Temperature-independent spin relaxation in heavily doped n -type germanium

Abstract

We experimentally study the spin relaxation mechanism in heavily doped $n$-type germanium (Ge) layers by electrically detecting pure spin current transport. The spin diffusion length (${\ensuremath{\lambda}}_{\mathrm{Ge}}$) in heavily doped $n$-type Ge layers at 125 K is less than $0.7\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$, much shorter than that expected in the recent study by Dushenko et al. We find that the spin relaxation time ${\ensuremath{\tau}}_{\mathrm{s}}$ is independent of temperature in the range of 8 to 125 K, which can be interpreted by the recent theory by Song et al. This study clarifies that the spin-relaxation mechanism at low temperatures in degenerate Ge is dominated by extrinsic scattering with impurities.