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Title: The properties and deposition process of GaN films grown by reactive sputtering at low temperatures

Abstract

Polycrystalline gallium nitride films, 100 nm to 1 {mu}m thick, were deposited under a range of conditions. Substrate electrode temperatures during sputtering were varied from room temperature to 450 deg. C, the pressure from 0.15 to 6.0 Pa, the nitrogen fraction of the deposition atmosphere from 10% to 100% and the target bias from -400 to -1800 V. The deposition rates as functions of these conditions are in the range 0.5-25 nm/min. The growth rate is considered to be controlled respectively by the thermally activated desorption from the substrate, changes in the mean free path and concentration of gas particles, differences between the sputter yields of Ga and GaN in Ar and N{sub 2}, and changes in the ion current and sputter yields. The films are generally columnar, with the grain size increasing with film thickness. The most crystalline films were grown at mid range temperatures, low N{sub 2} concentrations, and low target biases, and the most disordered were grown at low pressures. The latter two cases suggest that decreasing the energy of particles incident on the film during deposition results in a more ordered film. The biaxial stress is compressive and shows an increasing trend with the target biasmore » and N{sub 2} concentration, reaching 4.7 GPa at 75% N{sub 2}. Oxygen contamination of 3-30 at. % has a major effect on the optical properties of the films, increasing the band gap values from 3.02 to >4.0 eV and the Urbach tail energies from around 150 to 840 meV and decreasing the refractive index from 2.46 to 2.03. At a 40% N{sub 2} deposition fraction, the N:Ga ratio is more or less constant at 1:1. Since the absolute oxygen incorporation rate changes very little, it is the relative film deposition rate which determines the final oxygen concentration. Excess Ga at low N{sub 2} concentrations causes a decrease in the band gap and an increase in the Urbach tail energy.« less

Authors:
; ;  [1]
  1. Advanced Technology Institute, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)
Publication Date:
OSTI Identifier:
20788015
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 99; Journal Issue: 7; Other Information: DOI: 10.1063/1.2186380; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DEPOSITION; DESORPTION; ELECTRODES; ENERGY GAP; GALLIUM NITRIDES; GRAIN SIZE; MEAN FREE PATH; MEV RANGE 100-1000; NITROGEN; OXYGEN; POLYCRYSTALS; PRESSURE RANGE GIGA PA; REFRACTIVE INDEX; SEMICONDUCTOR MATERIALS; SPUTTERING; STRESSES; SUBSTRATES; TEMPERATURE RANGE 0273-0400 K; TEMPERATURE RANGE 0400-1000 K; THIN FILMS

Citation Formats

Knox-Davies, E C, Shannon, J M, and Silva, S R. P. The properties and deposition process of GaN films grown by reactive sputtering at low temperatures. United States: N. p., 2006. Web. doi:10.1063/1.2186380.
Knox-Davies, E C, Shannon, J M, & Silva, S R. P. The properties and deposition process of GaN films grown by reactive sputtering at low temperatures. United States. https://doi.org/10.1063/1.2186380
Knox-Davies, E C, Shannon, J M, and Silva, S R. P. Sat . "The properties and deposition process of GaN films grown by reactive sputtering at low temperatures". United States. https://doi.org/10.1063/1.2186380.
@article{osti_20788015,
title = {The properties and deposition process of GaN films grown by reactive sputtering at low temperatures},
author = {Knox-Davies, E C and Shannon, J M and Silva, S R. P.},
abstractNote = {Polycrystalline gallium nitride films, 100 nm to 1 {mu}m thick, were deposited under a range of conditions. Substrate electrode temperatures during sputtering were varied from room temperature to 450 deg. C, the pressure from 0.15 to 6.0 Pa, the nitrogen fraction of the deposition atmosphere from 10% to 100% and the target bias from -400 to -1800 V. The deposition rates as functions of these conditions are in the range 0.5-25 nm/min. The growth rate is considered to be controlled respectively by the thermally activated desorption from the substrate, changes in the mean free path and concentration of gas particles, differences between the sputter yields of Ga and GaN in Ar and N{sub 2}, and changes in the ion current and sputter yields. The films are generally columnar, with the grain size increasing with film thickness. The most crystalline films were grown at mid range temperatures, low N{sub 2} concentrations, and low target biases, and the most disordered were grown at low pressures. The latter two cases suggest that decreasing the energy of particles incident on the film during deposition results in a more ordered film. The biaxial stress is compressive and shows an increasing trend with the target bias and N{sub 2} concentration, reaching 4.7 GPa at 75% N{sub 2}. Oxygen contamination of 3-30 at. % has a major effect on the optical properties of the films, increasing the band gap values from 3.02 to >4.0 eV and the Urbach tail energies from around 150 to 840 meV and decreasing the refractive index from 2.46 to 2.03. At a 40% N{sub 2} deposition fraction, the N:Ga ratio is more or less constant at 1:1. Since the absolute oxygen incorporation rate changes very little, it is the relative film deposition rate which determines the final oxygen concentration. Excess Ga at low N{sub 2} concentrations causes a decrease in the band gap and an increase in the Urbach tail energy.},
doi = {10.1063/1.2186380},
url = {https://www.osti.gov/biblio/20788015}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 7,
volume = 99,
place = {United States},
year = {2006},
month = {4}
}