Electron and hole photoemission detection for band offset determination of tunnel field-effect transistor heterojunctions

We report 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, 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 the InAs and GaSb valence bands to the bottom of the Al2O3 conduction band is inferred from electron emission whereas hole emissions reveal the barrier height from the top of the Al2O3 valence band to the bottom of the InAs and GaSb conduction bands. Subsequently, the offset parameter at the broken gap InAs/GaSb interface is extracted and thus can be used to facilitate the development of predicted models of electron quantum tunneling efficiency and transistor performance. (c) 2014 AIP Publishing LLC.