Time domain thermoreflectance measurements and phonon gas modeling of the thermal conductivity of silicon doped indium phosphide pertinent to quantum cascade lasers

The thermal conductivity of Si-doped thin films of indium phosphide grown via metalorganic vapour-phase epitaxy at different carrier concentrations and thicknesses was measured from 80 to 450 K using time domain thermoreflectance. Additionally, phonon gas modeling was conducted to characterize the various scattering mechanisms that contribute to the thermal transport in these materials. A sensitivity analysis based on the phonon gas model showed that while thickness has a greater influence on the thermal conductivity than carrier concentration at the micron-scale for all samples, point defects due to Si-dopant atoms at carrier concentrations of ∼1019 cm−3, as well as the presence of extended defects that are most likely present due to dopant saturation, have a significant impact on thermal transport as a result of increased phonon scattering, decreasing the thermal conductivity by 40% or more.