Atomic layer deposition (ALD) is universally recognized as an effective approach to the growth of extremely conformal and uniform gate dielectric oxides with high permittivity (high-κ) for complementary metal-oxidesemiconductor (C-MOS) technology. Aiming at a post-Si electronics era, integration of high-κ dielectrics into III-V semiconductors with enhanced transport properties such as In0. 53Ga0. 47As is demanded [1]. In this respect, ALD of Al2O3 has been successfully adopted as gate oxide by taking benefit from the well-known self-cleaning effect played by the trimethylaluminum (TMA) precursor when used as a first pulse as long as electrically detrimental semiconductor oxide species at the interface can be effectively reduced [2]. The details of electrical response of Al2O3/In0. 53Ga0. 47As MOS capacitors are here revisited as a function of the surface treatment in both p-and ntype substrates therein suggesting …