Electron spin lifetimes in Hg0.78Cd0.22Te and InSb

We have made direct pump-probe measurements of spin lifetimes in long wavelength narrow-gap semiconductors at wavelengths between 4 and 10 mum and from 4 to 300 K. In particular, we measure remarkably long spin lifetimes, tau(s)similar to300 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 tau(s) is approximately constant in this temperature range. In order to determine the dominant spin relaxation mechanism we have investigated the temperature dependence of tau(s) in non-degenerate lightly n-type Hg0.78Cd0.22Te of approximately the same band gap as InSb, and find that tau(s) varies from 356 ps at 150 K to 24 ps at 300 K. Our results, both in magnitude and temperature dependence of tau(s), imply that the Elliott-Yafet model dominates in these materials. (C) 2003 Elsevier B.V. All rights reserved.