Ge self-assembled quantum dots were embedded into two-dimensional photonic crystal microcavities fabricated on silicon-on-insulator substrates by gas-source molecular beam epitaxy (GS-MBE), electron beam lithography, and reactive ion etching (RIE). Light-emission characteristics of Ge quantum dots in the microcavities were characterized by room-temperature microphotoluminescence. Multiple sharp resonant luminescent peaks with quality factors of up to 600, corresponding to the resonant modes supported by the cavity, were observed in the emission range of Ge quantum dots. Control of the wavelengths of the photoluminescence peaks over a wide range from 1.3 to 1.6 mm was demonstrated by adjusting the lattice constant of the photonic crystals. The results show that embedding Ge dots into optical microcavities is a possible candidate for silicon-based light emitting devices. #
We have studied quantum transport in both Si and GaAs interband tunneling diodes
(ITD's). In the simulation, a non-equilibrium Green's function method based an
empirical tight binding theory has been used to take into account evanescent-wave
matching at interfaces and realistic band structures. Comparison has been made
between the results of our multiband (MB) model and those of conventional two-band
(2B) model. As a result, it is found that the current–voltage (I–V) characteristics of the
Si ITD have considerably smaller peak current density than the conventional 2B model,
since our MB model reflects correctly the indirect gap band structure. On the other
hand, in the GaAs ITD, there is small difference between the two models, because
tunneling occurs between the conduction band and the valence band at F point. It is
also found that the matching of evanescent electron modes is essentially necessary to
include the valley-mixing effects at the tunneling interfaces.
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