Identification of a Cubic Phase in Epitaxial Layers of Predominantly Hexagonal
GaN
U. Strauss, H. Tews, H. Riechert, R. Averbeck, M. Schienle, B. Jobst
Siemens AG, Corporate Research and Development
D. Volm, T. Streibl, BK Meyer
Physikdepartment, Technische Universitaet Muenchen
W. W. Rühle
Max-Planck-Institut für Festkörperforschung
This article was received on June 3, 1996 and
accepted on December 17, 1996. Abstract
Epitaxial layers of GaN on c-plane sapphire are analyzed by
continuous-wave and time-resolved photoluminescence at 4K and by X-ray
diffraction. Besides the well-known emissions from hexagonal GaN we observe
luminescence bands at 3.279 and 3.15 to 3.21 eV which are identified as the
transition of the donor bound exciton and the donor-acceptor pair recombination
in cubic GaN, respectively. Measurements of the luminescence decay times are
essential for the clarification of the emission processes. Due to the probing
depth of about 200 nm in PL we find that the fraction of cubic phase typically
decreases with layer thickness. In our best samples, however, we do not detect
the cubic phase at all.
