FABRICATION OF QUANTUM WIRES BY SELECTIVE INTERMIXING INDUCED IN GAASALGAAS QUANTUM-WELL HETEROSTRUCTURES BY SIO2 CAPPING AND SUBSEQUENT ANNEALING/

Results are presented demonstrating that selective intermixing of GaAs /AlGaAs quantum well heterostructures by SiO2 capping and subsequent a nnealing can be spatially localized with a length scale compatible wit h the observation of lateral quantum confinement effects. Patterning o f a 400 nm-thick SiO2 encapsulation layer deposited by rapid thermal c hemical vapor deposition into arrays of wires was performed using high resolution electron beam lithography and subsequent reactive ion etch ing. After high temperature (850 degrees C) annealing, photoluminescen ce experiments indicate the creation of double barrier quantum wires w hen small trenches (<100 nm) are etched in the SiO2 film at a period g reater than 800 nm. Signatures of the formation of one-dimensional sub bands are observed both in photoluminescence excitation spectroscopy a nd linear polarization anisotropy analysis. A mechanism involving the ability of the stress field generated during annealing at the SiO2 him edges to pilot the diffusion of the excess gallium vacancies which ar e responsible for the enhanced interdiffusion under SiO2 is suggested to account for the high lateral selectivity achievable with this novel process. (C) 1995 Academic Press Limited