Regensburg 2002 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 14: III-V Halbleiter I
HL 14.3: Vortrag
Dienstag, 12. März 2002, 11:30–11:45, H13
Polarity inversion of GaN (0001) surfaces — •Andreia L. da Rosa1, Jörg Neugebauer1, John E. Northrup2, Chae-Deok Lee3, and Randall M. Feenstra3 — 1Fritz-Haber-Institut, Faradayweg 4-6, D14195, Berlin, Germany — 2Xerox PARC, Palo Alto, 94304, USA — 3Dept. of Physics, Carnegie Mellon University, Pittsburgh, 15213, USA
Recent experimental studies have shown that at high doping levels the GaN (0001) surface may become unstable against a polarity inversion to (0001). A prominent effect is Mg doping. This effect reduces the achievable doping concentration and results in a poor growth morphology. Based on an extensive study of Si-terminated GaN (0001) surfaces employing density-functional theory we have identified a low energy surface exhibiting polarity inversion. Although this structure is unstable against silicon nitride formation and thus is not expected to occur in experiment it allows to identify the mechanisms leading to a polarity inversion. Analyzing atomic relaxation, charge density and surface states we find as the main driving force compensation of the dopants by charge transfer to the surface states. This transfer stabilizes surface structures which in the absence of charge transfer are highly unstable. Based on these results we discuss how polarity inversion may be controlled.