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HL: Halbleiterphysik

HL 23: Poster II

HL 23.74: Poster

Mittwoch, 24. März 1999, 14:00–18:00, Z

Collective surface excitations at MOCVD-grown GaN(0001) — •V.M. Polyakov, F.S. Tautz, S. Sloboshanin, and J.A. Schaefer — Institut für Physik, Technische Universität Ilmenau, Postfach 100565, 98684 Ilmenau

We report on the Fuchs-Kliewer surface optical (FK) phonons and on the first observation of surface plasmons at MOCVD-grown homogeneously n-doped (2-5x10¹⁸ cm⁻³) and undoped GaN(0001) surfaces by high-resolution electron-energy-loss spectroscopy (HREELS). Dipole scattering theory is employed to calculate the surface energy-loss function and hence the expected energy-loss spectra. The dielectric response of free electrons is based on smooth free-electron density profiles, self-consistently calculated by Schrödinger and Poisson equations. The characteristic features of both the surface plasmons and the FK phonons are well reproduced for various primary electron-beam energies in the framework of this model. Fitting the measured HREEL spectra allows us to give estimates of important semiconductor parameters such as electron density, electron mobility and band bending. Moreover, it is found that the plasmon damping strongly depends on primary electron-beam energy. Similarly, the FK phonon damping and frequency are also affected by the variation of primary beam energy.