In this letter, the Metal-Insulator-Semiconductor (MIS) contacts are fabricated on the GaN substrates and compared to the Metal-Semiconductor (MS) contacts. To alleviate the Fermi level pinning effect at the Metal-Semiconductor interface, an Al2O3 interfacial layer (IL) (1 ~ 3 nm) is used to form the MIS contacts. By comparing the electrical characteristics, the contact with 0nm Al2O3 layer, i.e., MS contact, shows a lowest current compared to the contacts with an Al2O3 IL, i.e., MIS contact. Furthermore, the current at 0.5V in the fabricated Transmission Line Measurement (TLM) device with 1nm Al2O3 IL is 103 times higher the one without an Al2O3 IL. This proves that inserting an Al2O3 IL could mitigate the Fermi level pinning, resulting in a low Schottky barrier height. Finally, based on the TLM analysis, the resistivity of 5.1×10-4 Ω.cm2 is demonstrated in the MIS contact with 1nm Al2O3 IL.