Current—Voltage characteristics of bulk semiconductors on impact ionization

A simple theoretical model based on the concept of impact ionization of carriers is worked out to represent the current-voltage characteristics of bulk semiconductors. The underlying idea is that the carriers start attaining velocity saturation and multiplying themselves soon after acquiring a minimum energy required for impact ionization. Consequently, in a certain region of the device the rate of decrease of resistance with the increase of carrier concentration becomes very high giving rise to negative resistance. The above model agrees fairly well with the experimental results.