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

Highlights: • Interfacial electric field is exploited to reduce thermal conductivity of GaN/In_xGa_1-xN/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$\times$10^-9 m²KW⁻¹ closer to reported value of InGaAs SL. • k_cp in presence of field shows>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^-1K⁻¹. This paper demonstrates that interfacial polarization electric (IPE) field of GaN/In_xGa_1-xN/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-xN(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^-1K⁻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^-1K⁻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.