"Tunnel transistors are currently considered promising candidates for future low-power high performance information processing applications. The proposed project TETTRA – Towards Enhanced III-V Tunnel TRAnsistors – is dedicated to the fabrication and characterization of III-V nanowire tunnel field-effect transistors (FETs). III-V semiconductor heterostructure nanowires, grown on Si substrates by means of the selective-area-epitaxy method, serve as basis for the tunnel FETs. The project concentrates on n-type tunnel FETs and furthermore focuses on one specific realization with regard to the choice of materials involved; i.e. n-type tunnel FETs consisting of a p-type GaSb source, an InxGa1-xAs channel, and an n-type InAs drain. This sequence of III-V materials is grown in the form of vertical heterostructure nanowires directly on silicon substrates, with InAs being in contact with the substrate and GaSb forming the nanowire tip. The heterostructure nanowires are then processes into vertical, gate-all-around tunnel FETs. The fabrication of the nanowire heterostructure and the processing of the III-V nanowire tunnel represent one of two main objectives of the project. Investigations on the growth of GaSb on InxGa1-xAs, on the p-doping of GaSb, and on metal contacts to GaSb are preceding the tunnel FET fabrication. The second objective of the project comprises the electrical characterization of the nanowire-oxide interface properties and the electrical characterization of III-V tunnel FETs. For characterizing the nanowire-oxide interface properties two independent techniques will be employed: capacitance-voltage measurements and the charge-pumping technique. Both deliver the interface trap level density, Dit, and both have been demonstrated to be applicable to single nanowire capacitors and FETs, respectively. Characterization is complemented by detailed investigations of the electrical properties of the III-V nanowire tunnel FETs."
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