Molecular beam epitaxy and characterization of wurtzite InScN

Abstract

We report the molecular beam epitaxial growth and characterization of wurtzite InScN thin films. We find that wurtzite InScN can be grown on GaN substrates under metal-rich conditions, resulting in smooth surfaces with <1 nm roughness and a two-dimensional growth mode. We further find that InScN can be stabilized in the wurtzite crystalline phase for Sc content up to at least 10.4%. We measure and report the lattice parameters of wurtzite InScN as a function of Sc content and find that between ∼5% and 8% Sc mole fraction InScN has a similar a lattice constant to InN. The c/a ratio deviates from the ideal tetrahedral value of 1.633 as Sc content increases. The optical absorption edge of wurtzite InScN monotonically increases over a Sc content range of 0%–10.4% from 0.8 to 1.05 eV, accompanied by a shift in the peak index of refraction and extinction coefficient. The E2high Raman peak of InScN shows negligible shift with increasing Sc content compared to a gradual increase in the A1 (LO) peak position. These fundamental observations can facilitate the future design of InN-based devices.