Reduction of thermal conductivity due to interfacial polarization mechanism of GaN/InxGa1-xN superlattice

Abstract

In this work, it is theoretically investigated that interfacial polarization electric (IPE) field of GaN/In x Ga 1-x N superlattice (SL) can be exploited for further reduction of thermal conductivity ( k ). IPE field modifies SL's elastic constant and phonon velocity as a result of inverse piezoelectric effect. This enhances interfacial scattering and thermal boundary resistance due to unequal changes in specific heat and phonon velocity leading to decreased phonon transmission and more mismatches of acoustic properties causing reduction in in-plane ( k ip ) and cross-plane ( k cp ) thermal conductivities. Room temperature k ip in the presence (absence) of IPE field of GaN(10 nm)/In x Ga 1-x N(5 nm) SL are 7.807(8.921), 7.350(8.355), 7.018(8.090), 8.204(9.402) and 9.312(10.564) Wm −1 K −1 respectively, for x = 0.1, 0.3, 0.5, 0.7 and 0.9; whereas k cp for the same x are 4.652(5.710), 4.282(5.221), 4.081(5.185), 4.871(6.012) and 6.083(7.327) Wm −1 K −1 demonstrating more than 20% reduction. It reveals that desired k can be achieved by tailoring electric field of nitride SL for better thermoelectric improvements. • Interfacial electric field is exploited to reduce thermal conductivity of GaN/In x Ga 1-x N/GaN SLs. • Electric field modifies thermal parameters and phonon properties of SL via inverse piezoelectric effect. • TBR is enhanced from 2.10 to 5.30 × 10 −9 m 2 KW −1 closer to reported value of InGaAs SL. • k cp in presence of field shows more than 20% reduction due to enhanced TBR. • k cp in presence(absence) of field for x = 0.1 and 0.9 are 4.652 (5.710) and 6.083(7.327) Wm −1 K −1 .