Thermal resistance of VCSEL's bonded to integrated circuits

The thermal resistance of vertical-cavity surface-emitting lasers (VCSEL's) hip chip bonded to GaAs substrates and CMOS integrated circuits has been m easured. The measurements on GaAs show that if the bonding is done properly , the bonding does not add significantly to the thermal resistance. However , the SiO2 under the CMOS bonding pad can double the thermal resistance unl ess measures are taken to improve the thermal conductance of these layers, Finite element simulations indicate that the thermal resistance of bonded V CSEL's increases rapidly as the solder bond size and the aperture size decr ease below similar to 10 mu m.