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

Abstract

We have prepared light emitting nanocrystallline 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 the 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) ∝ V1/2. 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.