Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 27: GaN Preparation and Characterization
HL 27.1: Vortrag
Dienstag, 23. März 2010, 14:00–14:15, H15
Defect distributions at III-nitride interfaces from ab-initio-based thermodynamic data — •Christoph Freysoldt, Björn Lange, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung, Düsseldorf
The electrical, optical, and other properties of III-nitrides for optoelectronic devices are critically determined by dopants, vacancies, and other point defects. These defects have been extensively studied in experiment and theory. However, real devices contain inhomogeneities such as interfaces or electric fields, which affect the point defect distribution. We employ a multiscale approach to treat the interplay of local composition and macroscopic fields. The formation energies and charge transition levels of individual defects are obtained from density functional theory. These thermodynamical parameters then determine the local concentration in a continuum model for the device scale. However, defect concentrations and electric fields sensitively depend on each other and may vary over several orders of magnitude. In addition, defects may react to form complexes with different charge-transition characteristics, which makes these reactions explicitly potential-dependent. Instead of resorting to a time-demanding simulation of the equilibration process, we have developed an efficient method to compute the thermodynamic equilibrium directly. We apply our approach to the hydrogen distribution around Mg-induced inversion domain boundaries in p-GaN. Our results show that the enhanced affinity of Mg3N2 towards H+ produces significant space charge zones, even though the total amount of hydrogen in the boundary is very low.