Sie befinden Sich nicht im Netzwerk der Universität Paderborn. Der Zugriff auf elektronische Ressourcen ist gegebenenfalls nur via VPN oder Shibboleth (DFN-AAI) möglich. mehr Informationen...
The role of surface kinetics on composition and quality of AlGaN
Ist Teil von
Journal of crystal growth, 2016-10, Vol.451, p.65-71
Ort / Verlag
Elsevier B.V
Erscheinungsjahr
2016
Quelle
Alma/SFX Local Collection
Beschreibungen/Notizen
Metal–polar, Al-rich AlGaN films were grown on both single crystalline AlN and sapphire substrates. The role of surface morphology and surface kinetics on AlGaN composition is presented. With the reduced dislocation density of the films grown on AlN substrates, atomically smooth bilayer stepped surfaces are achieved with RMS roughness of less than 50pm for a 5×5µm2 AFM scan area. By controlling the surface supersaturation through adjusting the growth rate, a transition from 2D nucleation to step flow was observed. The critical misorientation angle for step-bunching in nominal Al0.70Ga0.30N grown with a growth rate of 600nm/h on AlN substrates was found to be 0.4°. The composition of bilayer stepped AlGaN was strongly dependent on substrate misorientation angle, where a compositional variation by a factor of two for a change in misorientation angle from 0.05 to 0.40° was observed; this is explained by the different surface diffusion lengths of Ga and Al. Step-bunching resulted in strong compositional inhomogeneity as observed by photoluminescence and scanning transmission electron microscopy studies.
•A kinetic framework for controlling the surface during AlGaN growth on Al-polar surfaces by MOCVD is developed.•The role of surface morphology and surface kinetics on AlGaN composition is presented.•Apparent phase separation of AlGaN was determined not to be an intrinsic property of AlGaN.