High Al Composition AlGaN-Channel High-Electron-Mobility Transistor on AlN Substrate

AlGaN-channel high-electron-mobility transistor (HEMT) with high Al composition of 0.51 has been developed. The epitaxial layers were grown on a free-standing AlN substrate to improve crystalline quality. The fabricated device exhibited a maximum drain current (Idsmax) of 25.2 mA/mm with a maximum transconductance (gmmax) of 4.7 mS/mm. The characteristic features of the device were a high source-to-drain breakdown voltage of 1800 V and a high applicable gate-to-source voltage of 4 V in the forward direction. Temperature dependence of DC characteristics demonstrated that the drain current degradation at elevated temperatures for the AlGaN-channel HEMT was appreciably small as compared with the conventional AlGaN/GaN HEMT. This is the first report showing successful DC operation of AlGaN-channel HEMT with high Al composition of over 0.5.