HIGH-RESOLUTION RESISTIVITY MAPPING OF BULK SEMIINSULATING GAAS BY POINT-CONTACT TECHNIQUE

Electrical non-uniformities connected with the cellular structure of d islocations have been investigated by high-resolution point-contact me asurements both in liquid encapsulated Czochralski (LEC)-grown and in vertical gradient freeze (VGF)-grown GaAs. Comparing maps of point-con tact current with those of the photoluminescence intensity, in most ca ses good agreement was observed. The reason for this correlation with regard to relevant defect levels is discussed. Improvements in the hom ogeneity of semi-insulating GaAs wafers by different ingot-annealing p rocesses are clearly proved by the point-contact technique. (C) 1997 E lsevier Science S.A.