Thermal behavior analysis of GaN based epi‐material on different substrates by means of a physical–thermal model

For gallium nitride (GaN) based microwave power devices, the thermal behavior due to the self‐heating effect constitutes a main limitation because the power dissipation is very high. For this study, a predictive physical–thermal model has been developed to analyze the physical and thermal phenomena observed in experiment. In this paper, the thermal performances of AlGaN/GaN epitaxies grown on different substrates are determined. It is found that compared with Si substrate, composite substrates: SopSiC (mono‐Si/poly‐SiC) and SiCopSiC (mono‐SiC/poly‐SiC) substrates (V. Hoel et al., Electron. Lett. 44 , 238 (2008) 1 and T.J. Anderson et al., J. Vac. Sci. Technol. B 24 , 2302 (2006) 2 ) present better thermal resistances especially at high dissipated power densities with an improvement of 18% for SopSiC substrate and 25% for SiCopSiC substrate at 12 W/mm. Furthermore, polycrystalline diamond is the most promising substrate with a thermal resistance of 5.4 W/m·K at 12 W/mm. The simulation results, such as lattice temperature and thermal resistance, are in good agreement with our measurements.