A new power receiving unit (PRU) is proposed in this paper for resonant wireless power transfer (WPT), which is characterized by the capability of attracting high power from the power transmitting unit (PTU). The resonant WPT is designed for delivering the electrical power to the PRU attached on an electrical vehicle (EV) chassis 50 cm away from a PTU installed on the ground. The proposed PRU uses only the passive elements such as inductors, diodes, and capacitors, which need no initial power from the EV. It is then applicable for charging a battery to several hundred volts for even a first-time charging battery. For a resonant WPT at a switching frequency of 4 MHz, the proposed PRU behaves as a negative impedance converter (NIC) itself in the subharmonics of 4 MHz. The NIC effect plus the subharmonic oscillation causes an instability current charging the battery connected to the PRU. In this paper, we simulated the PRU and performed the experiment. The experiment demonstrated a battery charging of 150 W from 50 cm away using three D-mode GaN HEMT transistors via the instability current ramp. The power transfer efficiency (PTE) improved as the power delivered to the load (PDL) increased. The peak PTE was 65% in the present findings. The simulation analysis showed that the circuit allowed itself be used to much higher power transfer when it is implemented with more GaN HEMT transistors connected in parallel. The theoretical derivation of the PRU circuit is also used to support both the experimental and simulation results.

This work demonstrates the E-mode active-passivation p-GaN gate HEMTs (AP-HEMTs) on sapphire substrate with blocking capabilities up to 6500 V. The AP-HEMT features an active passivation (i.e. a thinned p-GaN layer) extending from the gate edge towards near the drain contact. The 2DEG under the p-GaN gate and the active passivation is fully depleted at zero gate bias, resulting in E-mode operation with a V th = 0.8 V at I D = 10 μA/mm. With a positive V GS of 3.5 V, the AP-HEMT with L GD = 77 μm presents an R ON of 38.2 Ω-mm, and R ON,SP of 33.62 mΩ·cm 2 . In the OFF-state, the active passivation is depleted from the drain side towards the gate edge. For L GD = 77 μm, the AP-HEMT presents a high breakdown voltage of 6573 V, resulting in a FOM (BV 2 /R ON ) of 1.29 GW/cm 2 that approaches the SiC limit. In the AP-HEMT, the effect of surface charges is screened by the active passivation layer, resulting in ultralow dynamic R ON . For the AP-HEMT with L GD = 77 μm, the measured dynamic R ON /static R ON is 1.15 after a 10-ms 3000-V V DS-OFF stress (delay time = 150 μs) and 1.02 after a 3-s 4500-V V DS-OFF stress (delay time = 300 ms). The results demonstrate that the active passivation can extend the E-mode p-GaN gate HEMT technology to kV-level applications.

In this paper, we investigate the influence of group-III precursor injection rate on the material and electrical properties of InAlGaN/GaN heterostructures grown by Metalorganic Chemical Vapor Phase Deposition. It is demonstrated that high-quality GaN layers can be achieved by using the sputtered AlN/sapphire templates. During the barrier layer growth, the injection rate of the Trimethylindium plays an important role in the amount of Ga incorporation into the InAlGaN layer, while the variation of Trimethylaluminum has less impact. High mobility of 1800 cm(2)/(V.s) and high carrier electron density with an ultrathin of 3 nm thickness InAlGaN barrier layer simultaneously maintaining high crystallinity and smooth surface of InAlGaN barrier layer is achieved with sputtered AlN/sapphire templates and optimized group-III injection rate.

An AlGaN/GaN/Si high electron mobility transistor (HEMT) using a GaN:C buffer with a 2 nm AlGaN electron-blocking layer (EBL) is investigated for the first time for millimeter-wave applications. Compared with the double heterostructure field effect transistor (DHFET), the AlGaN/GaN HEMT with the GaN:C/EBL buffer has a lower vertical leakage, higher thermal stability, and better RF performance. In addition, AlGaN EBL can prevent carbon-related traps from GaN:C and improve electron confinement in 2DEG during high-frequency operation. Finally, a Pout of 31.2 dBm with PAE of 21.7% were measured at 28 GHz at 28 V. These results demonstrated the great potential of HEMTs using GaN:C with AlGaN EBL epitaxy technology for millimeter-wave applications.

In this work, a Schottky Barrier Diode (SBD) with an optimized ladder-shaped hybrid anode (LSHA) is demonstrated. The SBD devices in this work were fabricated on a GaN-on-Si wafer with in situ Si3N4 cap layer. To form the LSHA, a two-step recessed process was implemented. For device optimization, the recess depths of the two recess steps were carefully optimized. Devices with different LSHA recess profiles were fabricated, and their electrical characteristics were evaluated by measuring the forward current, reverse current and breakdown voltage (BV). Optimized device exhibited a low reverse leakage current ( ${I}_{R}$ ) of ${5.66} \times {10} ^{-{8}}$ (A/mm), a low turn-on voltage ( ${V}_{T}$ ) of 0.315 V, and a BV over 1000 V. In addition, ${I}_{R}$ (A/mm) versus ${V}_{T}$ ( ${V}$ ) of this work and ${R}_{{\text {on}, \text {SP}}}$ ( $\text{m}\Omega \cdot $ cm2) versus BV ( ${V}$ ) of this work are benchmarked. We demonstrated the lowest ${I}_{R}$ among the GaN SBDs with ${V}_{T} < 0.4$ V and the outstanding performance of ${R}_{{\text {on}, \text {SP}}}$ (0.88 $\text{m}\Omega \cdot $ cm2) with a hard BV of over 1000 V (1020 V) using the LSHA-SBD.

A high-performance E-mode hybrid ferroelectric charge storage gate (FEG) GaN HEMT with an innovative source-connected field plate (SCFP) structure is reported for the first time. The optimized E-mode FEG-HEMT implements a novel SCFP structure, which creates a cascode-like configuration with a D-mode GaN MISHEMT. This E-mode SCFP GaN FEG-HEMT has a positive V-th of 2.81 V, a high I-D,I-max of 757 mA/mm, and a BV of 866 V. Dynamic RON reduced 25% when operated at V-DSQ = 400 V. ON-state stress tests also show improved current collapse phenomena. Additionally, to address the charge storage abilities of FEG-HEMTs, a multi-cycle OFF-state (V-DS = 300 V, V-GS = 0 V) retention test was conducted. The SCFP FEG-HEMT showed 58.46% less V-th shift percentage than the FEG-HEMT without field plates.

We report synthesis of Au-free selective area epitaxy of InGaAs/InAs heterostructure nanopillars on patterned Si (111) substrate by metal-organic chemical vapor deposition. Effect of trimethylindium supply on InGaAs/InAs heterostructure nanopillars morphology and crystal structure is studied. Transmission electron microscopy images reveal subtle and consistent differences at the growth front of the InGaAs nanopillars for different indium-flow rate fraction. Notably, the nanopillar growth front exhibits zincblende-InAs cap for the low indium-flow rate fraction, whereas a sharp wurtzite-InAs segment is found at high indium-flow rate fraction. Nanopillar geometry profile fitting attributes that the wurtzite-InAs segment formation is ascribed to indium adatom diffusion on the sidewall surface along with direct impingement of indium growth species on the top facet of the nanopillar. Additionally, X-ray photoelectron spectroscopy confirms that indium segregation is more pronounced at the sidewall of the nanopillar under arsenic-limited region.

In this paper, we present the dependence of structural and electrical properties of AlN/GaN heterostructure on the growth temperature on sapphire substrates by metal organic chemical vapor deposition. The results revealed that higher Ga incorporation (similar to 47%) and higher trench density on the surface of AlN barrier layer when grown at 1125 degrees C. However, further decreasing the AlN growth temperature to 500 degrees C results in the lower Ga incorporation (similar to 5%), higher dislocation density, 3D island growth and larger tensile strain of AlN barrier layer. Degradation of structural properties and surface morphologies AlN barrier layer results in the higher resistivity of 2-dimensional electron gas transport properties. Low sheet resistance (255.45 Omega/sq), high free carrier electron density (2.86 x 10(13) cm(-2)), simultaneously maintaining low surface roughness and high crystal quality of AlN barrier were achieved at optimized growth temperature around 800 degrees C.

The optical blanking operation of pulsed laser deposition (PLD) using a picosecond laser enables the dramatic reduction of sheet resistance with excellent uniformity for the regrowth of heavily Ge‐doped GaN films. Attained carrier density exceeds over 3.5 × 1020 cm−3, which is good enough to achieve nonalloy ohmic contact. The obtained contact resistance is 0.05 Ω mm regardless of the overlaying metal. Blanking duty ratio for the pulse‐mode operation can be simply controlled by rotating the half‐wave plate outside the vacuum chamber. By introducing the blanking mode, the complete elimination of the Ga droplet is achieved even at a growth temperature of 500 °C, showing a decrease in sheet resistance. It is confirmed that the ohmic characteristics remain unchanged on annealing treatment up to 300 °C. The proposed growth technique using laser blanking is free from mechanical shutter; therefore, the technique has superior repeatability in GaN epitaxy. It is believed the present optical blanking operation is a useful technique for the industrialization of practical GaN devices.

Non-alloy ohmic contacts were implemented based on the heavily germanium-doped GaN regrown layer by using the pico-second laser ablation technique for the first time. Owing to the enhanced surface diffusion of the ablated high-energy atoms, smoothly refilled epitaxial layers were achieved in the AlGaN/GaN recess regions. Selective growth was successfully carried out by using hydrogen silsesquioxane (HSQ) film. Contact resistance of similar to 0.17 Omega. mm with a specific contact resistance in the order of similar to 10(-7) Omega. cm(2) was obtained by using non-alloy Hf/Al/Ti metal stacks.