Modulation Doping of GaAs/AlGaAs Core-Shell Nanowires With Effective Defect Passivation and High Electron Mobility

Jessica L. Boland, Sonia Conesa-Boj, Patrick Parkinson, Goezde Tuetuencueoglu, Federico Matteini, Daniel Rueffer, Alberto Casadei, Francesca Amaduzzi, Fauzia Jabeen, Christopher L. Davies, Hannah J. Joyce, Laura M. Herz, Anna Fontcuberta i Morral, Michael B. Johnston

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    Reliable doping is required to realize many devices based on semiconductor nanowires. Group III–V nanowires show great promise as elements of high-speed optoelectronic devices, but for such applications it is important that the electron mobility is not compromised by the inclusion of dopants. Here we show that GaAs nanowires can be n-type doped with negligible loss of electron mobility. Molecular beam epitaxy was used to fabricate modulation-doped GaAs nanowires with Al0.33Ga0.67As shells that contained a layer of Si dopants. We identify the presence of the doped layer from a high-angle annular dark field scanning electron microscopy cross-section image. The doping density, carrier mobility, and charge carrier lifetimes of these n-type nanowires and nominally undoped reference samples were determined using the noncontact method of optical pump terahertz probe spectroscopy. An n-type extrinsic carrier concentration of 1.10 ± 0.06 × 1016 cm–3 was extracted, demonstrating the effectiveness of modulation doping in GaAs nanowires. The room-temperature electron mobility was also found to be high at 2200 ± 300 cm2 V–1 s–1 and importantly minimal degradation was observed compared with undoped reference nanowires at similar electron densities. In addition, modulation doping significantly enhanced the room-temperature photoconductivity and photoluminescence lifetimes to 3.9 ± 0.3 and 2.4 ± 0.1 ns respectively, revealing that modulation doping can passivate interfacial trap states.
    Original languageEnglish
    Pages (from-to)1336-1342
    JournalNano Letters
    Issue number2
    Publication statusPublished - 20 Jan 2015


    • GaAs
    • modulation doping
    • terahertz spectroscopy
    • photoconductivity
    • surface plasmon
    • mobility
    • photoluminescence


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