Dresden 2020 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 51: Semiconductor lasers I

HL 51.1: Talk

Wednesday, March 18, 2020, 15:00–15:15, POT 51

Direct Band-Gap Emission from Hexagonal SiGe: Towards a SiGe Nanolaser — •Claudia Rödl, Jens Renè Suckert, Jürgen Furthmüller, Friedhelm Bechstedt, and Silvana Botti — Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

Incorporation of microelectronics and optoelectronics is expected to revolutionize various fields of technology, such as communication, sensing, and imaging. A Si-compatible nanolaser would be the key to achieve integrated silicon photonics. However, Si as well as Ge in their diamond-structure equilibrium phases are known to be optically inactive due to the indirect nature of their band gaps. The hexagonal allotropes of Si and Ge in the lonsdaleite phase, which can now be grown in good quality, may overcome this limitation. Hexagonal Si is still indirect, whereas hexagonal Ge is a direct semiconductor. Unfortunately, the dipole matrix elements of the lowest optical transitions are almost zero. Here, we show that it is possible to enhance the optical oscillator strengths of hexagonal Ge by applying tensile uniaxial strain or alloying it with Si. Upon structural modification, the two lowest conduction bands change order and the lowest optical transitions become strongly dipole active. We compare our results to recent data from our experimental collaborators. Using first-principles density-functional theory with hybrid functionals and the MBJLDA meta-GGA, we calculate structural and electronic properties and show how the absorption and emission spectra are affected by strain and alloying, respectively.