Boron and Phosphorus dopant activation in Germanium using laser annealing with and without preamorphization implant

Abstract

In this work, we studied excimer laser annealing at 308 nm with 180 ns pulse duration on phosphorus and boron implanted in germanium, with or without pre-amorphization implant (PAI) and co-implant. Using an industrial tool, experimental results show that we can achieve electrical activation levels up to 1.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> for P implant in Ge, which is the highest level regarding the appropriate mobility model. With the B implanted samples, we obtained an electrical activation level higher than 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> which is the better results obtained without PAI. Melt thresholds were determined to be 0.65 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in amorphized germanium (a-Ge) and 0.95 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in crystalline germanium (c-Ge). With P, the best activation was obtained after a complete melt of the amorphous layer and the amorphous / crystalline (a/c) interface, necessary to obtain a perfectly recrystallized layer. In the case of B, we found a better activation in the submelt regime compared the melt one, and no contribution on the electrical activation with PAI was observed.