Thermal transport in beta-gallium oxide thin-films using non-gray Boltzmann transport equation

Phonon transport in beta-Ga2O3 thin films and metal-oxide field effect transistors (MESFETs) are investigated using non-gray Boltzmann transport equations (BTEs) to decipher the effect of ballistic-diffusive phonon transport. The effects of domain size, and energy dissipation to various phonon modes and subsequent phonon-phonon energy exchange on the thermal transport and temperature distribution is investigated using non-gray BTE. Our analysis deciphered that domain size plays a major role in thermal transport in beta-Ga2O3 but energy dissipation to various phonon modes and subsequent phonon-phonon energy exchange does not affect the temperature field significantly. Phonon transport in beta-Ga2O3 MESFETs on diamond substrate is investigated using coupled non-gray BTE and Fourier model. It is established that the ballistic effects need to be considered for devices with beta-Ga2O3 layer thickness less than 1 mu m. A non-gray phonon BTE model should be used near hotspot in the thin beta-Ga2O3 layer as the Fourier model may not give accurate temperature distribution. The results from this work will help in understanding the mechanism of phonon transport in the beta-Ga2O3 thin films and energy efficient design of its FETs.