Light Element Impurities in Multi-crystalline Silicon

Light element impurities in multi-crystalline Si have been investigated with Fourier transform infrared spectroscopy. These experiments include defect studies in silicon with a high concentration of carbon and also with various concentrations of both nitrogen and oxygen.;A thermally stable VH4 center trapped by carbon was discovered. The vibrational properties of this defect have been studied for the case of mixed H and D isotopes to establish its structure. The new lines we have found are assigned to the Si-H(D) and C-H(D) stretching modes of the defect center.;We have studied N- and O-related defects in multi-crystalline Si used by industry to fabricate solar cells. The N-N center is the dominant N-related defect. However, N is also found to be bonded with O in multi-crystalline Si. NN-On centers are most likely seen when the oxygen concentration in the sample is high. We have also studied the properties of electrically active N-O centers that contain a single N atom. These N-O shallow donors are found to be present in multi-crystalline Si samples containing oxygen and nitrogen but with a lower concentration than is present in oxygen-rich Czochralski-grown Si that contains nitrogen.