Spin relaxation through lateral spin transport in heavily doped n-type silicon

We experimentally study temperature-dependent spin relaxation including lateral spin diffusion in heavily doped n-type silicon (n+-Si) layers by measuring nonlocal magnetoresistance in small-sized CoFe/MgO/Si lateral spin-valve (LSV) devices. Even at room temperature, we observe large spin signals, 50-fold the magnitude of those in previous works on n+-Si. By measuring spin signals in LSVs with various center-to-center distances between contacts, we reliably evaluate the temperature-dependent spin diffusion length (lambda(Si)) and spin lifetime (tau(Si)). We find that the temperature dependence of tSi is affected by that of the diffusion constant in the n+-Si layers, meaning that it is important to understand the temperature dependence of the channel mobility. A possible origin of the temperature dependence of tSi is discussed in terms of the recent theories by Dery and co-workers.