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The infrared absorption spectrum of n‐type GaAs
Author(s) -
Jensen B.
Publication year - 1978
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220860134
Subject(s) - boltzmann equation , relaxation (psychology) , boltzmann constant , refractive index , plasma oscillation , optical conductivity , electron , chemistry , condensed matter physics , dielectric , conductivity , physics , materials science , optics , quantum mechanics , psychology , social psychology
The optical conductivity of free electrons in polar semiconducting compounds has recently been calculated by use of a generalized Boltzmann equation derived from the equation of motion of the quantum density matrix. This reduces to the quasi‐classical Boltzmann transport equation in the low frequency limit. In this paper, the optical conductivity is calculated for GaAs as a function of carrier concentration in terms of a frequency dependent relaxation time which reduces to the usual relaxation time in the limit of low frequencies and an elastic scattering mechanism. The relation of the frequency dependent relaxation time to the electron cross section is discussed. The optical constants and the frequency dependent relaxation time are given for GaAs at 298 K over the spectral region from 45 to 3.5 × 10 3 cm −1 for carrier concentrations from 3.4 × 10 15 to 8.7 × 10 18 cm −3 . The real and imaginary parts of the complex refractive index and the reflectivity are calculated from the complex dielectric constant in terms of the frequency dependent relaxation times. The frequency at the minima of the reflectivity curve and at the plasma edge, where the real part of the electric constant vanishes, are correlated with carrier concentration. Comparison is made with recent experimental results.