Epitaxial growth of GaN thin films on sapphire (0001) by pulsed laser deposition: influence of surface preparation and nitridation

Thin epilayers of GaN have been grown on Al2O3(0001) substrates using a pulsed laser deposition technique. The morphology and crystallinity of the GaN films deposited on pre-nitridated substrates have been controlled by AFM, RHEED and XRD. The purpose of this study was to get a better understanding of the nitridation procedure and of the initial growth stages in order to obtain a reproducible film quality. From these observations, it is seen that the hexagonal GaN epilayers are grown in a 3D mode on some monolayers of 2D-cubic GaN, on top of cubic AlN formed by nitridation.