Cathodoluminescence microscopy of hydrothermal and flux grown ZnOsingle crystals

Abstract

Bulk ZnO single crystals grown by the hydrothermal and flux methodshave been characterized by steady-state and time resolved cathodoluminescencemeasurements performed on the different crystalline faces. A shift of thepeak near band edge towards lower energies is observed in spectrarecorded with increasing delay times. This behaviour is often observed in theetch pit regions in alkali flux grown crystals, which suggests the presence ofa band related to dislocations or to the point defects surrounding thedislocations. In the low-energy region, cathodoluminescence spectra show thatthe relative intensity of the different components of the deep level band alsodepends on the atomic structure of the face under study. This complexbehaviour is clearly revealed from the time resolved spectra. The differencesobserved are attributed to the nature of the defects present in each face and,in particular, to different impurity incorporation processes that could bemainly controlled by the atomic configuration and polarity of the planes.