FAR INFRARED MEASUREMENT OF DIELECTRIC PROPERTIES OF GAAS AND CDTE AT 300-K AND 8-K

The real refractive index n and power absorption coefficient a of high resistivity GaAs and CdTe have been directly measured at 300 K and 8 K in the wavelength region from 12.5 μ to 300 μ. This spectral region contains the fundamental lattice resonance of both materials: 37.2μ for GaAs and 71.4μ for CdTe. This resonance causes large dispersion in the linear material properties. Single Drude-type oscillators have been visually fit to the measured n data with the results that for GaAs, ɛdc′ = 12.8 ± 0.5 at 300 K and 12.6 ± 0.5 at 8 K, and ɛ∞′ = 10.9 ± 0.4 at 300 K and 8 K; for CdTe, ɛdc′ = 9.4 ± 0.4 at 300 K and 9.0 ± 0.4 at 8 K, and ɛ∞′ = 6.7 ± 0.3 at 300 K and 8 K. The GaAs data clarifies the role of dispersion in n in the 5–20 μ region where previous results differ considerably. For both materials the n and α data in the region past 30 μ are the first to be reported. © 1969 Optical Society of America.