Dependence on In content of In xGa 1− xAs quantum dots grown along GaAs multiatomic steps by MOVPE

Abstract

We fabricated self-organized In x Ga 1− x As quantum dots on GaAs(0 0 1) vicinal surfaces having multiatomic steps by using metalorganic vapor phase epitaxy. The dots preferentially grew along the GaAs multiatomic step edges. We investigated the density and uniformity of the dots as a function of the substrate misorientation angle, the layer thickness, the In content, and the growth temperature. Observation of grown surfaces by atomic force microscopy showed that the dot formation depended strongly on the In content and layer thickness. In general, for lower In contents and/or thinner layers, no dot formation was observed because the interface stresses were insufficient for three-dimensional island growth. For higher In content and/or thicker layers, high-density dots formed on the GaAs multiatomic steps. However, these dots were not always uniform: they included small dots (∼40 nm) and large islands (>100 nm). Under optimum growth conditions, that is, 3.2-monolayer In 0.8Ga 0.2As growth, we obtained high-density (6.2×10 10/cm 2) and highly uniform (10–25 nm) small quantum dots along the GaAs multiatomic step edges.