Single-crystalline Ni2Ge/Ge/Ni2Ge nanowire heterostructure transistors

摘要

In this study, we report on the formation of a single-crystalline Ni _2Ge/Ge/Ni_2Ge nanowire heterostructure and its field effect characteristics by controlled reaction between a supercritical fluid-liquid-solid (SFLS) synthesized Ge nanowire and Ni metal contacts. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies reveal a wide temperature range to convert the Ge nanowire to single-crystalline Ni_2Ge by a thermal diffusion process. The maximum current density of the fully germanide Ni_2Ge nanowires exceeds 3.5 × 10~7 A cm~(-2), and the resistivity is about 88 μΩ cm. The in situ reaction examined by TEM shows atomically sharp interfaces for the Ni_2Ge/Ge/Ni_2Ge heterostructure. The interface epitaxial relationships are determined to be Ge[011?] || Ni _2Ge[01?1] and Ge(11?1?) || Ni_2Ge(100). Back-gate field effect transistors (FETs) were also fabricated using this low resistivity Ni_2Ge as source/drain contacts. Electrical measurements show a good p-type FET behavior with an on/off ratio over 10~3 and a one order of magnitude improvement in hole mobility from that of SFLS-synthesized Ge nanowire.