Buried oxide and defects in oxygen implanted Si monitored by positron annihilation

One- and two-detector Doppler broadening measurements performed on low (similar to 10(14) to 10(15) O(+)/cm(2)) and high dose (similar to 10(17) to 10(18) O(+)/cm(2)) oxygen-irradiated Si using variable-energy slow positrons are analyzed in terms of S and W parameters. After annealing the low-dose samples at 800 degreesC, large V(x)O(y) complexes are formed at depths around 400 nm. These complexes produce a clear-cut signature when the ratio of S to that of defect-free bulk Si is plotted. Similar behavior is found for samples irradiated with 2 and 4x10(17) O(+)/cm(2) and annealed at 1000 degreesC. After irradiation with 1.7x10(18) O(+)/cm(2) and anneal at 1350 degreesC a 170 nm thick almost-bulk-quality Si surface layer is formed on top of a 430 nm thick buried oxide layer. This method of preparation is called separation by implantation of oxygen. S-W measurements show that the surface layer contains electrically inactive V(x)O(y) complexes not seen by electron microscopy. A method is presented to decompose the Doppler broadening line shape into contributions of the bulk, surface, and defect. (C) 2001 American Institute of Physics.