Cross-plane thermal diffusivity measurement of an operating vertical cavity surface emitting laser using thermoreflectance

Cross-plane thermal diffusivity of a GaAs/AlGaAs-based vertical cavity surface emitting laser (VCSEL) is measured under operating conditions and active heat sinking using a thermoreflectance technique. Perpendicular thermal diffusivity is determined from the measurements of phase difference between the heating source and the temperature as a function of temperature modulation frequency. The value of (1.22 +/- 0.23) x 10(-6) m(2)/s is obtained for thermal diffusivity, which is of the same order as previous values obtained on unbiased VCSEL structures. This is 10-14 times smaller than the corresponding bulk value. The reduction is attributed to the increase in phonon-boundary scattering in the multilayer structure of the VCSEL. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3581089]