2018, Zaumseil, P., Hou, Y., Schubert, M.A., von den Driesch, N., Stange, D., Rainko, D., Virgilio, M., Buca, D., Capellini, G.

We report on the direct observation of lattice relaxation and Sn segregation of GeSn/Ge/Si heterostructures under annealing. We investigated strained and partially relaxed epi-layers with Sn content in the 5 at. %-12 at. % range. In relaxed samples, we observe a further strain relaxation followed by a sudden Sn segregation, resulting in the separation of a β-Sn phase. In pseudomorphic samples, a slower segregation process progressively leads to the accumulation of Sn at the surface only. The different behaviors are explained by the role of dislocations in the Sn diffusion process. The positive impact of annealing on optical emission is also discussed.

2015, Peschka, D., Thomas, M., Glitzky, A., Nürnberg, R., Gärtner, K., Virgilio, M., Guha, S., Schroeder, T., Capellini, G., Koprucki, Th.

In this paper, we present a thorough modeling of an edge-emitting laser based on strained germanium (Ge) microstrips. The full-band structure of the tensile strained Ge layer enters the calculation of optical properties. Material gain for strained Ge is used in the 2D simulation of the carrier transport and of the optical field within a cross section of the microstrips orthogonal to the optical cavity. We study optoelectronic properties of the device for two different designs. The simulation results are very promising as they show feasible ways toward Ge emitter devices with lower threshold currents and higher efficiency as published insofar.