Comparative Study on Characteristics of AlGaN/GaN Metal-Insulator-Semiconductor High-Electron-Mobility Transistors

A metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) with Al2O3/SiN x (SiN x next to semiconductor) double insulators is proposed to obtain lower gate leakage and lower current collapse simultaneously and is comparatively studied in this article. SiN x directly next to the (Al)GaN induces fewer interface traps and provides better passivation, and Al2O3 can greatly reduce gate leakage. The Schottky gate HEMT and MIS-HEMTs with single SiN x and Al2O3 layer are also fabricated for comparison. The proposed structure shows the lowest gate leakage and the lowest current collapse as well as better output, transfer, breakdown performance. Besides, this proposed structure shows low requirements on fabrication techniques and induces fewer interface traps. Moreover, to further explore the reason behind those superior performances, the gate leakage mechanisms under reverse and forward bias conditions are studied and the interface traps are compared through capacitance-voltage (C-V) measurements in those four kinds of devices. The experimental results demonstrate that the MIS-HEMT with Al2O3/SiN x double insulators is a superior candidate for nitrides-based MIS-HEMT devices.