AbstractsPhysics

This project presents the study of luminescent devices and materials based on silicon for its use in the fabrication of an optical system that integrates light emitter, waveguide, and light sensor in a single chip obtained by the use of standard CMOS techniques and materials. The atomic and structural characteristics of the materials are analysed and related to its luminescent response. Taking into account the results from the active material characterization, the design, fabrication, and characterization of electroluminescent devices based on such materials is presented. Finally, the design, fabrication and characterization of a complete CMOS compatible Integrated Optical System consisting of a transceiver, is discussed and analysed. The active materials used for light emission were different Silicon Rich Silicon Dioxide(SRO) and SRO-Si3 N4 bi-layers, obtained by a variety of CMOS compatible techniques and fabrication parameters. Two contributing mechanisms to photoluminescence in SRO were identified in all cases, respectively linked to the presence of radiative defects, and to Quantum Confinement phenomena. It is proposed and tested a model to describe the latter, based on the effective mass approximation, and the relation between the amount of Si-Si links and the volume of nano-agglomerates present in the material. In bi-layer samples, an additional luminescence band was observed, found to be generated in the transition material between silicon nitride and dioxide, and related to energy states introduced by defects. Samples with SRO thickness ten times higher than that of nitride, presented a clear dominance of the photoluminescence related to the dioxide. The centres responsible for electroluminescence in the electronicd evices were found to be fundamentally the same as those for photoluminescence despite the differences in measured spectra, and it was concluded that the influence of the architecture on the light output is of significant importance. It was shown that bi-layered devices delivered better results in terms of efficiency, light emission control, distribution and stability. The carrier transport mechanisms observed in the devices were dominated by material breakdown in single-layered devices, and Trap-assisted Tunnelling in the bi-layers. The Optical System integrating the light emitter, a waveguide, and a light detector, was designed and fabricated based on the results from the fabrication and analysis of the stand alone light emitting devices. During the design stage, it was corroborated by computer simulations that the characteristics of thelight emittedby thedevices thatpresented thehighest e.ciency and reliability, were suitable for its transmission trough the pro­posed waveguide architecture. The detection capabilities of the designed light sensors were also theoretically corroborated to be appropriated for the detection of the emitted light type. The proper functioning of the elements conforming the finally fabricated system was probed. Differences were found in the operation of the…