Nitridation process of sapphire substrate surface and its effect on the growth of GaN
- 1 April 1996
- journal article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 79 (7) , 3487-3491
- https://doi.org/10.1063/1.361398
Abstract
The nitridated layer formed on a (0001) sapphire (α‐Al2O3) substrate surface by heating at 1050 °C in ammonia (NH3) gas was analyzed by x‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), transmission electron microscope (TEM) and energy dispersive x‐ray spectrometry (EDX). Their influence on the growth of GaN in the combined usage of initial nitridation and successive deposition of a buffer layer was examined by AFM observations. The intensity of the N1s nitrogen peak in the XPS rapidly increased with nitridation time, reaching saturation in a few minutes, and then continued to increase gradually. This change was found to correspond to morphological change revealed by AFM observations, that is, from a flat nitridated layer to high‐density (109–1010 cm−2) nitridated protrusions. TEM observations and EDX measurements showed that the nitridation forms an amorphous layer consisting of AlNxO1−x. The flat nitridated layer, when combined with a buffer layer, favors two‐dimensional growth of a thick GaN layer on it, while the layer with protrusions results in three‐dimensional growth. Thus, thick GaN layers with smooth surfaces can be grown by controlling the surface of the nitridated layer, where a crystal‐amorphous‐crystal growth mechanism is successfully operating.This publication has 16 references indexed in Scilit:
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