Infrared dielectric constant of gallium arsenide

The real dielectric constant of gallium arsenide has been determined at 300 and at 5 K from fits to observed interference in transmission of thin samples with parallel surfaces. Measurement was carried out over all or part of the range 30-4000 cm(-1). An accuracy of +/-0.5% is estimated based on the quality of the analytic fits and the sample thickness measurement technique. We find at 300 K, epsilon(0)=12.90 and epsilon(infinity)=10.86. At 5 K, E(0)=12.46 and E(infinity)=10.58. An analytic expression for the dielectric function is given which allows accurate values of the real dielectric constant to be determined throughout most of the 0-4000 cm(-1) spectral range. The observed ratio epsilon(0)/epsilon(infinity) agrees with the Lyddane-Sachs-Teller relation calculated with Raman values of transverse and longitudinal optical phonon frequencies to better than 0.1% at 300 and at 5 K.