Dynamical faceting and nanoscale lateral growth of GaAs by molecular beam epitaxy

Dynamical faceting during homoepitaxial growth of GaAs on nanoscale-patterned surfaces by molecular beam epitaxy is examined. Selective deposition on open GaAs(I 00) surfaces with lateral dimensions ranging from 130 to 250 nm, separated by 15-80 nm-wide (25-nm-thick) SiO2 stripes aligned along the [0 (1) over bar 1] direction results in facet formation and lateral growth over the SiO2 mask. At the early stage of growth, (3 1 1) facets appear on sidewalls near the boundary between an open GaAs surface and SiO2 mask, these are replaced by (1 1 1) facets starting from SiO2 boundaries as growth continues. After complete replacement, growth proceeds laterally in the direction perpendicular to [0 (1) over bar 1] retaining the (1 1 1) facets until coalescence occurs between adjacent triangular cross-sectioned GaAs stripes. Nanoscale fabrication nonuniformity results in dynamical formation and retention of multiple (3 1 1) facets even for growth thicknesses much greater than the thickness of the SiO2 mask stripes. This dynamical faceting is interpreted by minimization of total surface free energy based on equilibrium crystal shape, in qualitative agreement with our experimental results. (C) 2002 Elsevier Science B.V. All rights reserved.