Unpassivated GaN/AlGaN/GaN Power High Electron Mobility Transistors with Dispersion Controlled by Epitaxial Layer Design

In this paper, a novel GaN/AlGaN/GaN high electron mobility transistor (HEMT) is discussed. The device uses a thick GaN-cap layer (∼250 nm) to reduce the effect of surface potential fluctuations on device performance. Devices without Si3N4 passivation showed no dispersion with 200-ns-pulse-width gate-lag measurements. Saturated output-power density of 3.4 W/mm and peak power-added efficiency (PAE) of 32% at 10 GHz (VDS=+15 V) were achieved from unpassivated devices on sapphire substrates. Large gate-leakage current and low breakdown voltage prevented higher drain-bias operation and are currently under investigation