Epitaxial recrystallisation of gallium implanted (100) silicon

High depth resolution Rutherford backscattering/channelling and low angle X-ray texture camera analysis have been employed to study the recrystallisation behaviour of gallium implanted (100) silicon during low temperature furnace annealing at 465°C. The recrystallisation behaviour was found to depend strongly on the gallium concentration, exhibiting three distinct recrystallisation regimes. For low fluence gallium implants peak concentration ≈ 0.3 at.%, epitaxial recrystallisation was observed to proceed to completion with a substantial fraction of the implanted gallium being incorporated on to substitutional lattice sites. The epitaxial recrystallisation rate was enhanced by gallium concentrations ≳ 0.2 at.% and substitutional concentrations in excess of the maximum equilibrium value were observed. In addition, X-ray analysis implies the existence of a thin, ≲ 5 nm, preferentially oriented polycrystalline surface layer after annealing. For higher gallium fluences, peak concentration ≈ 1.8 at.% epitaxial recrystallisation no longer proceeded to completion but ceased some 20 nm from the silicon surface. Considerable gallium was observed to be redistributed towards the surface by the advancing crystal-amorphous interface and the epitaxial recrystallisation rate was again observed to be enhanced by gallium concentrations ≳ 0.2 at.%, reaching a maximum value of 7.5 times that of undoped amorphous silicon layers. Substitutional gallium concentrations ≈ 3.0×10²⁰ Ga/cm³ were observed, a value comparable to that measured following pulsed laser annealing. Finally, X-ray analysis confirms that the 20 nm surface region contains preferentially aligned polycrystallites. For the highest gallium fluences investigated, peak concentration ≈ 4.0 at.% epitaxial recovery was initially slow and extensive gallium redistribution was observed after ≈ 15 min annealing. X-ray analysis again confirmed the presence of preferentially oriented polycrystallites.