  A lateral-type spin-photodiode having a refracting facet on a side edge of
the device is proposed and demonstrated at room temperature. The light shed
horizontally on the side of the device is refracted and introduced directly
into a thin InGaAs active layer under the spin-detecting Fe contact in which
spin-polarized carriers are generated and injected into the Fe contact through
a crystalline AlOx tunnel barrier. Experiments have been carried out with a
circular polarization spectrometry set up, through which helicity-dependent
photocurrent component, dI, is obtained with the conversion efficiency F ~ 0.4
%, where F is the ratio between dI and total photocurrent Iph. This value is
the highest reported so far for pure lateral-type spin-photodiodes. It is
discussed through analysis with a model consisting of drift-diffusion and
quantum tunneling equations that a factor that limits the F value is unoccupied
spin-polarized density-of-states of Fe in energy region into which
spin-polarized electrons in a semiconductor are injected.
