Reduction of in-plane and cross-plane thermal conductivities by polarization electric field induced in InxGa1-xN/GaN superlattice

Abstract

In this paper, polarization electric field (PEF) induced in GaN/InxGa1-xN superlattice (SL) was studied and found it can be treated as a reductant of thermal conductivity (k). Elastic properties and phonon group velocity are modified by the impact of interfacial PEF as by inverse piezoelectric effect. It improves scattering and thermal resistance at the boundaries because of dissimilarity in specific heat and group velocity, that decreases transmission coefficient of phonon and more acoustic mismatches resulting in reduction of in-plane (kip) as well as cross-plane (kcp) thermal conductivities. kip of InxGa1-xN (5 nm)/ GaN (10 nm) SL with (without) interfacial PEF field are 7.807 (8.921), 7.350 (8.355) and 7.018 (8.090) Wm−1K−1 respectively, for x = 0.1, 0.3 and 0.5; whereas kcp for the similar compositions are respectively, 4.652 (5.710), 4.282 (5.221) and 4.081(5.185) Wm−1K−1 at 300 K demonstrating the reduction exceeds 20%. It shows that the optimal k can be accomplished with the adaptation of nitride SL's electric field for thermoelectric improvements.