Abstract　Photoelectric characteristics of SiC_1-xGe_x/SiC heterojunction diode were simulated using MEDICI tools, and the simulation results are presented and discussed in this letter. The abrupt heterojunction diode is composed of a 1 μm thick heavily doped n-type SiC layer and a 0.4 μm thick lightly doped p-type SiC_1-xGe_x layer with varied composition ratios. It has been shown that photocurrent of the p- n+ SiC_1-xGe_x/SiC diode is not decreased apparently by change the composition ratio from 0.2 to 0.3 for the applied reverse-bias voltage of 3 V and the incident light intensity of 0. 23 W/cm2.Corresponding photocurrents of the diodes are 7. 765 × 10 -7 A/μm and 7. 438 × 10-7 A/ μm, and the longest wavelength limits are 0.64 μm and 0.70 μm, respectively. It has also been shown by the simulation results that p-i-n structure composed by adding a p + -SiC_1-xGe_x thin layer on top of the lightly doped p-type SiC_1-xGe_x layer is much better for obtaining a higher photocurrent. Under the same conditions, photocurrents of 1. 6734 10-6 A/μm and 1. 844 × 10-6 A/μm can be obtained in the p-i-n SiC_1-xGe_x/SiC diodes with x = 0.2 and 0.3, respectively.