Surface-induced effects in GaN nanowires


Semiconductor nanowires (NWs) are characterized by an extraordinarily large surface-to-volume ratio. Consequently, surface effects are expected to play a much larger role than in thin films. Here, we review a research focused on the impact of the surface on the electrical and optical properties of catalyst-free GaN NWs with growth direction <0001>. Using a combination of complementary experimental techniques, it has been shown that the Fermi level is pinned at the NW sidewall surfaces, resulting in internal electric fields and in full depletion for NWs below a critical diameter. Deoxidation of the surfaces unpins the Fermi level, leading to enhanced radiative recombination of excitons. Prominent absorption below the bandgap is caused by the Franz-Keldysh effect. Close to the surface, the ionization energy of donors is reduced. The consideration of surface-induced effects is mandatory for an understanding of the physical properties of NWs as well as their application in devices.

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

FIG. 1.
FIG. 2.
FIG. 3.
FIG. 4.
FIG. 5.
FIG. 6.
FIG. 7.
FIG. 8.


  1. 1.

    C.M. Lieber and Z.L. Wang: Functional nanowires. MRS Bull. 32, 99 (2007).

    CAS  Article  Google Scholar 

  2. 2.

    P. Yang, R. Yan, and M. Fardy: Semiconductor nanowire: What’s next? Nano Lett. 10, 1529 (2010).

    CAS  Article  Google Scholar 

  3. 3.

    F. Glas: Critical dimensions for the plastic relaxation of strained axial heterostructures in free-standing nanowires. Phys. Rev. B 74, 121302(R) (2006).

    Article  CAS  Google Scholar 

  4. 4.

    M.T. Bjork, B.J. Ohlsson, T. Sass, A.I. Persson, C. Thelander, M.H. Magnusson, K. Deppert, L.R. Wallenberg, and L. Samuelson: One-dimensional heterostructures in semiconductor nanowhiskers. Appl. Phys. Lett. 80, 1058 (2002).

    CAS  Article  Google Scholar 

  5. 5.

    F. Patolsky, G. Zheng, and C.M. Lieber: Nanowire sensors for medicine and the life sciences. Nanomedicine 1, 51 (2006).

    CAS  Article  Google Scholar 

  6. 6.

    N.S. Ramgir, Y. Yang, and M. Zacharias: Nanowire-based sensors. Small 6, 1705 (2010).

    CAS  Article  Google Scholar 

  7. 7.

    M. Yoshizawa, A. Kikuchi, M. Mori, N. Fujita, and K. Kishino: Growth of self-organized GaN nanostructures on Al2O3 by RF-radical source molecular beam epitaxy. Jpn. J. Appl. Phys. 36, L459 (1997).

    CAS  Article  Google Scholar 

  8. 8.

    E. Calleja, M.A. Sánchez-Garciá, F.J. Sánchez, F. Calle, F.B. Naranjo, E. Muñoz, U. Jahn, and K. Ploog: Luminescence properties and defects in GaN nanocolumns grown by molecular beam epitaxy. Phys. Rev. B 62, 16826 (2000).

    CAS  Article  Google Scholar 

  9. 9.

    K.A. Bertness, A. Roshko, N.A. Sanford, J.M. Barker, and A.V. Davydov: Spontaneously grown GaN and AlGaN nanowires. J. Cryst. Growth 287, 522 (2006).

    CAS  Article  Google Scholar 

  10. 10.

    R. Calarco, R.J. Meijers, R.K. Debnath, T. Stoica, E. Sutter, and H. Lüth: Nucleation and growth of GaN nanowires on Si(111) performed by molecular beam epitaxy. Nano Lett. 7, 2248 (2007).

    CAS  Article  Google Scholar 

  11. 11.

    V. Consonni, M. Knelangen, L. Geelhaar, A. Trampert, and H. Riechert: Nucleation mechanisms of epitaxial GaN nanowires: Origin of their self-induced formation and initial radius. Phys. Rev. B 81, 085310 (2010).

    Article  CAS  Google Scholar 

  12. 12.

    T. Gotschke, T. Schumann, F. Limbachl, T. Stoica, and R. Calarco: Influence of the adatom diffusion on selective growth of GaN nanowire regular arrays. Appl. Phys. Lett. 98, 103102 (2011).

    Article  CAS  Google Scholar 

  13. 13.

    S.D. Hersee, X. Sun, and X. Wang: The controlled growth of GaN nanowires. Nano Lett. 6, 1808 (2006).

    CAS  Article  Google Scholar 

  14. 14.

    C. Chèze, L. Geelhaar, O. Brandt, W.M. Weber, H. Riechert, S. Münch, R. Rothemund, S. Reitzenstein, A. Forchel, T. Kehagias, P. Komninou, G.P. Dimitrakopoulos, and T. Karakostas: Direct comparison of catalyst-free and catalyst-induced GaN nanowires. Nano Res. 3, 528 (2010).

    Article  CAS  Google Scholar 

  15. 15.

    L. Geelhaar, C. Chèze, B. Jenichen, O. Brandt, C. Pfüller, S. Münch, R. Rothemund, S. Reitzenstein, A. Forchel, Th. Kehagias, Ph. Komninou, G.P. Dimitrakopulos, Th. Karakostas, L. Lari, P.R. Chalker, M.H. Gass, and H. Riechert: Properties of GaN nanowires grown by molecular beam epitaxy. IEEE J. Sel. Top. Quantum Electron. (August 2011, in press).

    Google Scholar 

  16. 16.

    T. Kuykendall, P. Pauzauskie, S. Lee, Y. Zhang, J. Goldberger, and P. Yang: Metalorganic chemical vapor deposition route to GaN nanowires with triangular cross sections. Nano Lett. 3, 1063 (2003).

    CAS  Article  Google Scholar 

  17. 17.

    F. Qian, Y. Li, S. Gradecak, D. Wang, C.J. Barrelet, and C.M. Lieber: Gallium nitride-based nanowire radial heterostructures for nanophotonics. Nano Lett. 4, 1975 (2004).

    CAS  Article  Google Scholar 

  18. 18.

    G.T. Wang, A.A. Talin, D.J. Werder, J.R. Creighton, E. Lai, R.J. Anderson, and I.A. Arslan: Highly aligned, template-free growth and characterization of vertical GaN nanowires on sapphire by metal–organic chemical vapour deposition. Nanotechnology 17, 5773 (2006).

    CAS  Article  Google Scholar 

  19. 19.

    C.C. Chen, C.C. Yeh, C.H. Chen, M.Y. Yu, H.L. Liu, J.J. Wu, K.H. Chen, L.C. Chen, J.Y. Peng, and Y.F. Chen: Catalytic growth and characterization of gallium nitride nanowires. Am. Chem. Soc. 123, 2791 (2001).

    CAS  Article  Google Scholar 

  20. 20.

    R.S. Chen, H.Y. Chen, C.Y. Lu, K.H. Chena, C.P. Chen, L.C. Chen, and Y.J. Yang: Ultrahigh photocurrent gain in m-axial GaN nanowires. Appl. Phys. Lett. 91, 223106 (2007).

    Article  CAS  Google Scholar 

  21. 21.

    J.P. Long, B.S. Simpkins, D.J. Rowenhorst, and P.E. Pehrsson: Far-field imaging of optical second-harmonic generation in single GaN nanowires. Nano Lett. 7, 831 (2007).

    CAS  Article  Google Scholar 

  22. 22.

    M. Kocan, A. Rizzi, H. Lüth, S. Keller, and U.K. Mishra: Surface potential at as-grown GaN(0001) MBE layers. Phys. Status Solidi B 234, 773 (2002).

    CAS  Article  Google Scholar 

  23. 23.

    R. Calarco, M. Marso, T. Richter, A.I. Aykanat, R. Meijers, A.v.d. Hart, T. Stoica, and H. Lüth: Size-dependent photoconductivity in MBE grown GaN-nanowires. Nano Lett. 5, 981 (2005).

    CAS  Article  Google Scholar 

  24. 24.

    T. Richter, H. Lüth, R. Meijers, R. Calarco, and M. Marso: Determining doping concentration in GaN nanowires by opto-electrical characterization. Nano Lett. 8, 3056 (2008).

    CAS  Article  Google Scholar 

  25. 25.

    H.Y. Chen, R.S. Chen, F.C. Chang, L.C. Chen, K.H. Chen, and Y.J. Yang: Size-dependent photoconductivity and dark conductivity of m-axial GaN nanowires with small critical diameter. Appl. Phys. Lett. 95, 143123 (2009).

    Article  CAS  Google Scholar 

  26. 26.

    A.A. Talin, B.S. Swartzentruber, F. Léonard, X. Wang, and S.D. Hersee: Unusually strong space-charge-limited current in thin wires. Phys. Rev. Lett. 101, 076802 (2008).

    Article  CAS  Google Scholar 

  27. 27.

    A.A. Talin, B.S. Swartzentruber, F. Léonard, X. Wang, and S.D. Hersee: Electrical transport in GaN nanowires grown by selective epitaxy. J. Vac. Sci. Technol., B 27, 2040 (2009).

    CAS  Article  Google Scholar 

  28. 28.

    M.T. Hirsch, J.A. Wolk, W. Walukiewicz, and E.E. Haller: Persistent photoconductivity in n-type GaN. Appl. Phys. Lett. 71, 1098 (1997).

    CAS  Article  Google Scholar 

  29. 29.

    C.H. Qiu and J.I. Pankove: Deep levels and persistent photoconductivity in GaN thin films. Appl. Phys. Lett. 70, 1983 (1997).

    CAS  Article  Google Scholar 

  30. 30.

    Y. Lin, H.C. Yang, and Y.F. Chen: Optical quenching of the photoconductivity in n-type GaN. J. Appl. Phys. 87, 3404 (2000).

    CAS  Article  Google Scholar 

  31. 31.

    G.M. Dalpian and J.R. Chelikowsky: Self-purification in semiconductor nanocrystals. Phys. Rev. Lett. 96, 226802 (2006).

    Article  CAS  Google Scholar 

  32. 32.

    D.J. Carter and C. Stampfl: Atomic and electronic structure of single and multiple vacancies in GaN nanowires from first-principles. Phys. Rev. B 79, 195302 (2009).

    Article  CAS  Google Scholar 

  33. 33.

    K. Jeganathan, R.K. Debnath, R. Meijers, T. Stoica, R. Calarco, D. Grützmacher, and H. Lüth: Raman scattering of phonon-plasmon coupled modes in self-assembled GaN nanowires. J. Appl. Phys. 105, 123707 (2009).

    Article  CAS  Google Scholar 

  34. 34.

    T. Stoica and R. Calarco: Doping of III-nitride nanowires grown by molecular beam epitaxy. IEEE J. Sel. Top. Quantum Electron. (August 2011, in press).

    Google Scholar 

  35. 35.

    N.A. Sanford, P.T. Blanchard, K.A. Bertness, L. Mansfield, J.B. Schlager, A.W. Sanders, A. Roshko, B.B. Burton, and S.M. George: Steady-state and transient photoconductivity in c-axis GaN nanowires grown by nitrogen-plasma-assisted molecular-beam epitaxy. J. Appl. Phys. 107, 034318 (2010).

    Article  CAS  Google Scholar 

  36. 36.

    B.S. Simpkins, M.A. Mastro, C.R. Eddy Jr., and P.E. Pehrsson: Surface depletion effects in semiconducting nanowires. J. Appl. Phys. 103, 104313 (2008).

    Article  CAS  Google Scholar 

  37. 37.

    L.M. Mansfield, K.A. Bertness, P.T. Blanchard, T.E. Harvey, A.W. Sanders, and N.A. Sanford: GaN nanowire carrier concentration calculated from light and dark resistance measurements. J. Electron. Mater. 38, 495 (2009).

    CAS  Article  Google Scholar 

  38. 38.

    B.S. Simpkins, M.A. Mastro, C.R. Eddy Jr., and P.E. Pehrsson: Surface-induced transients in gallium nitride nanowires. J. Phys. Chem. C 113, 9480 (2009).

    CAS  Article  Google Scholar 

  39. 39.

    J. Camacho, P. Santos, F. Alsina, M. Ramsteiner, K. Ploog, A. Cantarero, H. Obloh, and J. Wagner: Modulation of the electronic properties of GaN films by surface acoustic waves. J. Appl. Phys. 94, 1892 (2003).

    CAS  Article  Google Scholar 

  40. 40.

    J. Pedrós, Y. Takagaki, T. Ive, M. Ramsteiner, O. Brandt, U. Jahn, K.H. Ploog, and F. Calle: Exciton impact-ionization dynamics modulated by surface acoustic waves in GaN. Phys. Rev. B 75, 115305 (2007).

    Article  CAS  Google Scholar 

  41. 41.

    C. Pfüller, O. Brandt, F. Grosse, T. Flissikowski, C. Chèze, V. Consonni, L. Geelhaar, H.T. Grahn, and H. Riechert: Unpinning the Fermi level in GaN nanowires by ultraviolet radiation. Phys. Rev. B 82, 045320 (2010).

    Article  CAS  Google Scholar 

  42. 42.

    V. Dobrokhotov, D.N. McIlroy, M. Grant Norton, A. Abuzir, W.J. Yeh, I. Stevenson, R. Pouy, J. Bochenek, M. Cartwright, L. Wang, J. Dawson, M. Beaux, and C. Bervena: Principles and mechanisms of gas sensing by GaN nanowires functionalized with gold nanoparticles. J. Appl. Phys. 99, 104302 (2006).

    Article  CAS  Google Scholar 

  43. 43.

    W. Lim, J.S. Wright, B.P. Gila, J.L. Johnson, A. Ural, T. Anderson, F. Ren, and S.J. Pearton: Room temperature hydrogen detection using Pd-coated GaN nanowires. Appl. Phys. Lett. 93, 072109 (2008).

    Article  CAS  Google Scholar 

  44. 44.

    B.S. Simpkins, K.M. McCoy, L.J. Whitman, and P.E. Pehrsson: Fabrication and characterization of DNA-functionalized GaN nanowires. Nanotechnology 18, 355301 (2007).

    Article  CAS  Google Scholar 

  45. 45.

    D.J. Guo, A.I. Abdulagatov, D.M. Rourke, K.A. Bertness, S.M. George, Y.C. Lee, and W. Tan: GaN nanowire functionalized with atomic layer deposition techniques for enhanced immobilization of biomolecules. Langmuir 26, 18382 (2010).

    CAS  Article  Google Scholar 

  46. 46.

    C.P. Chen, A. Ganguly, C.Y. Lu, T.Y. Chen, C.C. Kuo, R.S. Chen, W.H. Tu, W.B. Fischer, K.H. Chen, and L.C. Chen: Ultrasensitive in situ label-free DNA detection using a GaN nanowire-based extended-gate field-effect-transistor sensor. Anal. Chem. 83, 1938 (2011).

    CAS  Article  Google Scholar 

  47. 47.

    A. Cavallini, L. Polenta, M. Rossi, T. Stoica, R. Calarco, R.J. Meijers, T. Richter, and H. Lüth: Franz-Keldysh effect in GaN nanowires. Nano Lett. 7, 2166 (2007).

    CAS  Article  Google Scholar 

  48. 48.

    N. Thillosen, K. Sebald, H. Hardtdegen, R. Meijers, R. Calarco, S. Montanari, N. Kaluza, J. Gutowski, and H. Lüth: The state of strain in single GaN nanocolumns as derived from micro-photoluminescence measurements. Nano Lett. 6, 704 (2006).

    CAS  Article  Google Scholar 

  49. 49.

    T. Stoica, E. Sutter, R.J. Meijers, R.K. Debnath, R. Calarco, H. Lüth, and D. Grützmacher: Interface and wetting layer effect on the catalyst-free nucleation and growth of GaN nanowires. Small 4, 751 (2008).

    CAS  Article  Google Scholar 

  50. 50.

    A. Armstrong, Q. Li, K.H.A Bogart, Y. Lin, G.T. Wang, and A.A. Talin: Deep level optical spectroscopy of GaN nanorods. J. Appl. Phys. 106, 053712 (2009).

    Article  CAS  Google Scholar 

  51. 51.

    A. Armstrong, Q. Li, Y. Lin, A.A. Talin, and G.T. Wang: GaN nanowire surface state observed using deep level optical spectroscopy. Appl. Phys. Lett. 96, 163106 (2010).

    Article  CAS  Google Scholar 

  52. 52.

    A. Cavallini, L. Polenta, M. Rossi, T. Richter, M. Marso, R. Meijers, R. Calarco, and H. Lüth: Defect distribution along single GaN nanowhiskers. Nano Lett. 6, 1548 (2006).

    CAS  Article  Google Scholar 

  53. 53.

    L. Polenta, A. Cavallini, M. Rossi, R. Calarco, M. Marso, T. Stoica, R. Meijers, T. Richter, and H. Lüth: Investigation on localized states in GaN nanowires. ACS Nano 2, 287 (2008).

    CAS  Article  Google Scholar 

  54. 54.

    O. Brandt, C. Pfüller, C. Chèze, L. Geelhaar, and H. Riechert: Sub-meV linewidth of excitonic luminescence in single GaN nanowires: Direct evidence for surface excitons. Phys. Rev. B 81, 045302 (2010).

    Article  CAS  Google Scholar 

  55. 55.

    C. Pfüller, O. Brandt, T. Flissikowski, C. Chèze, L. Geelhaar, H.T. Grahn, and H. Riechert: Statistical analysis of excitonic transitions in single, free-standing GaN nanowires: Probing impurity incorporation in the Poissonian limit. Nano Res. 3, 881 (2010).

    Article  CAS  Google Scholar 

  56. 56.

    J.D. Levine: Nodal hydrogenic wave functions of donors on semiconductor surfaces. Phys. Rev. 140, A586 (1965).

    Article  Google Scholar 

  57. 57.

    M. Diarra, Y.-M. Niquet, C. Delerue, and G. Allan: Ionization energy of donor and acceptor impurities in semiconductor nanowires: Importance of dielectric confinement. Phys. Rev. B 75, 045301 (2007).

    Article  CAS  Google Scholar 

  58. 58.

    P. Corfdir, P. Lefebvre, J. Ristić, P. Valvin, E. Calleja, A. Trampert, J.-D. Ganière, and B. Deveaud-Plédran: Time-resolved spectroscopy on GaN nanocolumns grown by plasma-assisted molecular-beam epitaxy on Si substrates. J. Appl. Phys. 105, 013113 (2009).

    Article  CAS  Google Scholar 

  59. 59.

    M.V. Fernández-Serra, Ch. Adessi, and X. Blasé: Surface segregation and backscattering in doped silicon nanowires. Phys. Rev. Lett. 96, 166805 (2006).

    Article  CAS  Google Scholar 

  60. 60.

    Q. Li and G.T. Wang: Spatial distribution of defect luminescence in GaN nanowires. Nano Lett. 10, 1554 (2010).

    CAS  Article  Google Scholar 

  61. 61.

    Z. Wang, J. Li, F. Gao, and W.J. Weber: Defects in gallium nitride nanowires: First-principles calculations. J. Appl. Phys. 108, 044305 (2010).

    Article  CAS  Google Scholar 

Download references


We thank all the coauthors of our own papers reviewed in this work, and in particular C. Pfüller for helping with the figures. We acknowledge U. Jahn for the careful and critical reading of the manuscript. Our own research reviewed here has been partially supported by the EU Marie Curie Research Training Network "Interfacial Phenomena at Atomic Resolution and multiscale properties of novel III-V SEMiconductors" (PARSEM) under Grant MRTN-CT-2004-005583 and through the Information Society Technologies project "Nanowire-based One-Dimensional Electronics" (NODE) under Grant 015783 as well as by the German Federal Ministry of Education and Research joint research project "MONALISA - Epitaxie von monolithisch-integrierten III-V Materialien auf Sili-zium als Lichtemitter" (Contract No. 01BL0810).

Author information



Corresponding author

Correspondence to Lutz Geelhaar.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Calarco, R., Stoica, T., Brandt, O. et al. Surface-induced effects in GaN nanowires. Journal of Materials Research 26, 2157–2169 (2011).

Download citation