We report strong heavy hole-light mixing in GaAs quantum dots grown by droplet epitaxy. Using the neutral and charged exciton emission as a monitor we observe the direct consequence of quantum dot symmetry reduction in this strain free system. By fit
ting the polar diagram of the emission with simple analytical expressions obtained from k$cdot$p theory we are able to extract the mixing that arises from the heavy-light hole coupling due to the geometrical asymmetry of the quantum dot.
By combining optical spin injection techniques with transport spectroscopy tools, we demonstrate a spin-photodetector allowing for the electrical measurement and active filtering of conduction band electron spin at room temperature in a non-magnetic
GaAsN semiconductor structure. By switching the polarization of the incident light from linear to circular, we observe a Giant Spin-dependent Photoconductivity (GSP) reaching up to 40 % without the need of an external magnetic field. We show that the GSP is due to a very efficient spin filtering effect of conduction band electrons on Nitrogen-induced Ga self-interstitial deep paramagnetic centers.
