Mg-compensation effect in GaN buffer layer for AlGaN/GaN high-electron-mobility transistors grown on 4H-SiC substrate

The present study investigated the Mg doping effect in the gallium nitride (GaN) buffer layers (BLs) of AlGaN/GaN high-electron-mobility transistor (HEMT) structures grown on semi-insulating 4H-SiC substrates by metal organic chemical vapor deposition. When the Mg concentration was increased from 3 × 10 17 to 8 × 10 18 cm −3 , the crystal quality slightly deteriorated, whereas electrical properties were significantly changed. The buffer leakage increased approximately 50 times from 0.77 to 39.2 nA at −50 V with the Mg doping concentration. The Mg-compensation effect and electron trapping effect were observed at Mg concentration of 3 × 10 17 and 8 × 10 18 cm −3 , respectively, which were confirmed by an isolation leakage current test and low-temperature photoluminescence. When the BL was compensated, the two-dimensional electron gas (2DEG) mobility and sheet carrier concentration of the HEMTs were 1560 cm 2 V −1 s −1 and 5.06 × 10 12 cm −2 , respectively. As a result, Mg-doped GaN BLs were demonstrated as a candidates of semi-insulating BLs for AlGaN/GaN HEMT.