Infrared Absorption of Indium Antimonide

Abstract

Indium antimonide samples of a wide range of carrier concentrations were measured from ∼5°K to 500°K, over a wavelength region of 3 to 35 microns. Experimental results on the shift of the absorption edge in degenerate $n$-type samples are presented and discussed. Both $n$-type and $p$-type samples show the same absorption at long wavelengths, after becoming intrinsic at elevated temperatures. At lower temperatures, the absorption in $n$-type samples increases with wavelength, whereas in $p$-type samples it remains practically constant over a wide wavelength region. The absorption coefficient in different samples, $n$-type or $p$-type, does not increase proportionately with the carrier concentration. Possible mechanisms for the absorption are discussed.