GaN metal–insulator–semiconductor high-electron-mobility transistor with plasma enhanced atomic layer deposited AlN as gate dielectric and passivation

Abstract

AlGaN/GaN based metal–insulator–semiconductor high-electron-mobility transistors (HEMTs) using a plasma enhanced atomic layer deposited 10 nm AlN as the gate insulator and passivation layer were demonstrated. A refractive index of 1.92 for the deposited AlN was measured using an ellipsometer, which was slightly lower than that of bulk AlN. The deviation of the refractive index from the ideal value was caused by AlN surface oxidation, and this was confirmed by X-ray photoelectron spectroscopy and Auger depth profiling analyses. The HEMT drain current was modulated with gate voltages ranging from −3 to +4 V. The HEMT exhibited an on-off ratio of 3.3 × 108 due to the low gate leakage current and a maximum saturation drain current of 600 mA/mm. Beside reducing the gate leakage current, the effectiveness of the HEMT passivation was confirmed by gate pulse measurements, which showed only a 7% decrease of the drain current.