High-density optical storage using arsenic nanoclusters in GaAs and AlGaAs

A novel GaAs-based photorefractive thin-film material with ultrashort transport lengths has been developed. This material consists of As nanoclusters in a high-quality GaAs matrix, denoted GaAs:As. The As clusters act as quantum antidots which exclude the wavefunctions of the electrons and holes. The resulting reduced space of the carrier wavefunctions results in quantum-confined excitons in the GaAs regions between the As clusters. Therefore, GaAs:As exhibits a large electrooptic effect at room temperature for photon energies close to the bandgap. This large electrooptic effect, along with charge trapping on the As clusters, provides a high-density holographic storage medium. The ultrafast lifetimes of the photogenerated carriers due to the As clusters produce excellent spatial resolution during writing of holographic space-charge gratings. Fringe spacings as small as 600 nm were supported in GaAs:As, yielding a volume optical data density greater than 10/sup 12 /b/cm/sup 3/.