Unified model of droplet epitaxy for compound semiconductor nanostructures: Experiments and theory

Abstract

We present a unified model of compound semiconductor growth based on kinetic Monte Carlo simulations in tandem with experimental results that can describe and predict the mechanisms for the formation of various types of nanostructures observed during droplet epitaxy. The crucial features of the model include the explicit and independent representation of atoms with different species and the ability to treat solid and liquid phases independently. Using this model, we examine nanostructural evolution in droplet epitaxy. The model faithfully captures several of the experimentally observed structures, including compact islands and nanorings. Moreover, simulations show the presence of Ga/GaAs core-shell structures that we validate experimentally. A fully analytical model of droplet epitaxy that explains the relationship between growth conditions and the resulting nanostructures is presented, yielding key insight into the mechanisms of droplet epitaxy.

Precise shape engineering of epitaxial quantum dots by growth kinetics

“…7(b)]; in the opposite case, when diffusion from the droplet edge controls the Ga crystallization dynamics, hollow morphologies, such as disks and rings, are expected [ Fig. 7(b)] [23,52]. In between these two extremes, more complex morphologies, such as double rings and molecules, can be obtained [30,35,37,40].…”

“…Under this assumption, the Ga concentration profile before crystallization is P (r) = A(r)/ξ , where A(r) is the experimental profile of the QD, in each series, crystallized at the lowest temperature or the highest As flux, and ξ is the proportionality factor. This permits us to reduce the effects of the diffusion of Ga from the droplet perimeter (process 2) at minimum, and it allows us to implicitly take into account, at least to the first order of approximation, the complex crystallization dynamics inside the metallic Ga droplet (process 1) [52,53]. However, this makes the model outcome clearly dependent on the choice of A(r).…”

“…During the Ga droplet crystallization under As flux, the relative importance of two processes proceeding in parallel determines the final crystal morphology (see Fig. 7) [23,52]:…”

Kinetic Monte Carlo simulation of heteroepitaxial growth: Wetting layers, quantum dots, capping, and nanorings

“…It should be remarked that this conclusion is not as obvious as it first sounds, because during the formation of the quantum dots increasing the temperature will enhance dot formation: compare Figures 13, 14 and 15. Finally we point out that Reyes et al [48] have argued that this mechanism is an important feature in liquid drop epitaxy.…”

Continuum modelling of semiconductor heteroepitaxy: an applied perspective

“…Worst, diffusion processes at semiconductor surfaces are typically influenced by local changes in orbital hybridization, so that reliable estimates of diffusion rates call for refined and computationally demanding ab initio calculations [48]. Nevertheless, it is worth mentioning some significant progress based on empirical approaches exploiting Kinetic Monte-Carlo schemes [49][50][51][52].…”