| Photoluminescence (PL) is an attractive semiconductor characterization technique because it is contactless and provides information on bulk impurities/defects, surface states and doping concentration. It can provide high resolution spectra usually with the sample at low temperature and room-temperature spectra and maps. PL was used to characterize silicon (Si), silicon-on-insulator (SOI), and strained silicon-germanium (SiGe)/Si samples. In some cases PL was augmented with surface photovoltage minority carrier diffusion length and photoconductance decay minority carrier lifetime measurements.; Experiments were carried out with the Silicon Photo-Enhanced Recombination (SiPHER) PL instrument, located at Sumitomo Mitsubishi Silicon Group (SUMCO) USA in Salem, Oregon. This instrument uses two wavelengths (lambda = 532 nm and lambda = 827 nm) and provides PL and surface reflectance (SR) data. To extract the maximum information, one-dimensional, two-dimensional, and three-dimensional theories were developed by calculating the excess carrier densities taking into account all relevant recombination mechanisms and optical parameters. The experiments were done this for bulk and epitaxial wafers, with the latter having different doping concentration in the epi-layer and the substrate.; A means of interpreting the PL and SR data through appropriate ratios to eliminate some unknowns was developed, allowing the surface recombination velocity of samples with known trap densities to be predicted. For today's high quality Si wafers, the trap densities are sufficiently low that their effect is minimal for the PL signal.; For SOI samples the predictions and experimental data are in good agreement, taking into account the interference/reflection at the various layers/interfaces and for strained SiGe/Si samples, misfit dislocations and other structural defects were determined. |
