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While selecting the most suitable infrared thermal imaging detection scheme for online inspection during laser cladding processing, this paper designs the RespathU-net semantic segmentation defect detection network for cladding coating defects in infrared images. The network is based on the U-net network framework. It is optimized and improved by redesigning the coding network structure, expanding the network perceptual field, and connecting the paths of residuals, thus enhancing the segmentation effect on the defective areas of the melt coating by addressing the problems that the original network cannot realize the end-to-end output and the poor segmentation effect on the complex objects. The generalization performance test and defect detection experiment of the RespathU-net network were conducted using the Kolektor SDD dataset and the infrared dataset constructed in this paper. The designed network is compared with fully convolutional networks, SegNet, U-net, and DeepLab_V3 in terms of average exchange ratio, similarity coefficient, and running time. The results show that the proposed RespathU-net achieves good multi-size feature recognition, and the effect is much better than other semantic segmentation networks. The via experimental results verify that the actual defect detection accuracy of the designed network is 87.01% .

It is assumed that the shift of a strong magnetic field region with a positive gradient from exit plane to outside, namely the transit from a normal loaded magnetic field to an aft-loaded one, enhances the multiple ionization process in the magnetically shielded Hall thruster. To confirm this conjecture, a comparative study is carried out numerically with a particle-in-cell method. The simulation results prove that compared with the normal loaded magnetic field, the application of aft-loaded magnetic field enhances the multiple ionization process. This study further analyzes the ionization characteristics of the transition from low-charged ions to high-charged ions under two magnetic field conditions and the influence of the magnetic strength of aft-loaded magnetic field on the multiple ionization characteristics. The study described herein is useful for understanding the discharge characteristics of Hall thruster with an aft-loaded magnetic field.

Fast radio bursts (FRBs) are radio transients that are bright and have short duration, with their physical mechanism not being fully understood. We conducted a targeted search for bursts from FRB 20201124A between 2021 June 2 and July 20. High time-resolution data were collected for 104.5 hr using the ROACH2-based digital backend. We introduce the details of our FRB search pipeline which is based on HEIMDALL and FETCH. Testing of the injected mock FRBs search could help us better understand the performance of the pipelines, and improve the search algorithms and classifiers. To study the efficiency of our pipeline, 5000 mock FRBs were injected into the data and searched using the pipeline. The results of the mock FRB search show that our pipeline can recover almost all (≳90%) the injected mock FRBs above a signal-to-noise ratio (S/N) threshold of 15, and the performance is still acceptable (≳80%) for injected S/Ns from 10 to 15. The recovery fraction displays relations with S/N, dispersion measure and pulse width. No bursts were detected from FRB 20201124A in the middle of 2021. The non-detection of FRB 20201124A may be due to its quiet phase window or no emission above the threshold of the Nanshan telescope.

Photonic states encoded in spatial modes of paraxial light fields provide a promising platform for high-dimensional quantum information protocols and related studies, where several pioneering theoretical and experimental demonstrations have paved the path for future technologies. Crucially, critical issues encountered in free-space propagation still represent a major challenge. This is the case of asynchronous diffraction between spatial modes with different modal orders, which experience variations in their transverse structure upon free-space propagation. Here we address this issue by proposing an encoding method based on the use of Laguerre–Gaussian modes of the same modal order N to define a N + 1 dimensional space. Noteworthy, such modes endowed with orbital angular momentum (OAM) experience the same propagation aberrations featuring an identical Gouy phase and wavefront curvature. We demonstrate our proposal experimentally by using time-correlated-single-photon imaging combined with a digital propagation technique. Importantly, our technique allows to eliminate, without the use of imaging systems, all issues related to asynchronous diffraction, providing an accessible way to generate propagation-invariant OAM qudits for quantum optical protocols.

The treatment effect of the oxygen plasma on the performance of recessed AlGaN/GaN Schottky barrier diodes has been investigated. After the oxygen plasma treatment, the turn-on voltage and reverse leakage current are slightly changed, while the current collapse could be effectively mitigated. The X-ray photoelectron spectroscopy results suggest that a thin surface oxide layer is formed by the oxygen plasma treatment, which is responsible for the reduced current collapse. In addition, the device treated by oxygen plasma has a relatively more inhomogeneous barrier height.

The key parameters of vertical AlN Schottky barrier diodes (SBDs) with variable drift layer thickness (DLT) and drift layer concentration (DLC) are investigated. The specific on-resistance (R on,sp) decreased to 0.5 mΩ ⋅ cm2 and the breakdown voltage (V BR) decreased from 3.4 kV to 1.1 kV by changing the DLC from 1015 cm−3 to 3 × 1016 cm−3. The V BR increases from 1.5 kV to 3.4 kV and the R on,sp also increases to 12.64 mΩ ⋅ cm2 by increasing DLT from 4-μm to 11-μm. The V BR enhancement results from the increase of depletion region extension. The Baliga’s figure of merit (BFOM) of 3.8 GW/cm2 was obtained in the structure of 11-μm DLT and 1016 cm−3 DLC without FP. When DLT or DLC is variable, the consideration of the value of BFOM is essential. In this paper, we also present the vertical AlN SBD with a field plate (FP), which decreases the crowding of electric field in electrode edge. All the key parameters were optimized by simulating based on Silvaco-ATLAS.

A novel vertical InN/InGaN heterojunction tunnel FET with hetero T-shaped gate as well as polarization-doped source and drain region (InN-Hetero-TG-TFET) is proposed and investigated by Silvaco-Atlas simulations for the first time. Compared with the conventional physical doping TFET devices, the proposed device can realize the P-type source and N-type drain region by means of the polarization effect near the top InN/InGaN and bottom InGaN/InN heterojunctions respectively, which could provide an effective solution of random dopant fluctuation (RDF) and the related problems about the high thermal budget and expensive annealing techniques due to ion-implantation physical doping. Besides, due to the hetero T-shaped gate, the improvement of the on-state performance can be achieved in the proposed device. The simulations of the device proposed here in this work show I ON of 4.45 × 10−5 A/μm, I ON/I OFF ratio of 1013, and SS avg of 7.5 mV/dec in InN-Hetero-TG-TFET, which are better than the counterparts of the device with a homo T-shaped gate (InN-Homo-TG-TFET) and our reported lateral polarization-induced InN-based TFET (PI-InN-TFET). These results can provide useful reference for further developing the TFETs without physical doping process in low power electronics applications.

Small rivers (width 2) in Alaska, which includes small rivers as narrow as 10 m. We quantified the river hydrography (stream order and river width, length,surface area, velocity, slope, sinuosity, and catchment area) of the Colville river network in detail, revealing the dominant role of small rivers. Our results show that: (1) small rivers occupy >80% of total river length and surface area of the Colville river network and drain >90% of the catchment area; (2) including numerous small rivers increases the peak of hillslope-channel travel time distribution (TTD) by ∼4 times and shortens the mean hillslope-channel travel time by at least an order of magnitude compared to coarser-resolution river hydrography products; and (3) 87% of the Colville River Basin’s carbon dioxide is emitted from small rivers. In sum, we show that small Arctic rivers greatly influence streamflow TTD and carbon cycle. These findings expand our understanding of Arctic river hydrography to a 10-m spatial resolution and raise prospects for tracking dynamic surface water processes with high-resolution satellite observations.

A novel CMOS image sensor (CIS) pinned photodiode (PPD) pixel, named as O-T pixel, is proposed and investigated by TCAD simulations. Compared with the conventional PPD pixel, the proposed pixel features the overlapping gate (OG) and the temporary storage diffusing (TSD) region, based on which the several-nanosecond-level charge transfer could be achieved and the complete charge transfer from the PPD to the floating node (FD) could be realized. And systematic analyses of the influence of the doping conditions of the proposed processes, the OG length, and the photodiode length on the transfer performances of the proposed pixel are conducted. Optimized simulation results show that the total charge transfer time could reach about 5.862 ns from the photodiode to the sensed node and the corresponding charge transfer efficiency could reach as high as 99.995% in the proposed pixel with 10 μm long photodiode and 2.22 μm long OG. These results demonstrate a great potential of the proposed pixel in high-speed applications.

DNA persistence length is a key parameter for quantitative interpretation of the conformational properties of DNA and related to the bending rigidity of DNA. A series of experiments pointed out that, in the DNA condensation process by multivalent cations, the condensed DNA takes elongated coil or compact globule states and the population of the compact globule states increases with an increase in ionic concentration. At the same time, single molecule experiments carried out in solution with multivalent cations (such as spermidine, spermine) indicated that DNA persistence length strongly depends on the ionic concentration. In order to revolve the effects of ionic concentration dependence of persistence length on DNA condensation, a model including the ionic concentration dependence of persistence length and strong correlation of multivalent cation on DNA is provided. The autocorrelation function of the tangent vectors is found as an effective way to detect the ionic concentration dependence of toroidal conformations. With an increase in ion concentration, the first periodic oscillation contained in the autocorrelation function shifts, the number of segment contained in the first periodic oscillation decreases gradually. According to the experiments, the average long-axis length is defined to estimate the ionic concentration dependence of condensation process further. The relation between long-axis length and ionic concentration matches the experimental results qualitatively.

In this study, a high specific impulse Hall thruster, HEP-140MF, having a high discharge voltage, was used to accelerate ions. We aimed to obtain a high specific impulse and an acceleration zone moving downstream toward the channel exit to reduce wall sputtering erosion of the walls of the discharge channel, hence ensuring an enhanced lifetime. To study the lifetime characteristics of the high specific impulse Hall thruster, a life test was performed on the HEP-140MF thruster for the first time, and performance parameters, such as thrust, specific impulse, and efficiency, were measured. Changes in the performance parameters and evolutions in the surface profiles of the discharge channel wall were summarized. The reasons contributing to these changes during the life test were analyzed. Moreover, the accelerated life test method was validated on the HEP-140MF.

A cylindrical Hall thruster with a magnetically insulated anode structure was found experimentally to experience erosion sputtering at the bottom of the ceramic channel. In this study, a Particle-In-Cell numerical simulation was used to analyze the influence of the magnetic mirror effect on the ion current density, ion energy, and deposition power density bombardment at the bottom of the discharge channel. The research findings show that, as the magnetic mirror ratio grows, the stronger magnetic mirror effect confines the ions in the boron nitride channel, leading to a decrease in the ion current density and ion energy bombarding the bottom of discharge bottom. Further statistics show that the deposition power density decreases as the magnetic mirror ratio grows, indicating that increasing the magnetic mirror ratio can effectively alleviate the erosion sputtering at the bottom.

A new design approach for TFETs without physical doping is provided and demonstrated based on the polarization effect for the first time in this paper. And a polarization-induced InN-based TFET (PI-InN-TFET) is proposed and investigated by two-dimensional numerical simulations. Compared with the conventional physical doping InN-based TFET (D-InN-TFET), the proposed device features the formation of P-type source and N-type drain induced by the polarization effect near the InN-based heterojunctions without the need for any physical doping, which makes it possible for the PI-InN-TFET to avoid the random dopant fluctuation (RDF) and the problems related to the high thermal annealing techniques. Simulation results exhibit that the performance of the PI-InN-TFET is better than that of the optimized D-InN-TFET. Besides, the proposed PI-InN-TFET could be realized by the mature fabrication processing of the field-plated GaN-based HEMTs and could be further improved by introducing other techniques such as L-shaped TFET, T-shaped TFET.

In this work, AlGaN/GaN FinFETs with different fin widths have been successfully fabricated, and the recessed-gate FinFETs are fabricated for comparison. The recessed-gate FinFETs exhibit higher transconductance value and positive shift of threshold voltage. Moreover, with the fin width of the recessed-gate FinFETs increasing, the variations of both threshold voltage and the transconductance increase. Next, transfer characteristics of the recessed-gate FinFETs with different fin widths and recessed-gate depths are simulated by Silvaco software. The relationship between the threshold voltage and the AlGaN layer thickness has been investigated. The simulation results indicate that the slope of threshold voltage variation reduces with the fin width decreasing. Finally, a simplified threshold voltage model for recessed-gate FinFET is established, which agrees with both the experimental results and simulation results.

A GaN-based current-aperture vertical electron transistor with source-connected field-plates (SFP-CAVET) is proposed and investigated by means of two-dimensional simulations. This device is characterized by the source-connected field-plates (SFP) at both sides, which leads to remarkable improvement of breakdown voltage (BV) without degradation of specific on-resistance (R on). Systematic analyses are conducted to reveal the mechanism of the SFP modulation effect on the potential and the electric field distributions and thus the BV improvement. Optimization and design of SFP-CAVET are performed for the maximum BV. Simulation results exhibit a R on of 2.25 mΩ cm2 and a significantly enhanced BV of 3610 V in SFP-CAVET, indicating an average breakdown electric field of more than 240 V μm−1. Compared with conventional CAVET, both BV and average breakdown electric field in SFP-CAVET are increased by more than 121% while R on remains unchanged. And the trade-off performance of BV and R on in SFP-CAVET is also better than that in GaN-based CAVET with superjunctions (SJ CAVET). In addition, the fabrication process issues of the proposed SFP-CAVET are also presented and discussed. These results could break a new path to further improve the trade-off performance of BV and R on in GaN-based vertical devices.

A novel GaN-based vertical heterostructure field effect transistor (HFET) with nonuniform doping superjunctions (non-SJ HFET) is proposed and studied by Silvaco-ATLAS, for minimizing the specific on-resistance (R on A) at no expense of breakdown voltage (BV). The feature of non-SJ HFET lies in the nonuniform doping concentration from top to bottom in the n- and p-pillars, which is different from that of the conventional GaN-based vertical HFET with uniform doping superjunctions (un-SJ HFET). A physically intrinsic mechanism for the nonuniform doping superjunction (non-SJ) to further reduce R on A at no expense of BV is investigated and revealed in detail. The design, related to the structure parameters of non-SJ, is optimized to minimize the R on A on the basis of the same BV as that of un-SJ HFET. Optimized simulation results show that the reduction in R on A depends on the doping concentrations and thickness values of the light and heavy doping parts in non-SJ. The maximum reduction of more than 51% in R on A could be achieved with a BV of 1890 V. These results could demonstrate the superiority of non-SJ HFET in minimizing R on A and provide a useful reference for further developing the GaN-based vertical HFETs.

A novel AlGaN/GaN high electron mobility transistor (HEMT) with a source-connected T-shaped field-plate (ST-FP HEMT) is proposed for the first time in this paper. The source-connected T-shaped field-plate (ST-FP) is composed of a source-connected field-plate (S-FP) and a trench metal. The physical intrinsic mechanisms of the ST-FP to improve the breakdown voltage and the FP efficiency and to modulate the distributions of channel electric field and potential are studied in detail by means of two-dimensional numerical simulations with Silvaco-ATLAS. A comparison to the HEMT and the HEMT with an S-FP (S-FP HEMT) shows that the ST-FP HEMT could achieve a broader and more uniform channel electric field distribution with the help of a trench metal, which could increase the breakdown voltage and the FP efficiency remarkably. In addition, the relationship between the structure of the ST-FP, the channel electric field, the breakdown voltage as well as the FP efficiency in ST-FP HEMT is analyzed. These results could open up a new effective method to fabricate high voltage power devices for the power electronic applications.

This paper shows that epsilon-near-zero (ENZ) / mu-near-zero material can be obtained by using the transformation optics (TO) approach. It shows that when a line is stretched to a cylinder the z component of permittivity and permeability is zero, while the rho and phi components are equal to one. Hence in the presence of a TE mode wave, the cylinder is equivalent to an isotropic ENZ column. We further show that some additional spatial mapping can be applied to eliminate or mimic the scattering of the ENZ cylinder. To verify our proposal, a rigorous analysis based on Maxwell's equations and numerical simulations based on the finite element method are provided. Finally, cloaking and coherence enhancement are taken as examples to demonstrate potential applications of the ENZ material from the viewpoint of TO.

The multi-cusped field thruster is a novel concept in electric propulsion, which employs alternating permanent polarity magnets to create a periodic magnetic field. As an important factor for the optimal design, the magnet length of a low-power thruster is designed to be changeable. The effects of the ultimate stage length (L u) and the middle stage length (L m) on the performance characteristics are studied in a series of experiments. The results show that increasing L u could prolong the axial motion range of the electrons and promote the ionization process. In addition, it can enlarge the relative distance between the ionization and the acceleration regions. Both of these aspects can help improve the thrust and the anode efficiency. With regard to he reverse trend, wefound that the longer L m leads to a reduction of the thruster's performance for the enhanced ion loss to the wall. Overall this study can provide some optimal design ideas on the magnet length to improve the total performance of the multi-cusped field thruster.

Energy relaxation of the hot electrons in GaN, AlN and InN is investigated and compared based on a simple analytical model with both the hot-phonon effect (HPE) and the nonparabolicity of the conduction band taken into account. The impact of the HPE on the energy relaxation time is estimated by using various optical phonon lifetimes. The calculation results show that for this group of III nitrides, the energy relaxation time first falls rapidly and then saturates with the increasing electron temperature, and is higher at a high electron density. The presence of the HPE slows down the power dissipation and increases the energy relaxation time of the hot electrons of the density 1 × 1018 cm−3 (or 1 × 1019 cm−3) by around one or two orders of magnitude at an electron temperature within 3000 K. In particular, the saturated energy relaxation times are 0.12 ps in the bulk GaN, 22 fs in AlN and 26 fs in InN for an electron density of 1 × 1018 cm−3, which imply a rather weak HPE in the AlGaN and AlInN alloys.

In this paper, a novel AlGaN/GaN HEMT with a Schottky drain and a compound field plate (SD-CFP HEMT) is presented for the purpose of better reverse blocking capability. The compound field plate (CFP) consists of a drain field plate (DFP) and several floating field plates (FFPs). The physical mechanisms of the CFP to improve the reverse breakdown voltage and to modulate the distributions of channel electric field and potential are investigated by two-dimensional numerical simulations with Silvaco-ATLAS. Compared with the HEMT with a Schottky drain (SD HEMT) and the HEMT with a Schottky drain and a DFP (SD-FP HEMT), the superiorities of SD-CFP HEMT lie in the continuous improvement of the reverse breakdown voltage by increasing the number of FFPs and in the same fabrication procedure as the SD-FP HEMT. Two useful optimization laws for the SD-CFP HEMTs are found and extracted from simulation results. The relationship between the number of the FFPs and the reverse breakdown voltage as well as the FP efficiency in SD-CFP HEMTs are discussed. The results in this paper demonstrate a great potential of CFP for enhancing the reverse blocking ability in AlGaN/GaN HEMT and may be of great value and significance in the design and actual manufacture of SD-CFP HEMTs.

The cusped field thruster has drawn much attention from many institutions due to its wide thrust range, high impulse, and long lifetime. However, lots of experimental results reveal that the cusped field thruster at low power has a poor performance. A cusped field thruster with a variable cross-section channel by putting a ceramic spacer in the channel is introduced in this paper, aimed at improving the thruster performance at low power. The DSMC results validate that the upstream atom density can be increased by a spacer, especially near the wall. Based on simulated results, spacers are put into different positions of the channel. The experimental results show that a suitable spacer can enhance thruster performance at low power, which can be confirmed by the results that the anode efficiency can achieve 40% at 400 V anode voltage and 20 sccm gas flow rate by contrast to 35% without a spacer under the same condition.

The degradation mechanism of enhancement-mode AlGaN/GaN high electron mobility transistors (HEMTs) fabricated by fluorine plasma ion implantation technology is one major concern of HEMT’s reliability. It is observed that the threshold voltage shows a significant negative shift during the typical long-term on-state gate overdrive stress. The degradation does not originate from the presence of as-grown traps in the AlGaN barrier layer or the generated traps during fluorine ion implantation process. By comparing the relationships between the shift of threshold voltage and the cumulative injected electrons under different stress conditions, a good agreement is observed. It provides direct experimental evidence to support the impact ionization physical model, in which the degradation of E-mode HEMTs under gate overdrive stress can be explained by the ionization of fluorine ions in the AlGaN barrier layer by electrons injected from 2DEG channel. Furthermore, our results show that there are few new traps generated in the AlGaN barrier layer during the gate overdrive stress, and the ionized fluorine ions cannot recapture the electrons.

In this paper, the influence of a drain field plate (FP) on the forward blocking characteristics of an AlGaN/GaN high electron mobility transistor (HEMT) is investigated. The HEMT with only a gate FP is optimized, and breakdown voltage VBR is saturated at 1085 V for gate—drain spacing LGD ≥ 8 μm. On the basis of the HEMT with a gate FP, a drain FP is added with LGD = 10 μm. For the length of the drain FP LDF ≤ 2 μm, VBR is almost kept at 1085 V, showing no degradation. When LDF exceeds 2 μm, VBR decreases obviously as LDF increases. Moreover, the larger the LDF, the larger the decrease of VBR. It is concluded that the distance between the gate edge and the drain FP edge should be larger than a certain value to prevent the drain FP from affecting the forward blocking voltage and the value should be equal to the LGD at which VBR begins to saturate in the first structure. The electric field and potential distribution are simulated and analyzed to account for the decrease of VBR.

We report the studies of In0.15Al0.85N/AlN/GaN metal-insulator-semiconductor (MIS) high electron mobility transistors with a field plate (FP) and a plasma-enhanced chemical vapor deposition (PECVD) SiN layer as the gate dielectric as well as the surface passivation layer (FP-MIS HEMTs). Compared with conventional In0.15Al0.85N/AlN/GaN high electron mobility transistors (HEMTs) of the same dimensions, the FP-MIS HEMTs exhibit a maximum drain current of 1211 mA/mm, a breakdown voltage of 120V, an effective suppression of current collapse, about one order of magnitude reduction in reverse gate leakage, as well as more than five orders of magnitude reduction in forward gate leakage. These results confirm the potential of PECVD SiN in the application of the InAlN/AlN/GaN FP-MIS HEMTs.

We investigate the characteristics of AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) with a NbAlO/Al2O3 lamination dielectric deposited by atomic layer deposition (ALD) as the gate insulator. A large gate voltage swing (GVS) of 3.96 V and a high breakdown voltage of −150 V for the MIS-HEMT were obtained. We present the gate leakage current mechanisms and analyze the reason for the reduction of the leakage current. Compared with traditional HEMTs, the maximum drain current is improved to 960 mA/mm, indicating that NbAlO layers could reduce the surface-related depletion of the channel layer and increase the sheet carrier concentration. In addition, the maximum oscillation frequency of 38.8 GHz shows that the NbAlO high-k dielectric can be considered as a potential gate oxide comparable with other dielectric insulators.

Nonpolar (112?0) and semipolar (112?2) GaN are grown on r-plane and m-plane sapphire by MOCVD to investigate the characteristics of basal plane stacking faults (BSFs). Transmission electron microscopy reveals that the density of BSFs for the semipolar (112?2) and nonpolar a-plane GaN template is 3?105 cm?1 and 8?105 cm?1, respectively. The semipolar (112?2) GaN shows an arrowhead-like structure, and the nonpolar a-plane GaN has a much smoother morphology with a streak along the c-axis. Both nonpolar (112?0) and semipolar (112?2) GaN have very strong BSF luminescence due to the optically active character of the BSFs.

A GaN/Al0.3Ga0.7N/AlN/GaN high-electron mobility transistor utilizing a field plate (with a 0.3 μm overhang towards the drain and a 0.2 μm overhang towards the source) over a 165-nm sputtered HfO2 insulator (HfO2-FP-HEMT) is fabricated on a sapphire substrate. Compared with the conventional field-plated HEMT, which has the same geometric structure but uses a 60-nm SiN insulator beneath the field plate (SiN-FP-HEMT), the HfO2-FP-HEMT exhibits a significant improvement of the breakdown voltage (up to 181 V) as well as a record field-plate efficiency (up to 276 V/μm). This is because the HfO2 insulator can further improve the modulation of the field plate on the electric field distribution in the device channel, which is proved by the numerical simulation results. Based on the simulation results, a novel approach named the proportional design is proposed to predict the optimal dielectric thickness beneath the field plate. It can simplify the field-plated HEMT design significantly.

This paper studies the drain current collapse of AlGaN/GaN metal—insulator—semiconductor high electron-mobility transistors (MIS-HEMTs) with NbAlO dielectric by applying dual-pulsed stress to the gate and drain of the device. For NbAlO MIS-HEMT, smaller current collapse is found, especially when the gate static voltage is −8 V. Through a thorough study of the gate—drain conductance dispersion, it is found that the growth of NbAlO can reduce the trap density of the AlGaN surface. Therefore, fewer traps can be filled by gate electrons, and hence the depletion effect in the channel is suppressed effectively. It is proved that the NbAlO gate dielectric can not only decrease gate leakage current but also passivate the AlGaN surface effectively, and weaken the current collapse effect accordingly.

We present an AlInN/AlN/GaN MOS—HEMT with a 3 nm ultra-thin atomic layer deposition (ALD) Al2O3 dielectric layer and a 0.3 μm field-plate (FP)-MOS—HEMT. Compared with a conventional AlInN/AlN/GaN HEMT (HEMT) with the same dimensions, a FP-MOS—HEMT with a 0.6 μm gate length exhibits an improved maximum drain current of 1141 mA/mm, an improved peak extrinsic transconductance of 325 mS/mm and effective suppression of gate leakage in both the reverse direction (by about one order of magnitude) and the forward direction (by more than two orders of magnitude). Moreover, the peak extrinsic transconductance of the FP-MOS—HEMT is slightly larger than that of the HEMT, indicating an exciting improvement of transconductance performance. The sharp transition from depletion to accumulation in the capacitance—voltage (C—V) curve of the FP-MOS—HEMT demonstrates a high-quality interface of Al2O3/AlInN. In addition, a large off-state breakdown voltage of 133 V, a high field-plate efficiency of 170 V/μm and a negligible double-pulse current collapse is achieved in the FP-MOS—HEMT. This is attributed to the adoption of an ultra-thin Al2O3 gate dielectric and also of a field-plate on the dielectric of an appropriate thickness. The results show a great potential application of the ultra-thin ALD-Al2O3 FP-MOS—HEMT to deliver high currents and power densities in high power microwave technologies.