Hyperdoping semiconductors and their nanostructures

We dope semiconductors and their nanostructures beyond the solubility limit of dopants by combining ion implantation and sub-second intense optical pulse processing. The following topics are under investigation.

  • n+ doping and bandgap engineering of Ge
  • Doping Si/Ge with deep level impurities
  • Doping wide bandgap semiconductors
  • Semiconductor nanostructures
  • (III,Mn)V ferromagnetic semiconductors

n+ doping and bandgap engineering of Ge

A key milestone for the next generation of high-performance multifunctional microelectronic devices is the monolithic integration of high-mobility materials with Si technology. Compared with Si, Ge has a much larger electron mobility and a smaller electron effective mass (0.12 me for Ge vs. 0.26 me for Si). Moreover, the fabrication of ultra-doped n-type Ge in a controllable way in combination with Sn doping and strain management allows for the conversion of Ge from an indirect to a direct bandgap semiconductor. However, it is challenging to fabricate heavily n-type doped Ge with effective carrier concentrations well above 1019 cm−3 and to achieve Ohmic contacts for n-type Ge. We aim to solve these problems by ion implantation and flash lamp annealing.

Our goals are

  • n+ doping of Ge and Ge nanowires
  • Ohmic contacts for n-type Ge
  • Direct bandgap Ge and GeSn
  • Mid-infrared optoelectronics

Cooperation partners

(1) Prof. Inga Anita Fischer

University of Cottbus, Germany

(2) Prof. Edmund P. Burte

University of Magdeburg

(3) Prof. Jörg Schulze

University of Stuttgart, Germany

(4) Prof. Joachim Knoch

RWTH Aachen

(5) Prof. Minghui Hong

University of Taipei, Taiwan, ROC

Related Publications

[1] 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

Semicond. Sci. & Tech., 33, 065008 (2018)

DOI: 10.1088/1361-6641/aabe05

[2] 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

Semicond. Sci. & Tech., 32, 115006 (2017)

DOI: 10.1088/1361-6641/aa8b2f

[3] 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

Scientific Reports 6, 27643 (2016)

DOI: 10.1038/srep27643


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 were overlooked due to their low solid solubility limits, which makes 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. By utilizing ion implantation, flash lamp and pulsed laser annealing, we aim at:

  • Modifying the bandgap of Ge and Si by doping of deep level impurities
  • Exploring their optoelectronic applications
  • Comparing the liquid phase and solid phase epitaxy

Cooperation partners

(1) Dr. Alberto Debernardi

CNR-IMM, Italy

(2) Prof. Deren Yang

Zhejiang Univ., China

Related Publications

[1] On the insulator-to-metal transition in titanium-implanted silicon

F. Liu, M. Wang, Y. Berencén, S. Prucnal, M. Engler, R. Hübner, Y. Yuan, R. Heller, R. Böttger, L. Rebohle, W. Skorupa, M. Helm and S. Zhou

Scientific Reports 8, 4164 (2018)

DOI: 10.1038/s41598-018-22503-6

[2] Realizing the insulator-to-metal transition in Se-hyperdoped Si via non-equilibrium material processing

F. Liu, S. Prucnal, Y. Berencén, Z. Zhang, Y. Yuan, Y. Liu, R. Heller, R. Boettger, L. Rebohle, W. Skorupa, M. Helm, S. Zhou

J. Phys. D: Appl. Phys., 50, 415102 (2017)

DOI: 10.1088/1361-6463/aa82f9

[3] Hyperdoping silicon with selenium: solid vs. liquid phase epitaxy

S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, M. Helm

Scientific Reports, 5, 8329 (2015)

DOI: 10.1038/srep08329


Doping semiconductor nanostructures

The need of using nanostructured materials or nanostructures such as quantum dots or nanowires (NWs) for applications including photovoltaics, nanoelectronics, neuroscience, plasmonics, sensing and optoelectronics is nowadays undisputed. The large surface area to volume ratio of nanomaterials provides further benefits as compared to bulk or thin films. The success of these materials ultimately depends on the possibilities of controlling their properties through doping. However, the possibility of doping semiconductor nanostructures in the same manner as their bulk counterparts, the type of microstructural defects and electronic states, the distribution of dopants and charge carriers as well as the resulting optical and transport properties have yet to be first addressed experimentally.

Cooperation partners

(1) Prof. Alois Lugstein

Institute for solid state electronics, Vienna University of Technology, Vienna, Austria

Related Publications

[1] CMOS‐compatible controlled hyperdoping of silicon nanowires

Y. Berencén, S. Prucnal, W. Möller, R. Hübner, L. Rebohle, R. Böttger, M. Glaser, T. Schönherr, Y. Yuan, M. Wang, Y. M. Georgiev, A. Erbe, A. Lugstein, M. Helm, S. Zhou, W. Skorupa

Advanced Materials Interfaces 5, 1800101 (2018)

DOI: 10.1002/admi.201800101

[2] Formation of n- and p-type regions in individual Si/SiO2 core/shell nanowires by ion beam doping

Y. Berencén, S. Prucnal, W. Möller, R. Hübner, L. Rebohle, T. Schönherr, M. Bilal Khan, M. Wang, M. Glaser, Y. M. Georgiev, A. Erbe, A. Lugstein, M. Helm, S. Zhou

Nanotechnology, In press (2018).


Doping wide bandgap semiconductors

Wide bandgap semiconductors (GaN as the typical example) are more and more important due to their applications for blue and UV lasers, light emitting diodes, solid state lighting, transparent conducting contacts and power electronics working in extreme conditions. However, as the material’s band gap opens up, it becomes increasingly and intrinsically difficult to introduce free carriers (particularly holes) into the system.

Related Publications

[1] Irradiation effects on the structural and optical properties of single crystal β-Ga2O3

C. Liu, Y. Berencén, J. Yang, Y. Wei, M. Wang, Y. Yuan, C. Xu, Y. Xie, X. Li, S. Zhou

Semiconductor Science and Technology 33, 095022 (2018)

DOI: 10.1088/1361-6641/aad8d1


(III,Mn)V ferromagnetic semiconductors

Combining semiconducting and ferromagnetic properties, dilute ferromagnetic semiconductors (DFS) have been under intensive investigation for more than two decades. Mn doped III-V compound semiconductors have been regarded as the prototype of DFS from both experimental and theoretic investigations. The magnetic properties of III-V:Mn can be controlled by manipulating free carriers via electrical gating, as for controlling the electrical properties in conventional semiconductors. For long time GaMnAs was one of the most (or somewhat the only one) investigated dilute ferromagnetic semiconductors. Benefited from the versatility of ion implantation, we work on the following questions:

  • Can Mn be successfully doped to other III-V compound semiconductors? Can the well-accepted mean-field theory well describe the whole III-Mn-V family?
  • Are the states close to the Fermi energy in GaMnAs localized or extended (in an impurity band or in a valence band)? Can we tune the Fermi level by ion beams?

Cooperation partners

(1) Prof. Tomasz Dietl and Prof. Maciek Sawicki

IFPAN, Poland

(2) Prof. Bryan Gallagher

Univ. Nottingham, UK

(3) Prof. Jianhua Zhao

CAS, China

Related Publications

[1] Electronic phase separation in insulating (Ga, Mn) As with low compensation: super-paramagnetism and hopping conduction

Y. Yuan, M. Wang, C. Xu, R. Hübner, R. Böttger, R. Jakiela, M. Helm, M. Sawicki, S. Zhou

J. Phys.: Conden. Matter 30, 095801 (2018)

DOI: 10.1088/1361-648X/aaa9a7

[2] Investigation of a possible electronic phase separation in the magnetic semiconductors Ga1−xMnxAs and Ga1−xMnxP by means of fluctuation spectroscopy

M. Lonsky, J. Teschabai-Oglu, K. Pierz, S. Sievers, H. W. Schumacher, Y. Yuan, B. Böttger, S. Zhou, J. Müller

Phys. Rev. B 97, 054413 (2018)

DOI: 10.1103/PhysRevB.97.054413

[3] Interplay between localization and magnetism in (Ga,Mn)As and (In,Mn)As

Y. Yuan, C. Xu, R. Hübner, R. Jakiela, R. Böttger, M. Helm, M. Sawicki, T. Dietl, S. Zhou

Phys. Rev. Mater. 1, 054401 (2017)

DOI: 10.1103/PhysRevMaterials.1.054401

[4] Dilute ferromagnetic semiconductors prepared by the combination of ion implantation with pulse laser melting (Topic Review)

S. Zhou

J. Phys. D: Appl. Phys. 48, 263001 (2015)

DOI: 10.1088/0022-3727/48/26/263001