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Updated: Jun 22, 2026

Theoretical Calculation and Experimental Verification for Dislocation Reduction in Germanium Epitaxial Layers with Semicylindrical Voids on Silicon
Published on: July 17, 2020
Prediction that uniaxial tension along produces a direct band gap in germanium
Feng Zhang1, Vincent H Crespi, Peihong Zhang
1Department of Physics and Materials Research Institute, The Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania, 16802-6300, USA.
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 <111> direction in Ge nanowires. Although a symmetry-breaking band splitting lowers the conduction band at the corner of the Brillouin zone (at the L point), a direct gap of 0.34 eV in the center of the Brillouin zone (at Gamma) can still be achieved at 4.2% longitudinal strain, through an unexpectedly strong nonlinear drop in the conduction band edge at Gamma for strain along this axis. These strains are well within the experimentally demonstrated mechanical limits of single-crystal Ge (or Ge(x)Si(1-x)) nanowires, thereby opening a new material system for fundamental optical studies and applications.
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