Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 25: Group IV (other than C): Si/Ge/SiC

HL 25.4: Vortrag

Mittwoch, 3. April 2019, 10:15–10:30, H33

Engineering the light emission properties of hexagonal Ge by structural modifications — •Jens Renè Suckert, Claudia Rödl, Jürgen Furthmüller, Friedhelm Bechstedt, and Silvana Botti — Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany

The design of CMOS integrable laser sources allows for intra- and inter-chip optical communications at an attojoule/bit energy consumption. To this end, a pure silicon laser would be the ideal solution, but unfortunately Si has an indirect gap and, therefore, it is not suitable for laser applications.

Hexagonal Ge, on the other hand, may represent a viable alternative: It features excellent CMOS compatibility and, even though its direct gap of 0.3 eV is only weakly dipole allowed, the strongly dipole-active optical transition to the second conduction band is only about 0.3 eV higher in energy. This opens the way to band-structure engineering by structural modifications, such as nanostructuring, alloying, or straining.

Here, we use ab initio density-functional theory to investigate the impact of various lattice strains (hydrostatic pressure, biaxial strain, uniaxial strain, etc.) on the electronic structure of hexagonal Ge. We demonstrate that the order of the two lowest conduction bands can be inverted with less than 5 % of tensile uniaxial strain which strongly improves the light-emission properties of hexagonal Ge.