Speaker
Description
M. Krämer$^a$, I. Dudko$^{b,c}$, A.D. Lamirand$^b$, C. Botella$^b$, P. Regreny$^b$, A. Danescu$^b$, M. Bugnet$^d$, S. Walia$^c$, J. Penuelas$^b$, N. Chauvin$^b$ and B. Gault$^{a,e}$
(a) Max Planck Institute for Sustainable Materials, Max-Planck-Straße 1, 40237 Düsseldorf, Germany
(b) Ecole Centrale de Lyon, CNRS, INSA Lyon, Université Claude Bernard Lyon 1, CPE Lyon, INL, UMR 5270, 69130 Ecully, France
(c) School of Engineering, RMIT University, Melbourne 3001, Victoria, Australia
(d) Univ Lyon, CNRS, INSA Lyon, UCBL, MATEIS, UMR 5510, 69621 Villeurbanne, France
(e) Department of Materials, Royal School of Mines, Imperial College London, London, SW7 2AZ UK
Semiconductors with strong light emission and absorption are required for optoelectronic applications, where an electronic signal is converted to an optical signal and vice versa. Hexagonal Ge is a promising candidate for group IV photonics because, unlike its natural cubic phase, it has a direct band gap and therefore stronger light emission. Hexagonal Ge can be synthesized by the crystal transfer method, in which the small lattice mismatch allows Ge to be grown, for example, on the facets of wurtzite GaAs nanowires by molecular beam epitaxy, thereby adopting the hexagonal structure.
Atom probe tomography and high-resolution transmission electron microscopy of such grown hexagonal Ge on GaAs nanowires reveal the formation of quantum dots, that coalesce into radial quantum wells with increasing growth time. Photoluminescence spectroscopy on heterostructures reveals strong quantum confinement in the quantum dots, resulting in strong light emission in the telecom bands, which disappears with the onset of coalescence.
