Optical properties of Bi2Se3-xAsx single crystals

Bi2Se3-xAsx single crystals with the As content of c(As) = 0 to 2.0x10(19) atoms/cm(3) prepared from the elements of 5N purity by means of a modified Bridgman method were characterized by measurements of infrared reflectance and transmittance. Values of the plasma resonance frequency omega (p), opti cal relaxation time tau, and high-frequency permittivity were determined by fitting the Drude-Zener formulas to tho reflectance spectra, It was found that the substitution of As atoms for Se atoms in the Bi2Se3 crystal lattic e leads to a decrease in the omega (p) values. This effect is accounted for by a model of point defects in the crystal lattice of Bi2Se3-xAsx. The dep endences of the absorption coefficient K on the energy of incident photons were determined from the transmittance spectra. The optical width of the en ergy gap is found to decrease with increasing As content. The values of the exponent beta from the relation of K similar to lambda (beta) for the long -wavelength absorption edge range within the interval 2.0 to 2.3, i.e. the dominant scattering mechanism of free current carriers in Bi2Se3-xAsx cryst als is the scattering by acoustic phonons.