Spin photodiodes for the detection of circularly polarized light

Solid-state detectors capable of directly sensing light helicity are essential components for polarization-encoded optical communication and circular-polarimetric imaging. Spin photodiodes (spin PDs) based on ferromagnet/tunnel-barrier/semiconductor heterostructures offer a promising approach for direct helicity detection. A spin PD can be regarded as the reverse operation of a spin-light emitting diode (spin-LED): circularly polarized light generates spin-polarized carriers in the semiconductor, which are electrically detected through spin-dependent tunneling. Although major advances have been achieved in recent years by our group in the development of spin-LEDs, including circular polarization degrees of approximately 40% at room temperature and electrical switching of magnetization, and consequently of the polarization of light [1], relatively little research has focused on the development of spin photodiodes. We have recently demonstrated that a Ge-based spin photodiode can operate without an externally applied magnetic field at wavelengths relevant to optical telecommunications [2]. However, the spin-dependent photocurrent asymmetry still less than 1%. The goal of the post-doc is to develop spin-photodiode based on different semiconductors (GaAs, Ge) to enhance the polarization detection efficiency. References: [1] P. A. Dainone et al., “Controlling the helicity of light by electrical magnetization switching”, Nature 627, 783 (2024) [2] A. Djeffal et al., "CoFeB/MgO/Ge spin photodiode operating at telecommunication wavelength with zero applied magnetic field”, Phys. Rev. Appl. 10, 044049 (2018)