DEPTH DISTRIBUTION OF SILICON-ION INDUCED DEFECTS IN CRYSTALLINE SILICON

In crystalline silicon, irradiated with 60 and 80 MeV energy silicon i ons, regions of high defect densities were located by repeatedly etchi ng the sample and measuring the lifetime of minority carriers, tau. Th e values of tau before etching were 10 and 8 mu s in the 60 and 80 MeV ion irradiated sides, respectively, and 19 mu s in the unirradiated s ide. On etching the samples, these values of the irradiated side initi ally increased slowly but later on, as the total thickness of the etch ed silicon approached the ion ranges, they increased steeply. However, the value of tau in the unirradiated side remained unchanged even aft er etching. These results show that the regions of high defect densiti es are situated below the surface at depths of 20 and 27 mu m, respect ively, in 60 and 80 MeV ion irradiated samples. These coincide, respec tively, with the projected depth in silicon at which the 60 and 80 MeV silicon ions deposit a maximum amount of energy through nuclear colli sions. (C) 1997 American Institute of Physics.