Low-temperature grown wurtzite InxGa1-xN thin films via hollow cathode plasma-assisted atomic layer deposition

摘要

Herein, we report on atomic layer deposition of ternary InGaN alloys with different indium contents using a remotely integrated hollow cathode plasma source. Depositions were carried out at 200 °C using organometallic Ga and In precursors along with N/H and N plasma, respectively. The effect of In content on structural, optical, and morphological properties of InGaN thin films was investigated. Grazing incidence X-ray diffraction showed that all InGaN thin films were polycrystalline with a hexagonal wurtzite structure. X-ray photoelectron spectroscopy depicted the peaks of In, Ga, and N in bulk of the film and revealed the presence of relatively low impurity contents. In contents of different InGaN thin films were determined by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Transmission electron microscopy also confirmed the polycrystalline structure of InGaN thin films, and elemental mapping further revealed the uniform distribution of In and Ga within the bulk of InGaN films. Higher In concentrations resulted in an increase of refractive indices of ternary alloys from 2.28 to 2.42 at a wavelength of 650 nm. The optical band edge of InGaN films red-shifted with increasing In content, confirming the tunability of the band edge with alloy composition. Photoluminescence measurements exhibited broad spectral features with an In concentration dependent wavelength shift and atomic force microscopy revealed low surface roughness of InGaN films with a slight increase proportional to In content. © 2015 The Royal Society of Chemistry.