Masahito Kodama

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.

A concept of SOI RESURF lateral devices with striped trench electrodes

This paper presents a concept of silicon-on insulator lateral devices based on a reduced surface field (RESURF) principle by striped trench electrodes formed along the current flow direction. These trench electrodes reduce the electric field at the pn junctions sandwiched between the electrodes. We experimentally applied this RESURF technology to a conventional pn/sup -/ lateral diode. As a result, the breakdown voltage was increased from 56 to 104 V without varying the impurity concentration and the length of the n/sup -/ region. This means that the RESURF effect was achieved with the striped trench electrodes. The LDMOS with this RESURF technology was evaluated by simulations. This would be available for 80-V class lateral MOSFETs, used in the forthcoming 42-V automotive systems.

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