Selective area epitaxy of GaAs films using patterned graphene on Ge

Abstract

We demonstrate selective area epitaxy of GaAs films using patterned graphene masks on a Ge (001) substrate. GaAs selectively grows on exposed regions of the Ge substrate for graphene stripe widths of 10 μm. The selectivity is highly dependent on the growth temperature and annealing time, which we explain in terms of temperature dependent sticking coefficients and surface diffusion. The high nucleation selectivity over several micrometers sets constraints on experimental realizations of remote epitaxy.

Nucleation Selectivity and Lateral Coalescence of GaAs over Graphene on Ge(111)

“…First, due to the weak van der Waals interactions of graphene, adatoms that land on the graphene are anticipated to have a high probability of desorption, that is, the sticking coefficient on graphene is expected to be low. ,,, This desorption rate from graphene should increase with temperature, whereas desorption from the covalent Ge surface or growing GaAs surface is nearly temperature independent for growth temperatures below 600 °C. Second, adatom diffusion on graphene is expected to be large and increase with temperature . With increasing temperature, adatoms that land on graphene are more likely to diffuse and then attach to exposed Ge regions .…”

“…Second, adatom diffusion on graphene is expected to be large and increase with temperature. 20 With increasing temperature, adatoms that land on graphene are more likely to diffuse and then attach to exposed Ge regions. 24 This crossover is expected to occur when the diffusion length λ becomes larger than the characteristic spacing L ∼ 1 μm between exposed Ge regions.…”

“…Recent experiments show that due to its relative inertness with weak van der Waals interactions out of plane, patterned graphene masks enable selective area epitaxy of III-Vs at openings to the substrate. 20 With continued growth, lateral overgrowth and coalescence over patterned graphene occurs after a few hundred nanometers to microns of thickness. 21 However, open questions remain regarding the mechanisms and growth conditions that optimize nucleation selectivity and what kinetic factors promote efficient lateral overgrowth, coalescence, and planarization.…”

“…Here, we explore whether a semimetallic graphene mask can also support ELO for direct synthesis of embedded metal/semiconductor nanostructures. Recent experiments show that due to its relative inertness with weak van der Waals interactions out of plane, patterned graphene masks enable selective area epitaxy of III-Vs at openings to the substrate . With continued growth, lateral overgrowth and coalescence over patterned graphene occurs after a few hundred nanometers to microns of thickness .…”

Controlling the Balance between Remote, Pinhole, and van der Waals Epitaxy of Heusler Films on Graphene/Sapphire

“…For example, pinhole-seeded lateral epitaxy can also produce single-crystalline exfoliatable films . A pinhole mechanism occurs when pinholes or other openings in the graphene selectively nucleate the direct epitaxy of film on a substrate, followed by lateral overgrowth and coalescence . These pinholes can appear natively in the graphene or they can be created during pregrowth annealing, due to desorption of native oxides or other contaminants at the transferred graphene/substrate interface. , van der Waals epitaxy, in which a film grows with epitaxial registry to the 2D material rather than the underlying substrate, can also produce exfoliatable single crystalline films.…”