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HL: Halbleiterphysik

HL 38: Poster III: Transporteigenschaften (1-14), Optische Eigenschaften (15-31), Grenz-/Oberfl
ächen (32-44), Heterostrukturen (45-57), Bauelemente (58-67), Gitterdynamik (68-69), Diamant (70), Raster-Tunnel-Mikroskopie (71)

HL 38.27: Poster

Thursday, March 30, 2000, 14:00–19:00, B

Impurity induced resonance Raman scattering below E₀ band gap in GaAs at 2K — •Qing Huang and Rainer G. Ulbrich — IV. Physikalisches Institut, Universität Göttingen, Bunsenstraße 13-15, 37073 Göttingen

Resonance Raman scattering (RRS) below E₀ band gap due to impurities in lightly doped GaAs is investigated at 2 K using a tunable Ti:Sapphire laser. The absolute scattering cross-sections are measured. Our measurement of RRS at 2 K shows clearly that the resonance occurs at the threshold of (e, A⁰) and also at the energy of (A⁰, X), thus it is impurity-induced. We tune the laser from 1.46 eV to 1.52 eV. Several features are focused on. When the excitation is at (D⁰, A⁰), we find an asymmetrical line shape for the LO phonon scattering. We explain this line shape by considering the statistical distribution of donors and acceptors in the real space, so the influences of both Coulomb potential between donor-acceptor pairs and the bound states of neighboring donors are considered. When the laser is tuned around (e, A⁰), we observe not only the enhanced scattering resonance at (e, A⁰), but also the multi-phonon scattering. We explain the scattering enhancement by considering the bound exciton effect. For the appearance of the dispersive LO phonon peak, which occurs when excitation is above 1.4955 eV, by analyzing the dispersive line shift and shape, we ascribe it to the scattering by combination of one LO phonon and acoustic phonons.