Predicting and Understanding Order of Heteroepitaxial Quantum Dots

TL;DR

This paper models the early stages of heteroepitaxial quantum dot formation to understand how crystal anisotropy and growth conditions influence the ordering of quantum dot arrays, which is crucial for electronic and optoelectronic applications.

Contribution

It introduces a stochastic surface diffusion model to analyze the effects of anisotropy, initial conditions, and thermal fluctuations on quantum dot order during growth.

Findings

Crystal anisotropy enhances quantum dot order.

Optimal film height near the wetting surface improves ordering.

Surface diffusion analysis reveals key factors influencing dot arrangement.

Abstract

Heteroepitaxial self-assembled quantum dots (SAQDs) will allow breakthroughs in electronics and optoelectronics. SAQDs are a result of Stranski-Krastanow growth whereby a growing planar film becomes unstable after an initial wetting layer is formed. Common systems are Ge$_{x}$Si$_{1-x}$/Si and In$_{x}$Ga$_{1-x}$As/GaAs. For applications, SAQD arrays need to be ordered. The role of crystal anisotropy, random initial conditions and thermal fluctuations in influencing SAQD order during early stages of SAQD formation is studied through a simple stochastic model of surface diffusion. Surface diffusion is analyzed through a linear and perturbatively nonlinear analysis. The role of crystal anisotropy in enhancing SAQD order is elucidated. It is also found that SAQD order is enhanced when the deposited film is allowed to evolve at heights near the critical wetting surface height that marks the onset of non-planar film growth.