@phdthesis{Arguirov2007, author = {Arguirov, Tzanimir Vladimirov}, title = {Electro-optical properties of dislocations in silicon and their possible application for light emitters}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-5837}, school = {BTU Cottbus - Senftenberg}, year = {2007}, abstract = {This thesis addresses the electro-optical properties of silicon, containing dislocations. The interest in those properties is driven mainly by two practical reasons. One is the optical characterisation of multicrystalline silicon for solar cells, and the other is the design of light emitting diodes based on silicon by enhancement of silicon radiative properties via introduction of dislocations. The work demonstrates that dislocation specific radiation may provide a means for optical diagnostics of solar cell grade silicon. It provides insight into the mechanisms governing the dislocation recombination activity, their radiation, and how are they influenced by other defects present in silicon. We demonstrate that photoluminescence mapping is useful for monitoring the recombination activity in solar cell grade silicon and can be applied for identification of contaminants, based on their photoluminescence signatures. It is shown that the recombination at dislocations is strongly influenced by the presence of metals at the dislocation sites. The dislocation radiation activity correlates with their electrical activity. Thus, photoluminescence mapping at room temperature may provide a means for revealing and characterising of dislocation-rich regions in multicrystalline silicon. It is shown that the dislocation and band-to-band luminescence are essentially anti-correlated. The band-to-band intensity being related to the diffusion length of minority carriers can be used for measurements of diffusion length, as long as the surface recombination rate is controlled. Moreover, photoluminescence mapping can be used for the detection of optically active defects in solar grade materials. Thus, betaFeSi2 precipitates, with a luminescence at 0.8 eV, were detected within the grains of block cast materials. They exhibit a characteristic feature of quantum dots, namely blinking. The second aspect of the thesis concerns the topic of silicon based light emitters for on-chip optical interconnects. The goal is an enhancement of sub-band-gap or band-to-band radiation by controlled formation of dislocation-rich areas in microelectronics-grade silicon as well as understanding of the processes governing such enhancement. For light emitters based on band-to-band emission it is shown, that internal quantum efficiency of nearly 2 \% can be achieved, but the emission is essentially generated in the bulk of the wafer. On the other hand, light emitters utilizing the emission from dislocation-rich areas of a well localized wafer depth were explored. Three different methods for reproducible formation of a dislocation-rich region beneath the wafer surface were investigated and evaluated in view of their room temperature sub-band-gap radiation: (1) silicon implantation and annealing, (2) epitaxially grown SiGe buffer, and (3) direct wafer bonding. The most promising dislocation-based emitter appears the utilization of a dislocation network produced by wafer bonding. It is shown, that monochromatic D1 radiation (wavelength 1.5 µm) can be generated in a well localised depth of the wafer. The radiation is not absorbed in silicon and such localized emitter can, potentially, be coupled with silicon waveguides and Ge-based detectors for optical interconnects.}, subject = {Silicium; Versetzung ; Lumineszenz; Lumineszenz; Versetzungen; Silizium; Luminescence; Dislocations; Silicon}, language = {en} }