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High-voltage GaN high-electron mobility transistors are prepared by using two types of heterostructures with different buffer layer structures and the effect of buffer layer structure on the crystal defect density in grown AlGaN/GaN heterostructure is examined. The results have shown that the dynamic on-resistance is increased with the edge dislocation density and is not affected by the screw dislocation density.

The use of dual-field-plate (FP) structure consisting of gate- and source-FPs was used for the suppression of the on-resistance increase by leveling of the electric-field distribution underneath the FP electrodes. Results suggest that low conduction loss and low switching loss assists in the realization of high-efficiency operation of power-supply systems.

The recessed-gate structure approach is very effective for realizing normally off high-voltage AlGaN/GaN HEMTs because the gate threshold voltage can be controlled by the etching depth of the recess without significant increase in on-resistance characteristics. Most of the AlGaN/GaN HEMTs demonstrated have, normally during depletion mode, characteristics with gate threshold voltage and with enhancement mode characteristics strongly required for the power electronics applications.

Si-MOSFETs with the breakdown voltage of over 1000 V were demonstrated, for the first time realizing low on-resistance below the theoretical Si limit. The results show the possibility of new Si power-MOSFET with a higher application voltage range.

The relation between Schottky gate leakage current and breakdown voltage of AlGaN-GaN high-electron mobility transistors (HEMTs) is discussed. The simulation results reproduced the relationship obtained experimentally between the gate leakage current and the breakdown voltage.

High breakdown voltage AlGaN-GaN power high-electron mobility transfers (HEMTs) on an insulating substrate were designed for the power electronics application. It was shown that the optimization of the contact length and contact resistivity reduction were effective to reduce the specific on-resistance, and that the tradeoff characteristics between the on-resistance and the breakdown voltage could be improved by the optimization of the above design parameters.

Undoped AIGaN-GaN power high electron mobility transistors (HEMTs) on sapphire substrate with 470-V breakdown voltage were fabricated and demonstrated as a main switching device for a high-voltage dc-dc converter. The results show the possibilities of AIGaN-GaN power HEMTs on sapphire substrate for future switching power devices.

A novel low on-resistance Schottky-Barrier diode structure with p-buried floating layer is examined by fabricating 300-V SBDs using a buried epitaxial growth technique. The presented structure is very attractive for reduction of power dissipation without electromagnetic interference noise increase.

AlGaN-GaN power high-electron mobility transistors (HEMT) with 600-V breakdown voltage are fabricated and demonstrated as switching power devices for motor drive and power supply applications. The findings present AlGaN-GaN power-HEMTs as switching power devices for motor drive and power supply applications.

The MOSFET with the superjunction (SJ) structure offering remarkable advantages over the conventional SJ structure is proposed and demonstrated. The high-voltage power semi-SJ MOSFET is very effective for reduction of power dissipation due to low on-resistance and soft recovery body diode.

High breakdown voltage AlGaN-GaN power high-electron mobility transfers (HEMTs) on an insulating substrate were designed for the power electronics application. The field plate structure was employed for high breakdown voltage. The field plate length, the insulator thickness and AlGaN layer doping concentration were design parameters for the breakdown voltage. The optimization of the contact length and contact resistivity reduction were effective to reduce the specific on-resistance. The tradeoff characteristics between the on-resistance and the breakdown voltage can be improved by the optimization of the above design parameters, and the on-resistance can be estimated to be about 0.6 mω · cm² for the breakdown voltage of 600 V. This on-resistance is almost the same as that for the device on a conductive substrate. [ABSTRACT FROM AUTHOR]