Berlin 2015 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 27: Doped Si nanostructures (DS with HL/TT)
HL 27.3: Invited Talk
Tuesday, March 17, 2015, 10:15–10:45, H 2032
Impurity doping of Si nanocrystals studied by single-quantum-dot spectroscopy — •Jan Valenta1, Ilya Sychugov2, Jan Linnros2, and Minoru Fujii3 — 1Department of Chemical Physics & Optics, Charles University, Prague, Czechia — 2Materials and Nano Physics, Royal Institute of Technology, Kista-Stockholm, Sweden — 3Department of Electrical & Electronic Engineering, Kobe University, Nada, Japan
Recent research effort proved that doping of nanostructured semiconductors is much more complicated than in bulk due to the self-purification effect, increasing formation energy of substitutional doping sites etc. In order to get a deeper insight on impurity effects in Si nanocrystals (NCs) we applied single NC spectroscopy to study luminescence of two types of samples: (i) random quantum dots prepared by etching of highly doped (B, P, As, Sb) SOI wafers, (ii) highly B and P co-doped Si NCs formed by sputtering, annealing and etching. The effect of B, P, As, and Sb impurities on individual emission spectra are determined by comparison with the undoped NCs. From the statistical analysis of the luminescence spectra, the donor ionization energies for NCs emitting in the range of 1.5-2 eV are estimated to be 140-200 meV, while the exciton-impurity binding energy for As and Sb-doped NCs is found to be about 40-45 meV. It means that both the donor ionization energy and the excitonic binding energy are increased by an order of magnitude compared to bulk Si. The luminescence spectra of heavily B,P co-doped Si NCs are characterized by a very broad emission band (>0.2eV) even at low temperature (10 K).