN, and AlN on the behavior of AlN/GaN MOSHEMTs. The performance metrics that are under study are the drain current (ID), transconductance (GM), threshold voltage (Vth), the gate capacitance (CGG), and cut-off frequency (fT). With proper back barrier layers, carrier confinement is increased resulting in better two-dimensional electron gas (2DEG) density and improved RF characteristics. Moreover, the effect of the thickness of the back barrier is also discussed in detail and the best thickness of each material is determined to achieve maximum device performance. The gate length scalability is also studied showing a decreasing short-channel effects (SCEs) and enhanced electrostatic control at nanoscale dimensions. The AlN/GaN MOSHEMT has a better performance among the studied structures, and the InGaN back barrier has been utilized. A device whose gate length (LG) is 40 nm and whose InGaN back barrier is 60 nm has a peak drain current of 2.142 A/mm, transconductance of 320.86 mS/mm and cut-off frequency of 244.21 GHz. The main benefit of these is due to increased carrier confinement and lower leakage currents. This paper presents an overall comparative evaluation of the concept of back barrier engineering in AlN/GaN MOSHEMTs, and its importance in maximizing the performance of the device to next-generation RF and high-power electronics.

Based on the Non-Ionizing Energy Loss (NIEL) theory and the Boltzmann transport equation, this study systematically examines the damage behavior of In x Ga 1-x As material under neutron irradiation, considering variations in layer thickness, indium mole fraction (x), and incident neutron energy. The findings reveal that in micron-scale thin targets, the NIEL values remain nearly composition-independent, whereas in thick targets, a pronounced attenuation of NIEL with depth is observed. The total number of Primary Knock-on Atoms (PKA) decreases noticeably with increasing neutron energy and indium content. In the low-energy region (<0.1 MeV), the damage primarily arises from elastic scattering, resulting in a relatively smaller number of displaced atoms. As neutron energy increases, inelastic scattering begins to play a significant role. In the high-energy region (>1 MeV), both scattering mechanisms act synergistically, with a single reaction capable of producing up to thousands of displaced atoms, leading to cascade damage. The non-ionizing energy deposition ( T dam ) under thin-target conditions shows differences among alloys of varying compositions mainly in magnitude, while under thick-target conditions, it demonstrates an exponential decay trend with depth.

Sub-10 nm nanoelectronics scaling demands channel materials combining superior electrostatic control, high mobility, and low power consumption. Tungsten diselenide ( ${\mathrm{WSe}}_{{2}}\text {)}$ has emerged as a premier 2-D candidate due to its tunable bandgap, atomic thickness, and ambipolar transport. This review systematically examines recent WSe2 field-effect transistor advancements across five core domains: architectures, doping, contact engineering, reliability, and applications. Advanced configurations, including dual-gate FETs, vertically stacked complementary FETs (CFETs), and steep-slope variants, significantly enhance scalability and energy efficiency. Surface charge transfer (SCT) and substitutional doping enable stable unipolar operation while preserving gate control. Contact optimization via van der Waals (vdW) interfaces and alloyed electrodes effectively mitigate Fermi-level pinning (FLP) and reduces contact resistance ( ${\mathrm{R}}_{\text {C}}\text {)}$ . Interfacial passivation with h-BN and plasma treatments robustly suppresses charge trapping and threshold voltage hysteresis. Finally, WSe2-FETs are positioned for transformative roles in low-power CMOS, flexible electronics, biosensors, neuromorphic computing, and optoelectronics, alongside key commercialization pathways.

To improve the gate reliability, a Field-Stopping GaN HEMT (FS-HEMT) is proposed and validated by TCAD simulations. The proposed HEMT introduces a heavily doped n+GaN layer at the top of the p-n junction gate, forming a p-i-n (p-GaN / n-GaN / n+GaN) diode configuration. The heavily doped n+GaN layer works as a field-stopping layer to prevent high electric field (E-field) reaching the surface gate metal and then avoid punch-through premature breakdown. Meanwhile, the introduced n+GaN layer flattens the energy band and increases the hole tunneling distance, leading to fewer holes injected from the gate into the n-GaN region. Therefore, the gate leakage (IG) is suppressed and the gate breakdown voltage (BVG) is improved. By optimizing the thickness and doping concentration of each layer in the gate stack, the simulated FSHEMT achieves better thermal stability and a high BVG of 18.1 V, improving by 117 % compared with the conventional Schottky junction gate HEMT. Moreover, it obtains an ultralow IG of 9.25 × 10-8 mA/mm at VGS = 16.6 V and a high threshold voltage (VTH) of 2.88 V.

Substrate bias significantly influences the characteristics of GaN power high-electron-mobility transistors (HEMTs). However, its role in the irradiation effects has not been thoroughly investigated. In this work, we systematically study how substrate bias influences the irradiation-induced degradation of GaN HEMTs through extensive comparative experiments. The underlying degradation mechanisms are further analyzed. It is found that the p-GaN gate HEMT with a floating substrate shows a more obvious post-irradiation degradation in threshold voltage, off-state drain leakage current, and dynamic on-resistance, when compared to the HEMT with a grounded substrate. The underlying mechanism is revealed by characterizing substrate leakage current and capacitance. The crosstalk effect induced by drain voltage during irradiation would intensify the generation of irradiation damages between the substrate and source/gate, owing to the enhanced electric field therein. Therefore, a floating substrate would make the device more susceptible to the total-ionizing-dose irradiation.

The effective separation and transfer of photogenerated carriers are pivotal in determining semiconductor photocatalytic activity. A p-n type II heterojunction can efficiently address this challenge through its staggered band alignment and built-in electric field. This study developed a novel H2O2-assisted redox method to construct a CuO/BiVO4 (CuO/BVO) p-n heterojunction, where CuO nanoparticles were uniformly dispersed on the BVO surface without agglomeration while extending visible-light absorption. The staggered band alignment directed photogenerated electrons and holes along separate pathways, while the interfacial built-in electric field accelerated their transfer. This synergy markedly enhanced the formation of reactive oxygen species (•O2⁻ and •OH), which in turn drove efficient degradation of pollutants. The optimized 3CuO/BVO composite demonstrated exceptional photocatalytic activity, achieving 91.5% degradation of Rhodamine B (RhB) under light irradiation (3.8 times higher than pristine BVO). This work provides a facile strategy for designing high-performance photocatalytic systems and offers mechanistic insights into interfacial charge transfer.

In this paper, the ESD protection circuit for p-GaN gate HEMTs with bidirectional clamp is proposed and investigated. ESD clamp circuits consist of several forward diodes in serials and a reverse diode. During the ESD pulse, a discharging channel in the proposed ESD clamp is built and the gate to source voltage for p-GaN HEMTs is clamped at safety value. Based on the experimental verification, the proposed ESD clamps have bidirectional protection functionality by being triggered by a required voltage and exhibit a high secondary breakdown current in both forward and reverse transient ESD events. Meanwhile, the proposed ESD clamp circuit can decrease the power loss in a static state.

Raman scattering measurements are performed on the pure benzene (B), 2,2’-bipyridine (BD), and the saturated BD-B solution at 295 and 80 K to investigate the solute–solvent interaction on the vibrational properties. The spectrum of the BD-B shows almost a simply addition of the individual spectra of BD and B, suggesting no strong interaction among BD and B molecules. At low temperature, the solution crystallizes and its spectrum shows obvious changes including the inter- and intramolecular modes, especially the modes associated with the lattice vibrations, C–H in-plane bending, C–C interring stretching, and high-frequency C–H stretching. Our work contributes to understand the interaction between organic solute and solvent.

To enhance the radiation resistance of the InP-based HEMT, a novel structure incorporating a graded In1-xGaxAs channel layer and double Si-doped structure (DPLC-HEMT) is proposed. First, a deeper quantum well is formed due to the introduction of graded In1-xGaxAs channel, that efficiently confines electrons within the quantum well, lead to the boosting of electron density in the channel. Second, the double Si-doped structure further boosts the electron density in the quantum well. The increase in native carriers reduces the effect of carrier removal caused by irradiation defects, thereby enhancing the radiation resistance of the DPLC-HEMT. The simulation results show that after 75-keV irradiation with a proton dose of 2 × 1012 cm−2, the saturation drain current (Isat), peak transconductance (gmax), fT and fmax of DPLC-HEMT are decreased by 23%, 13.2%, 9.3% and 5.2%, respectively, while, the Isat, gm,max, fT and fmax of conventional InP-based HEMT (C-HEMT) are decreased by 64%, 29.5%, 26.2% and 21.2%, respectively. It can be seen that DPLC-HEMT effectively enhances the anti-proton irradiation ability. Moreover, the DC and RF characteristics were also improved for the DPLC-HEMT. Compared to the C-HEMT, the peak value of the fT for DPLC-HEMT has increased from 248 GHz to 460 GHz, representing a 85.5% increase, the peak value of the fmax for DPLC-HEMT has increased from 640 GHz to 944 GHz, representing a 47.5% increase. The Isat and gmax of the DPLC-HEMT has improved by 125.1% and 83.0% compared to the C-HEMT.

In this paper, a novel ESD protection circuit incorporating GaN PNP BJT (Bipolar Junction Transistor) is proposed and simulated. Compared with the conventional diodes, resistive and capacitive GaN ESD clamp, the proposed new ESD circuit exhibits superior discharging capability on same chip area, and its clamping voltage is reduced by at least 5.1V under 1.5A TLP (transmission line pulsing) current. Meanwhile, the proposed ESD circuit reduces the overshoot voltage during its discharging channel opens. After that the characteristics of GaN BJT is also investigated. By introducing a p-GaN back barrier layer, new p-GaN HEMT's conduction characteristics and breakdown voltage are improved compared to the conventional p-GaN HEMT.

In this work, it is demonstrated for the first time that a negative gate voltage ( ${V} _{\text {GS}}$ ) during off-state can enhance the single-event effect (SEE) hardness of the 100-V E-mode p-GaN HEMTs. When subjected to irradiation from Ta ions with linear energy transfer of 78.40 MeV/(mg/cm2), the single-event transient (SET) current peak during irradiation can be significantly decreased if a negative ${V} _{\text {GS}}$ is applied, as opposed to using zero ${V} _{\text {GS}}$ . Furthermore, a negative ${V} _{\text {GS}}$ suppresses post-irradiation shifts in gate capacitance ( ${C} _{\text {G}}$ ), threshold voltage ( ${V} _{\text {th}}$ ) and off-state drain leakage current ( ${I} _{\text {DSS}}$ ), indicating improved stability against SEE. Numerical simulations have been performed to offer a physical insight into the underlying mechanisms. It is found that a negative ${V} _{\textit {GS}}$ enables the simultaneous removal for radiation-induced holes and thus suppresses the SET current. The post-irradiation degradation of ${C} _{G}$ , ${V} _{\text {th}}$ and ${I} _{\text {DSS}}$ are attributed to the radiation-induced acceptor-like traps at the Schottky junction, the AlGaN/GaN interface and the buffer layer, respectively.

To enhance the DC and RF performance of AlGaN/GaN HEMTs, a novel device structure was proposed and investigated through simulation. The key innovation of this new structure lies in the incorporation of an Al0.7In0.15Ga0.15N back-barrier layer and an N-type locally doped AlGaN barrier layer (BD-HEMT), based on conventional device architecture. The Al0.7In0.15Ga0.15N back-barrier layer effectively confines electrons within the channel, thereby increasing the electron concentration. Simultaneously, the N-type locally doped AlGaN barrier layer introduced beneath the gate supplies additional electrons to the channel, further enhancing the electron density. These modifications collectively lead to improved DC and RF characteristics of the device. Compared to the conventional AlGaN/GaN HEMT, BD-HEMT achieves a 24.8% increase in saturation drain current and a 10.4% improvement in maximum transconductance. Furthermore, the maximum cutoff frequency and maximum oscillation frequency are enhanced by 14.8% and 21.2%, respectively.

An investigation of single event transient (SET) effect in double-gate InP-based HEMT (DG-HEMT) was conducted by simulations. The effects of different drain voltages (VDS), ion incident positions and angles, linear energy transfer (LET) on SET effect in DG-HEMT were comprehensively analyzed. The simulation results showed that the incident position in gate for DG-HEMT is the most sensitive to SET effect. A higher transient peak drain current (Ipeak) induced by SET effect was obtained with the higher LET and VDS. At the larger LET and VDS, more electrons were produced by the larger impact ionization rate, leading to the higher Ipeak. As the incident angle reduces, the track length of incident ions become longer, that is, the sensitive area becomes larger, resulting in the higher Ipeak. Compared with the single gate InP-based HEMT, the irradiation resistance of device with double gate is improved significantly.

In order to promotion the RF performance, a grade In1-xGaxAs channel (G-HEMT) introduced to the AlGaAs/InGaAs HEMT. The G-HEMT with the grade In1-xGaxAs channel forms a deeper potential well and confines more electrons in the channel, results in improving the DC and RF characteristics. Moreover, because of the grade In1-xGaxAs is effectively reduced the peak electric field, and leads to a significant increase in breakdown voltage (BV). Moreover, the G-HEMT also increases resistance to single event effects (SEE). The simulation results indicate that the fmax is significantly increased to 889 GHz of G-HEMT from 616 GHz of conventional AlGaAs/InGaAs HEMT (C-HEMT). The the fT is significantly increased to 521 GHz of G-HEMT from 326 GHz of C-HEMT, as well as the IDsat is increased by 64.8% and the BV increases by 37%. In addition, the SEE peak drain current of G-HEMT is dramatically reduced 51%.

A novel AlGaN/GaN high-electron mobility transistor (HEMT) is put forward to promote its breakdown characteristics and anti-single-event transient (SET) effect. The features of the proposed device are a hybrid GaN/AlN buffer layer and a uniform-groove high-k passivation layer between the gate and drain electrodes (HGKB-HEMT). First, the uniform-groove high-k passivation layer not only reduces the peak electric field at the gate edges, but also modulates the electric field distribution between the gate and drain. Therefore, the breakdown voltage (BV) and the anti-SET effect show a great improvement. Second, the buffer leakage current was effectively reduced by the hybrid buffer layer, resulting in a further increase in the BV. The BV of the HGKB-HEMT reached 1672 V, which is 82.7

A vertical GaN-based field-effect transistor with an integrated MOS-channel diode (MCD) is used to improve the reverse conduction characteristic and transient single-event effect (SEE). The device features an MCD acting as a free-wheel diode formed between trench source metal on the source dielectric and a P-type blocking layer (PBL), wherein MIS structure is formed by trench source, source dielectric and N-drift. At the reverse conduction (V-SD > 0 V, V-GS <= 0 V), because the channel between the PBL and the MIS structure is opened, the MCD turns on to realize a low reverse turn-on voltage (V-RT) and the V-RT is independent of V-GS. At the forward conduction (V-DS > 0, V-GS > V-th), the MCD is pinched-off without influencing the on-state characteristic of the MCD-FET. Moreover, owing to the modulation effect of the PBL on electric-field distribution, both the impact ionization rate and transient SEE peak current (I-peak) is reduced. Consequently, a low V-RT = 0.67 V, low I-peak = 10.11 mA and high BV = 1573 V are achieved. The V-RT and I-peak are decreased by 46.4 % and 64.9 %, respectively, compared with those of the conventional current aperture vertical electron transistor (CAVET).

Transparency of the polycrystalline magnesium-aluminate spinel (MAS) in both the infrared and terahertz regions is evaluated and compared with other frequency-used window materials by Fourier transform infrared spectroscopy and terahertz time-domain spectroscopy. The MAS material exhibits higher transmissivity in both the infrared and terahertz regions than other materials. Excellent flexural strength also ensures that it can be subject to the atmospheric pressure. Therefore, this material is suitable to be applied as a broadband transparent window in the infrared synchrotron radiation pump-terahertz time-domain spectroscopy probe experimental platform which works in the low-temperature and high-vacuum conditions. Our work provides a groundwork for the understanding of the native properties of the polycrystalline MAS. The result suggests a new window material to be employed in the low-temperature and high-vacuum conditions.

In this paper, a novel AlGaN/GaN HEMT structure with a P-GaN buried layer in the buffer layer and a locally doped barrier layer under the gate (PN-HEMT) is proposed to enhance its resistance to single event transient (SET) effects while also overcoming the degradation of other characteristics. The device operation mechanism and characteristics are investigated by TCAD simulation. The results show that the peak electric field and impact ionization at the gate edges are reduced in the PN-HEMT due to the introduced P-GaN buried layer in the buffer layer. This leads to a decrease in the peak drain current (Ipeak) induced by the SET effect and an improvement in the breakdown voltage (BV). Additionally, the locally doped barrier layer provides extra electrons to the channel, resulting in higher saturated drain current (ID,sat) and maximum transconductance (gmax). The Ipeak of the PN-HEMT (1.37 A/mm) is 71.8% lower than that of the conventional AlGaN/GaN HEMT (C-HEMT) (4.85 A/mm) at 0.6 pC/µm. Simultaneously, ID,sat and BV are increased by 21.2% and 63.9%, respectively. Therefore, the PN-HEMT enhances the hardened SET effect of the device without sacrificing other key characteristics of the AlGaN/GaN HEMT.