We present the effects of hereto-interfaces and major key parameters on the thermal behaviors and performance of short wavelength mid-IR InAs/AlSb quantum cascade lasers (QCLs).We use a finite element method (FEM) with commercial software,ANSYS,to simulate the heat dissipation in QCLs in cw operation mode with an epilayer-down mounting package.The thermal performance is characterized by the temperature increase △T (self-heating effect) between the active region of QCLs and the heatsink.Results show that (1) the self-heating effects of InAs/AlSb QCLs are much less than those in AllnAs/GaInAs QCLs,(2) narrower ridges lead to significantly cooler active regions of InAs/AlSb QCLs due to poor heat transport in the cross-plane direction (across interfaces) and that most of the heat flows out of the active region in the lateral direction,and (3) the cavity length of the laser has little influence on the self-heating effect of the device,but the long cavity reduces mirror loss and threshold current density.