Intrinsic Gaps in the Classical Theory of p-n Junctions

Abstract

The classical analytical theory of p-n junctions successfully describes minority-carrier injection and predicts the ideal diode characteristic, but its conventional reduced formulation leaves the connection between internal transport and terminal response incompletely resolved. This paper critically examines five interrelated gaps in that formulation: the electrostatic justification of charge quasi-neutrality, the determination of the quasi-neutral-region electric field, the explicit treatment of majority-carrier transport, the spatial reconciliation of electron and hole currents, and the evaluation of terminal current from the resolved local transport. A review of representative foundational, textbook, and research treatments distinguishes recognition of individual issues from their integration into a self-consistent analytical description. The central finding is that these gaps constitute a common analytical closure problem: carrier densities, the internal field, and current partition must be determined consistently rather than treated as separate elements. This diagnosis concerns the reduced analytical description, not the validity of the underlying drift-diffusion equations or charge conservation. A two-carrier framework is outlined in which electrostatic consistency, coupled transport, and junction-edge and contact conditions connect local current balance to terminal response. The objective is to preserve the classical diode equation within its established domain while making its physical basis and approximation limits explicit.