Optical Properties of Doped Nanowires in External Electric and Magnetic Fields
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CS OF LOW-DIMENSIONAL STRUCTURES, MESOSTRUCTURES, AND METAMATERIALS
Optical Properties of Doped Nanowires in External Electric and Magnetic Fields E. P. Sinyavskiia and S. M. Sokovnichb, * a
Institute of Applied Physics, Academy of Sciences of Moldova, Kishinev, MD 2028 Moldova b Shevchenko Transnistria State University, Tiraspol, MD 3300 Moldova *e-mail: [email protected] Received May 19, 2020; revised May 19, 2020; accepted July 7, 2020
Abstract—Impurity-induced absorption of light in quantum wires in the presence of external collinear electric and magnetic fields directed perpendicular to the nanowire axis is studied theoretically. The dopants in the quantum wire are modeled by a zero-radius potential. Expressions governing the light absorption coefficient are derived, and specificities of impurity light absorption are studied for all possible directions of polarization of the light wave. In particular, some of optical transitions that are forbidden in the absence of fields become allowed in the presence of external fields. Frequency dependences of light-absorption coefficient, along with the influence of electric and magnetic fields on the magnitude of absorption induced by impurities, are investigated. The possibility of controlling optical characteristics of nanowires by means of an electric field is demonstrated. Keywords: nanowires, impurity absorption, external electric and magnetic fields DOI: 10.1134/S0030400X20110259
INTRODUCTION Additional channels of absorption (luminescence) of an electromagnetic wave that do not exist in bulk materials appear in confined systems (quantum wells, quantum wires, nanotubes) due to dimensional quantization. It is in these quantum systems that scattering of carriers from a rough surface [1] can become important. Sometimes, it determines optical properties and transport phenomena in nanosystems completely. Optical properties of semiconductor quantum wires, such as ZnO, GaN, CdS, InP, and GaAs, were studied intensively in recent years, because carriers in such quantum systems exhibit high mobility, and processes of scattering of charged particles from a rough surface are very active in them [4–6]. Luminescence associated with impurity states, such as donor–acceptor luminescence [6], luminescence related to electron transition from a dimensionally quantized band to acceptor states [7], were studied experimentally in these nanostructures. Similar optical transitions were observed in ZnS [8] and InN [9] nanowires. Investigation of optical properties of quantum wires attracts attention due to specific features in the density of electronic states that appear at the bottom of each dimensionally quantized conduction (valence) band. It is this circumstance that leads to specific features in the frequency dependence of the absorption coefficient of an electromagnetic wave and luminescence relative to two-dimensional systems.
Note that dimensional quantization substantially influences optical characteristics of quantum wires at relatively large values of nanowire radius (R ≥
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