ABSTRACT
The point-contact technique and its application for high resolution resistivity detection has been studied by I-V measurements and profiling of undoped GaAs wafers. At low bias (up to 0.2 V) the current is controlled by the probe-semiconductor barrier, according to the model of a Schottky diode, but at higher bias (1 V) the current is mainly limited by the bulk resistivity. Based on a calibration curve for the point-contact current the dislocation-related electrical non-uniformities and the improvement of homogeneity by annealing were detected quantitatively. In single-step annealed GaAs the resistivity p in cell interiors has been found nearly constant, whereas p in the cell walls varied in a wide range. This effect is connected with changes in the macroscopic electrical transport properties, especially with a significant lowering of the Hall mobility.
