ORIGIN OF CRACKS IN GAN ALGAN DH STRUCTURE GROWN ON 6H-SIC BY METALORGANIC VAPOR-PHASE EPITAXY/

Two types of cracks are observed in a cleaved facet of a GaN/Al0.1Ga0. 9N double-hetero (DH) structure grown on a (0 0 0 1)6H-SiC substrate b y low-pressure MOVPE. One type of crack starts from the interface betw een the substrate and the buffer layer (Type A). The other type starts from the interface between the n-AlGaN layer and the p-GaN layer (Typ e B).The Type A crack originates mainly due to the difference of the t hermal expansion coefficient between the epitaxial layer and the subst rate. The origin of the Type B crack appears to be in the hetero-inter face between the n-AlGaN layer and the p-GaN layer. It is important to control the hetero-interface conditions in order to reduce the Type B crack. (C) 1998 Elsevier Science B.V. All rights reserved.