Effect of Diatomic Silicon Molecular Impurities on the Luminescent Properties of Semiconductor Solid Solutions

Abstract

One of the urgent problems of materials science in the field of photovoltaics is obtaining promising novel photoactive semiconductor materials with predetermined photoelectric parameters to provide an efficient manifestation of photovoltaic, thermovoltaic, and emitting effects in the visible and near-infrared regions of the radiation spectrum. In this aspect, it is of great practical and fundamental interest to clarify the effect of diatomic molecular impurities on the electrophysical and photoelectric properties of semiconductor materials, as well as to reveal the energy levels of impurity molecules depending on the parameters of the base material. For this purpose, several semiconductor substitutional solid solutions based on elemental semiconductors such as Si and Ge, as well as III–V isoperiodic binary compounds such as GaAs and GaP, and II–VI isoperiodic binary compounds such as ZnSe and ZnS with Si2 molecular impurities have been obtained and studied. (Si2)1 – x – y(Ge2)x(GaAs)y, (ZnSe)1 – x – y(Si2)x(GaP)y, (Si2)1 – x(GaP)x and (Si2)1 – x(ZnS)x solid solutions have been grown on silicon Si (111) substrates from a limited volume of tin and lead solution-melt by means of liquid-phase epitaxy. The grown epitaxial layers have a monocrystalline structure with mirror-like smooth surfaces. The photoluminescence spectrum of solid solutions has been studied. The spectrum covers the photon energy range from 1.18 to 1.55 eV for (GaAs)0.95(Ge2)0.05〈Si2〉, from 1.38 to 3.1 eV for (GaP)0.98(Si2)0.02, from 1.55 to 3.1 eV for (ZnSe)0.88(Si2)0.03(GaP)0.09, and from 1.55 to 3.2 eV for (ZnS)0.97(Si2)0.03. It has been found that Si2 molecules in the case of (GaAs)0.95(Ge2)0.05〈Si2〉 solid solution form deep impurity energy levels lying at 1.33 eV below the bottom of the conduction band, in the case of (GaP)0.98(Si2)0.02, it is 1.47 eV, in the case of (ZnSe)0,88(Si2)0,03(GaP), 1.67 eV, and in the case of (ZnS)0.97(Si2)0.03, 1.82 eV. It is shown that in solid solutions with Si2 molecular impurities, an increase in the dissociation energy of the covalent bond in Si–Si impurity molecules is observed with increasing band gap and with decreasing crystal lattice parameter of the base semiconductor. Change in the dissociation energy of the Si–Si covalent bond in the tetrahedral crystal lattice of different semiconductors is caused by a change in the length of the Si–Si covalent bond, as well as by a change in the hybridization of the atomic electron shells of Si2 impurity molecules and base material molecules. The studied (Si2)1 – x(GaP)x and (Si2)1 – x(ZnS)x solid solutions can be used as a photoactive material for the development of photoconverters operating in the visible and near-infrared regions of the radiation spectrum.