Suppression of D’yakonov–Perel spin relaxation in InAs and InSb by n-type doping at 300 K

We have made direct pump-probe measurements of spin lifetimes in intrinsic and degenerate n-InAs at 300 K. In particular, we measure remarkably long spin lifetimes (τs∼1.6 ns) for near-degenerate epilayers of n-InAs. For intrinsic material, we determine τs∼20 ps, in agreement with other workers. There are two main models that have been invoked for describing spin relaxation in narrow-gap semiconductors: the D’yakonov–Perel (DP) model and the Elliott–Yafet (EY) model. For intrinsic material, the DP model is believed to dominate in III–V materials above 77 K, in agreement with our results. We show that in the presence of strong n-type doping, the DP relaxation is suppressed both by the degeneracy condition and by electron–electron scattering, and that the EY model then dominates for the n-type material. We show that this same process is also responsible for a hitherto unexplained lengthening of τs with n-type doping in our earlier measurements of n-InSb.