Infrared Refractive Index and Absorption of InAs and CdTe

Abstract

Transmission interference fringes from 2690 to 320 cm−1 for InAs and from 1330 to 320 cm−1 for CdTe have been analyzed with classical dispersion theory to obtain the room-temperature dielectric constants. For InAs the dielectric constant between the band edge and the reststrahl ε∞ and the static dielectric constant ε0 are: ε∞ = 11.8±0.1, ε0 = 14.55±0.3; and for CdTe: ε∞ = 7.05±0.05, ε0 = 10.60±0.15. These values agree favorably with previously reported values. The absorption of InAs has been measured from 2500 cm−1, near the fundamental absorption edge, to 260 cm−1. Eight absorption peaks were observed between 444 and 269 cm−1 which are attributed to multiphonon combinations with the following characteristic phonon frequencies: TO1 = 222 cm−1, TO2 = 214 cm−1, LO = 196 cm−1, and LA = 143 cm−1. The transmission of CdTe has been observed from 10 000 to 220 cm−1. From 10 000 to 450 cm−1 the transmission is essentially constant at ∼60%. Below 400 cm−1 only two previously reported transmission minima were observed.