On the Correlation Between the Self-Organized Island Pattern and Substrate Elastic Anisotropy

Self-organized quantum dots pattern depends strongly on the elastic strain energy of the substrate. It is well-known experimentally that for the elastic substrate with a high degree of anisotropy, the epitaxially grown island patterns are different for different growth orientations. In this report, by incorporating the anisotropic strain energy field into a kinetic Monte Carlo algorithm for adatom diffusion, we show that the self-organized island pattern on the surface of an anisotropic substrate is closely correlated to the elastic energy distribution on the surface. The anisotropic substrates studied are GaAs with different growth orientations 001, 111, and 113. An isotropic substrate Iso 001, reduced from GaAs, is also investigated for the purpose of comparison. The island patterns on these substrates with and without elastic strain energy are presented. Besides the effect of substrate anisotropy, different growth parameters, including temperature, coverage, and interruption time, are further investigated to identify the optimal growth values. It is observed that the strain energy field in the substrate is the key factor that controls the island pattern, and that the latter is closely correlated to the substrate orientation anisotropy. Our simulated patterns are also in qualitative agreement with recent experimental growth results.