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conference

Hexagonal silicon germanium as a direct bandgap light source

Wouter H. J. Peeters, Eindhoven University of Technology, Eindhoven, Nederland

Victor T. van Lange, Eindhoven University of Technology, Eindhoven, Nederland

Abderrezak Belabbes, Friedrich-Schiller-Universität Jena, , Germany

Riccardo Farina, Eindhoven University of Technology, Eindhoven, Nederland

Marco Vettori, Eindhoven University of Technology, Eindhoven, Nederland

Silvana Botti, Ruhr-Universität Bochum, Bochum, Germany

Jos E. M. Haverkort, Friedrich-Schiller-Universität Jena, Jena, Germany

Marvin A. J. van Tilburg, Eindhoven University of Technology, Eindhoven, Nederland

Marvin Jansen, Eindhoven University of Technology, Eindhoven, Nederland

Max C. van Hemert, Eindhoven University of Technology, Eindhoven, Nederland

Marcel A. Verheijen, Eurofins Materials Science Netherlands BV, , Nederland

Friedhelm Bechstedt, Friedrich-Schiller-Universität Jena, Jena, Germany

Time & Place
  • Date: 10.10.2024
  • Time: 8:00 a.m.
  • Place: PRiME 2024 Joint International Meeting, Honolulu, USA

Abstract

All SiGe alloys in the cubic crystal phase have an indirect bandgap. Therefore, SiGe alloys are typically considered as unusable as a light source. However, if the Si1-xGex atoms are arranged in a hexagonal crystal structure, the bandgap becomes direct for x>65%. The emission occurs with a nanosecond lifetime, and is tuneable from 1.8 to 3.4um by varying the SiGe composition. The hex-SiGe alloys have a relatively large separation between the direct and indirect conduction band minima, which makes it stand out as a Group IV light source [1]. The hex-SiGe alloys are realized as shells in a core-shell nanowire geometry, using wurtzite GaAs cores as epitaxial templates to copy the hexagonal stacking to the SiGe shells. Recently, photoluminescence studies of these core-shell nanowires resulted in the observation of amplified spontaneous emission (ASE) from hex-Si0.2Ge0.8, highlighting a positive material gain in this material system. The positive material gain is enabled by the direct bandgap of hex- Si0.2Ge0.8. Moreover, we have grown nanowires with multiple shells of different Si1-xGex compositions. Thus, these shells contain heterostructures of hex-Si1-xGe­x, having a type-I band alignment, allowing us to create hex-Ge/Si0.2Ge0.8 quantum wells with light emission up to room temperature. The observation of ASE, in combination with the ability to create type I QWs from hex-Si1-xGe­x, pave the way towards a laser based on hex-Si1-xGe­x alloys.

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