The surface, structural, and optical properties of InAs/InGaSb/AlSb mid-infrared lasers grown by molecular beam epitaxy have been systematically studied, respectively, by Nomarski differential interference contrast, high-resolution x-ray diffraction, and variable-temperature photoluminescence. It is found that the optimum growth temperature is between 400 and 450 degrees C, based on the calibrated transmission thermometry. In addition, the impact of interfacial bond type and Sb sources has been investigated. A 5.91 mu m laser, grown with the optimal growth parameters, exhibits a maximum cw operating temperature of 210 K. (C) 1999 American Institute of Physics. [S0021-8979(99)08716-2].