Structural ordering, morphology and optical properties of amorphous Al x In 1x N thin films grown by plasma-assisted dual source reactive evaporation M. Alizadeh a,⇑ , V. Ganesh a , H. Mehdipour b,c , N.F.F. Nazarudin a , B.T. Goh a , A. Shuhaimi a , S.A. Rahman a,⇑ a Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia b Plasma Nanoscience @ Complex Systems, The University of Sydney, New South Wales 2006, Australia c Department of Physics, Sharif University of Technology, Tehran 11155-9161, Iran article info Article history: Received 17 December 2014 Received in revised form 18 January 2015 Accepted 25 January 2015 Available online 7 February 2015 Keywords: Amorphous AlInN Plasma-assisted deposition XPS Raman spectra Band gap abstract Amorphous aluminum indium nitride (Al x In 1x N) thin films were deposited on quartz substrates by plasma-assisted dual source reactive evaporation system. In-rich (x = 0.10 and 0.18) and Al-rich (x = 0.60 and 0.64) films were prepared by simply varying an AC voltage applied to indium wire. The X-ray-diffraction patterns revealed a small broad peak assigned to Al 0.10 In 0.90 N (002) plane, but no perceivable peaks assigned to crystalline Al x In 1x N were observed for the films with x = 0.18, 0.60 and 0.64. The morphology of the film was changed from clusters of small grains to uniformly shaped particles with decrease of x. The band gap energy of the films increased from 1.08 eV to 2.50 eV as the Al composition varied from 0.1 to 0.64. Also, Raman results indicated that E 2 (high) and A 1 (LO) peaks of the Al x In 1x N films are remarkably blue-shifted by increasing x and the A 1 (LO) phonon mode of the Al- rich films exhibits two-mode behavior. A bowing parameter of 4.3 eV was obtained for AlInN films. The extrapolated value from bowing equation was 0.85 eV for band gap energy of InN. Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction The III-nitride ternary semiconductors have become increas- ingly important in applications such as light-emitting diodes, laser diodes, solar cells, high electron mobility transistors and highly reflective Bragg reflectors in the ultraviolet region [1–4]. Among the III-nitride ternary alloys, Aluminum indium nitride (Al x In 1x N) has a wide variable band gap of 0.7–6.2 eV [5] depending on the indium (or aluminum) composition in the film structure. This provides great degree of freedom in customizing the electronic structures of the alloy films for specific applications. For example, Al x In 1x N thin films with tunable band gap of 0.7–2.4 eV can be used for multi-junction solar cell devices since this band gap energy range covers most part of solar spectrum [6]. Crystalline Al x In 1x N (c-Al x In 1x N) films have been fabricated over the years by various techniques such as molecular beam epitaxy (MBE) [7–10], metal organic chemical vapor deposition (MOCVD) [11,12], and sputtering-based deposition [13–15]. In general, except for sputtered films, c-Al x In 1x N films are obtained at high substrate temperatures on specified substrates such as sapphire and GaN. Therefore, these methods are restricted by the type and temperature of substrate. On the other hand, it has been shown that amorphous III-nitride semiconductor films have several advantages such as cost-effectiveness, compositional flexi- bility, low temperature deposition, no dependency on substrates and greater control of electrical property [16–22]. Shim et al. [20] fabricated blue light emitting a-GaN films at room tempera- ture. Itoh et al. [21] reported low temperature deposition of photo- conductive a-In x Ga 1x N films and suggested that the films could to be utilized as photo-absorptive layer of top cell in multi-junction thin films solar cells. Amorphous In x Ga 1x N films with consider- able photosensitivity were obtained by Suzuki et al. [22] using simultaneous rf magnetron sputtering. Therefore, much investiga- tion should be considered on the properties of amorphous III- nitrides alloys for the aim of effective use of these materials in semiconductor device applications considering the above- mentioned advantages. Band gap energy (E g ) of Al x In 1x N is closely related to deposition technique and the properties of the film. There have been remark- able disagreements among the band gap energies measured for AlInN films using various growth methods. One possible reason is that some of the measurements were carried out before the establishment of 0.7 eV [5] for band gap energy of indium nitride http://dx.doi.org/10.1016/j.jallcom.2015.01.216 0925-8388/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding authors. Tel.: +60 1112279670 (M. Alizadeh). Tel.: +60 123290697 (S.A. Rahman). E-mail addresses: alizadeh_kozerash@yahoo.com (M. Alizadeh), saadah@um. edu.my (S.A. Rahman). Journal of Alloys and Compounds 632 (2015) 741–747 Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom