Resonant Tunneling Self-Assembled Quantum Dots for Memory Elements

Two main research topics were studied during this period: (1) Research on buried strain induced quantum dots (SIQDs) generated by self assembling quantum dot (QDs) layers. We investigated here a new type of quantum dots which are generated by the lateral band gap modulation of a quantum well GaAs/AlGaAs induced by a buried layer of self assembled quantum dots. Such SIQDs allow to move the OD confinement regime into the red region of the spectrum. The confinement energies for these SIQDs are function of the distance between the QDs layer and the QW and on the thickness of the QW. They also allow for a greater flexibility for integrating quantum dot devices in device structures. To this end, we have developed an exciton storage device based on quantum dot structures. The device uses pairs of SIQDs and QDs to store the exciton dissociated as an electron hole pair under an internal electric field. The stored e-h pair is restored as an exciton by applying a bias to the device. This method allows for exciton lifetimes of several seconds i.e., more than a billion times the lifetimes of excitons in normal QDs.