Atomic-layer-deposited Al2O3 films were grown on ultrathin-body In-0.53 Ga0.47As substrates for IIIV compound-semiconductor-based devices. Interface sulfur (S) passivation was performed with wet processing using ammonium sulfide ((NH4)(2)S) solution, and dry processing using post-deposition annealing (PDA) under a H2S atmosphere. The PDA under the H2S atmosphere resulted in a lower S concentration at the interface and a thicker interfacial layer than the case with (NH4)(2)S wet-treatment. The electrical properties of the device, including the interface property estimated through frequency dispersion in capacitance, were better for (NH4)(2)S wet-treatment than the PDA under a H2S atmosphere. They might be improved, however, by optimizing the process conditions of PDA. The PDA under a H2S atmosphere following (NH4)(2)S wet-treatment resulted in an increased S concentration at the interface, which improved the electrical properties of the devices. (C) 2014 Elsevier B.V. All rights reserved.