Cathodoluminescence microscopy of hydrothermal and flux grown ZnO single crystals

Abstract

Bulk ZnO single crystals grown by the hydrothermal and flux methods have been characterized by steady-state and time resolved cathodoluminescence measurements performed on the different crystalline faces. A shift of the peak near band edge towards lower energies is observed in spectra recorded with increasing delay times. This behaviour is often observed in the etch pit regions in alkali flux grown crystals, which suggests the presence of a band related to dislocations or to the point defects surrounding the dislocations. In the low-energy region, cathodoluminescence spectra show that the relative intensity of the different components of the deep level band also depends on the atomic structure of the face under study. This complex behaviour is clearly revealed from the time resolved spectra. The differences observed are attributed to the nature of the defects present in each face and, in particular, to different impurity incorporation processes that could be mainly controlled by the atomic configuration and polarity of the planes.

Correlation between Zn vacancies and photoluminescence emission in ZnO films

“…Meyer et al 13 concluded that a sharp line of excitonic character at around 3.333 eV found in bulk ZnO shows most of the established features of Y recombination line commonly seen in ZnSe and ZnTe ͑exciton bound to dislocations and other extended structural defects͒. Urbieta et al 24 observed in bulk ZnO samples an emission at 3.1 eV by cathodoluminescence and they concluded that it was related to dislocations.…”

Mobile donors in undoped ZnO

“…Decoration of dislocations with defects influences optical and luminescent characteristics of near-dislocations regions [16,17]. In particular, accumulation of shallow donors at dislocations was proved to result in the shift of optical absorption edge to the long wavelength side and distortion of edge luminescence spectrum in CdS [19].…”

Time-resolved cathodoluminescence and photocurrent study of the yellow band in Si-doped GaN

“…To record CL spectra at different delay times, the signal from a photomultiplier was collected by a boxcar integrator ͑PAR162͒ triggered by the pulse generator, and then fed to a computer ͑see Ref. 20 for further details͒. The time resolution of the TRCL setup is about 100 ns, while the spectral resolution is 2 nm.…”