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Free keywords:
self-assembled quantum dots; hut clusters; low-temperature epitaxial growth; point defects
Abstract:
The kinetic formation of self-assembled Ge/Si hut clusters grown by
ultra-high vacuum chemical-vapor deposition has been investigated by
means of reflection high-energy electron diffraction, atomic force
microscopy and photo luminescence spectroscopy. We show that point
defects that are induced in the epilayers grown at substrate
temperatures below 525 degrees C greatly influence the optical
properties of Ge/Si hut clusters. We have investigated two approaches
of sample annealing in order to remove point defects while minimizing
Ge/Si intermixing: a long annealing at the growth temperature and a
flash annealing at high temperatures for a very short period of time.
The obtained results indicate that a well-controlled flash annealing
for a very short period of time is efficient for removing point defects
while minimizing Ge/Si intermixing. We have then defined a processing
window to obtain proper photoluminescence signature of hut clusters,
which is a well-defined gaussian band located at the energy range
between 800 and 900 meV. Our experiments also illustrate a correlation
between the increase of Ge/Si intermixing and the evolution of the
optical properties from a quantum-dot to a quantum-well behavior. (c)
2005 Elsevier B.V. All rights reserved.
