GROUP III NITRIDE SEMICONDUCTOR DEVICE AND EPITAXIAL SUBSTRATE

摘要

Disclosed is a group III nitride semiconductor device wherein leakage current from a Schottky electrode is reduced. In a high-electron-mobility transistor (1), a supporting substrate (3) is composed of AlN, AlGaN and GaN. An Al<SUB>Y</SUB>Ga<SUB>1-Y</SUB>N epitaxial layer (5) has a surface roughness (Rms) of not more than 0.25 nm, and this surface roughness is defined by a 1 µm square area. A GaN epitaxial layer (7) is formed between the Al<SUB>Y</SUB>Ga<SUB>1-Y</SUB>N supporting substrate (3) and the Al<SUB>Y</SUB>Ga<SUB>1-Y</SUB>N epitaxial layer (5). A Schottky electrode (9) is formed on the Al<SUB>Y</SUB>Ga<SUB>1-Y</SUB>N epitaxial layer (5). A first ohmic electrode (11) is formed on the Al<SUB>Y</SUB>Ga<SUB>1-Y</SUB>N epitaxial layer (5), and a second ohmic electrode (13) is formed on the Al<SUB>Y</SUB>Ga<SUB>1-Y</SUB>N epitaxial layer (5). One of the first and second ohmic electrodes (11, 13) is a source electrode, and the other is a drain electrode. The Schottky electrode (9) is a gate electrode of the high-electron-mobility transistor (1).