The impact of the gate dielectric quality in developing Au-free D-mode and E-mode recessed gate AlGaN/GaN transistors on a 200mm Si substrate

摘要

The selection of the gate dielectric is one of the most critical stability issues in recessed gate AlGaN/GaN transistors. In this work, we show that the quality of the gate dielectric has a strong impact on: 1) the threshold voltage (V) hysteresis, 2) the drain current reduction for enhancement mode devices, and 3) the forward gate bias TDDB (time dependent dielectric breakdown). It will be shown that the V hysteresis and the current reduction can be minimized by using a dielectric with lower interface state density (D) and less border traps, e.g., a PE-ALD SiN dielectric. Furthermore, the 0.01% failures at 20 years TDDB requirement at 150°C for a large power device, e.g., gate width Wg=36mm, necessitates the use of at least a 25nm-thick PE-ALD SiN gate dielectric.