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A B S T R A C T S MONDAY, JUNE 28 N A N O S E A 2 0 1 0 In InN nanowires in contrast to GaN the Fermi-level pinning in the conduction band induces a highly conductive surface accumulation layer and as a result the nanowires display very high currents several orders of magnitude higher than in the GaN nanowires. In addition, the movement of the Fermi level within the conduction band results in changes of the photoluminescence (PL) peak position. Therefore, a detailed analysis of the PL spectra has been used to determine intrinsic properties of InN nanowires such as band gap and electron concentration and to proof the existence of a surface accumulation layer [12]. InN nanowires additionally represent ideal systems for the observation of ballistic transport and quantum effects ona nanometer scale [13]. 3 – Conclusion The effect of surface Fermi-level pinning and its interplay with the nanowire dimensions on the recombination behavior of electron hole pairs in photoconductivity were investigated. The distinct transport properties of GaN and InN are explained by the different surface Fermi level pinning leading to surface depletion and accumulation for GaN and InN, respectively. Particular emphasis has been given to the investigation of effects due to space charge layers.The space charge could be used as a design parameter for novel devices concept. [1] A. Greytak, L. Lauhon, M. Gudiksen, and C. M. Lieber, Appl. Phys. Lett. 84, 4176 (2004). [2] S. Gradečak, F. Qian, Y. Li, H.-G. Park, and C. M. Lieber, Appl. Phys. Lett. 87, 173111 (2005). [3] Y. Huang, X. Duan, Y. Cui, L. J. Lauhon, K.-H. Kim, and C. M. Lieber, Science 294, 9, 1313 (2001). [4] R. Calarco, M., Marso, T. Richter, A. I. Aykanat, R. Meijers, A. v.d. Hart, T. Stoica, and H. Lüth, Nano Letters 5, 981 (2005). [5] A. Cavallini, L. Polenta, M. Rossi, T. Richter, M. Marso, R. Meijers, R. Calarco, and H. Lüth, Nano Letters, 6(7), 1548-1551 (2006). [6] R. Meijers, T. Richter, R. Calarco, T. Stoica, H.-P. Bochem, M. Marso, and H. Lüth, J. Cryst. Growth 289, 381 (2006). [7] T. Stoica, R. Meijers, R. Calarco, T. Richter, and H. Lüth, J. Cryst. Growth 290, 241 (2006). [8] R. Calarco, R. J. Meijers, R. K. Debnath, T. Stoica, E. Sutter and H. Lüth Nano Letters, 7 (8), 2248 -2251, (2007). [9] R. K. Debnath, R. Meijers, T. Richter, T. Stoica, R. Calarco and H. Lüth, Appl. Phys. Lett., 90, 123117 (2007). [10] T. Stoica, E. Sutter, R. Meijers, R. K. Debnath, R. Calarco, and H. Lüth Small 4, 751 (2008). [11] A. Cavallini, L. Polenta, M. Rossi, T. Stoica, R. Calarco, R. J. Meijers, T. Richter and H. Lüth Nano Letters, 7, 2166 (2007). [12] T. Stoica, R. Meijers, R. Calarco, T. Richter, E. Sutter, and H. Lüth,, Nano Letters, 6(7), 1541-1547 (2006). [13] T. Richter, C. Blömers, H. Lüth, R. Calarco, M. Indlekofer, M. Marso, and T. Schäpers, Nano Lett. 8, 2834 (2008). 17H30-17H50 Probing Single AlGaAs Core-Shell Nanowires by Raman Spectroscopy. B. Buick*1, E. Speiser1, P. Prete2, P. Paiano3, N. Lovergine3, and W. Richter1 (1 Dipartimento di Fisica, CNISM, Universita‟ di Roma Tor Vergata, 00133 Roma, Italy. 2 IMM-CNR, Unità di Lecce, Via Arnesano, 73100 Lecce, Italy. 3 CNISM, and Dipartimento di Ingegneria dell‟Innovazione, Università del Salento, Via Arnesano, 73100 Lecce, Italy)* Corresponding author e-mail: benjamin.buick@roma2.infn.it 1 – Introduction Semiconductor nanowires (NWs) of III-V compounds are of central interest due to their innovative physical properties and due to potential applications in electronic and photo-electronic devices. Ternary nanowires are promising because their properties can be tailored by the stoichiometry. Furthermore, nanowires containing axial/ radial homo- or heterojunction are especially interesting. 2 – Abstract Freestanding AlGaAs NWs were grown by MOVPE by the Vapor Liquid Solid (VLS) method along the (111) direction on GaAs(111) substrates. Depending on the growth conditions, the nanowires show diameters < 100 nm or an unintetional/ intentional core-shell structure. Raman spectroscopy provides access to the vibrational/structural properties, carrier concentration (doping) and the material stoichiometry. 17
A B S T R A C T S MONDAY, JUNE 28 N A N O S E A 2 0 1 0 Raman measurements were done with a scanning confocal micro-Raman spectrometer providing both lateral (
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