Showing papers on "Quantum dot published in 1899"

Direct interband light absorption in strongly oblate semi-ellipsoidal quantum dots' ensemble

Abstract: Within the framework of adiabatic approximation the energy levels and direct interband light absorption in strongly oblate semiellipsoidal quantum dot’s ensemble are studied. Analytical expressions for the particle energy spectrum and absorption threshold frequency in the regime of strong size quantization are obtained. Selection rules for quantum transitions are revealed. To facilitate the comparison of obtained results with the probable experimental data, the small semiaxe size dispersion distribution of quantum dots growing by two experimentally realizing distribution functions have been taken into account. Distribution functions of Lifshits-Slezo v and Gaussian have been considered. Keywords: Oblate semiellipsoidal quantum dot, interband light absorption, selection rules, quantum dot ensemble 1. INTRODUCTION Development of the novel growth techniques, such as the Stranski–Krastanov epitaxial method etc., makes possible to grow semiconductor quantum dots ( QDs ) of various shapes and sizes

Tunability of absorption threshold frequencies and Stark shift in spherical quantum layer

Abstract: In the present work the interband optical absorption in the ensemble of spherical quantum layers with weak quantum interaction is investigated. The distribution of layers by their inner radii is taken into account. The effect of weak electric field on the energy levels coupling and absorption character is investigated as well. It is shown that the energy spectrum 1s1p1d2s1f2p for spherical quantum dot turns to the spectrum 1s1p1d1f2s2p for spherical quantum layer with enough large value of inner radius. It is also shown that in spherical quantum layer, where the coupling between neighboring states is not negligible, there is no square low dependence of Stark shift on electric field strength in contrast to the rotator model. Keywords: spherical quantum layer, abso rption coefficient, Stark shift 1. INTRODUCTION The experimental realization of layered and ring-like semiconductor nanostructures makes it possible to consider a range of solid state quantum mechanical problems in which electronic, optical, and other characteristics of such systems are observed

Direct interband absorption of light in the ensemble of cylindrical quantum dots having strongly oblate elliptical cross-section

Abstract: In the framework of adiabatic approximation the energy levels and direct interband absorption of light in the ensemble of cylindrical quantum dots having strongly oblate elliptical cross-section are studied. Analytical expressions for the energy spectrum and wave functions of the electron are obtained. For the slowŽ subsystem effective potential approximation, parabolic and modified Poschl-Teller potentials are used. Low-energy levels in the energy spectrum are shown to be equidistant in both cases. Modified Poschl-Teller potential approximation allows taking into account violation of equidistance of energy levels for higher exited states. Absorption coefficient and edge frequencies are obtained in the strong size quantization regime. Corresponding selection rules for quantum transitions are found. Keywords: cylindrical quantum dot, ensemble, modified Poschel-Teller potential, absorption of light 1. INTRODUCTION Modern methods of growth of semiconductor nanostructures like MBE, MOCVD, gas epitaxy, Stranski-Krastanov growth method etc. have become basic methods for experimental realization of quantum dots (QDs) of various geometric shapes. Spherical, pyramidal, ellipsoidal, lens-shaped, layered and other QDs are objects of great attention both theorists and experimentalists

Direct interband absorption of light in a falciform lens shaped quantum dot

Abstract: In the framework of adiabatic approximation the energy levels and direct interband absorption of light in the falciform lens shaped quantum dot are studied. Analytical expressions for energy spectrum and wave functions of the electron are obtained. It has been shown, that the particle energy spectrum is equidistant, and dependence of energy on geometrical parameters has root character. Dependences of absorption coefficient and edge frequencies on geometrical parameters of a quantum dot are obtained in the strong quantization regime. Corresponding selection rules for quantum transitions are revealed.© (1899) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Coupling effects in quantum dot molecules

Abstract: The electronic states and coupling effect in the laterally stacked symmetric and asymmetric 1 xx A lG a As − quantum-dotmolecules (QDMs) are studied. The formed potential of QDM is approximated with parabolic and modified PoschelTeller (MPT) potentials. It is shown that the coupling criterion of quantum dots (QDs) is the energy levels split due to the tunneling effect. In the case of the asymmetric QDM the electron relocalization step-like behavior is revealed, while in the symmetric case it is principally impossible. The obtained results for parabolic and modified Poschel-Teller potential confinements are compared. The formation of energy levels split for a given range of values of energy (coupling criterion) as a consequence of the finiteness of the confinement potential is revealed for the case of modified PoschelTeller potential approximation.