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

Abstract

Metastable pseudomorphic Si 0.83 Ge 0.17 with thickness of 135 nm was deposited on ͑001͒ Si substrate by molecular beam epitaxy and amorphized to a depth of ϳ360 nm, using 3 ϫ 10 15 cm −2 Ge ions at 270 keV. Samples were regrown by solid phase epitaxy in the 500-600°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: ͑1͒ a 20 nm defect-free layer close to the original crystal-amorphous interface, ͑2͒ a middle region with a high density of planar defects, and ͑3͒ 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 implants͒ 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.

Single crystalline SiGe layers on Si by solid phase epitaxy

“…Obtaining high quality and smooth crystalline SiGe, especially with high Ge content, directly on silicon is therefore challenging. SPE of amorphous SiGe layers produced by ion implantation has previously been studied in detail where it was shown that the SPE activation energy generally decreases with Ge content and that the amorphous-crystalline interface can become rough as a result of the strain [10,11]. Graded SiGe layers is a common method employed to control the formation of dislocations but such a process may require additional processing steps [12].…”