Dual-Surface Modification of AlGaN/GaN HEMTs Using TMAH and Piranha Solutions for Enhancing Current and 1/f-Noise Characteristics

We demonstrated dual-surface modification of GaN/AlGaN/GaN high-electron mobility transistors using tetramethylammonium hydroxide (TMAH) and piranha solutions prior to gate metallization. The TMAH-treated device exhibits improved performances with lower I-V hysteresis, in off-state leakage current and gate leakage current. The device performances were further significantly improved with applies additional piranha solution treatment right after the TMAH treatment, especially in hysteresis and 1/f-noise characteristics. It is found that the Schottky barrier height is high and ideality factor is low measured from I-V characteristics for the TMAH and piranha solution treated device. Reasonable gate leakage mechanisms were also discussed using Poole-Frenkel and Schottky emissions. In addition, it is observed that the magnitude of interface state density for the TMAH treatment after the piranha solution treated device shows significantly low compared to other devices. These excellent device-performances are observed due to the reason of dual-surface treatment which effectively decreases the surface trap density with an appropriate etching and passivation of the device surface exposed prior to the gate metallization.