Electron spin lifetimes in Hg_0.78Cd_0.22 Te and InSb

We have made direct pump-probe measurements of spin lifetimes in long wavelength narrow-gap semiconductors at wavelengths between 4 and 10 µm and from 4 to 300 K. In particular, we measure remarkably long spin lifetimes, t_s ~300 ps, even at 300 K for epilayers of degenerate n-type InSb. In this material the mobility is approximately constant between 77 and 300 K, and we find that t_s is approximately constant in this temperature range. In order to determine the dominant spin relaxation mechanism we have investigated the temperature dependence of t_s in non-degenerate lightly n-type Hg_0.78Cd_0.22Te of approximately the same band gap as InSb, and find that t_s varies from 356 ps at 150 K to 24 ps at 300 K. Our results, both in magnitude and temperature dependence of t_s, imply that the Elliott-Yafet model dominates in these materials. © 2003 Elsevier B.V. All rights reserved.