Thermal analysis of InP-based quantum cascade lasers for efficient heat dissipation

Abstract

We have theoretically investigated the thermal characteristics of double-channel ridge–waveguide InGaAs/InAlAs/InP quantum cascade lasers (QCLs) using a two-dimensional heat dissipation model. The temperature distribution, heat flow, and thermal conductance (Gth) of QCLs were obtained through the thermal simulation. A thick electroplated Au around the laser ridges helps to improve the heat dissipation from devices, being good enough to substitute the buried heterostructure (BH) by InP regrowth for epilayer-up bonded lasers. The effects of the device geometry (i.e., ridge width and cavity length) on the Gth of QCLs were investigated. With 5 μm thick electroplated Au, the Gth is increased with the decrease of ridge width, indicating an improvement from Gth=177 W/K⋅cm2 at W=40 μm to Gth=301 W/K⋅cm2 at W=9 μm for 2 mm long lasers. For the 9 μm×2 mm epilayer-down bonded laser with 5 μm thick electroplated Au, the use of InP contact layer leads to a further improvement of 13% in Gth, and it was totally raised by 45% corresponding to 436 W/K⋅cm2 compared to the epilayer-up bonded laser with InGaAs contact layer. It is found that the epilayer-down bonded 9 μm wide BH laser with InP contact layer leads to the highest Gth=449 W/K⋅cm2. The theoretical results were also compared with available obtained experimentally data.