Kinetically driven selective growth of InAs quantum dots on GaAs

Abstract

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

Manipulating surface diffusion and elastic interactions to obtain quantum dot multilayer arrangements over different length scales

“…The small As flux difference (DF/F % 4%) on the two sides of the mounds due to the fixed As beam direction, together with the high mobility of In cations at high temperature, cause a current of In adatoms from the side less exposed to the side more exposed to the As flux. We have found that the dots nucleating on the mound side opposite the direction of the As flux tend to dissolve 11,21 and their material move to the other side in a sort of ripening effect. 22,23 To explain the vertical stacking of dots, shown in Fig.…”

Single QD emission from arrays of QD chains obtained by patterning-free method

“…In previous reports 13, 14 we discussed the main mechanisms responsible for the selective growth and pointed out that the samples grown in CD mode showed only a poor selective growth. However, in light of the kinetic processes identified by our model, 13 we expect that a consistent reduction of the growth rate should enhance the selective growth in the CD mode as well.…”

“…1d) since the As flux gradient, due to the oblique evaporation, is responsible for an In-adatoms drift current over the surface which determines the position where the QDs grow, provided the growth temperature is sufficiently high to enhance the In surface mobility. 13,14 The comparison between CD and PD samples in Fig. 1 clearly shows that, by progressively reducing the growth rate to 1/6 with respect to the one used in the PD growth (Fig.…”

“…In the selective nucleation and growth of arrays of InAs QDs on GaAs a step forward has been reached recently [13][14][15] by exploiting the directionality of the As beam under critical growth conditions (high growth temperature and flux). The combined effect of the high In surface mobility, of a rippled GaAs buffer where steps and step bunching constitute preferential sites for dot nucleation, and of the oblique evaporation of As is responsible for an In-adatom drift current over the surface that determines the selective growth of QDs at specific locations.…”

Selective growth of InAs quantum dots on GaAs driven by as kinetics

“…We have recently shown that, when the InAs is deposited with the sample rotation off and with an oblique orientation of the As 4 flux with respect to the (110) plane of the sample, the QDs align along the step bunching of one single side of the mounds (right panel of figure ). We showed that the mound side where the QDs are located is determined by the direction of the impinging As 4 beam.…”