Effective Schottky Barrier Height Lowering of Metal/n-Ge with a TiO2/GeO2 Interlayer Stack

Gwang Sik Kim, Sun Woo Kim, Seung Hwan Kim, June Park, Yujin Seo, Byung Jin Cho, Changhwan Shin, Joon Hyung Shim, Hyun Yong Yu

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

A perfect ohmic contact formation technique for low-resistance source/drain (S/D) contact of germanium (Ge) n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) is developed. A metal-interlayer-semiconductor (M-I-S) structure with an ultrathin TiO2/GeO2 interlayer stack is introduced into the contact scheme to alleviate Fermi-level pinning (FLP), and reduce the electron Schottky barrier height (SBH). The TiO2 interlayer can alleviate FLP by preventing formation of metal-induced gap states (MIGS) with its very low tunneling resistance and series resistance and can provide very small electron energy barrier at the metal/TiO2 interface. The GeO2 layer can induce further alleviation of FLP by reducing interface state density (Dit) on Ge which is one of main causes of FLP. Moreover, the proposed TiO2/GeO2 stack can minimize interface dipole formation which induces the SBH increase. The M-I-S structure incorporating the TiO2/GeO2 interlayer stack achieves a perfect ohmic characteristic, which has proved unattainable with a single interlayer. FLP can be perfectly alleviated, and the SBH of the metal/n-Ge can be tremendously reduced. The proposed structure (Ti/TiO2/GeO2/n-Ge) exhibits 0.193 eV of effective electron SBH which achieves 0.36 eV of SBH reduction from that of the Ti/n-Ge structure. The proposed M-I-S structure can be suggested as a promising S/D contact technique for nanoscale Ge n-channel transistors to overcome the large electron SBH problem caused by severe FLP.

Original languageEnglish
Pages (from-to)35419-35425
Number of pages7
JournalACS Applied Materials and Interfaces
Volume8
Issue number51
DOIs
Publication statusPublished - 2016 Dec 28

Keywords

  • Fermi-level unpinning
  • Schottky barrier height
  • contact resistance
  • germanium
  • germanium dioxide
  • plasma oxidation
  • titanium dioxide

ASJC Scopus subject areas

  • Materials Science(all)

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