Eiko Hayashi

GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistor Fabricated with Novel Wet Etching

A novel method for fabricating trench structures on GaN was developed. A smooth non-polar (1100) plane was obtained by wet etching using tetramethylammonium hydroxide (TMAH) as the etchant. A U-shape trench with the (1100) plane side walls was formed with dry etching and the TMAH wet etching. A U-shape trench gate metal oxide semiconductor field-effect transistor (MOSFET) was also fabricated using the novel etching technology. This device has the excellent normally-off operation of drain current–gate voltage characteristics with the threshold voltage of 10 V. The drain breakdown voltage of 180 V was obtained. The results indicate that the trench gate structure can be applied to GaN-based transistors.

A Vertical Insulated Gate AlGaN/GaN Heterojunction Field-Effect Transistor

We fabricated a vertical insulated gate AlGaN/GaN heterojunction field-effect transistor (HFET), using a free-standing GaN substrate. This HFET has apertures through which the electron current vertically flows. These apertures were formed by dry etching the p-GaN layer below the gate electrodes and regrowing n--GaN layer without mask. The HFET exhibited a specific on-resistance of as low as 2.6 mΩcm2 with a threshold voltage of -16 V. This HFET would be a prototype of a GaN-based high-power switching device.

New 3-D lateral power MOSFETs with ultra low on-resistance

This paper presents a new 3D lateral power MOSFET which has a double gate and a trench gate/drain structure. The double gate structure decreased its channel resistance, and the trench gate/drain structure decreased its n drift resistance. We realized this structure using solid phase epitaxy and a conventional trench technology. From experimental results, a breakdown voltage of 49.5 V and a specific on-resistance of 42 m/spl Omega//spl middot/mm/sup 2/ were obtained.

A Study of MIS - AlGaN/GaN HEMTs with SiO/sub 2/ Films as Gate Insulator

Gate insulator formation methods for GaN based MIS-HEMTs were examined. A SiO2 film formed with the HTO deposition method (HTO film) showed excellent properties. The interface state density of the HTO/GaN structure was 2E11 eV -1 cm -2 and the breakdown field was 8.2 MV/cm. MIS-AlGaN/GaN HEMTs were fabricated using the HTO film. A MIS-HEMT with a gate width of 100Pm was characterized by a maximum drain current of 395 mA/mm and a specific on-resistance of 1.7 m:� cm 2 . A high power MIS-HEMT with a gate width of 31.04 mm showed a maximum drain current of more