Temperature dependent spin Hall conductivity in n-GaAs epitaxial layers measured by inverse spin Hall effect

The photo-induced inverse spin Hall effect (ISHE) experiments are conducted in heavily doped n-GaAs epitaxial layers by measuring the transverse electric current generated through the diffusion of optically injected spin orientations over a temperature range of 10-300 K. ISHE origin of the measured signal is confirmed through meticulous checks including the characteristic dependence of magnitude of signal on the angle of incidence. The measured value of ISHE current (I-ISHE) is observed to fall with the increase in temperature. Furthermore, the value of spin current density is theoretically estimated by solving the spin diffusion equation with appropriate boundary conditions for an epitaxial layer. It is shown that by near resonant excitation and subsequent solution of diffusion equation, the spin Hall angle (gamma) and spin Hall conductivity (sigma(SH)) can be estimated, provided the effective life time of spin polarized electrons(tau(S)) is known independently. By using the numerically calculated value of tau(S), the proposed method is implemented to estimate the values of gamma and sigma(SH). It is found that the fall in the values of I-ISHE at high temperatures is not governed by sigma(SH), rather by a rapid decrease in the values of tau(S). In fact, sigma(SH) is seen to increase with the temperature, which is compared with existing literature. The present work provides the necessary insight into material parameters which are essential for the development of advanced spin-photonic semiconductor devices. Published by AIP Publishing.