Condensed Matter Seminar Series
Ferromagnetism and superconductivity in hyperdoped semiconductors
Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. In this talk, we show that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. Mn hyperdoped III-V compound semiconductors become ferromagnetic, where Mn impurities are in 2+ valence and providing local moments of 5 μB and free holes [1-5]. Their Curie temperatures can be varied either by the Mn or free hole concentration, and also depend on the host semiconductors, which reveal different pd exchange strength. On the other hand, Ga and Al hyperdoped Ge exhibits superconductivity with controllable critical temperature [6, 7]. In combination with first-principles calculation, phonon-mediated superconductivity is counted for the mechanism. The critical-field reveals significant difference when the field is in-plane or out-of-plane. This remarkable anisotropy may be considered as proof that Ga is incorporated in the Ge matrix homogeneously in a thin layer. Ion implantation followed by annealing is a well-established method to dope Si and Ge, being maturely integrated with the IC industry production line. We propose ferromagnetic and superconducting semiconductors prepared by ion implantation can be a scalable platform for quantum technology.
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Shengqiang Zhou: Division Head “Semiconductor Materials”, Helmholtz-Zentrum Dresden-Rossendorf
Education: BSc (Peking Uni.) in Physics (1999); M.Sc. (Peking Univ.) in Nuclear Physics (2002); Ph.D. (TU-Dresden, Germany) in Physics (2008)
Previous working experience:
Helmholtz Young Investigator Group Leader, Helmholtz-Zentrum Dresden-Rossendorf (2011-2016)
Research Professor, Peking Univ. China (2010)
Postdoc researcher, Helmholtz-Zentrum Dresden-Rossendorf (2008-2010)
Current research focus: Hyperdoping semiconductors; III-V:Mn magnetic semiconductors; Defect engineering by ion irradiation; Ion beam analysis.