Low Temperature Nitridation Combined With High Temperature Buffer Annealing for High Quality GaN Grown by Plasma-Assisted MBE
Gon Namkoong, W. Alan Doolittle, Sangbeom Kang, Huang Sa, April S. Brown
Georgia Institute of Technology, School of Electrical and Computer Engineering
Stuart R. Stock
Georgia Institute of Technology, Materials Science and Engineering
This article was received on Friday, September 22, 2000 and
accepted on Monday, November 6, 2000. Abstract
The
effect of the initial nitridation of the sapphire substrate on the GaN crystal
quality as a function of substrate temperature was studied. GaN layers were
grown by plasma-assisted molecular beam epitaxy (MBE) on sapphire substrates
nitridated at different substrate temperatures. A strong improvement in the GaN
crystal quality was observed at 100 °C nitridation temperature.
Symmetric (0004) and asymmetric (10-5) full widths at half maximum (FWHM) of
the x-ray rocking curves were 136 and 261 arcsec, respectively. This compares
to an x-ray rocking curve full width at half maximum of 818 arcsec (0004) for
conventional MBE buffer conditions. For our conventional buffer conditions,
sapphire substrates were exposed to a N plasma at temperatures above 500
°C for 10min and then 25~50nm buffers were deposited without annealing
at high temperature. The low temperature nitridation also shows an enhancement
of the lateral growth of the GaN, resulting in larger grain sizes. The largest
grain size achieved was approximately 2.8µm, while the average grain size
was approximately 2.4µm at 100 °C nitridation temperature.
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 5, 10(2000).
last updated Monday, November 6, 2000 5:02:05 PM.© 2000 The Materials Research Society
