Fabrication of quantum wires by selective intermixing induced in GaAs/AlGaAs quantum well heterostructures by SiO 2 capping and subsequent annealing

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Results are presented demonstrating that selective intermixing of GaAs/AlGaAs quantum well heterostructures by SiO 2 capping and subsequent annealing can be spatially localized with a length scale compatible with the observation of lateral quantum confinement effects. Patterning of a 400 nm-thick SiO 2 encapsulation layer deposited by rapid thermal chemical vapor deposition into arrays of wires was performed using high resolution electron beam lithography and subsequent reactive ion etching. After high temperature (850°C) annealing, photoluminescence experiments indicate the creation of double barrier quantum wires when small trenches (< 100 nm) are etched in the SiO 2 film at a period greater than 800 nm. Signatures of the formation of one-dimensional subbands are observed both in photoluminescence excitation spectroscopy and linear polarization anisotropy analysis. A mechanism involving the ability of the stress field generated during annealing at the SiO 2 film edges to pilot the diffusion of the excess gallium vacancies which are responsible for the enhanced interdiffusion under SiO 2 is suggested to account for the high lateral selectivity achievable with this novel process.