Optical Properties of Bi2Se3-xAsx Single Crystals

✍ Scribed by A. Sklenár; C. Drasar; A. Krejcová; P. Losták

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 177 KB
• Volume: 35
• Category: Article
• ISSN: 0232-1300
• DOI: 10.1002/1521-4079(200009)35:9<1069::aid-crat1069>3.0.co;2-o

✦ Synopsis

Bi 2 Se 3-x As x 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 ω p , optical relaxation time τ, and high-frequency permittivity were determined by fitting the Drude-Zener formulas to the reflectance spectra. It was found that the substitution of As atoms for Se atoms in the Bi 2 Se 3 crystal lattice leads to a decrease in the ω p values. This effect is accounted for by a model of point defects in the crystal lattice of Bi 2 Se 3-x As x . The dependences of the absorption coefficient K on the energy of incident photons were determined from the transmittance spectra. The optical width of the energy gap is found to decrease with increasing As content. The values of the exponent β from the relation of K ∼ λ β 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 Bi 2 Se 3-x As x crystals is the scattering by acoustic phonons.