Nanoengineered Quantum Dot Medium for Space Optoelectronic Devices

Resistance to temperature and ionizing radiation of space optoelectronic devices can be improved through control of carrier kinetics in nanoscale systems. Recent results in the science and technology of self-assembled heteroepitaxial InAs quantum dot (QD) medium related to photonic applications are discussed. Focus is placed on management of carrier kinetics via nanoengineering of electronic spectrum and potential profiles in the QD ensemble using modeling and controlled fabrication of QDs with molecular beam epitaxy. Shape-engineered QD sheets embedded into GaAs quantum wells were found to withstand two orders of magnitude higher proton dose than QWs and to account for high luminescence efficiency and thermally stable laser diodes. Built-in charge in QDs is responsible for improvement of both near and mid-IR optical absorption, but also control photoelectron lifetime in the structures. The negatively charged QD medium was the first QD material that has recently shown credible improvement of solar cell efficiency. It has resulted from IR energy harvesting and suppressed fast electron capture processes. It is thus expected that QD InAs/GaAs photovoltaics will overcome the efficiency and lifespan of multi-junction solar cells. Potentials due to QD built-in charge are also responsible for improved photoelectron lifetime in QD infrared photodetectors. QD correlated clusters provide even higher collective potential barriers around clusters and constitute the novel approach to the optoelectronic materials combining manageable photoelectron lifetime, high mobility, and tunable localized and conducting states.