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HL: Halbleiterphysik

HL 3: GaN I

HL 3.1: Vortrag

Montag, 22. März 1999, 10:30–10:45, H2

Lattice Dynamics of Group III Nitride Semiconductor Compounds — •P. Pavone, M. Pabst, R. Plomer, S. Bruckmoser, and D. Strauch — Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg

The recent tremendous research activity in the area of nitride semiconductors compounds is mainly motivated by expectations of novel applications for the electronics industry. In the characterization of these systems a fundamental role is played by the experimental (e.g., by Raman scattering) and theoretical investigation of their vibrational properties. In this work, we present an extended ab initio study of the lattice dynamics of Ga, Al, and B nitrides in the wurtzite structure. The density-functional and the density-functional perturbation theory, respectively, have been used for the determination of the equilibrium configuration and of the lattice-dynamical properties. Full phonon-dispersion curves have been calculated for these compounds and compared with those of other reference hexagonal structures such as 2H-SiC and graphite. We have also examined the effects of external pressures and finite temperature on the lattice dynamics by using the equation of state and the quasi-harmonic approximation, respectively. Within this context, we have obtained for these compounds the pressure dependence of the Raman lines, the dispersion curves of the mode Grüneisen parameters, the specific heat, and the thermal expansion coefficient. Finally, we have investigated the relative stability of the wurtzite phase of these materials with respect to the rocksalt one. Where available, experimental data confirm the theoretical results.