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Germanium under High Tensile Stress: Nonlinear Dependence of Direct Band Gap vs Strain

Kevin Guilloy 1 Nicolas Pauc 1 Alban Gassenq 1 Yann-Michel Niquet 2 Jose-Maria Escalante 2 Ivan Duchemin 2 Samuel Tardif 3 Guilherme Osvaldo Dias 4 Denis Rouchon 4 Julie Widiez 4 Jean-Michel Hartmann 4 Richard Geiger 5 Thomas Zabel 5 Hans Sigg 5 Jerome Faist 6 Alexei Chelnokov 7 Vincent Reboud 4 Vincent Calvo 1
1 SiNaps - Silicon Nanoelectronics Photonics and Structures
PHELIQS - PHotonique, ELectronique et Ingénierie QuantiqueS : DRF/IRIG/PHELIQS
2 LSIM - Laboratory of Atomistic Simulation
MEM - Modélisation et Exploration des Matériaux : DRF/IRIG/MEM
3 NRS - Nanostructures et Rayonnement Synchrotron
MEM - Modélisation et Exploration des Matériaux : DRF/IRIG/MEM
4 CEA-LETI - Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information
5 PSI - Paul Scherrer Institute
6 Institute of Quantum Electronics
7 DOPT - Département d'Optronique
Abstract : Germanium is a strong candidate as a laser source for silicon photonics. It is widely accepted that the band structure of germanium can be altered by tensile strain so as to reduce the energy difference between its direct and indirect band gaps. However, the conventional gap deformation potential model most widely adopted to describe this transition happens to have been investigated only up to 1% uniaxially loaded strains. In this work, we use a microbridge geometry to uniaxially stress germanium along [100] up to epsilon(100) = 3.3% longitudinal strain and then perform electroabsorption spectroscopy. We accurately measure the energy gap between the conduction band at the Gamma point and the light- and heavy-hole valence bands and calculate the theoretical dependency using a tight-binding model. We measure the hydrostatic and tetragonal shear deformation potential of germanium to be a = -9.1 +/- 0.3 eV and b = -2.32 +/- 0.06 eV and introduce a second-order deformation potential that provides a better fit for both experimental and theoretical relations. These new high-strain coefficients will be suitable for the design of future CMOS-compatible lasers and optoelectronic devices based on highly strained germanium.
Keywords : germanium tensile strain electromodulation band gap tight-binding Deformation Potentials Electrooptical Properties Hydrostatic-Pressure Absorption-Edge Uniaxial-Stress Electroreflectance
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https://hal-cea.archives-ouvertes.fr/cea-01849851
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Submitted on : Thursday, July 26, 2018 - 3:16:11 PM
Last modification on : Thursday, May 27, 2021 - 1:54:06 PM

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CEA | INAC-SP2M | DRT | CEA-DRF | LETI | IRIG | CEA-GRE | UGA | PHELIQS

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Kevin Guilloy, Nicolas Pauc, Alban Gassenq, Yann-Michel Niquet, Jose-Maria Escalante, et al.. Germanium under High Tensile Stress: Nonlinear Dependence of Direct Band Gap vs Strain. ACS photonics, American Chemical Society,, 2016, 3 (10), pp.1907-1911. ⟨10.1021/acsphotonics.6b00429⟩. ⟨cea-01849851⟩

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