Dislocations located in the space charge region of a Schottky diode are recombination centers for electron hole pairs. We assume that minority carriers created within a region where the dislocation electrical field is larger than the Schottky field are recombined at the dislocation line. Therefore, a capture cylinder radius can be defined by the criterium Quantitative values of the EBIC contrast have been calculated on this assumption. We only deal with electrical fields associated with the

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... ged line of the dislocation. The screening charge, solution of the Poisson's equation, is numerically calculated. The radius of the cylinder, which is selfconsistently calculated, depends on the doping level of the specimen, on temperature, electron beam intensity and on dislocation characteristics: its capture crosssection and its energy level position in the band gap. The numerical values and their dependences with beam intensity are compared with experimental values obtained on a and P dislocations freshly introduced in a bulk n type (N a = 5.10 16 cm -3 ) GaAs specimen. In order to localize the generation of electron hole pairs within the SCR of the Schottky diode, an accelerating voltage of 8 kV and an applied reverse bias of 1.5 V have been used. The numerical EBIC values are similar to the experimental ones (2-3%) when the influence of the electron beam intensity is not taken into account ( figure 1 and table 1 ). Article published online by EDP Sciences and available at http://dx.