DISTRIBUTION OF POINT-DEFECTS IN SI(100)/SI GROWN BY LOW-TEMPERATURE MOLECULAR-BEAM EPITAXY AND SOLID-PHASE EPITAXY

Positron annihilation in Si is a quantitative, depth-sensitive technique for the detection of vacancy--like defects or voids. A sensitivity of 5 x 10(15) cm-3 for voidlike defects is easily achieved. The technique has been applied to a study of point-defect distributions in thin films of Si grown by molecular-beam epitaxy. A special procedure was developed to remove the influence of the native oxide on the positron measurement. 200-nm-thick films grown at temperatures between 475 and 560-degrees-C show no defects below the sensitivity limit and are indistinguishable from the bulk substrate. So are films grown at 220-degrees-C, provided a 2-min high-temperature anneal to a peak temperature of greater-than-or-equal-to 500-degrees-C is executed every congruent-to 30 nm during growth. If T(RTA) = 450-degrees-C, part of the film contains va-cancylike defects to a concentration of congruent-to 10(18) cm-3. These results correlate well with current-voltage characteristics of p-n junctions grown with different rapid thermal anneal (RTA) temperatures. Ion scattering, with a defect sensitivity of almost-equal-to 1%, shows no difference between films grown with different T(RTA). Recrystallization of amorphous films, deposited at room temperature and annealed in situ at 550-degrees-C, always leaves a significant defect concentration of congruent-to 2 x 10(18) cm-3; those defects are reduced but still present even after a 2-h, 800-degrees-C furnace anneal.