Summary
In this work we report on the formation, of copper-germanide/germanium nanowire (NW) heterostructures with atomically sharp interfaces. The copper-germanide (Cu3Ge) formation process is enabled by a chemical reaction between metallic Cu pads and vapor-liquid-solid (VLS) grown Ge-NWs. The atomic scale aligned formation of the Cu3Ge segments is controlled by in situ SEM monitoring at 310 °C thereby enabling length control of the intrinsic Ge-NW down to a few nm. The single crystal Cu3Ge/Ge/Cu3Ge heterostructures were used to fabricate Ω-gated Ge-NW field effect transistors with Schottky Cu3Ge source/drain contacts. Temperature dependent I/V measurements revealed the metallic properties of the Cu3Ge contacts with a maximum current carrier density of 5 × 107 A/cm2. Prior to the gate deposition the intrinsic Ge-NW was modified with a focussed Ga+ ion beam. According to the thermoionic emission theory we determined an effective Schottky barrier height reduction from 218 meV to about 115 meV due to Ga+ implantation.