Method for determining crystal defect concentration lower than 10 ppm in semiconductors based on photomodulated reflectance measurement

In case of semiconductor samples, the method enables the determination of the charge carrier lifetime and crystal defect concentration related to the recombination defect centers present in the material based on photomodulated reflection (PMR) measurement operating in the quasi-static modulation frequency range. The defect centers present in the basically single-crystal semiconductor sample (Ml) can be of intrinsic or extrinsic origin, typically electrically active de- feet sites created by the implantation of low-mass - H+, He+ - high-energy ions, or impurity atoms, e.g., metal contaminants introduced during other technological steps. The method can be used in all cases where the crystal defect concentration is typically in the ppb-ppm range, its depth distribution is almost uniform, and the size of the excitation/analyzing laser spot in the PMR measurement is significantly smaller than the thickness of the zone containing the crystal defects. The excess charge carrier concentration obtained from the PMR measurement using the described procedure gives the total lifetime Ttot, from which, knowing the lifetimes of other charge carrier recombination processes and the time constants of diffusion processes, the life- time and concentration assigned to intrinsic or extrinsic defects can be determined, and can be correlated with the implantation related or other technological parameters.