Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

Radial modulation doping in core–shell nanowires

Nature Nanotechnology volume 9, pages 116–120 (2014)Cite this article

Subjects

Abstract

Semiconductor nanowires are potential candidates for applications in quantum information processing1,2, Josephson junctions3,4 and field-effect transistors5,6,7,8 and provide a unique test bed for low-dimensional physical phenomena9. The ability to fabricate nanowire heterostructures with atomically flat, defect-free interfaces enables energy band engineering in both axial10,11,12 and radial13,14,15,16 directions. The design of radial, or core–shell, nanowire heterostructures relies on energy band offsets that confine charge carriers into the core region, potentially reducing scattering from charged impurities on the nanowire surface13,14,15,16. Key to the design of such nanoscale heterostructures is a fundamental understanding of the heterointerface properties, particularly energy band offsets and strain. The charge-transfer and confinement mechanism can be used to achieve modulation doping17,18,19 in core–shell structures20,21. By selectively doping the shell, which has a larger bandgap, charge carriers are donated and confined in the core, generating a quasi-one-dimensional electron system with higher mobility. Here, we demonstrate radial modulation doping in coherently strained Ge–SixGe1−x core–shell nanowires and a technique to directly measure their valence band offset. Radial modulation doping is achieved by incorporating a B-doped layer during epitaxial shell growth. In contrast to previous work showing site-selective doping in Ge–Si core–shell nanowires13,22, we find both an enhancement in peak hole mobility compared with undoped nanowires and observe a decoupling of electron transport in the core and shell regions. This decoupling stems from the higher carrier mobility in the core than in the shell and allows a direct measurement of the valence band offset for nanowires of various shell compositions.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Nanowire growth and structural characterization.
Figure 2: Modulation-doped core–shell nanowire FETs.
Figure 3: Decoupled core and shell transport in modulation-doped nanowires.
Figure 4: Valence band offset extraction.

Similar content being viewed by others

References

  1. Hu, Y. et al. A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor. Nature Nanotech. 2, 622–625 (2007).

    Article  CAS  Google Scholar 

  2. Nadj-Perge, S., Frolov, S. M., Bakkers, E. P. A. M. & Kouwenhoven, L. P. Spin–orbit qubit in a semiconductor nanowire. Nature 468, 1084–1087 (2010).

    Article  CAS  Google Scholar 

  3. Xiang, J., Vidan, A., Tinkham, M., Westervelt, R. M. & Lieber, C. M. Ge/Si nanowire mesoscopic Josephson junctions. Nature Nanotech. 1, 208–213 (2006).

    Article  CAS  Google Scholar 

  4. Nilsson, H. A., Samuelsson, P., Caroff, P. & Xu, H. Q. Supercurrent and multiple Andreev reflections in an InSb nanowire Josephson junction. Nano Lett. 12, 228–233 (2012).

    Article  CAS  Google Scholar 

  5. Auth, C. P. & Plummer, J. D. Scaling theory for cylindrical, fully-depleted, surrounding-gate MOSFETs. IEEE Electron. Dev. Lett. 18, 74–76 (1997).

    Article  Google Scholar 

  6. Wang, D. et al. Germanium nanowire field-effect transistors with SiO2 and high-κ HfO2 gate dielectrics. Appl. Phys. Lett. 83, 2432–2434 (2003).

    Article  CAS  Google Scholar 

  7. Bryllert, T., Wernersson, L-E., Froberg, L. E. & Samuelson, L. Vertical high-mobility wrap-gated InAs nanowire transistor. IEEE Electron. Dev. Lett. 27, 323–325 (2006).

    Article  CAS  Google Scholar 

  8. Xiang, J. et al. Ge/Si nanowire heterostructures as high-performance field-effect transistors. Nature 441, 489–493 (2006).

    Article  CAS  Google Scholar 

  9. Kloeffel, C., Trif, M. & Loss, D. Strong spin–orbit interaction and helical hole states in Ge/Si nanowires. Phys. Rev. B 84, 195314 (2011).

    Article  Google Scholar 

  10. Wu, Y., Fan, R. & Yang, P. Block-by-block growth of single-crystalline Si/SiGe superlattice nanowires. Nano Lett. 2, 83–86 (2002).

    Article  CAS  Google Scholar 

  11. Björk, M. T. et al. Few-electron quantum dots in nanowires. Nano Lett. 4, 1621–1625 (2004).

    Article  Google Scholar 

  12. Fuhrer, A. et al. Few electron double quantum dots in InAs/InP nanowire heterostructures. Nano Lett. 7, 243–246 (2007).

    Article  CAS  Google Scholar 

  13. Lauhon, L. J., Gudiksen, M. S., Wang, D. & Lieber, C. M. Epitaxial core–shell and core–multishell nanowire heterostructures. Nature 420, 57–61 (2002).

    Article  CAS  Google Scholar 

  14. Lu, W., Xiang, J., Timko, B. P., Wu, Y. & Lieber, C. M. One-dimensional hole gas in germanium/silicon nanowire heterostructures. Proc. Natl Acad. Sci. USA 102, 10046–10051 (2005).

    Article  CAS  Google Scholar 

  15. Jiang, X. et al. InAs/InP radial nanowire heterostructures as high electron mobility devices. Nano Lett. 7, 3214–3218 (2007).

    Article  CAS  Google Scholar 

  16. Nah, J., Dillen, D. C., Varahramyan, K. M., Banerjee, S. K. & Tutuc, E. Role of confinement on carrier transport in Ge–SiGe core–shell nanowires. Nano Lett. 12, 108–112 (2011).

    Article  Google Scholar 

  17. Dingle, R., Störmer, H. L., Gossard, A. C. & Wiegmann, W. Electron mobilities in modulation-doped semiconductor heterojunction superlattices. Appl. Phys. Lett. 33, 665–667 (1978).

    Article  CAS  Google Scholar 

  18. People, R. et al. Modulation doping in GeSi/Si strained layer heterostructures. Appl. Phys. Lett. 45, 1231–1233 (1984).

    Article  CAS  Google Scholar 

  19. Abstreiter, G., Brugger, H., Wolf, T., Jorke, H. & Herzog, H. J. Strain-induced two-dimensional electron gas in selectively doped Si/SiGe superlattices. Phys. Rev. Lett. 54, 2441–2444 (1985).

    Article  CAS  Google Scholar 

  20. Lee, H. & Choi, H. J. Single-impurity scattering and carrier mobility in doped Ge/Si core–shell nanowires. Nano Lett. 10, 2207–2210 (2010).

    Article  CAS  Google Scholar 

  21. Amato, M., Ossicini, S. & Rurali, R. Band-offset driven efficiency of the doping of SiGe core–shell nanowires. Nano Lett. 11, 594–598 (2011).

    Article  CAS  Google Scholar 

  22. Fukata, N. et al. Characterization of impurity doping and stress in Si/Ge and Ge/Si core–shell nanowires. ACS Nano 6, 8887–8895 (2012).

    Article  CAS  Google Scholar 

  23. Varahramyan, K. M., Ferrer, D., Tutuc, E. & Banerjee, S. K. Band engineered epitaxial Ge–SiGe core–shell nanowire heterostructures. Appl. Phys. Lett. 95, 033101 (2009).

    Article  Google Scholar 

  24. Menéndez, J., Singh, R. & Drucker, J. Theory of strain effects on the Raman spectrum of Si–Ge core–shell nanowires. Ann. Phys. (Leipz.) 523, 145–156 (2011).

    Article  Google Scholar 

  25. Dillen, D. C., Varahramyan, K. M., Corbet, C. M. & Tutuc, E. Raman spectroscopy and strain mapping in individual Ge–SiGe core–shell nanowires. Phys. Rev. B 86, 045311 (2012).

    Article  Google Scholar 

  26. Nah, J., Varahramyan, K., Liu, E-S., Banerjee, S. K. & Tutuc, E. Doping of Ge–SiGe core–shell nanowires using low energy ion implantation. Appl. Phys. Lett. 93, 203108 (2008).

    Article  Google Scholar 

  27. Schäffler, F. High-mobility Si and Ge structures. Semicond. Sci. Technol. 12, 1515–1549 (1997).

    Article  Google Scholar 

  28. Morar, J. F., Batson, P. E. & Tersoff, J. Heterojunction band lineups in Si–Ge alloys using spatially resolved electron-energy-loss spectroscopy. Phys. Rev. B 47, 4107–4110 (1993).

    Article  CAS  Google Scholar 

  29. Rieger, M. M. & Vogl, P. Electronic-band parameters in strained SiGe alloys on SiGe substrates. Phys. Rev. B 48, 14276–14287 (1993).

    Article  CAS  Google Scholar 

  30. Liang, Y., Nix, W. D., Griffin, P. B. & Plummer, J. D. Critical thickness enhancement of epitaxial SiGe films grown on small structures. J. Appl. Phys. 97, 043519 (2005).

    Article  Google Scholar 

  31. Schmidt, V., McIntyre, P. C. & Gösele, U. Morphological instability of misfit-strained core–shell nanowires. Phys. Rev. B 77, 235302 (2008).

    Article  Google Scholar 

  32. Grönqvist, J. et al. Strain in semiconductor core–shell nanowires. J. Appl. Phys. 106, 053508 (2009).

    Article  Google Scholar 

  33. Bai, W. P., Lu, N. & Kwong, D-L. Si interlayer passivation on germanium MOS capacitors with high-κ dielectric and metal gate. IEEE Electron. Dev. Lett. 26, 378–380 (2005).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

This work was supported by the National Science Foundation (grants DMR-0846573 and DMR-0819860) and by the Norman Hackerman Advanced Research Program. The authors thank K. Varahramyan for technical discussions and assistance.

Author information

Authors and Affiliations

  1. Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Road, Austin, 78758, Texas, USA

    David C. Dillen, Kyounghwan Kim, En-Shao Liu & Emanuel Tutuc

Authors
  1. David C. Dillen
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Kyounghwan Kim
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. En-Shao Liu
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Emanuel Tutuc
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

D.C.D. performed nanowire sample growth, nanowire device fabrication and characterization, with assistance from K.K. and E-S.L. D.C.D. and E.T. analysed the data and wrote the paper, with input from all authors.

Corresponding author

Correspondence to Emanuel Tutuc.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary Information (PDF 385 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Dillen, D., Kim, K., Liu, ES. et al. Radial modulation doping in core–shell nanowires. Nature Nanotech 9, 116–120 (2014). https://doi.org/10.1038/nnano.2013.301

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nnano.2013.301

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing