Dresden 2003 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 55: Störstellen / Amorphe Halbleiter
HL 55.3: Vortrag
Freitag, 28. März 2003, 12:15–12:30, BEY/154
Photoionization of deep defect centers in low temperature grown GaAs — •C. Steen1, P. Kiesel2, M. Öchsner1, V. Donchev1, S. Malzer1, and G.H. Döhler1 — 1Institut für Technische Physik I, FAU Erlangen-Nürnberg, Erlangen, Germany — 2Palo Alto Research Center Incorporated, Palo Alto, California
GaAs, grown by molecular beam epitaxy (MBE) at low substrate temperatures (190 ∘C - 300 ∘C), (“Low Temperature Grown GaAs", LT-GaAs) contains a high concentration of (non-stoichiometric) excess Arsenic. This excess Arsen is incorporated as EL2-like point defects (AsGa-antisites) and Arsenic precipitates. In this study we have investigated the photoionization of these deep defects. These results corroborate the dominating role of the EL2-like center in LT-GaAs. We are using a p-i-n structure with a thin, only a few nm thick layer of LT-GaAs embedded in the i-region of a n-i-p diode in which the n-layer can be depleted by applying a reverse bias [1]. In this structure we can vary the occupation of the deep donors from completely filled to fully depleted by applying a according bias voltage. Spectrally resolved mid-IR photo-conductance measurements at 90 K (i.e. negligible n-i-p dark current) were performed to determine the optical cross sections for electrons and holes, respectively. Completely filled defects result in a dominant photo-emission of electrons, measured by increasing photo-conductance. In the case of fully depleted defects the photo-emission of holes is dominating, which yields a decreasing photo-conductance.
[1] K.-F.-G. Pfeiffer et al., Appl. Phys. Lett. 77, 2349 (2000)