Light Emission from Silicon Quantum Dots
P. K. Kashkarov, O. A. Shalygina, M. G. Lisachenko, D. M. Zhigunov,
S. A. Teterukov, V. Yu. Timoshenko
Moscow State M.V. Lomonosov University, Faculty of Physics, 119992 Moscow, Russia
Phone/Fax: +7(095)9392193, E-mail: pavel@vega.phys.msu.su
Light emission from silicon can be considerably enhanced by formation of
nanostrutures or by doping with luminescence activators. In this work both
approaches are combined. Erbium ions in a solid matrix can emit sharp luminescence
line at 1.5 m (4I13/2→4I15/2 transitions in the internal 4f-shell), which matches the
silica fiber-based optical communication systems. A promising host for Er+3 ions is
silica with embedded Si nanocrystals of several nm sizes, i.e. Si quantum dots (QDs).
We report on an efficient sensitizing of the room temperature Er+3 photoluminescence
in Si nanocrystals /SiO2 structures. The energy of optical excitation of Si QDs is
almost completely transferred to the Er3+ ions in surrounding SiO2 and a strong
emission line at 1.5 m appears. The luminescence yield of the Er-doped structure
increases for higher energy of exciting photons and for smaller size of the
nanocrystals. For Si QDs of 2 nm diameter the efficiency of the Er3+ emission exceeds
the total luminescence yield of the undoped structure. This highly efficient sensitizing
of the luminescence is explained by a coupling between excitons in Si QDs and Er 3+
ions in their upper excited states. The coupling is so strong that it competes
successfully with nonradiative recombination losses in Si QDs ensembles.