Thermal conductivity reduction by interfacial electric field of GaN/InGaN/GaN superlattice

摘要

This paper demonstrates that interfacial polarization electric (IPE) field of GaN/In_xGa_(1-x)N/GaN superlattice (SL) can be utilized to reduce thermal conductivity (k) further. IPE field initiates inverse piezoelectric effect which modifies elastic property and phonon velocity. This increases phonon scattering and thermal resistance at interfaces owing to unequal changes in specific heat and phonon velocity leading to more discontinuity in acoustic properties of SL. Result shows that it decreases phonon transmission causing reduction in in-plane (k_(ip)) and cross-plane (k_(cp)) thermal conductivities. Room temperature k_(ip) in presence (absence) of IPE field of GaN (10 nm)/ In_xGa_(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 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>20% reduction and are in excellent agreement with experiments. It suggests that required k may be reached by changing interfacial electric field of nitride SL.