Evaluation of the thermal resistance in GaN-diodes by means of electro-thermal Monte Carlo simulations

In this paper we use an electro-thermal method [solver of the heat-flux equation coupled with an ensemble Monte Carlo (MC) simulator] to extract the value of the thermal resistance, R_th, in diodes consisting in un-gated Al_0.27Ga_0.73N/GaN heterostructures. Different substrates (polycrystalline diamond - PCD, diamond, silicon and sapphire), and die dimensions will be analysed. When a temperature-independent thermal conductivity is considered, the obtained values of R_th depend on the geometry and substrate material, and are constant with the dissipated power (P_diss). When a temperature-dependent thermal conductivity is needed to correctly reproduce the thermal behaviour of the device, R_th exhibits a strong dependence on P_diss.