It was noted that an emission band at 3.31eV was frequently observed in lowtemperature

photoluminescence measurements of ZnO which was p-doped with

group-V elements, and also in nominally undoped ZnO layers and nanostructures.

It was also alternatively attributed to LO- or TO-phonon replicas of free excitons,

to acceptor-bound excitons, to donor–acceptor pair transitions, to two-electron

satellites of donor-bound excitons or to free-to-bound transitions. This band

frequently dominated the photoluminescence of ZnO nanostructures and layers at

room temperature. Annealing led to drastic changes in its intensity. Lowtemperature

cathodoluminescence measurements of very high spatial resolution

and high-resolution transmission electron microscopic investigations were carried

out on the same pieces of hetero-epitaxial ZnO sample with an unusual layer

orientation. The data permitted an unambiguous correlation of this emission with cplane

stacking faults. The emission was found to be due to the recombination of a

free electron with a hole bound to a relatively shallow acceptor state some 130meV

above the valence band edge. Locally, these acceptor states occurred in

concentrations of up to 1018/cm3, and thus led to strong two-dimensional

perturbations of the free carrier concentration. They had severe implications for the conductivity of layers and nanostructures in general, and for the interpretation of

Hall and luminescence data in particular.

The Role of Stacking Faults and Their Associated 0.13eV Acceptor State in Doped

and Undoped ZnO Layers and Nanostructures. K.Thonke, M.Schirra, R.Schneider,

A.Reiser, G.M.Prinz, M.Feneberg, J.Biskupek, U.Kaiser, R.Sauer:

Microelectronics Journal, 2009, 40[2], 210-4