Abstract
We predict a new way to achieve a direct band gap in germanium, and hence optical emission in this technologically important group-IV element: tensile strain along the direction in Ge nanowires. Although a symmetry-breaking band splitting lowers the conduction band at the corner of the Brillouin zone (at the point), a direct gap of 0.34 eV in the center of the Brillouin zone (at ) can still be achieved at 4.2% longitudinal strain, through an unexpectedly strong nonlinear drop in the conduction band edge at for strain along this axis. These strains are well within the experimentally demonstrated mechanical limits of single-crystal Ge (or ) nanowires, thereby opening a new material system for fundamental optical studies and applications.
- Received 20 May 2008
DOI:https://doi.org/10.1103/PhysRevLett.102.156401
©2009 American Physical Society