Growth of semiconductors on patterned substrates provides an effective approach to fabricate ordered surface structures such as quantum-dots. Advancements in patterning techniques, e.g., self-assembly processes, make it now possible to prepare large-scale arrays with a precisely tailored shape, size, and crystallographic orientation. Of particular interest to this study is the use of patterned substrates to grow III-V semiconductor thin films. The goal of this project is to develop a phase field model of growth, which model combines the effects of elastic strain, strain relaxation due to plastic deformation, kinetics of the film deposition process, and thermodynamics of a multicomponent alloy (e.g., phase separation). This model will be used to explore possibilities of growing new types of multi-component semiconductors with a desirable bandgap.
We have already developed a phase field model coupled with elasticity and non-uniform deposition flux to investigate the role of lateral confinement on morphology of thin films grown heteroepitaxially on patterned substrates. Parameters of the model were chosen to represent InxGa1-xAs thin film growing on GaAs patterned with SiO2. We determined the effects of the deposition flux rate and uniformity, strain energy, and surface energy of the thin film on the nucleation and growth of islands. Our results show that the growth of islands near the walls of the patterns can be controlled by both, the overflow of deposition flux near the SiO2 pattern walls and by the strain energy due to the lattice mismatch. By increasing strain energy due to lattice mismatch islands nucleate near the SiO2 walls even under conditions of a spatially uniform deposition flux. This nucleation of islands near the walls is a new mechanism that can release elastic strain accumulated in the growing film.
 M. Arjmand, N. Swaminathan, J. Deng, D. Morgan, I. Szlufarska, Effect of confinements on morphology of model InxGa1-xAs thin film grown on a patterned GaAs substrate, Submitted
Fig.9: Phase field simulations of GaxIn1-xAs growth on GaAs substrate patterned with SiO2.