One of the major challenges in realizing the GaAs channel in the metal oxide semiconductor field effect transistor is the degrading in electron transport properties at the interface between GaAs and the gate oxide. In this study, Hf0.6La0.4Ox gate oxide films were deposited at a low temperature (200 °C) on GaAs(111)A and GaAs(100) substrates by plasma enhanced atomic layer deposition. Microstructure analysis indicates that residuals of gallium oxide, arsenic oxide, and As element remained at the interface of Hf0.6La0.4Ox/GaAs(100). On contrast, a smoother interface is observed between Hf0.6La0.4Ox thin film and GaAs(111)A substrate. Furthermore, a reduction of interfacial layer is observed in Hf0.6La0.4Ox/GaAs(111)A. Electrical characterization of the metal-insulator-semiconductor Pt/Hf0.6La0.4Ox/n-GaAs(111)A capacitor indicated a reduction of Dit and leakage current compared with the capacitor fabricated on GaAs(100).