On the current-voltage characteristics of n+-p-p+diodes

The characteristics of n⁺-p-p⁺diodes are analyzed based on the assumption of negligible recombination in the lowly-doped base. The analysis represents a generalization of the approach used by Mertens et al. [1] for high-injection conditions and is valid for all injection levels. Two coupled nonlinear equations from which the characteristics can be calculated are derived. It is shown that under high-injection conditions the equations reduce to those by Mertens et al. For low-injection conditions the electron current density Jnand hole current density Jpare decoupled and single equations are obtained for Jnand Jp, respectively. For the case where the back side contact approaches an ohmic contact, the classical equation for a short-base diode results. The analysis is justified by very close correspondence with exact numerical calculations using the Finite Element Device Analysis Program (FIELDAY).