Infrared Absorption and Valence Band in Indium Antimonide

Infrared absorption is studied at near liquid helium temperature for n- and p-type degenerate samples of various carrier concentrations. The absorption in p-type samples, at photon energies larger than the energy gap, depends on the hole concentration. The results show that the valence band is warped and that the energy at $k=0$ is very close to the maximum energy of the band. A step in the absorption of n-type samples is observed which gives an estimate of ~0.012m for the effective mass of light holes. The long wavelength absorption in p-type samples is characteristic of intervalence band transitions.