Theory of diffusion-induced selective area growth of III-V nanostructures

Selective area growth of nanomembranes (NMs), nanofins, and planar nanowires (NWs) can pave the way for monolithic integration of III-V photonics with Si electronics and enable fabrication of scalable NW networks required for fundamental studies in low-temperature transport physics. Herein, we present an attempt to develop the kinetic growth theory of III-V NMs and related nanostructures in selective area epitaxy. The growth process is assumed to be driven by surface diffusion of group III adatoms. The populations of adatoms diffusing on the mask surface, NM sidewalls, and the top are described by three diffusion equations linked by six boundary conditions. The resulting growth equation provides the NM height as a function of time, slit width and pitch, and deposition conditions. The width and pitch dependences of the NM growth rate are found to be qualitatively different for different directions of the adatom diffusion fluxes (from the mask surface onto the NM or in the opposite direction). A good correlation of the model with the data on the growth kinetics of GaAs NMs by selective area molecular beam epitaxy is demonstrated.