Fabrication and Characterization of Self-organized Quantum Nano-structures.

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We have fabricated AlGaAs/GaAs quantum dot structures using selective area metalorganic vapor phase epitaxy (MOVPE). First, GaAs pyramidal structures with four-fold symmetric {011} facet side walls are formed on SiN_x masked (001) GaAs with square openings. Once the pyramidal structures were completely formed, no growth occurs on the top and side walls of the pyramids. Furthermore, the shape and width of the top area observed by a scanning electron microscope (SEM) and an atomic force microscope (AFM) shows to be highly uniform. This indicates that self-limited growth mode occurs. Next, using these uniform pyramids, GaAs quantum dots are overgrown on the top of pyramids using different growth conditions. Sharp photoluminescence (PL) spectra are observed from uniform quantum dots.