Effect of interface and bulk traps on the C–V characterization of a LPCVD-SiNx/AlGaN/GaN metal-insulator-semiconductor structure

Abstract

Silicon nitride (SiNx) film grown by low-pressure chemical vapor deposition (LPCVD) is utilized as a gate dielectric for AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Trap distribution at the gate-dielectric/III-nitrides interface is characterized by a temperature-dependent ac-capacitance technique. The extracted interface state density Dit decreases from 2.92 × 1013 to 1.59 × 1012 cm−2 eV−1 as the energy level depth (EC-ET) increases from 0.29 to 0.50 eV, and then levels off to EC-ET = 0.80 eV. Capacitance-mode deep level transient spectroscopy (C-DLTS) and energy band diagram simulations reveal that deep levels with EC-ET > 0. 83 eV are responsible for the dispersion of capacitances at high temperature (>125 °C) and low frequencies (<1 kHz). A high-resolution transmission electron microscope (TEM) reveals that re-oxidation of the RCA-treated AlGaN barrier surface may be responsible for the relatively high density of shallow states at the LPCVD-SiNx/III-nitride interface.