Rashba semiconductor as spin Hall material: Experimental demonstration of spin pumping in wurtzite $n$-GaN:Si

Pure spin currents in semiconductors are essential for implementation in the next generation of spintronic elements. Heterostructures of III- nitride semiconductors are currently employed as central building-blocks for lighting and high-power devices. Moreover, the long relaxation times and the spin-orbit coupling (SOC) in these materials indicate them as privileged hosts for spin currents and related phenomena. Spin pumping is an efficient mechanism for the inception of spin current and its conversion into charge current in non-magnetic metals and semiconductors with Rashba SOC $via$ spin Hall effects. We report on the generation in $n$-GaN:Si\,--\,at room temperature and through spin pumping\,--\,of pure spin current, fundamental for the understanding of the spin dynamics in these non-centrosymmetric Rashba systems. We find for $n$-GaN:Si a spin Hall angle $\theta_{\mathrm{SH}}$=$3.03\times10^{-3}$, exceeding by one order of magnitude those reported for other semiconductors, pointing at III-nitrides as particularly efficient spin current generators.