High-resolution resistivity mapping of bulk semi-insulating GaAs by point-contact technique

Electrical non-uniformities connected wih the cellular structure of dislocations have been investigated by high-resolution point-contact measurements both in liquid encapsulated Czochralski (LEC)-grown and in vertical gradient freeze (VGF)-grown GaAs. Comparing maps of point-contact current with those of the photoluminescence intensity, in most cases good agreement was observed. The reason for this correlation with regard to relevant defect levels is discussed. Improvements in the homogeneity of semi-insulating GaAs wafers by different ingot-annealing processes are clearly proved by the point-contact technique.