Thermal conductance of laterally-wet-oxidised GaAs/AlxOy Bragg reflectors

Thermal resistivity measurements were carried out on GaAs-based monolithic saturable absorber microcavities. Two-types of microcavity mirrors were compared: GaAs/AlAs against GaAs/AlxOy Bragg reflectors processed by lateral-wet-oxidation of Al(Ga)As layers. It is found that GaAs/AlxOy mirrors are not efficient heat dissipators, the GaAs/AlxOy microcavity structure showing a thermal resistivity more than ten times higher than the GaAs/AlAs structure. Using modelling to fit the experimental data, thermal conductivity of the 250 nm AlxOy layers is estimated to be approximately 0.007 WK(-1)cm(-1). These results illustrate a significant drawback related to the use of thick wet-oxidised Al(Ga)As/GaAs layers.