Engineering topics

Marques, G. E.

Publications and source records attributed to Marques, G. E..

3 records

DOE OSTI2016

Light sensitive memristor with bi-directional and wavelength-dependent conductance control

We report the optical control of localized charge on positioned quantum dots in an electro-photo-sensitive memristor. Interband absorption processes in the quantum dot barrier matrix lead to photo-generated electron-hole-pairs that, depending on the applied bias voltage, charge or discharge the quantum dots and hence decrease or increase the conductance. Wavelength-dependent conductance control is observed by illumination with red and infrared light, which leads to charging via interband and discharging via intraband absorption. The presented memristor enables optical conductance control and may thus be considered for sensory applications in artificial neural networks as light-sensitive synapses or optically tunable memories.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Carrier transfer in vertically stacked quantum ring-quantum dot chains

The interplay between structural properties and charge transfer in self-assembled quantum ring (QR) chains grown by molecular beam epitaxy on top of an InGaAs/GaAs quantum dot (QD) superlattice template is analyzed and characterized. The QDs and QRs are vertically stacked and laterally coupled as well as aligned within each layer due to the strain field distributions that governs the ordering. The strong interdot coupling influences the carrier transfer both along as well as between chains in the ring layer and dot template structures. A qualitative contrast between different dynamic models has been developed. By combining temperature and excitation intensity effects, the tuning of the photoluminescence gain for either the QR or the QD mode is attained. The information obtained here about relaxation parameters, energy scheme, interlayer and interdot coupling resulting in creation of 1D structures is very important for the usage of such specific QR–QD systems for applied purposes such as lasing, detection, and energy-harvesting technology of future solar panels.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2014

Low temperature magneto-photoluminescence of GaAsBi /GaAs quantum well heterostructures

Strong optical anisotropy is observed in the emission from a GaAs{sub 1−x}Bi{sub x} (x ∼ 0.04) quantum well grown by low temperature molecular beam epitaxy on (001) GaAs by means of low temperature magneto-photoluminescence (MPL) taken at 2 K in Faraday geometry for magnetic fields, B, up to 10 T. A significant diamagnetic shift (∼2.5 meV) develops for magnetic fields above ∼8 T, which is accompanied by a narrowing of the emission bandwidth and a substantial increase in the difference between the integrated intensities of the σ{sup +} and σ{sup −} polarizations in the MPL spectra. This, along with a peculiar spectral dependence of the polarization degree which evolves with increasing magnetic field, is interpreted in terms of bound and free magneto excitons in the system where Bi-related levels become hybridized to different extents with the valence and conduction bands of the GaAs host material.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗