Light helicity detection in MOS-based spin-photodiodes: An analytical model

Abstract

In a metal-oxide-semiconductor-based spin-photodiode, the helicity of an incoming light is efficiently converted into an electrical signal by exploiting (i) the helicity dependence of the degree of optical spin orientation for photogenerated carriers in the semiconductor and (ii) the spin-dependent tunneling transmission of the insulating barrier between the semiconductor and a ferromagnetic metal. Here, we propose a theoretical model for predicting the electrical response of the device to a circularly polarized light, by integrating the Fert-Jaffrès framework [A. Fert and H. Jaffrès, Phys. Rev. B 64, 184420 (2001)] with a helicity-dependent photo-generation term. A figure of merit, related to the variation of the electrical response to the switching of the light helicity from right to left, is defined, and its dependence on the constitutive parameters of the device (barrier resistivity and spin selectivity, semiconductor resistivity and spin diffusion length) is shown. Finally, a simple analytical formula for identifying the optimal resistance barrier leading to the maximum efficiency is found and experimentally validated on Fe/MgO/Ge spin-photodiodes

Comparison of spin photocurrent in devices based on in-plane or out-of-plane magnetized CoFeB spin detectors

“…[14,15], where spin imaging is obtained through spatially resolved Kerr rotation or full electrical measurements. By reversing the operation condition of spin LED, one can also realize the spin photodiode function by illuminating the device with circularly polarized light and obtain the helicity asymmetry of the photocurrent [16,17]. Several research groups have investigated the possibility of detecting a spin-polarized photocurrent generated under circular polarized light using spin-LED structures [18,19].…”