Capacitance-voltage characterization of Al2O3/GaN-on-insulator (GaNOI) structures with TMAH surface treatment

Abstract

The capacitance-voltage (C-V) characterizations of Al2O3/GaN-on-insulator (GaNOI) structure, prepared with the Smart Cut™ technology, with and without tetramethylammonium hydroxide (TMAH) surface treatment have been investigated. The GaNOI structure consists of a 150nm-thick GaN layer and a 800μm-thick Si3N4/SiO2 buried insulating layer deposited on sapphire substrate. For fabrication of the MIS capacitor, an Al2O3 layer with thickness of 28nm as a gate dielectric was deposited on the GaNOI wafer by atomic layer deposition (ALD). The calculated carrier concentration of the GaN layer on the buried insulator was increased to 2.8×1017cm−3 from the value of ~5×1016cm−3 for the as-grown undoped GaN layer prior to the wafer transfer. The MIS capacitor with TMAH surface treatment showed a positive threshold voltage shift with negligible hysteresis and low interface trap density compared to the capacitor without TMAH surface treatment. Severe frequency dispersion was observed regardless of the TMAH treatment due to the crystal defects generated during the complicated wafer transfer process.