Doping and defect engineering by ions

Ion beams are an indispensable tool in semiconductor technology. On one hand, implanted ions—often substituting host atoms—can introduce free charge carriers. This enables doping of semiconductors and their nanostructures well beyond the solubility limit. Heavily doped semiconductors such as GaAs, Ge, and Si are particularly attractive for near- and mid-infrared plasmonics, where the plasma frequency is governed by the carrier concentration. On the other hand, energetic ions interact with materials through ionization and nuclear collisions, leading to the formation of electronic defects and atomic displacements. The concentration and distribution of these defects can be precisely controlled by adjusting the ion fluence and energy. As such, ion beams offer a powerful method for defect engineering. 

Doping Si/Ge with deep level impurities

In the last decades, ion implantation has been extremely successful in doping semiconductor with shallow impurities, such as boron and phosphors in Si. Ion implantation followed by annealing has been maturely integrated with the IC industry production line. Here, “shallow” refers to a relatively small ionization energy of impurities in the host semiconductors. In contrast, deep level impurities like transition metal elements in either Si or GaAs and chalcogens in Si and Ge were overlooked due to their low solid solubility limits, which make the doping rather impossible by thermal equilibrium processing. Interestingly, the emergent exotic properties in deep-level impurity doped semiconductors provide functionality ingredients for photovoltaics and optoelectronics. Here, the challenges are: how to introduce enough non-conventional impurities into semiconductors and how to activate these impurities by bringing them into substitutional lattice sites. We address these challenges through ion implantation combined with short-time annealing.

Related Publications

A high-performance all-silicon photodetector enabling telecom-wavelength detection at room temperature
M. S. Shaikh, M. Catuneanu, A. Echresh, R. Li, S. Wen, G. Godoy-Pérez, S. Prucnal, M. Helm, Y. M. Georgiev, K. Jamshidi, S. Zhou, Y. Berencén
Under Review in Nature Photonics (2025). https://www.researchsquare.com/article/rs-5623025/v1

Temperature-Dependent Dynamics of Charge Carriers in Tellurium Hyperdoped Silicon
K. Ashikur Rahman, M. Saif Shaikh, Q. Yue, S. Senali Dissanayake, M. Wang, S. Zhou, M.-J. Sher
Advanced Electronic Materials, published online, 2400417 (2025)

Impact of post-ion implantation annealing on Se-hyperdoped Ge
X. Liu, P. McKearney, S. Schäfer, B. Radfar, Y. Berencen, U. Kentsch, V. Vähänissi, S. Zhou, S. Kontermann, H. Savin
Applied Physics Letters 125, 042102 (2024)

Achieving ultralow contact resistivity in Si via Te hyperdoping and millisecond post-metallization annealing
H. Liu, Y. Zhou, M.S. Shaikh, Y. Huang, J. Zhu, R. Heller, U. Kentsch, L. Li, M. Tian, S. Zhou, M. Wang
Acta Materialia 278, 120269 (2024)

On-chip lateral Si:Te PIN photodiodes for room-temperature detection in the telecom optical wavelength bands
M. Shaikh, S. Wen, M. Catuneanu, M. Wang, A. Erbe, S. Prucnal, L. Rebohle, S. Zhou, K. Jamshidi, M. Helm, Y. Berencén
Optics Express 31, 26451-26462 (2023)

Functionalizing 2D materials

For many 2D materials, achieving controllable doping or property modulation remains an unsolved challenge. Ion implantation followed by thermal annealing is the most established doping technique, widely used in Si-based nanoelectronics. Developing a tailored implantation and annealing strategy for 2D materials is the primary objective of our current research. This approach will enable precise tuning of properties such as conductivity (e.g., n-type or p-type doping), magnetism, or valley polarization in virtually any 2D material—thanks to the versatility of ion beam technology.

Rise and Fall of the Ferromagnetism in CrSBr Flakes by Non‐Magnetic Ion Irradiation
Fangchao Long, Yi Li, Yu Cheng, Kseniia Mosina, Ulrich Kentsch, Zdenek Sofer, Slawomir Prucnal, Manfred Helm, Shengqiang Zhou
Advanced Physical Research, 3, 2400053 (2024)

Ferromagnetic interlayer coupling in CrSBr crystals irradiated by ions
F. Long, M. Ghorbani-Asl, K. Mosina, Y. Li, K. Lin, F. Ganss, R. Hübner, Z. Sofer, F. Dirnberger, A. Kamra, A. V. Krasheninnikov, S. Prucnal, M. Helm, S. Zhou
Nano Lett. 23, 8468–8473 (2023)

Chlorine doping of MoSe2 flakes by ion implantation
S. Prucnal, A. Hashemi, M. Ghorbani Asl, R. Hübner, J. Duan, Y. Wei, D. Sharma, D. R. T. Zahn, R. Ziegenrücker, U. Kentsch, A. Krasheninnikov, M. Helm, S. Zhou
Nanoscale 13, 5834 (2021)

Defect enginnering for quantum technologies

Certain defects in a crystal lattice create localized electronic states — like artificial atoms trapped in a solid. When these defect states are excited (usually by a laser), they can relax by emitting a single photon. We are working on the creation of single color centers in silicon and 2D materials by ion irradiation with nanometer-scale precision and their further integration into high-quality photonic cavities to achieve an efficient single-photon source.

Wen, S., et al, Optical spin readout of a silicon color center in the telecom L-band, submitted to Nature Communications (2025). https://doi.org/10.48550/arXiv.2502.07632