Thermal conductivity and large isotope effect in GaN from first principles

• Published in: Physical review letters Vol. 109; no. 9; p. 095901
• Main Authors: Lindsay, L, Broido, D A, Reinecke, T L
• Format: Journal Article
• Language: English
• Published: United States 28.08.2012
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.109.095901

We present atomistic first principles results for the lattice thermal conductivity of GaN and compare them to those for GaP, GaAs, and GaSb. In GaN we find a large increase to the thermal conductivity with isotopic enrichment, ~65% at room temperature. We show that both the high thermal conductivity and its enhancement with isotopic enrichment in GaN arise from the weak coupling of heat-carrying acoustic phonons with optic phonons. This weak scattering results from stiff atomic bonds and the large Ga to N mass ratio, which give phonons high frequencies and also a pronounced energy gap between acoustic and optic phonons compared to other materials. Rigorous understanding of these features in GaN gives important insights into the interplay between intrinsic phonon-phonon scattering and isotopic scattering in a range of materials.