期刊
ACS NANO
卷 5, 期 7, 页码 6008-6015出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn2017777
关键词
germanium nanowire heterostructure; oxide confinement; nickel germanide; atomically sharp interface; field-effect transistor
类别
资金
- Western Institution of Nanoelectronics (WIN)
- Focus Center on Functional Engineered Nano Architectonics (FENA)
- National Science Council [NSC 98-2221-E-007-104-MY3]
Over the past several years, the formation of nanowire heterostructures via a solid-state reaction between a semiconductor nanowire and metal contact pads has attracted great interest. This is owing to its ready application in nanowire field-effect transistors (FETs) with a well-controlled channel length using a facile rapid thermal annealing process. We report the effect of oxide confinement on the formation of Ge nanowire heterostnictures via a controlled reaction between a vapor-liquid-solid-grown, single-crystalline Ge nanowire and Ni pads. In contrast to the previous formation of Ni(2)Gb/Ge/Ni2Ge nanowire heterostructures, a segment of high-quality epitaxial NiGe was formed between Ni2Ge and Ge with the confinement of Al2O3 during annealing. Significantly, back-gate FETs based on this Ni2Ge/NiGe/Ge/NiGe/Ni2Ge heterostructure demonstrated a high-performance p-type transistor behavior, showing a large on/off ratio of more than 10(5) and a high normalized transconductance of 2.4 mu S/mu m. The field-effect hole mobility was extracted to be 210 cm(2)/(V s). Temperature-dependent I-V measurements further confirmed that NiGe has an ideal ohmic contact to p-type Ge with a small Schottky barrier height of 0.11 eV. Moreover, the hysteresis during gate bias sweeping was significantly reduced after Al2O3 passivation, and our Omega-gate Ge nanowire FETs using Al2O3 as the top-gate dielectric showed an enhanced subthreshold swing and transconductance. Therefore, we conclude that the Al2O3 layer can effectively passivate the Ge surface and also serve as a good gate dielectric in Ge top-gate FETs. Our innovative approach provides another freedom to control the growth of nanowire heterostructure and to further achieve high-performance nanowire transistors.
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