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

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• 作者：Jessica L. Boland ; Sonia Conesa-Boj ; Patrick Parkinson ; G枚zde T眉t眉nc眉oglu ; Federico Matteini ; Daniel R眉ffer ; Alberto Casadei ; Francesca Amaduzzi ; Fauzia Jabeen ; Christopher L. Davies ; Hannah. J. Joyce ; Laura M. Herz ; Anna Fontcuberta i Morral ; Michael B. Johnston
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：February 11, 2015
• 年：2015
• 卷：15
• 期：2
• 页码：1336-1342
• 全文大小：393K
• ISSN：1530-6992

文摘

Reliable doping is required to realize many devices based on semiconductor nanowires. Group III鈥揤 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 Al_0.33Ga_0.67As 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 卤 0.06 脳 10¹⁶ cm^鈥? was extracted, demonstrating the effectiveness of modulation doping in GaAs nanowires. The room-temperature electron mobility was also found to be high at 2200 卤 300 cm² V^鈥? s^鈥? 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 卤 0.3 and 2.4 卤 0.1 ns respectively, revealing that modulation doping can passivate interfacial trap states.