Thermal Conductivity of Amorphous Indium–Gallium–Zinc Oxide Thin Films

We investigated the thermal conductivity of 200-nm-thick amorphous indium–gallium–zinc-oxide (a-IGZO) films. Films with a chemical composition of In:Ga:Zn= 1:1:0.6 were prepared by dc magnetron sputtering using an IGZO ceramic target and an Ar–O 2 sputtering gas. The carrier density of the films was systematically controlled from 10 14 to >10 19 cm -3 by varying the O 2 flow ratio. Their Hall mobility was slightly higher than 10 cm 2 ·V -1 ·s -1 . Those films were sandwiched between 100-nm-thick Mo layers; their thermal diffusivity, measured by a pulsed light heating thermoreflectance technique, was ∼5.4 × 10 -7 m 2 ·s -1 and was almost independent of the carrier density. The average thermal conductivity was 1.4 W·m -1 ·K -1 .