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

• Published in: Applied solar energy 2020-05, Vol.56 (3), p.178-185
• Main Authors: Saidov, A. S., Usmonov, Sh. N., Saparov, D. V., Akhmedov, A. M.
• Format: Article
• Language: English
• Subjects: Chemical bonds; Conduction; Conduction bands; Covalence; Covalent bonds; Crystal lattices; Electrical Machines and Networks; Energy; Energy levels; Energy of dissociation; Engineering; Epitaxial growth; Epitaxial layers; Free energy; Gallium arsenide; Germanium; Heat of formation; Heliotechnical Materials Science; Hybridization; I.R. radiation; Impurities; Liquid phase epitaxy; Liquid phases; Materials science; Near infrared radiation; Optical properties; Photoelectric effect; Photoelectric properties; Photoelectricity; Photoluminescence; Photons; Photovoltaic cells; Photovoltaics; Power Electronics; Radiation; Semiconductor materials; Semiconductors; Silicon; Solar energy; Solid solutions; Substitutional solid solutions; Tin
• ISSN: 0003-701X; 1934-9424
• DOI: 10.3103/S0003701X20030093

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 Si 2 molecular impurities have been obtained and studied. (Si 2 ) 1 –  x  –  y (Ge 2 ) x (GaAs) y , (ZnSe) 1 –  x  –  y (Si 2 ) x (GaP) y , (Si 2 ) 1 –  x (GaP) x and (Si 2 ) 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 (Ge 2 ) 0.05 〈Si 2 〉, from 1.38 to 3.1 eV for (GaP) 0.98 (Si 2 ) 0.02 , from 1.55 to 3.1 eV for (ZnSe) 0.88 (Si 2 ) 0.03 (GaP) 0.09 , and from 1.55 to 3.2 eV for (ZnS) 0.97 (Si 2 ) 0.03 . It has been found that Si 2 molecules in the case of (GaAs) 0.95 (Ge 2 ) 0.05 〈Si 2 〉 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 (Si 2 ) 0.02 , it is 1.47 eV, in the case of (ZnSe) 0,88 (Si 2 ) 0,03 (GaP), 1.67 eV, and in the case of (ZnS) 0.97 (Si 2 ) 0.03 , 1.82 eV. It is shown that in solid solutions with Si 2 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