Thermal analysis of InAs quantum dot laser diodes with an additional Au layer on p-metal

The thermal characteristics of laser diodes (LDs) are analyzed by using a finite element method. A change in the junction temperature depending on the thickness of the additional Au layer, which might be deposited or plated on the p-contact metal of the LD, has been observed. As the Au layer thickness increases, the junction temperature of the LDs, which are epi-up mounted on a Cu sub-mount, goes down drastically and then saturates. On the other hand, the junction temperature of LDs epi-down mounted on a Cu sub-mount shows relatively little variation with the Au thickness, although it is lowered by more than 30 degrees C at an electrical input power of 1.2 W compared to that of epi-up mounted LDs. We measure the junction temperatures of InAs quantum dot (QD) LDs and compare them with simulation results. The junction temperatures increased at a rate of 86 degrees C/W and 48 degrees C/W for epi-up and epi-down mounting with an additional An layer of 0.2 mu m, respectively.