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.