Theory and experiments on open circuit voltage decay of p-n junction diodes with arbitrary base width, including the effects of built-in drift field in the base and recombinations in the emitter

Abstract

An expression for the forward current induced open circuit voltage decay of a p-n junction diode with a finite base width is derived. The expression includes the effects of recombination in the emitter and the built-in drift field in the base which may arise due to a nonuniform impurity profile. The voltage decay rate is dependent on the base thickness, base drift field, emitter dark saturation current, the effective surface recombination velocity at the back contact, and the minority carrier lifetime in the base. The effects of the drift field in the emitter, emitter lifetime, and surface recombination velocity at the emitter surface are completely taken into account by the emitter saturation current. Experimentally observed voltage decay plots for thin base hyperabrupt varactor diodes with retrograded impurity gradients in the base are reported. It is shown that the experimental results can be interpreted satisfactorily using the above theory. The values of the minority-carrier lifetime in the base are determined from the experimental results.