Step-graded interlayers for the improvement of MOVPE InxGa1-xN (x ∝ 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 Inx Ga1-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 3 x 1010 cm-2 is obtained for a simple with 0.25 In composition, that seems to come from the GaN layer beneath the step-graded interlayers (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)