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.
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 À -GaN layer without mask. The HFET exhibited a specific on-resistance of as low as 2.6 mÁcm 2 with a threshold voltage of À16 V. This HFET would be a prototype of a GaN-based high-power switching device.
Gate insulator formation methods for GaN based MIS-HEMTs were examined. A SiO 2 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 100 m 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 than 8A.
IntroductionRecently, in addition to the exhaust gas problem in urban areas, the CO 2 problem has grown into a global-scale environmental problem, and for those who are engaged in automobile production, it has become a pressing issue. Internal combustion engine cars continue to improve. However, it is necessary to further reduce the amount of CO 2 emissions through the development and improvement of HVs, EVs, and FC vehicles. Si IGBTs are now used for inverters that control HV motors [1]. At present, there is nothing better than the Si IGBT as a switching device capable of satisfying the demands of the inverter for HVs. However, in the near future, demands (low energy loss, small size, low cost, etc.) on the inverter will become even more severe. In order to meet these demands, novel switching devices must be developed, which are made of wideband gap semiconductors that are attractive for low on-state loss, high breakdown voltage and high temperature operation. As a candidate for a wideband gap semiconductor, we chose GaN and started research on an insulated gate type power
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.