Photoluminescence characterization of defects in Si and SiGe structures

Low-temperature photoluminescence (PL) spectroscopy is a very sensitive too l to investigate the presence of dislocations in Si. The main dislocation-r elated bands (D1-D4) have been attributed to a wide range of causes, either intrinsic properties of the dislocation or impurity related. PL is a compe titive recombination process and the non-radiative processes need to be mea sured to understand the overall effect of impurities. PL spectroscopy sampl es a large volume in comparison to the dislocation itself and therefore giv es an average effect. High-resolution room-temperature PL mapping (SiPHER) has been used to detect defects in both Si and SiGe wafers. Whole-wafer PL maps reveal the presence of slip on 300 mm Si wafers. Comparison studies wi th defect etching show that there is a one-to-one correlation between defec ts detected in the PL micro-scans and those revealed by defect etching. Who le-wafer mapping has revealed a number of different defect types in SiGe ep ilayers. The ability to record whole-wafer PL maps facilitates the rapid id entification of inhomogeneities and defects. High-resolution PL micro-maps showed the defect area to contain a high density of misfit dislocations, an d the nucleation site has strong non-radiative recombination. One common de fect type was analysed using plan view transmission electron microscopy (TE M) and optical microscopy: these results revealed the presence of a high de nsity of defect loops and stacking faults consistent with the high recombin ation rate at the defect site.