Münster 1997 – wissenschaftliches Programm

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O: Oberflächenphysik

O 8: Elektronische Struktur I

O 8.11: Vortrag

Montag, 17. März 1997, 18:30–18:45, S 1

Post-annealing-induced free-electron compensation in shallow buried δ-layers of GaAs(100) — •V. M. Polyakov and J. A. Schaefer — Institut f"ur Physik, TU Ilmenau, 98684 Ilmenau

The post-annealing influence on the spatial redistribution of Si dopants in δ-doped GaAs(100) was studied by high-resolution electron-energy-loss spectroscopy (HREELS). Samples with different δ-layer depths were investigated. By comparison to calculated energy-loss spectra the areal free-electron density and the silicon spatial spreading from the intended δ-doping plane can be estimated. Plasmons of the two-dimensional electron gas in the δ-layer couple to phonons giving rise to the plasmaron modes. The low-energy plasmaron ω⁻ causes an appreciable broadening of the quasi-elastic peak in HREELS-spectra, if compared to undoped GaAs(100). For the samples with the doping plane 200 Åãnd 300 Åbelow the surface the quasi-elastic-peak broadening still persists after annealing to the highest temperature of 850 K. In contrast, after annealing the sample with the doping plane 100 Åbelow the surface the energy-loss spectrum appears to be very similar to that of the undoped sample. This effect manifests the nearly full free-electron compensation in this sample, contrary to the samples with the deeper position of δ-layer beneath the surface. The free-electron compensation can be explained by trapping of free electrons onto acceptor-like surface states, which are effectively produced during annealing.