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Abstract:
Low-temperature epitaxial growth of Si-Ge heterostructures
opens possibilities for synthesizing very small and abrupt low-
dimensional structures due to the low adatom surface
mobilities. We present photoluminescence from Ge quantum
structures grown by molecular-beam epitaxy at low temperatures
which reveals a transition from two-dimensional to three-
dimensional growth. Phononless radiative recombination is
observed from <105> faceted Ge quantum dots with height of
approximately 0.9 nm and lateral width of 9 nm. Postgrowth
annealing reveals a systematic blueshift of the Ge quantum
dot's luminescence and a reduction in nonradiative
recombination channels. With increasing annealing temperatures
Si-Ge intermixing smears out the three-dimensional carrier
localization around the dot. (C) 2002 American Institute of
Physics.
