OPEN-VOLUME DEFECT TAILS IN GE-IMPLANTED SI PROBED BY SLOW POSITRONS

Positron annihilation spectroscopy has been used in conjunction with a nodic oxidation and etching to profile the distribution of open-volume defects beyond the range of 120 keV Ge ions implanted into (100) Si a t a dose of 1 X 10(14) cm(-2). For a time-averaged dose rate (J(t)) of 0.02 mu A/cm(-2) and incident angle of 7 degrees, open-volume defects are found to exist at concentrations exceeding 10(16) cm(-3) at depth s up to 600 nm, whereas the peak of the depth distribution of the impl anted Ge ions (R-p) is 76 nm, measured using secondary ion mass spectr oscopy. An increase in the depth of the defects observed when the impl ant is intentionally channeled on the [100] axis is thought to be simp ly correlated with a corresponding increase in R-p to 79 nm. When the time-averaged current is increased by a factor of 10 (incident angle = 7 degrees), defects persist at concentrations in excess of 10(17) cm( -3) beyond 1 mu m and the R-p increases to 101 nm; this extended tail is attributed primarily to increased defect diffusion. (C) 1998 Americ an Institute of Physics. [S0003-6951(98)01036-5].