LIGHT ABSORPTION COEFFICIENT CAUSED BY SUB-BAND TRANSITIONS OF ELECTRONS IN SPHERICAL QUANTUM DOT SUPERLATTICES.

We analyze the electron energy spectrum in three-dimensional arrays of semiconductor quantum dots (QD) a model of 3D-superlattice and its optical properties. Some numerical simulations have been suggested for the real spherical AlxGa1-xAs quantum dot superlattice, where the concentration of Al changes within x = 0:2,...,1:0. In the tight-binding approximation, the dispersion law of electrons is obtained and analyzed. The dependence of the electron energy on the wave vector for 1s- and three (m = 0, ± 1) 1p-sub-bands for QDs of different radii and Al concentrations in the matrix of AlxGa1-xAs are calculated in details. The dependences of density of electron states on energy in the 1s- and 1p-sub-bands are obtained. It is shown that the density of states as a function of energy depends strongly on the QD size, distances between QDs and concentration x. Subsequetly, we can control the electronic band structure of this spherical quantum dot superlattice when some parameters of the system are changed. The absorption coeffcient of direct sub-band transitions is written in terms of a squared matrix element of the electronic transition and combined density of states. The conducted calculations have shown that in the dipole approximation electronic transitions are allowed between the sub-bands with m = 0. The absorption coeffcient is characterized by two peaks that correspond to the electron wave vector in the center and at the edge of the Brillouin zone. [ABSTRACT FROM AUTHOR]