Photoluminescence properties of ZnO single crystals with polar and non-polar faces

Photoluminescence (PL) was circumstantially measured for ZnO single crystals with polar and non-polar faces. PL spectra of ZnO single crystals depended on the sector and polarity of ZnO single crystals. Emissions due to excitons from c -plane substrates sliced from the +c sector were strong, and FWHMs of the emissions were smaller than those from substrates sliced from the –c sector. An emission due to neutral-donor-bound exicitons (D⁰X) at 3.361 eV was dominantly observed on all surfaces of ZnO single crystals, and an emission due to ionized-donor-bound excitons (D⁺X) around 3.366 eV was observed on the O-face but not on the Zn-face at 4.2 K. It is thought that surface state densities due to oxygen caused this difference in PL emission for polarity of ZnO. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)