The surface defects of short.wave infrared indium gallium arsenide (InGaAs) detector materials are one of the core problems in the development of large.scale small.pixel focal plane arrays, and the surface defects of extended.wavelength detector materials with lattice mismatch to the substrate are particularly difficult to control. The temperature setting of indium cell in molecular beam epitaxy (MBE) system is optimized. The results show that the surface defect density of short.wave infrared lattice.mismatched In0.83Ga0.17As detector material is the lowest when the temperature difference between the top and bottom of the indium cell is 130℃, thus effectively reducing the surface defect density of the material from about 3000 cm-2 to about 500 cm-2. Combined with the room.temperature photoluminescence test of the short.wave infrared lattice.mismatched InGaAs materials, the analysis shows that the optimal temperature difference between the top and bottom temperatures of the indium cell is due to the combined effect of the two mechanisms of oval defects caused by indium metal droplets and impurities at the top of the cell. The lattice.mismatched InGaAs detector materials with low surface defect density prepared in this paper laid the foundation for the development of high.performance extended.wavelength short.wave infrared focal plane arrays.