The identification of Urbach, acceptor impurity, and phonon-assisted components of the optical absorption band tail of n-type InSb

New measurements are presented of the interband absorption edge, in the range 0.01 to 100 cm-1, for uncompensated n-type InSb obtained using a photo-Hall technique. A spectral Urbach edge is observed in the range of sample temperature (20 to 77 K) and it is shown that the form of the experimental results derives from a broadening due to the interaction of acceptor impurity states. A phonon-assisted component is also identified at sample temperatures above 40 K. (author)