A study was made of the electrical activity of threading dislocation defects, in relaxed films, by using a near-field scanning optical microscope to measure the spatially resolved photo-response while simultaneously imaging the surface topography. It was clearly established that shallow topographic depressions in these films were electrically active threading dislocations. The apparent sizes of dislocations in the photo-voltage images agreed with estimates that were based upon the junction geometry and the near-field optical excitation spot size. Photo-response changes were clearly observed at a linear scale of less than 100nm. This was a 10-fold improvement over far-field optical techniques. The higher resolution was due to a reduction in excitation volume and carrier lifetime near to defects.

J.W.P.Hsu, E.A.Fitzgerald, Y.H.Xie, P.J.Silverman: Journal of Applied Physics, 1996, 79[10], 7743-50