Visual indication of locally varying photoconductivity

The paper deals with the visual indication of a locally varying carrier density or photoconductivity, which is optically generated within a semiconductor substrate and extends over a distance of some millimetres up to some tens of millimetres. The induced profile is conventionally displayed on a CRT using a special substrate-edge excited microstrip device that works as the sensing element. The technique can be adapted to CW or pulse excitation, and allows an immediate study of absorption and diffusion effects under varying excitation conditions.