Graphene as Transparent Electrode for Direct Observation of Hole Photoemission from Silicon to Oxide

TL;DR

This paper demonstrates using graphene as a transparent electrode in internal photoemission spectroscopy to directly observe hole injection from silicon, enabling detailed band alignment and interface analysis.

Contribution

It introduces graphene as an effective collector electrode in IPE, allowing for direct hole injection observation and improved interface characterization.

Findings

Electron and hole barrier heights measured at 3.5 eV and 4.1 eV

Bandgap of Al2O3 deduced to be 6.5 eV

Enhanced carrier injection with minimal contribution from the collector electrode

Abstract

The outstanding electrical and optical properties of graphene make it an excellent alternative as a transparent electrode. Here we demonstrate the application of graphene as collector material in internal photoemission (IPE) spectroscopy; enabling the direct observation of both electron and hole injections at a Si/Al2O3 interface and successfully overcoming the long-standing difficulty of detecting holes injected from a semiconductor emitter in IPE measurements. The observed electron and hole barrier heights are 3.5 eV and 4.1 eV, respectively. Thus the bandgap of Al2O3 can be further deduced to be 6.5 eV, in close agreement with the valued obtained by vacuum ultraviolet spectroscopic ellipsometry analysis. The detailed optical modeling of a graphene/Al2O3/Si stack reveals that by using graphene in IPE measurements the carrier injection from the emitter is significantly enhanced and the contribution of carrier injection from the collector electrode is minimal. The method can be readily extended to various IPE test structures for a complete band alignment analysis and interface characterization.