Electrical and EBIC Investigations of GaP Grain Boundaries

From polycrystalline GaP grown by the SSD method or by the pressure synthesis samples are prepared which contain single large-angle grain boundaries. I-U and C–U characteristics are measured across the grain boundaries and compared with EBIC investigations performed on the same specimen using the barriers of the grain boundary itself for charge collection. Electrical measurements refer to symmetric and asymmetric grain boundaries, whereas the EBIC picture shows an asymmetry also for electrically symmetric grain boundaries due to a strong dependence of the EBIC contrast on differences of the barrier heights not detectable by these electrical measurements. A model is proposed which enables quantitatively to calculate the EBIC current across the grain boundary also with applied bias voltages. The investigated grain boundaries show often local inhomogeneities.