Berlin 2008 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

HL: Fachverband Halbleiterphysik

HL 47: GaN: preparation and characterization I

HL 47.13: Vortrag

Donnerstag, 28. Februar 2008, 17:15–17:30, EW 202

Thermodynamics and adatom kinetics of non-polar GaN surfaces. — •Liverios Lymperakis and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung, Max-Planck-Strasse 1, 40237, Düsseldorf, Germany

III-Nitride based nanowires have recently attracted considerable interest due to their potential applications for novel nano-optoelectronic devices. The shape and size of the nanostructure as well as the quality of the grown material depends strongly on the atomistic mechanisms taking place on the facets of the nanowires during growth. GaN nanowires usually grow having the c-axis as axial direction while the side facets are expected to exhibit non-polar surfaces. While extensive and detailed theoretical studies on the thermodynamics and kinetics of the polar c-plane GaN surfaces exist, a detailed analysis which will combine thermodynamics and kinetics of the non-polar α- and m-plane surfaces is still lacking. We have therefore performed planewave pseudopotential calculations within the density functional theory in order to study the thermodynamics and the adatom kinetics on α- and m-plane GaN surfaces. The mapping of the potential energy surface for the Ga adatoms (minority species for N rich growth) reveals a strong anisotropy for the diffusion barriers for both a- and m-plane surfaces. For N adatoms (minority species for Ga rich growth) our results show a subsurface diffusion channel which becomes activated already at low growth temperatures. Based on these results we have been able to explain recent experimental observations on the growth anisotropy of GaN non-polar surfaces as well as on the growth of GaN nanowires.