Kinetically driven selective growth of InAs quantum dots on GaAs

We show that, by changing and tuning the direction of the As flux on a rippled substrate, at temperatures higher than 530 degrees C and high As/In flux ratio, a selective growth of InAs dots can be obtained on GaAs. This is an undisclosed effect related to the Arsenic flux in the molecular beam epitaxial growth of InAs quantum dots (QDs) on GaAs(001). This effect cannot be explained by a shadowing effect, due to the gentle slopes of the mounds (1-3 degrees), and reveals instead that As plays a fundamental role at these growth conditions. We have developed a kinetic model, which takes into account the coupling between cations and anions, and found that the very small surface gradient in the anion flux, due to the oblique evaporation on the mounded surface, is responsible for a massive drain of cations toward the surface anion-rich areas, thus generating the selective growth of QDs.