Control of Doping and Electronic Transport in Nanowires
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Control of Doping and Electronic Transport in Nanowires Jianxin Zhong1 and G. Malcolm Stocks2 1
Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6016 2 Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6114 ABSTRACT We propose a novel concept, namely, delta-doping of nanowires, to control the carrier mobility in nanowires. Different from the traditional doping, our approach features doping of a nanowire only on its surface. Our calculations based on Anderson models for nanowires with surface disorder showed remarkably different results from the traditional doping where impurities are distributed inside the nanowire. We found that there exist transition energy levels similar to the mobility edges in three-dimensional disordered systems. If the Fermi energy is below the transition energy level, the delta-doped nanowire is simply an insulator. But once the Fermi energy exceeds this energy level, the carrier mobility increases significantly. The transition levels are almost independent of the degree of disorder in the regime of strong disorder. INTRODUCTION Recent breakthrough in growth of semiconductor nanowires [1-4] offers great opportunities to revolutionize technologies in electronics. We believe that the key toward such potential applications is a clear understanding of the fundamental mechanism of doping in nanowires for manipulating carrier transport and signal processing. Traditional theory of electronic disorder [6] predicts that doping in one-dimensional systems leads to carrier localization, limiting practical applications of nanowires because of poor carrier mobility. In this paper, we propose a novel concept, namely, delta-doping of nanowires, to control the carrier mobility. Different from the traditional doping, our approach features doping of a nanowire only on its surface. In the case of delta-doping of a nanowire, dopant atoms locate on the surface of the nanowire, leading to a disordered surface with impurities, vacancies, and lattice distortion. We use the Anderson model of disorder to study electronic properties of nanowires with surface disorder induced by the delta-doping. Our calculations showed remarkably different results from the traditional doping where impurities are distributed inside the nanowire. We found that there exist transition energy levels similar to the mobility edges in three-dimensional disordered systems. If the Fermi energy is below the transition energy level, the delta-doped nanowire is simply an insulator. But once the Fermi energy exceeds this energy level, the carrier mobility increases significantly. The transition levels are almost independent of the degree of disorder in the regime of strong disorder. We believe this novel concept may find many important applications in future nanowire-based nanoelectronics and microsystems.
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Disordered surface Perfect core
Impurity atoms Figure 1. Schematic illustration of a nanowire with surface disorder induced by delta-dopi
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