Monolithic growth of ultra-thin Ge nanowires on Si(001)

TL;DR

This paper reports the monolithic growth of ultra-thin, self-assembled germanium nanowires on silicon, demonstrating their potential for advanced nanoelectronic applications due to their uniformity and electrical properties.

Contribution

It introduces a catalyst-free molecular beam epitaxy method for growing ultra-thin Ge nanowires with controlled dimensions and explores their electrical characteristics for nanoelectronics.

Findings

Nanowires are only 3 unit cells high and up to 2 micrometers long.

The wires grow along [100] or [010] directions with uniform triangular cross sections.

First transistor devices show low-resistance contacts and single-hole transport.

Abstract

Self-assembled Ge wires with a height of only 3 unit cells and a length of up to 2 micrometers were grown on Si(001) by means of a catalyst-free method based on molecular beam epitaxy. The wires grow horizontally along either the [100] or the [010] direction. On atomically flat surfaces, they exhibit a highly uniform, triangular cross section. A simple thermodynamic model accounts for the existence of a preferential base width for longitudinal expansion, in quantitative agreement with the experimental findings. Despite the absence of intentional doping, first transistor-type devices made from single wires show low-resistive electrical contacts and single hole transport at sub-Kelvin temperatures. In view of their exceptionally small and self-defined cross section, these Ge wires hold promise for the realization of hole systems with exotic properties and provide a new development route for silicon-based nanoelectronics.