Use of optical scattering to characterize dislocations in semiconductors

Optical scattering from a defect-etched semiconductor sample is used to characterize dislocations in the material. It is shown that when the sample is illuminated normally with a He-Ne (lambda = 6328-A) laser beam the reflection pattern can be used to identify the shapes of the etch pits and hence the directions of the dislocation propagation. The integrated light flux scattered by the illuminated sample, normalized by the incident flux, is shown to be proportional to the dislocation density. This principle is applied in two ways to count dislocations at the sample surface. In one case the defect-etched sample is scanned under a light beam, and the scattered flux is collected by an integrating sphere and measured. In the second case the defect-etched sample is illuminated with incoherent light of a broad angular spectrum, and a photographic transparency is produced which registers an image of the dislocation density distribution of the original sample. These two methods for counting dislocations, mapping dislocation distribution, and measuring average dislocation density of the sample are discussed.