We compared the thermal performance of mid-IR GaInAs/AlInAs quantum cascade lasers QCLs\ud
having identical gain medium, but different heat sinking configurations. By using a two-dimensional\ud
anisotropic thermal model, we have calculated the temperature profiles and the heat flow patterns of\ud
ridge waveguide QCLs, either buried or planarized, and mounted substrate-side or epilayer-side\ud
down. Device planarization with Y2O3:Si3N4 dielectric layers gives an 7% reduction of the\ud
device thermal resistance with respect to InP buried heterostructures. If this planarization is\ud
combined with thick gold electroplating and epilayer-side mounting of the device, the thermal\ud
resistance is reduced by 35% and 50%, respectively, with respect to conventional ridge\ud
waveguide structures