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Department Physics of semiconductorsMBE group (Dr. S. Franchi) : 

Department Physics of semiconductorsMBE group (Dr. S. Franchi) Self-assembled Semiconductor Nanostructures for the Information Society The Information Society requires millions of low-cost semiconductor lasers for telecom and datacom broad band networks Present devices are based on InGaAsP/InP quantum wells on InP substrates: adequate for transoceanic links not suited for large-scale application, due to i) high cost of substrates, ii) physical properties that do not allow VCSEL fabrication InGaAs/GaAs quantum dots may have emission in the spectral windows of interest (0.98 µm, 1.31 µm and 1.55 µm) and advantages as: use of GaAs substrates mature technology for VCSEL fabrication ultra-low threshold current densities (intrinsic feature of confined carrier systems) High-yield fabrication of low-cost, high-performance telecom lasers

Atomic Force Microscopy (AFM) image of self-assembled nanostructures : 

Atomic Force Microscopy (AFM) image of self-assembled nanostructures Nano-islands of InAs are self-assembled during MBE growth so as to minimize elastic energy due to high lattice-mismatch between substrate and epitaxial deposits No need of complex nanolithographic techniques Quantum dots consist of nano-islands capped with suitable semiconductor layers Due to band discontinuities, carriers are 3D quantum confined and acquire 0D character and properties 100 nm Innovative material

The CNR-IMEM research : 

The CNR-IMEM research i) the development of MBE of quantum dot nanostructures ii) the correlation between preparation conditions and optoelectronic, electric and morphological properties iii) the engineering of light emission in the spectral windows of optoelectronic interest (0.98 µm, 1.31 µm and 1.55 µm) The results allowed : i) the acquisition of technologies for the preparation of 0.98 µm structures, used by a world leader in photonics (Avanex Corporation) to fabricate lasers with interesting properties. This activity has been carried out within the MIUR-CNR “Nanotechnologies” Project, in cooperation with Avanex ii) to develop the concept of strain-engineering to tune the emission in the 1.31 and 1.55 µm windows. This activity takes place within the MIUR-FIRB “Nanotechnologies and Nanodevices for the Information Society” Project. Relevant contributions of: CNR-IFN, Un. Milano Bicocca, Un. Firenze, Un. Pavia, Un. Roma “La Sapienza”, Politecnico di Torino Network of excellence of the 6th Framework Program of EU: Self-Assembled semiconductor Nanostructures for new Devices in photonics and Electronics (SANDiE)