Effect of an External Electric Field on the Intracenter Optical Transitions in Quasi-Zero-Dimensional Semiconductor Structures

The development of the double selective doping technique has stimulated interest in the optical properties of semiconductor nanostructures containing the H--similar impurity centers and their molecular complexes. Interest in the optical properties of quantum dots with the D-2(-) centers in an electric field is due, first of all, to the possibility of effective control of both the binding energy of impurity states and the photoexcitation spectra of molecular impurities. Depending on the quantum dot radius and the spatial configuration of impurity molecules, the D-2(-) photoexcitation band can be in the visible, IR, or terahertz frequency range, which significantly expands the range of instrumental applications of quantum dots with impurity states. Therefore, great interest is presented by quasi-zero-dimensional structures with the D-2(-) impurity states, which can be used to create IR and terahertz receivers. The aim of this study is to theoretically investigate the features of the spectra of intracenter optical transitions in quasi-zero-dimensional structures with the D-2(-) centers in an electric field. The binding energy of the D-2(-) states has been calculated by the zero-radius potential method in the effective mass approximation. The expression for the coefficient of impurity absorption of light has been obtained in the dipole approximation within the perturbation theory. It has been shown that the violation of symmetry in the arrangement of the D-0 centers leads to the removal of degeneracy between the g and u terms. It is shown that an external electric field leads to a decrease in the splitting between the g- and u-terms. It has been established that the photoexcitation spectrum is a band the position of which depends on the external electric-field strength. The quasi-zero-dimensional structures with the D-2(-) centers in an external electric field can be used to create IR and terahertz detectors with controllable characteristics.