Spectroscopic ellipsometry studies of GaN films deposited by reactive rf sputtering of GaAs target

Journal Article · Tue Apr 15 04:00:00 EDT 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2903443· OSTI ID:21137163

Biswas, A; Bhattacharyya, D; Sahoo, N K ^[1]; Yadav, Brajesh S; Major, S S ^[2]; Srinivasa, R S ^[3]

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1. Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)
2. Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India)
3. Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400 076 (India)

GaN films have been deposited by reactive rf sputtering of GaAs target in 100% nitrogen ambient on quartz substrates at different substrate temperatures ranging from room temperature to 700 deg. C. A series of films, from arsenic-rich amorphous to nearly arsenic-free polycrystalline hexagonal GaN, has been obtained. The films have been characterized by phase modulated spectroscopic ellipsometry to obtain the optical parameters, viz., fundamental band gap, refractive index, and extinction coefficient, and to understand their dependence on composition and microstructure. A generalized optical dispersion model has been used to carry out the ellipsometric analysis for amorphous and polycrystalline GaN films and the variation of the optical parameters of the films has been studied as a function of substrate temperature. The refractive index values of polycrystalline films with preferred orientation of crystallites are slightly higher (2.2) compared to those for amorphous and randomly oriented films. The dominantly amorphous GaN film shows a band gap of 3.47 eV, which decreases to 3.37 eV for the strongly c-axis oriented polycrystalline film due to the reduction in amorphous phase content with increase in substrate temperature.

• OSTI ID: 21137163
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 8 Vol. 103; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMORPHOUS STATE
ARSENIC
CRYSTAL GROWTH
CRYSTAL STRUCTURE
ELLIPSOMETRY
ENERGY GAP
GALLIUM ARSENIDES
GALLIUM NITRIDES
GRAIN ORIENTATION
NITROGEN
OPTICAL DISPERSION
POLYCRYSTALS
POLYMERS
QUARTZ
REFRACTIVE INDEX
SEMICONDUCTOR MATERIALS
SPUTTERING
SUBSTRATES
TEMPERATURE RANGE 0273-0400 K
THIN FILMS