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HL: Fachverband Halbleiterphysik

HL 30: Si/Ge

HL 30.2: Vortrag

Mittwoch, 25. März 2009, 09:45–10:00, POT 51

Interplay between Si dangling bond states and P doping in freestanding Si nanocrystals — •Andre R. Stegner¹, Rui N. Pereira^1,2, Jinming Lu¹, Hartmut Wiggers³, Martin S. Brandt¹, and Martin Stutzmann¹ — ¹Walter Schottky Institut, Technische Universität München, Am Coulombwall 3, 85748 Garching — ²University of Aveiro, 3810-193 Aveiro, Portugal — ³Universität Duisburg-Essen, Institut für Verbrennung und Gasdynamik, Lotharstrasse 1, 47048 Duisburg

Electron paramagnetic resonance (EPR) and secondary ion mass spectroscopy (SIMS) have been used to investigate the phosphorus doping of freestanding silicon nanocrystals (Si-NCs) with mean diameters selected between 4 nm and 45 nm which were produced by microwave-induced decomposition of silane and phosphine in a low-pressure plasma reactor. SIMS results do not indicate a size dependence of the P incorporation efficiency. However, it is found that approx. 95% of the P segregates to the Si-NC surface region during growth, which is oxidized after exposure to air. The concentration of electrically active, paramagnetic P detected by EPR further falls below this SIMS concentration by about one order of magnitude for Si-NCs with diameters larger than 15 nm. Charge compensation by Si dangling bonds, which are investigated using room temperature EPR and which can be passivated by H, is shown to be the reason for this deviation and can quantitatively be described by a statistical model. For smaller Si-NCs, a further strong drop of the concentration of paramagnetic donors is observed, which cannot be explained by the compensation model alone.