Photocurrent spectroscopy of single ZB GaAs and GaAs/AlGaAs core-shell nanowires

ORAL

Abstract

We investigate the band structure of single ZB GaAs nanowires and GaAs/Al$_{0.5}$Ga$_{0.5}$As core shell nanowires using photocurrent spectroscopy at room and low temperatures. The single nanowire devices were fabricated photolithographically to define Ti (20nm)/Al (300nm) metal contacts on either end the nanowire. Photocurrent measurements were performed using CW excitation from a tunable CW Ti-Sapphire laser (775nm-890nm) and a broadly tunable (550-960 nm) pulsed excitation from a coherent super continuum photonic crystal fiber. At room temperature we observe an Urbach tail near the absorption edge at 1.42 eV for both GaAs and GaAs/ Al$_{0.5}$Ga$_{0.5}$As core-shell nanowires. In the core shell structure, we also observe the exponential tail from the Al$_{0.5}$Ga$_{0.5}$As superimposed on the GaAs absorption in the core. The 2eV onset is consisant with 50{\%}. At low temperature, 10K, similar measurements were performed and a peak is observed near the band edge $\sim$ 1.50-1.51 eV for both bare and core-shell structure for GaAs reflecting the contribution of excitons to the photocurrent.

*We acknowledge the NSF through DMR-1105362, 1105121 and ECCS-1100489, and the ARC.

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Authors

  • Bekele Badada

    • Department of Physics, University of Cincinnati, Ohio 452210-0011, USA

  • Leigh Smith

    • University of Cincinnati
    • Department of Physics, University of Cincinnati, Ohio 452210-0011, USA
    • University of Cincinnati, OH
    • Dep. of Physics, University of Cincinnati, Cincinnati, OH
    • University of Cincinati

  • Howard Jackson

    • Department of Physics, University of Cincinnati, Ohio 452210-0011, USA

  • Jan Yarrison-Rice

    • Department of Physics, Miami University, Oxford, Ohio 45056, USA

  • Tim Burgess

    • Department of Electronic and Materials Engineering, Australian National University, Canberra, ACT, 0200, Australia
    • Dep. of Electronic Materials Engineering, Australian National University, Australia, Canberra, ACT, Australia
    • Australian National University

  • Chenupati Jagadish

    • Department of Electronic and Materials Engineering, Australian National University, Canberra, ACT, 0200, Australia
    • Australian National University, Canberra, Australia
    • Australian National University
    • Dep. of Electronic Materials Engineering, Australian National University, Australia, Canberra, ACT, Australia