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Advanced doping of Ge and GeSn
Prucnal, S.; Berencén, Y.; Hübner, R.; Böttger, R.; Rebohle, L.; Skorupa, W.; Wang, M.; Helm, M.; Zhou, S.;
One of the main obstacles towards wide application of Ge in nanoelectronics is the indirect band gap of Ge and the lack of an efficient doping method with well controlled junction depth. Heavily n-type doped Ge becomes a quasi-direct bandgap semiconductor [1] which makes it very attractive for modern optoelectronics but n-type Ge doped above 5×10^19 cm-3 is metastable and thus difficult to be achieved [2]. In contrast to Ge, the GeSn alloy with direct band gap is the most promising semiconductor material for light emitters integrated with CMOS technology [3]. Here an overview of different doping techniques of Ge and fabrication methods to form GeSn will be presented. Special attention will be focused on the use of ion implantation followed by flash-lamp (FLA) annealing for the fabrication of heavily doped n-type Ge and GeSn with direct band gap [4]. In contrast to conventional annealing procedures, rear-side FLA leads to full recrystallization of Ge and GeSn, and simultaneously the Sn segregation and diffusion of n-type dopants are supressed. The maximum electron concentration is well above 10^20 cm-3 both in Ge and in GeSn with Sn concentration up to 6%. Due to the ultra-high n-type doping, Ge becomes a quasi-direct band gap semiconductor showing room-temperature photoluminescence from G-HH transitions [4]. The recrystallization mechanism and the dopant distribution in Ge and GeSn alloy synthesized by ion implantation during rear-side FLA are discussed in detail.
Moreover, we report on the strong mid-IR plasmon absorption in heavily n-type doped Ge and GeSn thin films in the wavelength range from 3000 nm to 10 000 nm.

[1] R. E. Camacho-Aguilera et al., Optics Express 20, 11316-11320 (2012)
[2] S. Prucnal et al., Sci. Rep. 6, 27643 (2016).
[3] S. Wirths et al., Nat. Photon., 9, 88–92 (2015)
[4] S. Prucnal et al., Semicond. Sci. Technol. 32, 115006 (2017).
Keywords: Ge, GeSn, ion implantation, flash lamp annealing, n-type doping
  • Lecture (Conference)
    34th International Conference on the Physics of Semiconductors, 29.07.-03.08.2018, Montpellier, France

Publ.-Id: 28569 - Permalink