Transition from small interstitial clusters to extended {311} defects in ion-implanted Si

We have investigated the transition from small interstitial clusters to {31 1} defects in ion-implanted Si. Czochralski Si wafers were implanted with 1 .2 MeV Si ions to fluences in the range 10(12)-5 x 10(13)/cm(2) and anneale d at temperatures of 600-750 degrees C for times as long as 15 h. Photolumi nescence and transmission electron microscopy analyses allowed us to analyz e the transition of small interstitial clusters, formed by the agglomeratio n of the excess interstitials introduced by the beam, into {311} defects. I t is found that {311} defects form only at fluences greater than or equal t o 10(13)/cm(2) and at temperatures above 600 degrees C. When {311} are obse rved in transmission electron microscopy, the luminescence spectrum is domi nated by a sharp signal at 1376 nm which has been correlated with optical t ransitions occurring at or close to these defects. At lower temperatures or at lower fluence, no extended defects are observed in transmission electro n microscopy and the luminescence spectrum present two broad signatures ari sing from carrier recombination at interstitial clusters. These data strong ly indicate that a severe structural transformation occurs in the evolution from small interstitial clusters to extended {311} defects. (C) 2000 Ameri can Institute of Physics. [S0003-6951(00)01601-6].