Fabrication of unconventional GaAs nanostructures by Droplet Epitaxy
What makes Quantum Nanostructures (QNs) so attractive is the ability
to tune their optoelectronic properties by careful design of their size,
composition, strain and shape. These parameters set the confinement
potential of electrons and holes thus determining the electronic and
optical properties of the QNs. In fact, for the realization of QNs-based
devices, the optical properties of the QNs such as the emission
wavelength, the intersublevel spacing energy, and even the interactions
between nearby QNs, should be freely accessible for engineering. Even
though DE is a successful method for the fabrication of such
semiconductor complex QNs, its full potential as source of
nanostructures with designable and intriguing new geometries still
remains mostly unexplored. Our aim is to show how to obtain, single,
designable structures, with localized states, different dimensionality
and tunable coupling. The DE fabrication procedure allows the
possibility to finely tune the QN shape thus allowing the design of the
desired electronic density of states. GaAs integration on Si for CMOS technology
Integrating III-V-based semiconductor devices for applications in
optoelectronics and photonics directly on Si substrates would allow the
use of the highly refined silicon infrastructure, based on CMOS
technology, and offer the option of integrating a few specialized III-V
devices within a large number of Si devices. Of particular technological
interest is the possibility of carrying out the III-V device
fabrication as a back-end process, that is, after the CMOS circuitry has
been already realized. In this case, strict constraints on thermal
budget for growth and processing of the epilayer are imposed by the
compatibility with the underlying CMOS circuit. Nanostructures realized
in III-V semiconductor materials hold a great technological interest,
since quantum confinement leads to devices where strongly correlated
few-electron/exciton systems play a fundamental role, such as single
photon emitters. The key ingredient we adopted in order to achieve this
goal is the use of DE and Ge
virtual substrates to match the GaAs-based III-Vs and the Si substrate. |