Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 33: III-V semiconductors II
HL 33.10: Vortrag
Mittwoch, 27. Februar 2008, 16:45–17:00, EW 201
Enhancing nitrogen solubility in diluted nitrides by surface kinetics: An ab initio study — •Hazem Abu-Farsakh1,2 and Jörg Neugebauer1,2 — 1Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany — 2Universität Paderborn, Warburger Straße 100, 33098 Paderborn, Germany
GaAs1−xNx alloys with low N content have recently attracted a lot of attention as material system of choice for making infrared laser diodes relevant e.g. for optical fiber communications. A specific challenge for practical applications is the low equilibrium solubility of N in bulk GaAs at typical growth temperatures (500 K). Interesting options to enhance N solubility are: (i) employing surface kinetics and (ii) growing quaternary InyGa1−yAs1−xNx alloys. In order to further explore/optimize these methods it is crucial to identify the atomistic growth processes of N adatoms on/in the GaAs surface.
We have therefore employed density functional theory to calculate the complete surface phase diagram of N at GaAs(001) surfaces, considering all relevant reconstructions and different layers. Besides, we studied the kinetic barriers and surface segregation of N on these surfaces and found clear evidence that N can be incorporated only in the topmost surface layer [1]. Using the phase diagrams we provide an estimate of N concentration as function of growth conditions. The surface solubility shows a rich behavior depending strongly on the specific surface structure. Based on these results we have been able to identify optimal growth conditions allowing for maximum N incorporation.
[1] M. Albrecht, H. Abu-Farsakh et al., Phys. Rev. Lett. 99, (2007).