Thermal Transport in Gallium Nitride Materials and Heterostructures

Gallium nitride (GaN) and its heterostructures have been proposed for high-power electronic and optoelectronic device applications. Accurate knowledge of the thermal conductivity of these materials and understanding of the underlying mechanism for thermal transport are important for the thermal performance simulations of GaN-based devices. This review focuses on the theoretical modeling of phonon thermal transport in GaN materials and heterostructures. It begins with a review of the experimental observations of the thermal conductivity of GaN and their discrepancy with the early theoretical predictions. This is followed by a detailed discussion of a recent theoretical model for heat conduction in GaN films, which considers explicitly both intrinsic and extrinsic phonon scattering processes important for GaN. The effects of dislocations and impurities are analyzed. Theoretical modeling of the thermal conductivity of low-dimensional GaN materials, such as nanoscale AIN/GaN/AIN heterostructures, is presented next. Modification of phonon dispersion due to acoustic mismatch across the interior interfaces is taken into account. Its influence on phonon group velocity and density of states is discussed. The possibility of improving thermal conduction in semiconductors through phonon engineering is also addressed. Also presented here is the recent experimental observation of the thermal conductivity of GaN nanowires and its comparison with the theoretical models.