Hetero-epitaxy of epsilon-Ga2O3 layers by MOCVD and ALD

Growth of gallium oxide thin films was carried out by Metalorganic Chemical Vapor Deposition (MOCVD) at different temperatures. Pure epsilon-phase epilayers of Ga2O3, with good morphology and structural properties, were obtained, for the first time with this technique, on sapphire at the temperature of 650 degrees C. XRD analysis performed by high-resolution diffractometry confirmed the good crystallographic quality of the grown layers. At temperatures higher than 700 degrees C the usual stable beta-Ga2O3 phase was obtained. The epsilon-films were successfully deposited also on (0001)-oriented GaN and (111)- and (001)-oriented 3C-SiC templates, provided that the appropriate temperature was chosen. This indicates that the temperature, rather than substrate structure, is the growth parameter which decides what phase actually forms. The growth proceeds via coalescence of hexagonal islands and is favored when a substrate with an in-plane hexagonal arrangement of the atoms is employed. By applying Atomic Layer Deposition (ALD), epitaxial growth of the e-phase was achieved at lower temperature, while the overall uniformity resulted improved, even on large sapphire substrates. (C) 2016 Elsevier B.V. All rights reserved.