Thermally stable and low trap density SiN_x/AlON bi-layer structure for AlGaN/GaN MIS-HEMTs

We investigated a thermally stable and low trap density insulator for AlGaN/GaN metal-insulator-semiconductor (MIS) high-electron-mobility transistors (HEMTs). Current-voltage and capacitance-voltage measurements were performed before and after post deposition annealing (PDA) at 700 degrees C. A large increase in leakage current and high interface state density were observed after the PDA in the MIS structure with AlOx. The interface state density was reduced to one-third in the MIS structure with AlON, probably due to the reduced carbon impurity density at the AlOx/GaN HEMT interfaces. Meanwhile, the MIS structure with SiNx maintained high breakdown voltages of over 200 V, even after the PDA. By employing SiNx/AlON layers, we demonstrated low interface state density of 2.3 x 10(13) cm(-2) eV(-1) at E-c - 0.31 eV and suppressed leakage current at -200 V. We believe that the thermally-stable bi-layer structure is a promising technology for diamond deposition to improve heat dissipation.