Effective suppression of interface states in recessed-gate MIS-HEMTs by TMAH wet etching

The effect of tetramethylammonium hydroxide (TMAH) treatment prior to gate dielectric deposition on the performance of recessed-gate AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) was investigated. Through the use of TMAH wet etching, a low roughness etched surface of 0.173 nm was obtained. The capacitance-voltage characteristics of MIS heterostructures showed that the interface states reduced by one order of magnitude. When the temperature was increased to 473 K, the treated MIS-HEMTs delivered a small threshold voltage shift (Delta V TH) of similar to-0.53 V. From the dynamic measurement, the Delta V TH obtained without treatment was observed more severely (similar to-1 V) when compared to the treated one (similar to-0.01 V).