Au/Ti/HfO2/n-GaAs MIS (metal/insulating layer/semiconductor) diodes were fabricated by atomic layer deposition technique and their electrical properties were investigated in detail by the help of current-voltage (I-V) and admittance measurements in the temperature range of 60-320 K. Together with the surface morphology analysis on the HfO2 thin-film layer, main electrical parameters such as series resistance (R-s), zero bias barrier height (phi(Bo)), ideality factor (n), impedance (Z) and phase angle were determined and effects of temperature on these parameters of the MIS diodes were discussed. The evaluation of I-V data exhibits a decrease in R-s and phi(Bo), however an increase in n, with a decrease in temperature. Temperature-dependent conductance (G) and capacitance (C) characteristics of the MIS diode were investigated at 1000 kHz in the voltage interval in between - 3 and 2 V. G and C values were found in a direct relation with the change in temperature. On the other hand, Z values showed an inverse proportionality with temperature. The phase angle versus voltage plots were evaluated at different temperatures (60-320 K) at 1000 kHz and the obtained results indicated that the device behaves more capacitive in the voltage range of - 3 V and about 0.4 V for all temperature, and phase angle decreases with increasing temperature from 0.4 to 1.6 V. In addition, the interface state density (D-it), the effective oxide charge density (Q(eff)) and effective number of charges per unit area (N-eff) of the fabricated diodes were investigated over temperature range 60-320 K in which these values were found in a decreasing trend with increasing temperature.