Growth of high-quality GaN by low-pressure metal-organic vapour phase epitaxy (LP-MOVPE) from 3D islands and lateral overgrowth

In this work, we present a novel growth method to obtain high structural qu ality GaN films on sapphire by low-pressure metal-organic vapour phase epit axy (LP-MOVPE). Our purpose is to achieve epitaxy by lateral overgrowth (EL O) starting from self-organised islands on a GaN layer. Classical ELO is ca rried out by coalescence of the crystal grown selectively through striped w indows opened into a dielectric mask. This classical process implies the de position and the etching of the mask (commonly SiO2 or SixNy.). The use of self-organised islands enables to suppress these two technological steps. S uch islands are obtained after a growth mode change induced by silicon as c hemical impurity. They present {1 (1) over bar 0 1} lateral facets and a to p {0 0 0 1} facet. Their densities and sizes depend on the silicon treatmen t and the growth temperature and can be controlled by these two factors. An overgrowth of optimised islands leads to a drastic improvement of the mate rial quality. The defect analysis reveals the presence of only threading di slocations, with a density of 5 x 10(8) and 9 x 10(8) cm(-2) compared to 10 (10) cm(-2) for classical layers. (C) 1999 Elsevier Science B.V. Al rights reserved.