Power-law transient leakage in Czochralski silicon pn-junctions: Dispersive transport induced by exponential trap distributions

Abstract

We propose an analytical model for the power-law transient leakage current observed in pn-junctions fabricated in Czochralski silicon (Cz-Si). The model assumes an exponential distribution of trap states within the bandgap, attributed to oxygen-related defects. The transient current is analyzed within the framework of the multiple-trapping model of dispersive transport, originally developed for disordered semiconductors. Carrier populations in the conduction band, shallow traps, and deeply frozen traps are evaluated using the density of states and Fermi–Dirac statistics. The power-law decay of the leakage current is derived as a drift-limited hole current in the neutral region, where carriers previously swept out from the junction are transported with an effective drift mobility governed by the evolving quasi-Fermi level within the exponential trap distribution. The model provides a unified physical interpretation of the observed power-law behavior, suggesting that the exponential trap distribution may originate from interfacial states, band-tail states, or border traps associated with oxygen aggregation.