Electron and Hole Photoemission Detection for Band Offset Determination of Tunnel Field-Effect Transistor Heterojunctions

TL;DR

This paper introduces an experimental method using graphene-enhanced internal photoemission to accurately measure band offsets at InAs/GaSb heterojunctions, crucial for optimizing tunnel FET performance.

Contribution

It presents a novel approach to determine complete energy band alignment at heterojunctions using optical photoemission with graphene as a transparent electrode.

Findings

Quantified electron and hole barrier heights at InAs/GaSb interface.

Extracted band offset parameters critical for device modeling.

Facilitated improved understanding of tunneling efficiency in TFETs.

Abstract

The electrical performance of a tunnel field-effect transistor depends critically on the band offset at their semiconductor heterojunction interface. Historically, it has been difficult to experimentally determine how the electronic bands align at the heterojunction interface. We report here on experimental methods to ascertain a complete energy band alignment of a broken-gap tunnel field-effect transistor based on an InAs/GaSb hetero-junction. By using graphene as an optically transparent electrode in a traditional internal photoemission measurement, both the electron and hole barrier heights at the InAs/GaSb interface can be quantified. For a Al2O3/InAs/GaSb layer structure, the barrier height from the top of InAs and GaSb valence band to the bottom of Al2O3 conduction band is inferred from electron emission whereas hole emissions reveal the barrier height from the top of Al2O3 valence band to the bottom of InAs and GaSb conduction band. Subsequently, the offset parameter at the broken gap InAs/GaSb interface is extracted and thus can be used to facilitate the development of predicted model of electron quantum tunneling efficiency and transistor performance.