Cathodoluminescence characteristics of InGaN/GaN quantum wells grown by MOCVD

Phase separation and In segregation in InGaN/GaN quantum wells (QWs) grown by metalorganic chemical vapor deposition (MOCVD) were studied by cathodoluminescence (CL) imaging and spectroscopy. The spatial homogeneity of optical properties in InGan/GaN QW was studied. It is found that the CL images taken at different wavelengths show very little difference for the In-low QW, while some parts are complementary for the In-low QW. This result strongly suggests that the additional intensity fluctuation which appears with increasing indium composition is due to phase separation in the InGaN layers. Especially, In0.16Ga0.84N quantum wells with In compositional non-uniformity and a small number of structural defects originating at the InGaN/GaN interface showed sharp and intense InGaN emission in CL spectroscopy. Increasing the In composition caused surface roughness in the InGaN layer and the formation of stacking faults/dislocations originating at InGaN/GaN interface. This resulted in a reduction of the InGaN emission peak intensity. (C) 2001 Elsevier Science B.V. All rights reserved.