The Ag/Mg3N2/p-Si heterojunction diode (HD) with rectifier contacts (RCs) with the same area in various geometries were fabricated through thermal evaporation, and the electrical performances of these diodes was compared. The geometry of the RC was found to affect various electrical properties such as ideality factor, saturation current and barrier height of HD, the rectifier rate, and the leakage current of the diodes. The experimental demonstrated the HD with a circular RC exhibited a higher rectifying ratio and lower leakage current compared to the other RCs. Hence, the design and optimization of the RC play a critical role in achieving the desired electrical properties of diode. These diodes, featuring an Mg3N2 interfacial layer and showcasing photoconductive behavior, can be utilized as photodiodes in various optoelectronic devices.