New Aspects of (Semi-Insulating) GaP:Cu

C. Eder¹, V. Schlosser¹, R.P. Leon², K.M. Yu³, E.R. Weber^2,3

1. Institut für Festkörperphysik, Universität Wien, Strudlhofg. 4, A-1090 Wien and
   Ludwig Boltzmann Institut für Festkörperphysik, Kopernikusg. 15, A-1060 Wien, Austria.

2. Department of Materials Science, University of California, Berkeley, CA 94720, USA

3. Materials Science Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA

Keywords: GaP, Copper, Semi-insulating, Precipitates, Mobility

ABSTRACT
Experiments were performed to investigate the possible relevance of the buried Schottky contact model for the complex behavior of Cu in GaP. PIXE studies show that Cu can reach very high concentrations in that material. Channeling indicates that a part of the Cu forms precipitates. Hall measurements on sets of samples were made to examine the electrical transport coefficients. The mobilities of the samples with the most abundant concentration of Cu were found to be dominated by a term ∝ T ^-0.5 which was identified as a component induced by metallic spikes with non-overlapping depletion zones. We come to the conclusion that Cu introduces an acceptor like defect as well as precipitates. For high initial carrier concentrations, however, the depletion widths are probably too small for the buried Schottky contact model to apply. For doping concentrations lower than 5×10¹⁶cm^-3 the model might be of considerable relevance.