Selective growth of GaAs by HVPE: Keys for accurate control of the growth morphologies

GaAs selective growth experiments were carried out on (0 0 1) GaAs-patterned substrates by HVPE. Mesas grown on [1 1 0] and [1 1̄ 0] oriented stripes exhibited various morphological profiles bounded by the low growth rate faces (0 0 1), (1 1 0), (1 1 1)A and (1 1 1)B, depending on the III/V ratio in the vapour phase, on the supersaturation and the growth temperature. The shape of the mesas results from the hierarchy of the growth rates of the low index faces. The latter growth rates were independently determined on un-masked substrates. Kinetic Wulff constructions were then built by referring to these growth rates. A good agreement was obtained between the morphologies of the selectively grown mesas and the constructions built from the only knowledge of the growth rate anisotropy, demonstrating that HVPE growth is mainly governed by surface kinetics. Qualitative growth mechanisms involving As and GaCl net adsorption fluxes as well as chlorine desorption kinetics are proposed for the various low index faces.