Lawrence H. Friedman

Anisotropy and order of epitaxial self-assembled quantum dots

Epitaxial self-assembled quantum dots (SAQDs) represent an important step in the advancement of semiconductor fabrication at the nanoscale that will allow breakthroughs in electronics and optoelectronics. In these applications, order is a key factor. Here, the role of crystal anisotropy in promoting order during early stages of SAQD formation is studied through a linear analysis of a commonly used surface evolution model. Elastic anisotropy is used a specific example. It is found that there are two relevant and predictable correlation lengths. One of them is related to crystal anisotropy and is crucial for determining SAQD order. Furthermore, if a wetting potential is included in the model, it is found that SAQD order is enhanced when the deposited film is allowed to evolve at heights near the critical surface height for three-dimensional film growth.

Predicting and Understanding Order of Heteroepitaxial Quantum Dots

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

Feasibility study for thermal-field directed self-assembly of heteroepitaxial quantum dots

\hbox{Ge}_{x}\hbox{Si}_{1-x}/\hbox{Si}

Decoupling small-scale roughness and long-range features on deep reactive ion etched silicon surfaces

and

Anisotropy and morphology of strained III-V heteroepitaxial films

\hbox{In}_{x}\hbox{Ga}_{1-x}\hbox{As/GaAs}.

Stochastic continuum modeling self-assembled epitaxial quantum dot formation

For applications, SAQD arrays need to be ordered. The roles of crystal anisotropy, random initial conditions and thermal fluctuations in influencing SAQD order during early stages of SAQD formation are studied through a simple stochastic model of surface diffusion. Surface diffusion is analyzed through a linear and perturbatively non-linear 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.