Interface roughening and defect nucleation during solid phase epitaxy regrowth of doped and intrinsic Si0.83Ge0.17 alloys

Metastable pseudomorphic Si0.83Ge0.17 with thickness of 135 nm was deposited on (001) Si substrate by molecular beam epitaxy and amorphized to a depth of similar to 360 nm, using 3x10(15) cm(-2) Ge ions at 270 keV. Samples were regrown by solid phase epitaxy in the 500-600 degrees C temperature range. The regrowth rate was measured in situ by time resolved reflectivity, while the structure of the epilayers was investigated by transmission electron microscopy. Three regions can be distinguished in SiGe after solid phase epitaxy, independent of the annealing temperature: (1) a 20 nm defect-free layer close to the original crystal-amorphous interface, (2) a middle region with a high density of planar defects, and (3) a layer with dislocations and stacking faults extending up to the surface. The activation energy of the SiGe solid phase epitaxy is equal to the activation energy of Si except in the middle region. The amorphous-crystal interface evolution was studied by transmission electron microscopy of partially regrown samples. In order to study the effects of dopants, some samples were also implanted with B+ and Sb+ ions. At the ion projected range (125 nm for both implants) the regrowth rate increases by a factor of 3 with respect to the unimplanted SiGe, but the defect-free layer again is found to be about 20 nm in all cases. Moreover, the activation energy of the solid phase epitaxy regrowth process does not depend on dopant introduction, while the only observable effect of B or Sb incorporation is a smoothness of the amorphous-crystal interface during solid phase epitaxy. (c) 2007 American Institute of Physics.