Abstract: The performance of infrared detector is affected by the doping concentration of each layer of internal structure, and the doping concentration of multiplication layer will significantly change the performance of the device. In order to reduce the dark current and improve the performance of the device, the ternary compound In_0.83Al_0.17As was used as the multiplication layer material, and with the help of simulation software Silvaco, the effects of the doping concentration in the multiplication layer of In_0.83Al_0.17As/ In_0.83Ga_0.17As infrared detector on the electric field intensity, current characteristics and optical responsivity of the device were studied in detail. The results show that with the increase of doping concentration in the multiplication layer, the peak value of electric field intensity in the multiplication layer increases, and the dark current and optical responsivity of the device decreases respectively. It is further found that when the doping concentration in the multiplication layer is 2×10¹⁶ cm⁻³, the device obtains the optimal performance, the dark current density is 0.621 44 A/cm², and when the wavelength is 1.5 μm, the optical responsivity and specific detectivity are 0.954 4 A/W and 1.947 5×10⁹ cmHz^1/2W⁻¹, respectively.