Gate-Tunable Electron Transport Phenomena in Al-Ge111>-Al Nanowire Heterostructures

• Published in: Nano letters Vol. 15; no. 11; pp. 7514 - 7518
• Main Authors: Brunbauer, Florian M, Bertagnolli, Emmerich, Lugstein, Alois
• Format: Journal Article
• Language: English
• Published: 11-11-2015
• Subjects: Aluminum; Electric fields; Field effect transistors; Heterostructures; Ionization; Nanostructure; Nanowires; Semiconductor devices
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.5b03169

Electrostatically tunable negative differential resistance (NDR) is demonstrated in monolithic metal-semiconductor-metal (Al-Ge-Al) nanowire (NW) heterostructures integrated in back-gated field-effect transistors (FETs). Unambiguous signatures of NDR even at room temperature are attributed to intervalley electron transfer. At yet higher electric fields, impact ionization leads to an exponential increase of the current in the 111> oriented Ge NW segments. Modulation of the transfer rates, manifested as a large tunability of the peak-to-valley ratio (PVR) and the onset of impact ionization is achieved by the combined influences of electrostatic gating, geometric confinement, and heterojunction shape on hot electron transfer and by electron-electron scattering rates that can be altered by varying the charge carrier concentration in the NW FETs. Keywords: nanowire; heterostructure; negative differential resistance; impact ionization; gate-tunable; germanium