<i>Ab initio</i> calculation for an initial growth process of GaN on (0001) and (000$ \bar 1 $) surfaces by vapor phase epitaxy

<jats:title>Abstract</jats:title><jats:p>The adsorption processes of group‐III and group‐V sources used in metalorganic vapor phase epitaxy (MOVPE) and hydride vapor phase epitaxy (HVPE) were investigated using <jats:italic>ab initio</jats:italic> calculations based on the density functional theory (DFT) to understand the initial growth process of GaN on GaN(0001) and (000<jats:styled-content>$ \bar 1 $<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/tex2gif-ueqn-2.gif" xlink:title="equation image" /></jats:styled-content>) substrates. In order to understand the influence from the decomposition of ammonia, NH<jats:sub>2</jats:sub>, NH and N were considered as adsorption species. We assume group‐V source preflow in the case of GaN(0001) and group‐III preflow in the case of GaN(000<jats:styled-content>$ \bar 1 $<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/tex2gif-ueqn-3.gif" xlink:title="equation image" /></jats:styled-content>). From the calculations, the initial GaN growth process in the vapor phase epitaxy is clarified. When GaN is grown on the GaN(0001) substrate, NH<jats:sub>3</jats:sub> molecules adsorb to the on‐top site or NH<jats:sub>2</jats:sub> molecules adsorb to the bridge site. Also, it was found that the surface structures with both NH<jats:sub>2</jats:sub> and NH<jats:sub>3</jats:sub> are stable under a hydrogen atmosphere. When GaN is grown on the GaN(000<jats:styled-content>$ \bar 1 $<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/tex2gif-ueqn-4.gif" xlink:title="equation image" /></jats:styled-content>) substrate, Ga atoms adsorb to the H3 site in the case of MOVPE and GaCl molecules adsorb to the H3 site with the Ga atom facing the surface in the case of HVPE. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)</jats:p>