Electrical properties of metal-oxide-semiconductor field effect transistors (MOSFETs) on InP substrate with atomic layer deposited (ALD) high kappa dielectrics of HfO2 layer, or Al2O3/HfO2 bilayer with and without low power SF6 plasma treatment have been investigated. The interfacial Al2O3 layer provides better oxide interface quality with devices subthreshold swing (SS) of 94 mV/dec. With both Al2O3/HfO2 bilayer and SF6 plasma treatment, the transconductance, mobility, and drain current are improved by 50, 56, 100% respectively compared with those of a single HfO2 gate oxide layer without SF6 plasma treatment. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3582939] All rights reserved.