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

TL;DR

This study investigates the electronic properties of c-Si/porous silicon heterojunctions, revealing Schottky-like behavior and band offset characteristics through temperature-dependent I-V measurements.

Contribution

It provides a detailed analysis of carrier transport mechanisms and proposes an energy band diagram for c-Si/porous silicon heterojunctions, highlighting the role of defect levels and band offsets.

Findings

Reverse bias I-V behaves like Schottky junctions

Fermi level pinning due to interface defect levels

Barrier height equals conduction band offset

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.