Opti-Helice: Optical and electrical spin detection in defect-engineered GaAs-based semiconductors: towards an electrical photon helicity detector
Research project selected under the 2016 call for proposals
Principal Investigator :
Andrea Balocchi ()
LPCNO (Groupe d’optoélectronique quantique)
Type of project : Collaborative Project
Partner team(s) :
CEMES (Nanomatériaux nMat)
Date (start/end) : 2017 - 2019
Main figure: Time dependence of the spin polarization of defect electrons (blue solid line) and nuclei (dashed line) z projections after being excited by the pump pulse. In the probe pulse (t1) defect electrons are spin polarized in the same direction as CB electrons and in the probe pulse (t2) defect electrons are spin polarized in the opposite direction to CB electrons. The resulting probe pulse luminescence (black solid line) will trace the defect electron-nuclear spins coherent oscillations without the need of any electron spin resonance technique. Inset: Illustration of the spin dependent recombination mechanism and its detection possibilities in the defect system. The Ga 2+ atom with its localized electron coupled by the hyperfine interaction (HFI) and the selective capture of photogenerated conduction band electrons are showed.
Abstract
The control of the carriers’ spin in solid materials for potential use in secure communications devices or quantum information applications has attracted a great attention in recent years. In this context, spins of well-isolated point defects in insulators or semiconductors play a crucial role: their spin state can be efficiently initialized, manipulated and readout (typically by means of magnetic resonance techniques) and their coherence time, one of the necessary conditions for quantum computing, can reach record values in the millisecond to second time range. Similarly on one side to nitrogen vacancies in diamond, and on the other side to shallow defects in silicon, paramagnetic Ga 2+ defects in dilute nitrides GaAsN semiconductors combines the strength of both systems: Ga 2+ defects form well isolated deep paramagnetic centers in the semiconductor gap (i.e. possessing one single electron) that can be optically and electrically addressed at room temperature and can benefit moreover from the mature industrial microelectronic fabrication techniques (doping and band gap engineering for instance). Interestingly, dilute nitride III–V semiconductors have been the subjects of intensive research for the past decade mainly for telecommunication applications, thanks to their widely adjustable bandgap (-150 meV per percentage of nitrogen incorporation in GaAs). It is only since our first discoveries of the remarkable spin properties of these materials and our demonstration that nitrogen-induced deep Ga 2+ interstitials paramagnetic defects are at the core of these unique properties (and not nitrogen itself) that the attention has shifted from optoelectronics to spintronics and quantum information. In this project, By taking advantage of different facets of the same giant spin dependent recombination phenomenon of conduction band electrons to paramagnetic Ga 2+ defects sites in GaAs-based semiconductors, we aim at tackling the double challenge of: (i) Demonstrating a novel all-optical readout scheme of the coherent oscillations of hyperfine-coupled electron-nuclear spins without the need of any electron resonance technique; (ii) Proposing a prototype photo-detector to electrically determine the circular polarization state of light.