In this paper is presented a theoretical study of effects of Hafnium dioxide on the electrical properties of (Pd/n-GaN) Schottky diode under a temperature of 300°K, using the forward bias I-V measurements. A simulation on the (Pd/n-GaN) and (Pd/HfO2/n-GaN) structure is presented, then simulation results are compared with experimental results. A well matching was found between simulations and experimental results. Barrier height (Φb), ideality factor (n) and series resistance (Rs) effects was also studied. In addition, (I-V), Norde, Cheung and Cheung, H(I) and G(I), Chattopadhyay and Mikhelashvili methods are used to extract different parameters. Obtained theoritical results are well matched with experimental measurements. The ATLAS module of SILVACO-TCAD software has been used in numeric simulations.