Optoelectronic devices operated in the near- and mid-infrared range are used in sensing, telecommunication and are attractive for the intra/inter chip optical interconnection. Highly doped semiconductors like GaAs, Ge and Si are attractive for near and mid-infrared plasmonics, where the plasma frequency is controlled by the carrier concentration. The mid-infrared spectral range from 2 to 10 μm overlaps with the characteristic vibration modes of green-house gasses like NO, SO, CO2, … and C-H groups which are present in different explosives. Therefore plasmonic devices operated in mid-infrared are very attractive for monitoring of air pollutions and for the safety section.
In principle there are two basic concepts for the development of plasmonic devices: (i) the use of metal nanoparticles and (ii) ultradoped semiconductors. Our work focuses on the doping of GaAs, Ge and Si beyond the solid solubility limit. The ultra-high doping is realized by utilization strongly non-equillibrium processing like ion implantation followed by either ms-range flash lamp annealing or ns-range pulsed laser annealing. During FLA the implanted layer recrystallizes via solid phase epitaxy while the PLA causes the recrystallization via liquid phase. The material of choice is taken based on the carrier mobility and required plasma edge. For the n-doping of GaAs we use chalcogen elements (S and Te). The p-type GaAs is realized by doping with Zn. For both cases the doping above 1020 cm-3 is achieved. This allows fabrication of plasmonic devices with tunable plasma frequency down to 4 μm. The tuning of the plasma frequency in Ge based devices can be realized by the controlling of the electron concentration and by the modification of the carrier mobility via alloying of Ge with Sn.
(1) Prof. Jörg Schulze
University of Stuttgart, Germany
(2) Prof. E. Napolitani
University of Padova, Italy
(3) Prof. G. Isella
Universy of Milano, Italy
(4) Prof. Lasse Vines
University of Oslo, Norway
 In-situ ohmic contact formation for n-type Ge via non-equilibrium processing
S. Prucnal, J. Frigerio, E. Napolitani, A. Ballabio, Y. Berencén, L. Rebohle, M. Wang, R. Boettger, M. Voelskow, G. Isella, R. Hübner, M. Helm, S. Zhou, W. Skorupa
 Ultra-doped n-type germanium thin films for sensing in the mid-infrared
S. Prucnal, F. Liu, M. Voelskow, L. Vines, L. Rebohle, D. Lang, Y. Berencén, S. Andric, R. Boettger, M. Helm, S. Zhou, W. Skorupa
The integration of the photonic devices with silicon based microelectronic would enable faster devices with lower power consumption. Nowadays this dream can be true thanks to Ge. Intrinsic Ge is indirect band gap semiconductor but alloying with Sn, and n-type doping beyond 1020 cm-3 and/or biaxial tensile strain engineering can convert Ge into direct band gap semiconductor. A combination of Sn alloying with n-type doping and tensile strain has a potential to make stable direct band gap Ge with emission covering the telecommunication window. Moreover Ge together with Si belongs to group IV semiconductors which makes it compatible with CMOS technology. We are alloying Ge with Sn using Sn implantation followed by FLA for 3 ms. Co-implantation of Sn and P allows us to fabricate direct band gap Ge with carrier concentration above 1020 cm-3.
(1) Prof. Inga Anita Fischer
University of Cottbus, Germany
(2) Prof. J. Żuk
University of Lublin, Poland
(3) Prof. Robert Kudrawiec
Universty of Wrocław, Poland
 Ex situ n+ doping of GeSn alloys via non-equilibrium processing
S. Prucnal, Y. Berencén, M. Wang, L. Rebohle, R. Böttger, I. A. Fischer, L. Augel, M. Oehme, J. Schulze, M. Voelskow, M. Helm, W. Skorupa and S. Zhou
The room-temperature broadband photoresponse of silicon in the infrared region is of great interest for on-chip photonic platforms, but is fundamentally limited to the near infrared, due to the particular value of the band gap. We combine ion implantation with pulsed laser melting in a CMOS-compatible approach to introducing Te dopant into the Si crystal, at concentrations orders of magnitude above the solid solubility limit. This leads to the formation of an intermediate band in the upper half of silicon’s band gap, extending the photoresponse of Te-hyperdoped p−n photodiodes to the midinfrared range.
(1) Dr. E. García-Hemme
Univ. Complutense de Madrid, Spain
 Extended Infrared Photoresponse in Te-Hyperdoped Si at Room Temperature
Mao Wang, Y. Berencén, E. García-Hemme, S. Prucnal, R. Hübner, Ye Yuan, Chi Xu, L. Rebohle, R. Böttger, R. Heller, H. Schneider, W. Skorupa, M. Helm, and Shengqiang Zhou
Phys. Rev. Applied 10, 024054 (2018)
 Room-temperature short-wavelength infrared Si photodetector
Y. Berencén, S. Prucnal, F. Liu, I. Skorupa, R. Hübner, L. Rebohle, S. Zhou, H. Schneider, M. Helm, W. Skorupa