Investigations of AlGaN/GaN MOS-HEMT with Al2O3 deposition by ultrasonic spray pyrolysis method

Abstract

This work investigates Al2O3/AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) grown on SiC substrate by using the non-vacuum ultrasonic spray pyrolysis deposition (USPD) method. The Al2O3 was deposited as gate dielectric and surface passivation simultaneously to effectively suppress gate leakage current, enhance output current density, reduce RF drain current collapse, and improve temperature-dependent stabilities performance. The present MOS-HEMT design has shown improved device performances with respect to a Schottky-gate HEMT, including drain-source saturation current density at zero gate bias (IDSS: 337.6 mA mm−1 → 462.9 mA mm−1), gate-voltage swing (GVS: 1.55 V → 2.92 V), two-terminal gate-drain breakdown voltage (BVGD: −103.8 V → −183.5 V), unity-gain cut-off frequency (fT: 11.3 GHz → 17.7 GHz), maximum oscillation frequency (fmax: 14.2 GHz → 19.1 GHz), and power added effective (P.A.E.: 25.1% → 43.6%). The bias conditions for measuring fT and fmax of the studied MOS-HEMT (Schottky-gate HEMT) are VGS = −2.5 (−2) V and VDS = 7 V. The corresponding VGS and VDS biases are −2.5 (−2) V and 15 V for measuring the P.A.E. characteristic. Moreover, small capacitance-voltage (C–V) hysteresis is obtained in the Al2O3-MOS structure by using USPD. Temperature-dependent characteristics of the present designs at 300–480 K are also studied.