The highly reactive GaSb surface was passivated with a thin InAs layer to limit interface trap state density (D-it) at the III-V/high-k oxide interface. This InAs surface was subjected to various cleaning processes to effectively reduce native oxides before atomic layer deposition (ALD). Ammonium sulfide pre-cleaning and trimethylaluminum/water ALD were used in conjunction to provide a clean interface and annealing in forming gas (FG) at 350 degrees C resulted in an optimized fabrication for n-GaSb/InAs/high-k gate stacks. Interface trap density, D-it approximate to 2-3 x 10(12) cm(-2)eV(-1) resided near the n-GaSb conductance band which was extracted and compared with three different methods. Conductance-voltage-frequency plots showed efficient Fermi level movement and a sub-threshold slope of 200 mV/dec. A composite high-k oxide process was also developed using ALD of Al2O3 and HfO2 resulting in a D-it 6-7 x 10(12) cm(-2)eV(-1). Subjecting these samples to a higher (450 degrees C) processing temperature results in increased oxidation and a thermally unstable interface. p-GaSb displayed very fast minority carrier generation/recombination likely due to a high density of bulk traps in GaSb. (C) 2012 Elsevier Ltd. All rights reserved.