Peripheral electron-beam induced current response of a shallow p-n junction

A theory is given for the response of a shallow p-n junction to a small spot of light or electrons that impinges near its periphery. This gives a basis for numerical analyses of a number of situations that are of practical interest. In particular, the results provide a method for determining minority-carrier diffusion lengths by scanning electron microscopy of the surfaces of devices. It is shown that the response of a shallow junction is quite different from that of the deep junction that has been considered in previous treatments. The response is influenced by reduction of the semiconductor thickness or of the junction dimensions to values less than the minority-carrier diffusion length and also by competition with adjacent junctions and by surface recombination. All of these effects are considered.