Molecular beam epitaxial growth of III-V semiconductor ... - KOBRA

Heteroepitaxial Growth of III-V Semiconductor on Silicon Substrates
be denoted as ABCABACBA. There is a change in crystal orientation at the
twinning plane. Here the normal crystal and its twin share a single plane of atoms
(the twinning plane or composition plane) and there is reection symmetry about
the twinning plane as shown in Fig. 3.12. In other words, the MTs defect occurs
when the stacking faults sequence is disturbed in such a way as to create a mirror
image of itself, as in ABCABCCBAACBA [31]. Twinning involves a change in
long-range order of the crystal; it therefore cannot result from the simple insertion
or removal of an atomic plane, as in the case of the stacking fault. Therefore,
twins cannot be created by the glide of dislocations. Instead, twinning occurs
during crystal growth, either bulk growth or heteroepitaxy.
Finding ways to reduce the density of dislocations at a given mismatch starin
level is an important goal for successful strained-layer heteroepitaxy. As mentioned
before, dislocations and defects can act as non-radiative recombination
centers in optoelectronic devices, because the localized mid-bandgap energy levels
in the dislocations cores will act as highly ecient trap states for injected
minority carriers [14].
A great volume of research activities has already been dedicated to the various
barriers to III-V integration on silicon. Nevertheless, it has yet to be shown the
quality of III-V on Si material can oer reliability and performance demanded
optoelectronic and other device applications. In this research work, a new approach
for III-V on silicon heterepitaxy based on self-assembled and localized
growth of nanostructures like quantum dots and dashes will be investigated. The
idea is to minimize the above mentioned problems of the formation of dislocations
during the growth of relaxation layers. However, the materials integration
processes were conducted by the means of the epitaxial growth of III-V quantum
dots and dashes on silicon substrates via MBE technique, using the most
challenging materials integration approach, by limiting the III-V material to the
active region.
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