Spin-dependent Transport in Spin-photodiode Consisting of a p-n III-V Heterojunction

Abstract

Understanding spin-dependent transport in semiconductor structures is very important to realize semiconductor spintronics devices. Early theoretical works have suggested unique spin-dependent transport phenomena in semiconductor structures having spatially inhomogeneous spin splitting in the conduction and/or valence bands [1,2]. Spin-voltaic effect (SVE), an electromotive force caused by the spin splitting, is one of such phenomena proposed for the homogeneous and graded p-n junctions [3,4]. SVE is useful for electrical detection of spin polarization. Utilizing this effect, we proposed and are working experimentally on "spin-photodiode" (spin-PD) which directly converts circular polarization of light into an electrical signal [5]. This device should be built by semiconductor layers with different g-factor and thus different band gap, we must understand spin transport across the heterointerface having finite band discontinuities. This paper describes theoretical treatments and experimental results of spin-dependent transport in a spin-PD consisting of a p-n, Ill-V heterojunction in which conduction band inp-region is spin-split (Fig. 1). Let us consider optical spin-injection into n-layer by right-circularly-polarized (es) light irradiation under the forward bias (Vf) condition. The optical spin-injection results in a spin polarization P11 of electrons in the n-layer. Applying the thermionic-diffusion theory [6,7] to this situation, a photocurrent due to SVE [3], AIsvE, can be expressed as follows;