An exact expression is found for the potential of a point charge in a periodic layered system, consisting of alternating layers with two different values of the dielectric constant. The most interesting limiting cases for this potential are considered. Energy spectrum, bound energy, and the ground stat,e radius of the exciton, which is formed by an electron and a hole, belonging t o the same layer of the superlattice, are found.Hai3neHo TosHoe mipameme noTeHqMana, coanaaae~oro TosewmM a a p~n o~ 3 nepnonasecrcoii CJIOHCTOB CHcTeMe, cocTomqeFi t13 .repeAyIoqMxcH cnoeB c HBYMR p a 3 n m u~b 1~~ 3Ha'XeHMIRMH nE13JIeIETpIl~eCIEOii IlPOHHUaeMOCTH. PaCCMOTpeHbI ~a~l 6 o n e e HHTepeCHbIe IIpeneJIbHbIe CJlysaM. HaiineHbr ClIeKTp, 3HeprliFI CBH3M M panMyC OCHOBHOrO COCTOFIHLlFI 3KCMTOHB, 06pa303aHHOrO 3JIeHTpOHOM M AbIpHOfi E13 O n H O r O EI T O r O ZfEe CJIOFI CBepXpeIIXeTKIl.

On the basis of the exact expression for the potential of a point charge in a superlattice, consisting of alternating layers with two different values of the dielectric constant, the energy spectrum is found of an exciton motion, perpendicular to the superlattice layer direction, a t small values of the exciton quasi-momentum component parallel to the layer plane. An evident form of an exciton energy dependence on the cross component of quasi-momentum which is perpendicular to the layer plane is adduced. The exciton energy has a maximum a t the centre of the Brillouin zone of the cross quasi-momentum and a minimum a t its boundaries.

In /1/ the exact expression for the potential of a point charge in a periodic layered system, consisting of alternating layers with two different values of the dielectric constant is found. Knowing of the potential enables one to solve an exciton spectrum problem in such a system and this problem was solved in a certain region of parameter values. However, a s for the excitonic spectrum and for the single-particle one the interaction of each charge with the surrounding medium, which is polarized by the charge itself, may turn out to be essential. Such a "self-force" in the case of separate film, which is surrounded by a medium, the dielectric constant of which is much smaller than that of the film, was found in /2/.

The electrical and galvanomagnetic properties of unrelaxed heteroepitaxial structures of InAs1-xSbx (x = 0.43 and x = 0.38) were studied in a wide temperature range of 5-300K and magnetic fields up to 8 T. The band gap of the composition InAs0.57Sb0.43 was estimated from the thermo-activation dependence of the electrical conductivity, and is equal to 120 meV. The electron concentration in InAs1-xSbx (n=6·1016 cm-3 for InAs0.62Sb0.38 and n=5·1016 cm-3 for InAs0.57Sb0.43) determined from the Hall effect and consistent with the electron concentration calculated from Shubnikov-de Haas oscillations. Also, implemented spectral ellipsometric studies of unrelaxed heteroepitaxial structures of InAs1-xSbx (x = 0.43 and x = 0.38) in the photon energy range of 1-6 eV. The spectral dependences of the imaginary and real parts of the dielectric constant are determined. The dispersion dependences of the refractive indices and extinction are calculated and given.

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