In this study, a high-performance AlGaN/GaN high electron mobility transistor (HEMT) is presented to improve its electrical operation by employing an inner field-plate (IFP) structure. Prior to the IFP structure analysis, we compared the measured and simulated direct current characteristics of the fabricated two-finger conventional T-shaped gate HEMTs. Then, the AlGaN/GaN HEMT with a drain-side field plate (FP) structure was suggested to enhance the breakdown voltage characteristics. The maximum breakdown voltage recorded with a 0.8 μm stretched FP structure was 669 V. Finally, the IFP structure was interfaced with the gate head of the device to compensate the radio frequency characteristics, choosing the optimum length of the drain-side FP structure. Compared to the 0.8 μm stretched FP structure, the IFP structure showed improved frequency characteristics with minimal difference to the breakdown voltage. The frequency variation caused by changing the passivation thickness was also analyzed, and the optimum thickness was identified. Thus, IFP AlGaN/GaN HEMT is a promising candidate for high-power and high-frequency applications.

In this study, we investigated the operational characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) by applying the copper-filled trench and via structures for improved heat dissipation. Therefore, we used a basic T-gate HEMT device to construct the thermal structures. To identify the heat flow across the device structure, a thermal conductivity model and the heat transfer properties corresponding to the GaN, SiC, and Cu materials were applied. Initially, we simulated the direct current (DC) characteristics of a basic GaN on SiC HEMT to confirm the self-heating effect on AlGaN/GaN HEMT. Then, to verify the heat sink effect of the copper-filled thermal structures, we compared the DC characteristics such as the threshold voltage, transconductance, saturation current, and breakdown voltage. Finally, we estimated and compared the lattice temperature of a two-dimensional electron gas channel, the vertical lattice temperature near the drain-side gate head edge, and the transient thermal analysis for the copper-filled thermal trench and via structures. Through this study, we could optimize the operational characteristics of the device by applying an effective heat dissipation structure to the AlGaN/GaN HEMT.

We report a facile and direct growth of NiMoO₄ nanostructures on a nonreactive stainless steel substrate using a single-step hydrothermal method and investigated hydrothermal growth duration effects on morphology and electrochemical characteristics. The highest specific capacitances of 341, 619, and 281 F/g were observed for NiMoO₄ with 9, 18, and 27 h growth, respectively, at 1 A/g. Thus, grown samples preserved almost 59% of maximum specific capacitance at a high current density of 10 A/g. All samples exhibited a respectable cycling stability over 3000 charge-discharge operations. NiMoO₄ grown for 18 h exhibited 7200 W/kg peak power density at 14 Wh/kg energy density. Thus, the proposed single-step hydrothermal growth is a promising route to obtain NiMoO₄ nanostructures and other metal oxide electrodes for supercapacitor applications.

This study investigates metal-insulator-semiconductor high electron mobility transistor DC characteristics with different gate dielectric layer compositions and thicknesses, and lattice temperature effects on gate leakage current by using a two-dimensional simulation. We first compared electrical properties, including threshold voltage, transconductance, and gate leakage current with the self-heating effect, by applying a single Si₃N₄ dielectric layer. We then employed different Al₂O₃ dielectric layer thicknesses on top of the Si₃N₄, and also investigated lattice temperature across a two-dimensional electron gas channel layer with various dielectric layer compositions to verify the thermal effect on gate leakage current. Gate leakage current was significantly reduced as the dielectric layer was added, and further decreased for a 15-nm thick Al₂O₃ on a 5-nm Si₃N₄ structure. Although the gate leakage current increased as Al₂O₃ thickness increased to 35 nm, the breakdown voltage was improved.