Low-temperature grown wurtzite In sub(x)Ga sub(1-x)N thin films via hollow cathode plasma-assisted atomic layer deposition

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2015-09, Vol.3 (37), p.9620-9630
• Main Authors: Haider, Ali, Kizir, Seda, Ozgit-Akgun, Cagla, Goldenberg, Eda, Leghari, Shahid Ali, Okyay, Ali Kemal, Biyikli, Necmi
• Format: Article
• Language: English
• Subjects: Alloys; Concentration (composition); Deposition; Diffraction; Gallium base alloys; Thin films; Wurtzite; X-rays
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c5tc01735a

Herein, we report on atomic layer deposition of ternary In sub(x)Ga sub(1-x)N alloys with different indium contents using a remotely integrated hollow cathode plasma source. Depositions were carried out at 200 degree C using organometallic Ga and In precursors along with N sub(2)/H sub(2) and N sub(2) plasma, respectively. The effect of In content on structural, optical, and morphological properties of In sub(x)Ga sub(1-x)N thin films was investigated. Grazing incidence X-ray diffraction showed that all In sub(x)Ga sub(1-x)N 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 In sub(x)Ga sub(1-x)N 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 In sub(x)Ga sub(1-x)N thin films, and elemental mapping further revealed the uniform distribution of In and Ga within the bulk of In sub(x)Ga sub(1-x)N 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 In sub(x)Ga sub(1-x)N 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 In sub(x)Ga sub(1-x)N films with a slight increase proportional to In content.