A high-resolution non-destructive optical technique (laser beam-induced current) was developed for the spatial imaging of electrically active defects in liquid-phase epitaxial material. The technique consisted of mapping the induced current, between 2 remote contacts on a sample, as a function of the incident focused laser beam position. The induced current was a result of the charge-separating effect of built-in fields in the vicinity of defects. The low laser power which was used did not damage the sample, and the resolution of the technique was limited by the diffusion length of the carriers in the material. Also, since device structures such as p-n junctions were special cases of electrically active regions, laser beam-induced current imaging could be used to study the opto-electronic properties of these structures in a non-destructive manner; without requiring any electrical contact to be made to the active elements. The method was also used to study electrical non-uniformities at CdHgTe interfaces with a ZnS passivation layer.

J.Bajaj, W.E.Tennant: Journal of Crystal Growth, 1990, 103[1-4], 170-8