High Electron Mobility Transistor, Field-Effect Transistor, and Epitaxial Substrate

摘要

Affords high electron mobility transistors having a high-purity channel layer and a high-resistance buffer layer. A high electron mobility transistor (11) is provided with a supporting substrate (13) composed of gallium nitride, a buffer layer (15) composed of a first gallium nitride semiconductor, a channel layer (17) composed of a second gallium nitride semiconductor, a semiconductor layer (19) composed of a third gallium nitride semiconductor, and electrode structures (a gate electrode (21), a source electrode (23) and a drain electrode (25)) for the transistor (11). The band gap of the third gallium nitride semiconductor is broader than that of the second gallium nitride semiconductor. The carbon concentration NC1 of the first gallium nitride semiconductor is 4×1017 cm−3 or more. The carbon concentration NC2 of the second gallium nitride semiconductor is less than 4×1016 cm−3.