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

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• 作者：Gwang-Sik KimSun-Woo Kim ; Seung-Hwan KimJune Park ; Yujin SeoByung Jin Cho ; Changhwan Shin ; Joon Hyung Shim ; Hyun-Yong Yu
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：December 28, 2016
• 年：2016
• 卷：8
• 期：51
• 页码：35419-35425
• 全文大小：519K
• ISSN：1944-8252

文摘

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 TiO<sub>2sub>/GeO<sub>2sub> interlayer stack is introduced into the contact scheme to alleviate Fermi-level pinning (FLP), and reduce the electron Schottky barrier height (SBH). The TiO<sub>2sub> 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/TiO<sub>2sub> interface. The GeO<sub>2sub> layer can induce further alleviation of FLP by reducing interface state density (D<sub>itsub>) on Ge which is one of main causes of FLP. Moreover, the proposed TiO<sub>2sub>/GeO<sub>2sub> stack can minimize interface dipole formation which induces the SBH increase. The M–I–S structure incorporating the TiO<sub>2sub>/GeO<sub>2sub> 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/TiO<sub>2sub>/GeO<sub>2sub>/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.