Thin amorphous gallium nitride ®lms formed by ion beam synthesis S.R.P. Silva * , S.A. Almeida, B.J. Sealy School of Electronic Engineering, Information Technology and Mathematics, University of Surrey, Guildford, Surrey GU2 5XH, UK Abstract Ion implantation and plasma enhanced chemical vapour deposition (PECVD) have been used to synthesise an amorphous gallium nitride compound (a-GaN) within an amorphous silicon nitride (a-SiN x :H y ) matrix by implanting Ga  into a-SiN x substrates. This route may enable the synthesis of large area a-GaN substrates for the use as possible seed layers for the growth of crystalline GaN as well as an amorphous semiconductor in its own right. A study of an entire range of a-SiN x with dierent compositions ÔxÕ has enabled the choice of the most suitable type of target substrate. It has been shown that nitrogen-rich a-SiN x has a high stress as well as a steady incorporation of N. X-ray Photo- electron Spectroscopy (XPS) and Rutherford Backscattering Spectroscopy (RBS) studies yield information on the chemistry and elemental depth pro®les of the material synthesised. Low temperature annealing, compatible with large area glass substrates is then used to increase the thickness of the a-GaN layer and transform more of the nitrogen rich a- SiN x . Ó 1999 Elsevier Science B.V. All rights reserved. Keywords: Amorphous semiconductors; Ion implantation; Amorphous gallium nitride; Thin ®lms; Silicon nitride 1. Introduction The possibility of producing high eciency blue laser diodes has created an ever-increasing re- search eort to improve the material properties of crystalline GaN (c-GaN) and its electronic device structure. The fact as to why c-GaN is a feasible blue electroluminescent material despite having a very large defect state density (of the order of 10 10 cm 2 ) is widely debated. Since light emission from highly defective c-GaN is possible, it is probable that forms of gallium nitride that are amorphous and disordered too would be suitable for light emission. Amorphous GaN (a-GaN) was ®rst synthesised by reactive sputtering of Ga in a ni- trogen atmosphere by Hariu et al. [1]. Since then Nonomura et al. [2] too have shown that good quality a-GaN can be produced by reactive sput- tering. These ®lms were shown to have a low electron spin density and were photoconductive by nature [2]. Potential applications of a-GaN ®lms include two main possibilities. Firstly, there is a diculty at present to lattice match c-GaN with other suitable substrates, and, secondly, the pos- sible use of a-GaN in itself as a viable large area light emitting material. Nuclear Instruments and Methods in Physics Research B 147 (1999) 388±392 * Corresponding author. Tel.: 00 44 1483 259 825; fax: 00 44 1483 534 139; e-mail: s.silva@ee.surrey.ac.uk 0168-583X/98/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 8 ) 0 0 5 5 0 - 3