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

Abstract 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, τ 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 τ s is approximately constant in this temperature range. In order to determine the dominant spin relaxation mechanism we have investigated the temperature dependence of τ s in non-degenerate lightly n-type Hg 0.78 Cd 0.22 Te of approximately the same band gap as InSb, and find that τ s varies from 356 ps at 150 K to 24 ps at 300 K . Our results, both in magnitude and temperature dependence of τ s , imply that the Elliott–Yafet model dominates in these materials.