Anisotropic Diffusion of In Atoms from an In Droplet and Formation of Elliptically Shaped InAs Quantum Dot Clusters on (100) GaAs

Abstract

The surface diffusion of In atoms from an In droplet and their subsequent reaction with As4 molecules lead to the formation of InAs quantum dots elliptically distributed around the initially formed droplet. The size of this elliptic dot cluster depends sensitively on the growth conditions. For instance, as the substrate temperature Ts is raised from 220 to 350 °C, the shorter and longer diameters of the elliptic clusters, elongated in the [011] direction, increase exponentially with Ts, expanding from the range of 0.8−1.6 μm to 2−7 μm. When the pressure PAs of As4 is increased from 0.7 to 10 × 10−5 Torr at Ts = 300 °C, the cluster diameters shrink from 3−6 μm to 1−2 μm in inverse proportion to PAs0.3−0.4. These findings are interpreted in terms of anisotropic diffusion of In atoms from the droplet.