A Pathway to Type-I Band Alignment in Ge/Si Core-Shell Nanowires
- A Pathway to Type-I Band Alignment in Ge/Si Core-Shell Nanowires
- Jongseob Kim; 이정훈; Ki-Ha Hong
- type-I/II transition; quantum well; quantum confinement; strain; density functional theory
- Issue Date
- Journal of Physical Chemistry Letters
- VOL 4, NO 1, 121-126
- We investigate the electronic band structures of Ge/Si core–shell nanowires (CSNWs) and devise a way to realize the electron quantum well at Ge core atoms with first-principles calculations. We reveal that the electronic band engineering by the quantum confinement and the lattice strain can induce the type-I/II band alignment transition, and the resulting type-I band alignment generates the electron quantum well in Ge/Si CSNWs. We also find that the type-I/II transition in Ge/Si CSNWs is highly related to the direct to indirect band gap transition through the analysis of charge density and band structures. In terms of the quantum confinement, for  and  directional Ge/Si CSNWs, the type-I/II transition can be obtained by decreasing the diameters, whereas a  directional CSNW preserves the type-II band alignment even at diameters as small as 1 nm. By applying a compressive strain on  CSNWs, the type-I band alignment can be formed. Our results suggest that Ge/Si CSNWs can have the type-I band alignment characteristics by the band structure engineering, which enables both n-type and p-type quantum-well transistors to be fabricated using Ge/Si CSNWs for high-speed logic applications.
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