Design of Dipole-Allowed Direct Band Gaps in Ge/Sn Core−Shell Nanowires

Noviani, Elisabeth Pratidhina Founda and Kim, Sunghyun and Chang, K.J. (2016) Design of Dipole-Allowed Direct Band Gaps in Ge/Sn Core−Shell Nanowires. The Journal of PHYSICAL CHEMISTRY, 120 (49). pp. 1932-7447. ISSN 1932-7455

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Official URL: http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b087...

Abstract

Owing to the indirect band gap nature, Ge exhibits poor optical properties, limiting its usage for optical devices. However, since the direct band gap of Ge is only higher by 0.14 eV than the indirect band gap, band gap engineering has drawn much attention to realize the direct band gap. Here, we report a strategy to design the direct band gap in Ge/Sn core−shell nanowires (NWs), based on firstprinciples calculations. For [111]-oriented NWs, we show that the direct band gaps can be tuned by controlling the diameter and the coreto-shell ratio. We find that the intrinsic strain induced by the lattice mismatch between Ge and Sn drives an indirect-to-direct band gap transition. Even for Ge/Sn core−shell NWs with intrinsically indirect band gaps, the direct band gaps can be achieved by applying an external tensile strain lower than the critical values for pure Ge NWs and bulk Ge. The optical transitions of the direct band gaps are all dipoleallowed, suggesting that [111]-oriented Ge/Sn core−shell NWs are promising for applications as light emitters.

Item Type: Article
Subjects: Physic Education
Divisions: Journal Publication
Depositing User: F.X. Hadi
Date Deposited: 08 Jun 2018 05:26
Last Modified: 19 Oct 2018 08:30
URI: http://repository.wima.ac.id/id/eprint/14679

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