1. Strain and Band-Gap Engineering in Ge-Sn Alloys via P Doping
- Author
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Prucnal, S., Berencén, Y., Wang, M., Grenzer, J., Voelskow, M., Hübner, R., Yamamoto, Y., Scheit, A., Bärwolf, F., Zviagin, V., Schmidt-Grund, R., Grundmann, M., Żuk, J., Turek, M., Droździel, A., Pyszniak, K., Kudrawiec, R., Polak, M. P., Rebohle, L., Skorupa, W., Helm, M., and Zhou, S.
- Subjects
GeSn ,Condensed Matter::Materials Science ,Condensed Matter - Materials Science ,Ge ,strain ,x-ray diffraction ,Raman spectroscopy ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,ion implantation ,n-type doping - Abstract
Ge with a quasi-direct band gap can be realized by strain engineering, alloying with Sn, or ultrahigh n-type doping. In this work, we use all three approaches together to fabricate direct-band-gap Ge-Sn alloys. The heavily doped n-type Ge-Sn is realized with CMOS-compatible nonequilibrium material processing. P is used to form highly doped n-type Ge-Sn layers and to modify the lattice parameter of P-doped Ge-Sn alloys. The strain engineering in heavily-P-doped Ge-Sn films is confirmed by x-ray diffraction and micro Raman spectroscopy. The change of the band gap in P-doped Ge-Sn alloy as a function of P concentration is theoretically predicted by density functional theory and experimentally verified by near-infrared spectroscopic ellipsometry. According to the shift of the absorption edge, it is shown that for an electron concentration greater than 1x10^20 cm-3 the band-gap renormalization is partially compensated by the Burstein-Moss effect. These results indicate that Ge-based materials have high potential for use in near-infrared optoelectronic devices, fully compatible with CMOS technology., 20 pages, 6 figures
- Published
- 2019