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HL: Fachverband Halbleiterphysik
HL 16: Theory: Metal-insulator transitions / Electronic structure calculations
HL 16.8: Talk
Monday, March 11, 2013, 17:30–17:45, H13
Calculation of branch points and band offsets for cubic GaxAl1−xN — •Daniel Mourad — Insitut für Theoretische Physik, Universität Bremen
The anisotropic valence band offset (VBO) across the interface between two materials is an important material parameter and can approximately be calculated from the branch points (BPs, aka charge neutrality levels) of the constituent materials. GaxAl1−xN is a technologically important semiconductor alloy and often used as barrier material in optoelectronic devices. Nevertheless, most work and available data concentrates on the hexagonal modification, while there is considerably less data for the zincblende phase of the alloy. The latter also shows an interesting direct to indirect band gap transition on the Al-rich side, which makes it an interesting model system for the calculation of concentration-dependent properties.
We show how the concentration-dependent BP of the disordered GaxAl1−xN alloy can be calculated within a combination of a suitable tight-binding model and the coherent potential approximation (CPA). We then analyse the resulting VBOs for several material combinations and interface orientations and discuss the extension to the wurtzite phase and further nitride alloys like InxGa1−xN.