Hydride vapour phase epitaxy growth and characterisation of GaN layers

A vertical hydride vapour phase epitaxial reactor was applied for the growt h of GaN layers on (0001) sapphire. In this paper, the growth parameters an d the results of optical investigations are reported. It is seen that the l ayers grown at high temperature have better crystallographic properties tha n those grown at 600-800 degreesC, although the latter show a smoother surf ace. The absorption spect ra exhibited a tail from the absorption edge down to about 1 eV that may be fitted by the Lukovsky model considering the pre sence of a level at about 1.2 eV from the conduction band. The cathodolumin escence spectra show three main emissions: the yellow band, a blue band (BB ) centred at 2.8 eV and the near band edge recombination. The BE is mostly originated close to the layer/substrate interface and practically extinguis hed at the layer surface. It is seen that when the intensity of the BE incr eases that of the fundamental recombination decreases and vice versa. (C) 2 001 Elsevier Science B.V. All rights reserved.