Spontaneous Emission of a Semiconductor Quantum Dot without the Dipole Approximation
- PDF / 427,981 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 90 Downloads / 161 Views
taneous Emission of a Semiconductor Quantum Dot without the Dipole Approximation G. A. Muradyana, L. R. Arzumanyana, and A. Zh. Muradyana, * a
Yerevan State University, Yerevan, Armenia *e-mail: [email protected]
Received June 3, 2020; revised July 22, 2020; accepted July 30, 2020
Abstract—The spontaneous emission of a spherical semiconductor quantum dot is considered without using the dipole approximation. It is shown that the dipole-forbidden radiation of a shallow potential well with one electron level becomes more intense than the dipole-permitted radiation of a deeper potential well and that the potential deepening makes the dipole approximation closer. It is also shown that the cylindrically symmetric anisotropic radiation can be obtained from a spherical quantum dot if the direction of the quantization axis remains unchanged for the acts of photon emission. Keywords: semiconductor quantum dot, anisotropic spontaneous emission DOI: 10.3103/S106833722004012X
1. INTRODUCTION A quantum dot (QD) is a semiconductor nanocrystal embedded in another semiconductor material that can restrict electrons or other carriers in all three dimensions [1–3]. It is made up of 103−105 atoms. The physical properties of the QD differ from the bulk medium because of the wave nature of quantum mechanics. A theoretical QD modeling is usually performed on the basis of a potential well, usually a spherical shape [4, 5]. When the size of QD changes, the energy levels of the electron and hole shift in opposite directions. If an electron is ripped out from the atom under external influence, it moves throughout the nanoparticle (the Wannier-Mott exciton), creating a conduction band in the spectrum. Falling back into the outer orbit around the atom, the valence band, it emits light [6, 7]. The quantum effects of spherical QD are characterized by the radius of the potential sphere and the effective Bohr radius aB of the exciton. If R exceeds aB significantly, then this is a weak or excitonic regime. Then the electron-hole pair behaves like an exciton, and the confinement quantizes the motion of the center of mass of the exciton. In another case, when R surpasses aB a little, the regime becomes strong or individual. Then the interaction of an electron and a hole with a confining potential is much greater than their Coulomb interaction. Therefore, an electron and a hole are considered as independent particles, which separately form a discrete structure of energy levels [8]. Repeated experimental studies have confirmed the theoretical concepts of weak and strong confinement, and the large-scale achievements of QD semiconductor technology allow them to be used in a wide range of applied and fundamental problems of natural sciences [9–12]. One of the important tasks in this area is the development of single-photon light sources [13, 14], in particular, for the needs of quantum teleportation and quantum cryptography [15, 16]. The working mechanism, the spontaneous emission, is usually considered in the dipole approximation [11], in which ikr the ex
Data Loading...
