Abstract
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.
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References
C.M. Lieber and Z.L. Wang: Functional nanowires. MRS Bull. 32, 99 (2007).
P. Yang, R. Yan, and M. Fardy: Semiconductor nanowire: What’s next? Nano Lett. 10, 1529 (2010).
F. Glas: Critical dimensions for the plastic relaxation of strained axial heterostructures in free-standing nanowires. Phys. Rev. B 74, 121302(R) (2006).
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).
F. Patolsky, G. Zheng, and C.M. Lieber: Nanowire sensors for medicine and the life sciences. Nanomedicine 1, 51 (2006).
N.S. Ramgir, Y. Yang, and M. Zacharias: Nanowire-based sensors. Small 6, 1705 (2010).
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).
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).
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).
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).
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).
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).
S.D. Hersee, X. Sun, and X. Wang: The controlled growth of GaN nanowires. Nano Lett. 6, 1808 (2006).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
M.T. Hirsch, J.A. Wolk, W. Walukiewicz, and E.E. Haller: Persistent photoconductivity in n-type GaN. Appl. Phys. Lett. 71, 1098 (1997).
C.H. Qiu and J.I. Pankove: Deep levels and persistent photoconductivity in GaN thin films. Appl. Phys. Lett. 70, 1983 (1997).
Y. Lin, H.C. Yang, and Y.F. Chen: Optical quenching of the photoconductivity in n-type GaN. J. Appl. Phys. 87, 3404 (2000).
G.M. Dalpian and J.R. Chelikowsky: Self-purification in semiconductor nanocrystals. Phys. Rev. Lett. 96, 226802 (2006).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
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).
J.D. Levine: Nodal hydrogenic wave functions of donors on semiconductor surfaces. Phys. Rev. 140, A586 (1965).
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).
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).
M.V. Fernández-Serra, Ch. Adessi, and X. Blasé: Surface segregation and backscattering in doped silicon nanowires. Phys. Rev. Lett. 96, 166805 (2006).
Q. Li and G.T. Wang: Spatial distribution of defect luminescence in GaN nanowires. Nano Lett. 10, 1554 (2010).
Z. Wang, J. Li, F. Gao, and W.J. Weber: Defects in gallium nitride nanowires: First-principles calculations. J. Appl. Phys. 108, 044305 (2010).
Acknowledgment
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).
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Calarco, R., Stoica, T., Brandt, O. et al. Surface-induced effects in GaN nanowires. Journal of Materials Research 26, 2157–2169 (2011). https://doi.org/10.1557/jmr.2011.211
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DOI: https://doi.org/10.1557/jmr.2011.211