In this paper, a low temperature sputtered AlN cap-layer p-GaN HEMT with high gate breakdown and improved reliability is realized. XPS test shows that the valence band offset of p-GaN and low-temperature magnetron sputtered AlN is 1.2 eV, which successfully suppresses the gate leakage current and greatly improves the gate reliability. Low capacitance-voltage hysteresis and small pulsed threshold voltage shift predict good AlN/p-GaN interface quality. The threshold voltage of the AlN/p-GaN HEMT is improved from 0.61 V to 0.82 V compared to the conventional p-GaN HEMT with tungsten Schottky gate (W/p-GaN HEMT), the DIBL decrease from 34.4 mV/ V in W/p-GaN HEMT to 1.1 mV/V in AlN/p-GaN HEMT. The gate forward and reverse leakage is significantly suppressed, and the gate forward breakdown voltage is improved to 17 V. The gate operating range is improved from 7 V to 12 V, and the I D / I G under saturation state is improved from 104 to 107. In addition, a smaller on- resistance of 67.5 Omega & sdot; mm was obtained, which is 15.3 % lower than that of the W/p-GaN HEMT, minimizing on-state loss. The gate leakage mechanism of the AlN/p-GaN HEMT is mainly dominated by the PF emission in the medium gate voltage range. Based on this leakage mechanism, the maximum forward V G for a ten-year lifetime was extracted as 6.8 V at room temperature at a failure level of 63.2 % for the AlN/p-GaN HEMT, while this value for W/p-GaN HEMT is 5.4 V. In addition, the AlN cap layer attenuates the depletion region of metal/p-GaN by the gate Schottky metal, which keeps the GaN channel better depleted, thus keeping a higher off-state breakdown voltage. These results demonstrate the good potential of magnetron sputtering AlN as a lowcost, methodologically simple growth method for the commercial use of p-GaN HEMTs.

In this paper, a novel GaN on Si quasi-vertical reverse conducting insulated gate bipolar transistor (RC-IGBT) with NPN structure is proposed. The distinctive feature of this device structure is that the collector, emitter and gate are all fabricated on the wafer surface, eliminating the two major challenges associated with conventional PNPN structures: the difficulty in forming ohmic contacts due to the activation difficulty of the bottom p-GaN layer and the necessity of creating backside via holes for the collector electrode. Additionally, the heavily doped n+ GaN in the emitter and RC region can be selectively regrown by Metal-organic Chemical Vapor Deposition (MOCVD) /MBE. It avoids the deterioration of ohmic contact characteristics caused by etching of p-GaN on the top layer of n+ GaN during p-collector electrode fabrication. Compared to fully vertical GaN-based IGBT devices, the device has the feasibility of wafer level preparation technology. In this paper, Silvaco TCAD is used to simulate the static and dynamic characteristics of this novel device. The simulation results reveal that the device has a high saturation current density of 10 528.16 A cm-2 at Vg = 14 V, a threshold voltage (Vth) of 5 V, a breakdown voltage of 1103 V, and a total turn-on time of 3.14 ns, total turn-off time of 9.19 ns. The calculated turn-on and turn-off conduction losses for the RC-IGBT device are 0.438 mJ cm-2 and 9.12 mJ cm-2. Compared to other GaN-based IGBT devices, the novel GaN-based IGBT device has faster switching speed, lower switching loss and smaller chip area. Furthermore, we investigated the effects of the doping concentration of the field stop layer, drift region doping concentration, and collector region p/n+ length ratio on the 'snapback' phenomenon of the RC-IGBT device. We also studied the impact of stage etching width and depth on the device's output current capability and latch-up characteristics.

To improve the threshold voltage and gate reliability of conventional enhancement-mode p-GaN-gated AlGaN/GaN high electron mobility transistors while maintaining a low on-resistance, an improved design solution for p-GaN HEMTs with P-I-N junction gate (PIN-HEMTs) has been proposed. Simulation results show that energy band modulation is achieved by adjusting the doping concentration and thickness of each layer of the PIN junction, and high-performance p-GaN gate HEMTs with adjustable threshold voltages ranging from 0.56 V to 4.75 V and gate breakdown voltages ranging from 19.8 V to 30.3 V would be prepared. The PIN-HEMT has a quasi-self-alignment property, which means that good gate control is independent of gate metal alignment. This not only improves the production efficiency but also solves the problems of weak gate control and electric field aggregation at the gate edge caused by the gate misalignment in conventional p-GaN gate HEMTs, thus realizing lower on-resistance and higher gate breakdown voltage, which demonstrates this proposed structure has excellent potentials for realizing effective and reliable high-power transistors.

In the field of Generalized Zero-Shot Learning (GZSL), the challenge lies in learning attribute-based information from seen classes and effectively conveying this knowledge to recognize both seen and unseen categories during the training process. This paper proposes an innovative approach to enhance the generalization ability and efficiency of GZSL models by integrating a Convolutional Block Attention Module (CBAM). The CBAM blends channel-wise and spatial-wise information to emphasize key features, thereby improving the model’s discriminative and localization capabilities. Additionally, the method employs a ResNet101 backbone for systematic image feature extraction, enhanced contrastive learning, and a similarity map generator with attribute prototypes. This comprehensive framework aims to achieve robust visual–semantic embedding for classification tasks. The proposed method demonstrates significant improvements in performance metrics in benchmark datasets, showcasing its potential in advancing GZSL applications.

>GaN has several advantages, such as a large bandgap（3.44 eV）, high critical electric field（3.3 MV/cm）, and high carrier mobility（900 cm 2 /Vs）, making it a strong candidate for next-generation high-power applications. In recent years,vertical Schottky barrier diodes（SBDs） have garnered significant attention due to their ability to achieve high breakdown voltage in small device sizes, insensitivity to surface states, improved heat dissipation, and enhanced reliability,distinguishing them from lateral diodes.

In this work, we report the ultra-high RF power performance of GaN HEMTs at X- and Ka-band achieved by AlGaN/GaN/AlN:Fe heterostructure. Without field-plate design, a record output power density (P out ) of 33.1 W/mm and a peak power added efficiency (PAE) of 62.9% at X-band were achieved when tuned for maximum power and PAE, respectively. In addition, the laterally scaled-down device delivers a maximum P out up to 14.4 W/mm at Ka-band. These excellent load-pull results, spanning a broad frequency range, demonstrate the potential of the AlGaN/GaN/AlN:Fe epitaxial structure as an attractive material platform for advancing GaN/SiC HEMTs in RF power amplifier applications.

In the emerging 5G and beyond 5G (B5G) era, the spotlight is sharply focused on the power amplifier, a critical component with stringent specification requirements that dictates the performance of the transmitter. The gallium nitride (GaN) device, with its superior inherent properties, is surfacing as a front-runner for power amplifier applications. The increasing demand for high frequency, high linearity, and cost-effective GaN power amplifiers is driven by anticipated traffic surges and the need for extensive 5G deployment. This paper offers a thorough review and future perspective on research developments in RF GaN device technology. It encompasses critical issues in advanced device and circuit technology, with a focus on high frequency, high linearity, cost-effective GaN-on-Si high electron mobility transistors (HEMTs), and compact modeling. This work aims to serve as a guide for the utilization of GaN HEMTs in 5G communication applications.

In this letter, we apply an oxidation technique for p-GaN to a normally-off p-GaN /AlGaN/GaN HEMT to improve the threshold voltage and gate reliability. Oxygen-plasma and low-temperature Oxygen post-annealing treatment (OPAT) of p-GaN before the deposition of gate metal has introduced a 5 nm oxidation interlayer, resulting in a significant improvement in gate breakdown voltage, from 10.4 V to 20.6 V. Thanks to this interlayer, the threshold voltage of p-GaN gate HEMTs is increased from 1.9 V to 4.6 V, while an almost same on- state resistance and a higher drain breakdown voltage are obtained. Time-dependent gate breakdown measurement shows OPAT-HEMTs have a maximum on- state gate drive voltage of 9.2 V for a 10-year lifetime with a 63 % gate failure rate. In addition, a more stable threshold voltage under gate stress indicates the promising application of this technology in GaN power devices.

The N2O radicals in-situ treatment on gate region has been employed to improve device performance of recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). The samples after gate recess etching were treated by N2O radicals without physical bombardment. After in-situ treatment (IST) processing, the gate leakage currents decreased by more than one order of magnitude compared to the sample without IST. The fabricated HEMTs with the IST process show a low reverse gate current of 10−9 A/mm, high on/off current ratio of 108, and high f T × L g of 13.44 GHz⋅μm. A transmission electron microscope (TEM) imaging illustrates an oxide layer with a thickness of 1.8 nm exists at the AlGaN surface. X-ray photoelectron spectroscopy (XPS) measurement shows that the content of the Al–O and Ga–O bonds elevated after IST, indicating that the Al–N and Ga–N bonds on the AlGaN surface were broken and meanwhile the Al–O and Ga–O bonds formed. The oxide formed by a chemical reaction between radicals and the surface of the AlGaN barrier layer is responsible for improved device characteristics.

In this work, a high performance GaN-on-Si quasi vertical PiN diode was demonstrated by the combination of a beveled sidewall and self-aligned fluorine plasma treatment. The didoes achieved a remarkable breakdown voltage ( $\text{V}_{\text {BR}}{)}$ of 930 V and an ultra-low reverse leakage current. Meanwhile the didoes showed a low specific on-resistance ( $\text{R}_{ \mathrm{\scriptscriptstyle ON},\textit {sp}}$ ) of 0.43 $\text{m}\Omega \cdot $ cm 2 , a high on/off current ratio ( $\text{I}_{ \mathrm{\scriptscriptstyle ON}}/\text{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ) of $10^{{11}}$ , and an excellent Baliga’s figure of merit (BFOM) of 2.01 GW/cm 2 . The measurement results of X-ray spectroscopy (XPS) and Kelvin Probe Force Microscopy (KPFM) proved the presence of F ions and the decrease of surface potential, which reduced the electric field peak and suppressed the leakage current. These results show a great potential of GaN on Si PiN diode for power applications.

An atomic-level controlled etching (ACE) technology is invstigated for the fabrication of recessed gate AlGaN/GaN high-electron-mobility transistors (HEMTs) with high power added efficiency. We compare the recessed gate HEMTs with conventional etching (CE) based chlorine, Cl2-only ACE and BCl3/Cl2 ACE, respectively. The mixed radicals of BCl3/Cl2 were used as the active reactants in the step of chemical modification. For ensuring precise and controllable etching depth and low etching damage, the kinetic energy of argon ions was accurately controlled. These argon ions were used precisely to remove the chemical modified surface atomic layer. Compared to the HEMTs with CE, the characteristics of devices fabricated by ACE are significantly improved, which benefits from significant reduction of etching damage. For BCl3/Cl2 ACE recessed HEMTs, the load pull test at 17 GHz shows a high power added efficiency (PAE) of 59.8% with an output power density of 1.6 W/mm at V d = 10 V, and a peak PAE of 44.8% with an output power density of 3.2 W/mm at V d = 20 V in a continuous-wave mode.

To realize the complementary circuit on the GaN-on-Si platform, an investigation of p-channel heterostructure field-effect transistors (p-HFETs) is necessary. In this study, an analytical model for the estimation of the threshold voltage ( ${V}_{\text {TH}}$ ) for GaN-based p-HFETs was developed. In this model, the impact of polarization charges at different interfaces, the influence of interface charges at oxide/GaN interface, as well as the out-diffusion effect of Mg dopant in the p-GaN layer were all taken into consideration for systematic exploration. Herein, GaN-based p-HFETs were fabricated to verify the relationship between the ${V}_{\text {TH}}$ and the thickness of the GaN channel layer by using the proposed model. The ${V}_{\text {TH}}$ model was further confirmed through TCAD simulations. The influences of the thickness of oxide layer, Mg doping concentration in p-GaN layer, and the Al mole fraction of Al x Ga $_{{1}-{x}}\text{N}$ layer on ${V}_{\text {TH}}$ were also discussed in detail. The model serves as more accurate guidance for the optimization of such p-HFETs design and complementary circuits.

The gate and drain bias dependence of hot electron-induced degradation in GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) was investigated in this work. Devices exhibit an abnormal increase in peak transconductance ( G m ,max) during hot carrier stress (HCS) and a partially quick recovery of that after removing the electrical stress. A physical model is proposed to explain the abnormal electrical characteristics caused by HCS. By using density functional theory (DFT), we calculated the energy for electrons to dehydrogenate preexisting [N Ga H 3 ] -1 complexes in GaN layer during stress. The dehydrogenation of defects affects the G m,max of devices. Meanwhile, the neutralization of donor traps in AlGaN barrier layer also plays a significant role in the increase of G m,max and the detrapping effect of electrons from these traps after removing the electrical stress accounts for the partially quick recovery of G m, max .

Carbon nanotube (CNT) film has great potential in the application as a cold cathode in vacuum power electron devices. Pulse field emission of CNT film is investigated to achieve large current and current density. A maximum current of 16 mA is obtained from a 0.02-cm 2 CNT film with a current density of 800 mA/cm 2 . The pulsewidth and area of CNT film have strong effects on field emission characteristics of CNT film, such as total current, current density, and current stability. The reason for this is discussed in detail. The results are useful for the design of the large current and current density CNT cold cathodes.

In an early report, some of us have demonstrated that graphene-sheet films prepared by electrophoretic deposition (EPD) method have great potential as high-performance field emission cathode. We report that the field emission performance from such graphene-sheet films may be enhanced. We have investigated the correlation between topographic structures and local field emission characteristics of graphene-sheet films, prepared with changing EPD deposition time. Detailed experiments show that samples prepared with longer deposition time have better field emission performance. Both scanning electron microscopy and high resolution transmission electron microscopy images show that the topographic structure of the surface layer of the samples deposited with longer time is formed with higher density of graphene sheets with shorter length and fewer graphene layers, in comparison with those with shorter deposition times. Such topographic structure is found experimentally to give large field enhancement. Computer simulation further confirms that a thinner graphene sheet will give more significant geometrical field enhancement at the corner of graphene sheet. Theoretical analysis shows that in an EPD process, longer-length graphene sheets will be deposited before shorter ones, explaining why with longer deposition time, the topographic structure of surface layer consists of shorter-length graphene sheets.

Vertical few-layer graphene (FLG) sheets have been fabricated by using microwave-plasma-enhanced chemical vapour deposition. Their shape was manipulated through adjusting the growth time and hydrocarbon gas ratio. The growth mechanism during different growth stages is discussed. The field emission characteristics for different FLG shapes were tested and found to be strongly influenced by the tip shape, the height and the amorphous carbon content. The optimal shape of vertical FLG for field emission had fewer layers, sharp corners, large height and was free of amorphous carbon. The best field emission properties with the optimal shape were observed with a turn-on field of 1:8 V μm(-1) and maximum current density of 7 mA cm(-2).

Increasing interest in field emission from graphene has led us to conduct a detailed investigation into the field emission characteristics of various microstructures of as-grown graphene films. Significant difference in the field emission from different microstructures is found. This can provide guidance to the control growth of graphene films.