Nucleation-controlled low-temperature solid-phase crystallization for Sn-doped polycrystalline-Ge film on insulator with high carrier mobility (∼550 cm2/V s)

Chang Xu, Hongmiao Gao, Takayuki Sugino, Masanobu Miyao, Taizoh Sadoh

Research output: Contribution to journalArticle

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Abstract

High-speed thin-film transistors (TFTs) are required to develop the next generation of electronics, such as three-dimensional large-scale integrated circuits and advanced system-in-displays. For this purpose, high-carrier-mobility semiconductor films on insulator structures should be fabricated with low-temperature processing conditions (≤500 °C). To achieve this, we investigate solid-phase crystallization of amorphous-GeSn (a-GeSn) films (Sn concentration: 2% and thickness: 50-200 nm) on insulating substrates, where thin a-Si under-layers (thickness: 0-20 nm) are introduced between a-GeSn films and insulating substrates. The GeSn films are polycrystallized by annealing (450 °C, 20 h) for all samples irrespective of a-GeSn and a-Si thickness conditions, while the Si films remain amorphous. Analysis of crystal structures of GeSn films (thickness: 50 nm) reveals that grain sizes decrease from ∼10 μm to 2-3 μm by the introduction of a-Si under-layers (thickness: 3-20 nm). This phenomenon is attributed to the change in dominant nucleation sites from the interface to the bulk, which significantly decreases grain-boundary scattering of carriers through a decrease in the barrier heights at grain boundaries. Bulk-nucleation further becomes dominant by increasing the GeSn film thickness. As a result, a high carrier mobility of ∼550 cm2/V s is realized for GeSn films (thickness: 100 nm) grown with a-Si under-layers. This mobility is the largest among ever reported data for Ge and GeSn grown on an insulator. This technique will facilitate realization of high-speed TFTs for use in the next generation of electronics.

Original languageEnglish
Article number242103
JournalApplied Physics Letters
Volume112
Issue number24
DOIs
Publication statusPublished - Jun 11 2018

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carrier mobility
solid phases
insulators
nucleation
crystallization
film thickness
transistors
grain boundaries
high speed
thin films
electronics
integrated circuits
grain size
crystal structure
annealing
scattering

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

Cite this

Nucleation-controlled low-temperature solid-phase crystallization for Sn-doped polycrystalline-Ge film on insulator with high carrier mobility (∼550 cm2/V s). / Xu, Chang; Gao, Hongmiao; Sugino, Takayuki; Miyao, Masanobu; Sadoh, Taizoh.

In: Applied Physics Letters, Vol. 112, No. 24, 242103, 11.06.2018.

Research output: Contribution to journalArticle

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