"Step-Graded Interlayers" For The Improvement Of Movpe Inxga1-Xn (X Similar To 0.4) Epi-Layer Quality

This paper reports the effect of step-graded interlayers on MOVPE InGaN epi-layer quality. Multilayer epitaxial structures consisting of InxGa1-xN layers with various compositions have been successfully grown. HRXRD measurements reveal that the insertion of step-graded interlayers significantly reduces the twist while little effects are observed on tilt. Decreasing of twist with increasing the number of interlayers is found to be remarkable up to a certain value and then maintain nearly the same even with increasing the In composition. Different types of dislocation density have also been studied using the X-ray diffraction analysis. Dislocation densities, particularly the edge dislocation density, decrease considerably with the insertion of interlayers for higher In composition. An edge dislocation of 3x10(10) cm(-2) is obtained for a smple with 0.25 In composition, that seems to come from the GaN layer beneath the step-graded interlayers. (c) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim