He/N 2 reactive gas composition and the structural and electrical properties of InN thin films grown on A1N-nucleated (00.1) sapphire by planar magnetron sputtering

Abstract

The effects of He/N 2 reactive gas composition on the structural and electrical properties of InN thin films deposited by magnetron sputtering on A1N-nucleated (00.1) sapphire substrates have been investigated. X-ray scattering studies demonstrate that the films are an aggregate of strained heteroepitaxial domains and highly relaxed textured domains and that their apportionment is strongly tied to the reactive gas composition. The sputtering rate, as evidenced by film thickness, nominally increases with increasing volume fraction of N 2, but enhanced growth and epitaxial volume are observed at concentrations of N 2 near 60%. The variation in electrical transport properties with increasing N 2 fraction in the gas mixture is smoother, with the n-type Hall mobility rising monotonically from 35 cm 2 V −1 s −1 for films deposited in a 30% N 2 volume fraction to 55 cm 2 V −1 s −1 for growth in pure N 2, largel y due to an increase in the volume of heteroepitaxial domains, the consequent reduction in the density of high-angle grain boundaries, and the resulting decrease in intergrain resistance and film resistivity.