In order to achieve high sensitivity detection, infrared detectors need to be optimized. Based on the Silvaco device simulation tool, the photoelectric characteristics of p-i-n InP/In0.53Ga0.47As/In0.53Ga0.47As photodetector is analyzed. The effects of absorption concentration and mesa width on dark current and junction capacitance in the structure are simulated. The results show that as the doping concentration of the absorption layer gradually increases, the dark current of the device gradually decreases, and the junction capacitance gradually increases. When the mesa width becomes narrower, the dark current of the device decreases, and the junction capacitance becomes smaller. Finally, the effect of light intensity and frequency on the device junction capacitance is studied. At low light intensity, the device junction capacitance is basically unchanged. When the light intensity increases to 1 W/cm2, the device junction capacitance increases rapidly. The device junction capacitance increases with frequency decreasing. The peak is caused by defect levels.