Importance of As and Ga Balance in Achieving Long GaAs Nanowires by Selective Area Epitaxy

We report on the selective area growth (SAG) of GaAsnanowires(NWs) by the catalyst-free vapor-solid mechanism. Well-ordered GaAsNWs were grown on GaAs(111)B substrates patterned with a dielectricmask using hydride vapor phase epitaxy (HVPE). GaAs NWs were grownalong the ⟨111⟩B direction with perfect hexagonal shapewhen the hole's opening diameter in SiN x or SiO x mask was varied from 80to 340 nm. The impact of growth conditions and the hole size on theNW lengths and growth rates was investigated. A saturation of theNW lengths was observed at high partial pressures of As-4, explained by the presence of As trimers on the (111)B surface atthe NW top surface. By decreasing As-4 partial pressureand decreasing the hole size, high aspect ratio NWs were obtained.The longest and thinnest NWs grew faster than a two-dimensional layerunder the same conditions, which strongly suggests that surface diffusionof Ga adatoms from the NW sidewalls to their top contributes to theresulting axial growth rate. These findings were supported by a dedicatedmodel. The study highlights the capability of the HVPE process togrow high aspect ratio GaAs NW arrays with high selectivity. The growth of GaAs nanowires (NWs) onpatterned SiN x /GaAs-(111)B substrate byhydride vapor phaseepitaxy (HVPE) is demonstrated. A model was developed to describethe saturation of the NW lengths at high partial pressures of As-4, explained by the presence of As trimers. By decreasing As-4 partial pressure and hole size, high aspect ratio NWs wereobtained.

Automated summary

The selective area growth (SAG) of GaAs nanowires (NWs) by catalyst-free vapor-solid mechanism was achieved. Well-ordered GaAs NWs in perfect hexagonal shape were grown on GaAs (111)B substrates patterned with a dielectric mask using hydride vapor phase epitaxy (HVPE). The study investigated the impact of growth conditions and hole size on NW lengths and growth rates. High aspect ratio NWs were obtained by reducing As-4 partial pressure and decreasing the hole size, indicating the contribution of surface diffusion of Ga adatoms to axial growth rate.