Eur. Phys. J. B (2013) 86: 50
https://doi.org/10.1140/epjb/e2012-30502-7

Regular Article

Enhancement effects on excitonic photoluminescence intensity originating from misaligned crystal blocks and polycrystalline grains in a ZnO wafer^*

Department of Electronic Systems Engineering, School of Engineering, The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, 522-8533 Shiga, Japan

^a e-mail: takeuchi.h@e.usp.ac.jp

Received: 25 June 2012
Received in final form: 27 September 2012
Published online: 11 February 2013

Abstract

We have systematically investigated a relation between excitonic photoluminescence intensity and crystal quality in a (0001)-oriented ZnO wafer. We visualize the crystal quality of a whole wafer using a circular polariscopic measurement and a reflection-type X-ray topograph measurement. The reflection-type X-ray topograph exhibits regions of grain-like patterns that result from internal strains. The circular polariscopic map shows that the internal strains induce local stresses. The θ-2θ X-ray diffraction pattern indicates the presence of misaligned crystal blocks and polycrystalline grains. We have measured photoluminescence spectra and found that the presence of misaligned crystal blocks and polycrystalline grains leads to enhancement of the excitonic photoluminescence intensity. The present phenomenon is attributed to the suppression of exciton diffusion caused by the grain and domain boundaries that connect with the grain-like patterns in the X-ray topograph.