Toshiyuki Oishi

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GaN HEMTs have demonstrated higher power density and efficiency over existing technologies such as silicon and gallium arsenide (GaAs) based RF and microwave transistors [1]. Until recently, improvements in the design of GaN semiconductor device had focused on Ga-polar GaN based HEMTs. Lately, N-polar GaN shows the advantage over Ga-polar device in making(More)
A RF leakage phenomenon in GaN HEMTs on Si substrates is analyzed with taking atomic diffusion at buffer/substrate interface into consideration, and a novel physical model of RF leakage based on the analysis is proposed. The Al or Ga atoms are moved from buffer layer to Si substrate at an epitaxial growth. Then, an acceptor layer with high hole density and(More)
On-state gate leakage current behavior of AlGaN/GaN high electron mobility transistors (HEMTs) has been studied by using Technology Computer Aided Design (TCAD) simulation. We found the gate leakage current increases above the pinch-off voltage, which is different from the case of a two-terminal operation. This gate leakage current increase is due to(More)
Diamond possesses exceptional physical properties, such as a high breakdown field and carrier mobility. It is therefore expected to be highly efficient for high-power RF devices. We identify hole carrier doping in diamond using nitrogen dioxide (NO<sub>2</sub>). Furthermore, we find that an aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) passivation layer(More)
Using the nitrogen dioxide (NO<sub>2</sub>) adsorption and aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) passivation technique, we have solved the thermal instability problem of hydrogen-terminated (H-terminated) diamond field-effect transistors (FETs). The diamond FET showed high maximum I<sub>DS</sub> of -1.35 A/mm, cut-off frequencies, f<sub>T</sub> of 35(More)
We propose the design and simulation study of novel gallium nitride (GaN) devices, consisting of nitride stacks with different polarity, to provide multiple channels by flexible gate(s) control. Calibrated TCAD device simulations visualize device characteristics of 0.62-m-gate-length multi-channel transistors. E-mode operations demonstrate a positive small(More)
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