Thermal properties of cubic GaN/GaAs heterostructures grown by molecular beam epitaxy

Abstract

Cubic GaN/GaAs (001) heterostructures were grown by RF-plasma assisted molecular beam epitaxy with different GaN nucleation temperatures. The heterostructures were studied by an open cell configuration of a photoacoustic experiment to obtain the effective thermal diffusivity (α) of the composite, which presented values varying from 14 to 28mm2/s. Also, a two-layer model was used in order to obtain the interfacial thermal conductivity (η), revealing values from 5 to 35W/cm2 K. Both α and η presented higher values for cubic GaN films grown with higher nucleation temperatures. The crystalline quality of the samples, studied with high resolution x-ray diffraction and photoluminescence measurements, showed that the increase in the nucleation temperature produced films with fewer defects, implying a dependence between the interfacial thermal properties and the bulk crystalline quality. This variation of η can be associated with phonon scattering due to disorder at the interface region. The results provide an important understanding of how the growth temperature of the nucleation layer can affect the quality and the properties of the cubic GaN.