Electrical detection of light helicity using a quantum-dot-based hybrid device at zero magnetic field

Photon helicity-dependent photocurrent is measured at zero magnefic field thanks to a device based on an ensemble of (In,Ga)As/GaAs quantum dots that are embedded into a GaAs-based p-i-n diode. Our main goal is to take advantage of the long electron spin-relaxation time expected in these nano-objects. In these experiments, no external magnetic field is required thanks to the use of an ultrathin magnetic CoFeB/MgO electrode, presenting perpendicular magnetic anisotropy. We observe a clear asymmetry of the photocurrent measured under respective right and left polarized light that follows the hysteresis of the magnetic layer. The amplitude of this asymmetry at zero magnetic field decreases with increasing temperatures and can be controlled with the bias. Polarization-resolved photoluminescence is detected in parallel while the device is operated as a photodetector. This demonstrates the multifunctional capabilities of the device and gives valuable insights into the spin relaxation of the electrons in the quantum dots.