Optically Induced Persistent Charge Storage Effects in Self Assembled InAs Quantum Dots

Resonant optical excitation of the quantum dot (QD) ensemble produces a strong increase of the lateral resistance of a spatially separated InGaAs n-channel. This is shown to arise from the preferential storage of electrons within the QD layer. The induced photoeffect is persistant over timescales of many hours at 140 K and can be controllably erased by injecting holes into the QD layer from a separate p-contact. The magnitude of the induced photo-effect is found to be sensitive to the excitation energy with a number of resonances observed which reflect inelastic excitation of the QD ensemble. By performing power dependent measurements a similar resonance is observed in the device switching time after illumination. The potential operation of the device as a novel, wavelength selective, optical memory is suggested.