Characteristics of strained-germanium p- and n-channel field effect transistors on a Si (1 1 1) substrate

S. Maikap, Min-Hung Lee, S. T. Chang, C. W. Liu

    Research output: Contribution to journalArticle

    25 Citations (Scopus)

    Abstract

    Characteristics of strained-germanium (Ge) p- and n-channel field effect transistors directly on Si (1 1 1) substrates have been investigated. A strained-Ge layer with a thickness of ∼4 nm has been grown on the relaxed Si/Si (1 1 1) substrate by ultra-high-vacuum chemical vapour deposition. To improve the oxide/strained-Ge interface, a thin Si-cap layer with a thickness of 3 nm has been grown on the strained-Ge layer. After the device process, 1 nm thickness of Si-cap layer remains on the strained-Ge layer. Thicknesses of all epitaxial layers have been measured by transmission electron microscopy. Raman spectroscopy measurement on the Si-cap/strained-Ge layer shows that the strained-Ge layer has a compressive strain of ∼1.25%. A hole confinement shoulder on the capacitance-voltage curve at the accumulation region has been observed due to carrier confinement at the Si-cap/strained-Ge hetero-interface. A metal-oxide-semiconductor (MOS) structure on the strained-Ge layer shows a moderate interface trap charge density of ∼2.8 × 1011 cm-2 eV-1. Strained-Ge p- and n-channel field effect transistors show low off-state leakage currents of ∼3.8 × 10 -13 A νm-1 and ∼6.5 × 10-13 A νm-1, respectively. Drive currents of strained-Ge p- and n-channel field effect transistors are enhanced by ∼100% and ∼40%, respectively, as compared with bulk Si (1 1 1) transistors. Peak hole and electron mobility of strained-Ge (1 1 1) field effect transistors at the low effective field are found to be ∼110% and ∼30% enhancement, respectively, as compared with bulk Si (1 1 1) transistors, due to high hole and electron mobility enhancement factor as well as strain-induced lower conduction mass in the strained-Ge channel.

    Original languageEnglish
    Article number008
    Pages (from-to)342-347
    Number of pages6
    JournalSemiconductor Science and Technology
    Volume22
    Issue number4
    DOIs
    Publication statusPublished - 2007 Apr 1

    Fingerprint

    Germanium
    Field effect transistors
    germanium
    field effect transistors
    Substrates
    caps
    Hole mobility
    Electron mobility
    hole mobility
    electron mobility
    Transistors
    transistors
    germanium oxides
    augmentation
    Epitaxial layers
    Ultrahigh vacuum
    shoulders
    Charge density
    metal oxide semiconductors
    Leakage currents

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics
    • Electrical and Electronic Engineering
    • Materials Chemistry

    Cite this

    Characteristics of strained-germanium p- and n-channel field effect transistors on a Si (1 1 1) substrate. / Maikap, S.; Lee, Min-Hung; Chang, S. T.; Liu, C. W.

    In: Semiconductor Science and Technology, Vol. 22, No. 4, 008, 01.04.2007, p. 342-347.

    Research output: Contribution to journalArticle

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    abstract = "Characteristics of strained-germanium (Ge) p- and n-channel field effect transistors directly on Si (1 1 1) substrates have been investigated. A strained-Ge layer with a thickness of ∼4 nm has been grown on the relaxed Si/Si (1 1 1) substrate by ultra-high-vacuum chemical vapour deposition. To improve the oxide/strained-Ge interface, a thin Si-cap layer with a thickness of 3 nm has been grown on the strained-Ge layer. After the device process, 1 nm thickness of Si-cap layer remains on the strained-Ge layer. Thicknesses of all epitaxial layers have been measured by transmission electron microscopy. Raman spectroscopy measurement on the Si-cap/strained-Ge layer shows that the strained-Ge layer has a compressive strain of ∼1.25{\%}. A hole confinement shoulder on the capacitance-voltage curve at the accumulation region has been observed due to carrier confinement at the Si-cap/strained-Ge hetero-interface. A metal-oxide-semiconductor (MOS) structure on the strained-Ge layer shows a moderate interface trap charge density of ∼2.8 × 1011 cm-2 eV-1. Strained-Ge p- and n-channel field effect transistors show low off-state leakage currents of ∼3.8 × 10 -13 A νm-1 and ∼6.5 × 10-13 A νm-1, respectively. Drive currents of strained-Ge p- and n-channel field effect transistors are enhanced by ∼100{\%} and ∼40{\%}, respectively, as compared with bulk Si (1 1 1) transistors. Peak hole and electron mobility of strained-Ge (1 1 1) field effect transistors at the low effective field are found to be ∼110{\%} and ∼30{\%} enhancement, respectively, as compared with bulk Si (1 1 1) transistors, due to high hole and electron mobility enhancement factor as well as strain-induced lower conduction mass in the strained-Ge channel.",
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