Oxide-confined formation of germanium nanowire heterostructures for high-performance transistors

Jianshi Tang, Chiu Yen Wang, Faxian Xiu, Murong Lang, Li Wei Chu, Cho Jen Tsai, Yu Lun Chueh, Lih Juann Chen, Kang L. Wang

Research output: Contribution to journalArticlepeer-review

45 Citations (Scopus)


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 heterostructures via a controlled reaction between a vapor-liquid-solid-grown, single-crystalline Ge nanowire and Ni pads. In contrast to the previous formation of Ni2Ge/Ge/Ni 2Ge nanowire heterostructures, a segment of high-quality epitaxial NiGe was formed between Ni2Ge and Ge with the confinement of Al 2O3 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 105 and a high normalized transconductance of 2.4 μS/μm. The field-effect hole mobility was extracted to be 210 cm2/(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 Ω-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.

Original languageEnglish
Pages (from-to)6008-6015
Number of pages8
JournalACS nano
Issue number7
Publication statusPublished - 2011 Jul 26

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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