(633e) Probing the Growth of III/V Semiconductor Interfaces with Accelerated Rare-Event Simulations

Thin-film growth on GaAs(001) is both fundamentally and technologically significant, with applications in electronic, optoelectronic, and spintronic devices. From a fundamental perspective, recent experimental work has shown that the GaAs(001) b2(2x4) substrate can transform and play an active role in diffusion and the morphologies that form during homoepitaxy.  This system breaks the conventional paradigm that the substrate is a static template and the way that adatom diffusion, island nucleation, and multi-layer growth occur in such a dynamical environment may be considerably different than that envisioned in the conventional picture of thin-film growth.

In our recent work, we used accelerated molecular dynamics simulations to study time-dependent structural transformations of GaAs(001) b2(2x4).  Our results are consistent with results from experimental STM and RHEED studies and confirm the dynamical character of this surface.  In a second study, we probed Ga adatom diffusion and GaAs homoepitaxy on this surface.  The diffusion of Ga is a complex phenomenon involving many local minima.  According to an analytic bond-order potential, up to 23 local minima can be involved in motion between two nearest-neighbor binding sites – although this number is less when first-principles density-functional theory is used to quantify the minima.  We develop a kinetic Monte Carlo code to probe diffusion and growth on this surface.  Our results compare well to recent experiments.

*This work is supported by NSF DMR-1006452