We describe the growth and characterization of InAs quantum dots (QDs) on a patterned GaAs substrate using metalorganic chemical vapor deposition. The QDs nucleate on the ͑001͒ plane atop GaAs truncated pyramids formed by a thin patterned SiO 2 mask. The base diameter of the resulting QDs varies from 30 to 40 nm depending on the size of the mask. With specific growth conditions, we are able to form highly crystalline surface QDs that emit at 1.6 m under room-temperature photopumped conditions. The crystalline uniformity and residual strain is quantified in high-resolution transmission electron microscopy images and high-resolution x-ray reciprocal space mapping. These strained QDs may serve as a template for selective nucleation of a stacked QD active region.
The faceting of a quasi-two-dimensional nanoscale crystal (quasi-2D nanocrystal) grown by metal-organic vapor phase epitaxy is reported. Homoepitaxial selective growth is performed on a 200nm wide, [110]-directed stripe opening fabricated in a 30nm thick SiO2 film atop a GaAs(001) substrate. In the cross section perpendicular to the stripe opening, a selectively grown epilayer is regarded as a quasi-2D nanocrystal, which is close to a hexagonal shape symmetrically surrounded with (111)B-, (110)- and (111)A-type facets from the top as growth proceeds both vertically and laterally. The resulting faceting is interpreted on the basis of equilibrium crystal shape (ECS). The comparison of the observed crystal shape with theoretical modeling enables the measurement of the relative surface energies of the low index orientations. The ECS of a GaAs 2D crystal under the given growth conditions is proposed.
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