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Amorphous GaN films deposited by DC sputtering

LU JIA1, XIAOJUN PAN1, ZHENXING ZHANG1, ERQING XIE1,*

Affiliation

  1. Department of Physics, Lanzhou University, Lanzhou 730000, P. R. China

Abstract

The films are deposited by direct current (DC) planar magnetron sputtering at different argon concentration in the sputtering gas (defined as Ar%). X-ray diffraction (XRD), Fourier Transform Infrared spectra (FTIR) and Raman spectra indicate that the films are amorphous. The main absorption of the FTIR is due to Ga-N bond stretching vibration. Spectroscopic Ellipsometry (SE) and UV-VIS spectra show that the refractive index of the a-GaN is very similar to that of crystalline GaN (c-GaN). When increasing Ar concentration from 10 % to 40 %, the thicknesses of the films change from 565.6 nm to 1526.1 nm linearly, which implies that Ar promotes the deposition rate. The Tauc band gap of the film deposited at lower Ar (~ 0%) is 3.9 eV, which is much larger than that of c-GaN, due to the structural disorder. While the films deposited at higher Ar%, the band gaps become much smaller (3.3 eV~2.8 eV), probably because of more excess Ga in the films. The band tails extending to lower energies are modeled, and the parameters indicate that a-GaN films have a wider absorption tail than that of c-GaN film.

Keywords

Amorphous GaN, DC sputtering, Absorption.

Citation

LU JIA, XIAOJUN PAN, ZHENXING ZHANG, ERQING XIE, Amorphous GaN films deposited by DC sputtering, Optoelectronics and Advanced Materials - Rapid Communications, 2, 2, February 2008, pp.71-75 (2008).

Submitted at: Jan. 24, 2008

Accepted at: Feb. 11, 2008