We investigated the thermal stability of ZrO2/GaAs structures deposited by pulsed laser deposition as a function of the post-annealing temperature. During the annealing process the interfacial layer between the pulsed laser deposited ZrO2 thin film and GaAs substrate increased significantly at the temperature of 500 degrees C, and the ZrO2 thin film became fully crystallized to the monoclinic phase at the temperature of 600 degrees C. This resulted in the degradation of electrical properties such as the leakage current and the breakdown voltage, and an interfacial trap charge density. In order to improve the thermal stability, we pre-deposited an Al2O3 passivation layer by atomic layer deposition followed by pulsed laser deposited ZrO2 deposition. The amorphous Al2O3 passivation layer hindered the crystallization of the ZrO2 thin film during the annealing process, significantly improving the electrical characteristics of the resulting structure compared to the ZrO2/GaAs structures without an Al2O3 passivation layer. In particular, the interfacial reaction was effectively suppressed up to a temperature of 600 degrees C so that the interface trap charge density was significantly decreased due to the low oxygen diffusivity of Al2O3 layer. (C) 2014 Elsevier B.V. All rights reserved.