[Zurück]

M. Seifner, A. Dijkstra, J. Bernardi, A. Steiger-Thirsfeld, M. Sistani, A. Lugstein, J. Haverkort, S. Barth:
"Epitaxial Ge_0.81Sn_0.19 Nanowires as Nanoscale Mid-Infrared Emitters";
ACS Nano, 13 (2019), S. 8047 - 8054.

Highly oriented Ge_0.81Sn_0.19 nanowires have been synthesized by a low temperature chemical vapor deposition growth technique. The nanostructures form by a self-seeded vapor-liquid-solid mechanism. In this process, liquid metallic Sn seeds enable the anisotropic crystal growth and act as sole source of Sn for the formation of the metastable Ge_1-xSn_x semiconductor material. The strain relaxation for a lattice mismatch of  = 2.94 % between the Ge (111) substrate and the constant Ge_0.81Sn_0.19 composition of nanowires is confined to a transition zone of <100 nm. In contrast, Ge_1-xSn_x structures with diameters in the micrometer-range show a fivefold longer compositional gradient very similar to epitaxial thin film growth. Effects of the Sn growth promoters´ dimensions on the morphological and compositional evolution of Ge1-xSnx are described. The temperature and laser power dependent photoluminescence analyses verify the formation of a direct band gap material with emission in the mid-infrared region and values expected for unstrained Ge_0.81Sn_0.19 (e.g. band gap of 0.3 eV at room temperature). These materials with band gaps in the mid-IR hold promise in applications such as thermal imaging and photodetection as well as building blocks for group IV-based mid- to near-IR photonics.

semiconductor; nanowires; epitaxy; direct band gap; germanium; tin

http://dx.doi.org/10.1021/acsnano.9b02843