Band edge discontinuities and carrier transport in c-Si/porous silicon heterojunctions

Abstract

We have prepared light emitting nanocrystalline porous silicon (PS) layers by electrochemical anodization of crystalline silicon (c-Si) wafer and characterized the c-Si/PS heterojunctions using temperature dependence of dark current-voltage (I-V) characteristics. The reverse bias I-V characteristics of c-Si/PS heterojunctions are found to behave like Schottky junctions where carrier transport is mainly governed by the carrier generation-recombination in the depletion region formed on the PS side. Fermi level of c-Si gets pinned to the defect levels at the interface resulting in ln(I) proportional to V^0.5. The barrier height in the reverse bias condition is shown to be equal to the band offset at the conduction band edges. An energy band diagram for the c-Si/PS heterojunction is proposed.