APPROACH TO QUANTITATIVE DETERMINATION OF DEFECT CONCENTRATION ON SURFACES BY LASER-INDUCED ATOMIC EMISSION

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The object of the research project is to provide a method of easily dterming a quantitative surface defect concentration using atomic emission by pulsed laser irradiation. This idea is based on the early experimental evidence that the atomic emission can be induced only at the defect sites on the semiconductor surface under laser irradiation of fluence below the damage threshold. The emission of nutral atoms induced by electronic excitation of defects, whose concentration is not high were measured by a detection system of an extremely high sensitivity. These measurements of laser-induced atomic emission from semiconductor surfaces have been carried out for Ga atoms from GaAs (110), GaP (110) and (100) and for Si atoms from Si (111) and (100) surfaces. It was found that three different types of the defect (adatom-type, kink-type and vacancy-type) on the surface can be differentiated by the measurement of the yield of the atomic emission. Emission from the adatom-type defect sites was confirmed from teh evidence that the yield is enhanced proportionally to the number of the deposited atoms. The evidence for the defect-related atomic emission also confirmed from the enhancement of the yield by the selective halogen adsorption at defect sites. More direct evidence for the emission from the defects at the surface was given by the observation of the scanning tunneling micrographs of Si (111) 7x7 surfaces before and after laser irradiation. It showed clearly the missint adatoms from the 7x7 unit cells withoug indication of melting. Moreover, it revealed that the number of the vacancies formed at the center-adatom sites is much larger than that at the corner sites, showing the strong dependence of the atomic emission on the bonding nature at the defect sites.