Superconducting Ge:Ga layers produced by ion implantation and flash lamp annealing


Superconducting Ge:Ga layers produced by ion implantation and flash lamp annealing

Heera, V.; Herrmannsdörfer, T.; Ignatchik, O.; Mücklich, A.; Posselt, M.; Reuther, H.; Schmidt, B.; Skorupa, W.; Voelskow, M.; Wündisch, C.; Wosnitza, J.; Helm, M.

Recently, superconductivity has been discovered in heavily boron-doped group IV semiconductors like diamond [1] and silicon [2]. Because theoretical studies predict only a weak tendency to superconductivity in heavy p-type doped Ge [3] investigations of the low-temperature transport behaviour in Ge are still lacking.
In order to obtain superconductivity in group IV semiconductors, heavy p-type doping above the metal-insulator-transition and low lattice damage is required. The combination of both conditions make it difficult to apply ion implantation as doping technique. The challenge is to reconstruct the damaged or even amorphized crystal lattice and to activate the acceptor atoms after implantation by annealing, avoiding at the same time long range diffusion and precipitation of the acceptors in the supersaturated semiconductor. So far only in-situ doping during growth (high-temperature-high-pressure synthesis [1] and chemical vapour deposition) for boron-doped diamond and ultra-short-time laser melting of the Si surface in BCl3 atmosphere (gas immersion laser doping [2]) have met these conditions.
Here an alternative process compatible with semiconductor technology is presented. Ga implantation and flash lamp annealing in the ms range enables the production of Ga supersaturated (up to 15 at%) crystalline Ge layers which become superconducting below 0.5 K.
The layer structure investigated by AES, XTEM, RBS/C and the electrical transport properties at low temperatures are reported.

[1] E. A. Ekimov, V. A. Sidorov, E. D. Bauer, et al. , Nature 428 (2004) 542
[2] E. Bustarret, C. Marcenat, P. Achatz, et al., Nature 444 (2006) 465
[3] L. Boeri, J. Kortus, O. K. Anderson, J. Phys. Chem. Solids 67 (2006) 552

Keywords: Germanium; Ga-Implantation; Flash lamp annealing; superconductivity

  • Poster
    IBMM 2008 - 16th International Conference on Ion Beam Modification of Materials, 31.08.-05.09.2008, Dresden, Deutschland

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Publ.-Id: 11985