Cathodoluminescence studies of in-plane and in-depth properties of GaN epilayers

The influence of sample morphology on optical properties of GaN epilayers i s studied. We show that a granular/columnar structure of MOCVD- and MBE-gro wn films results in strong planar fluctuations of the "edge" emission of Ga N,which is strongly deactivated at grain boundaries. In contrast, the yello w emission of GaN is relatively in-plane homogeneous. We further show large in-depth inhomogeneity of GaN samples and discuss a possible origin of in- plane homogeneity of the yellow photoluminescence. (C) 2000 Elsevier Scienc e B.V. All rights reserved.