Co-implantation germanium with laser thermal annealing for the formation of np junction

摘要

Germanium (Ge) is a potential candidates to replace silicon (Si) due to its higher carrier mobility, which is the key point for realizing device high-drive-current. However, fabricating highly activated np junction in Ge is challenging due to the severe damages introduced from ion-implantation interact with dopant during subsequent annealing process, and results in dopant deactivation. Further optimization of fabrication process parameters is needed to overcome this problem. Co-implantation technique has gained attention due to its stress-induced carrier activation by implanting two atoms with different size. Combining with laser thermal annealing promise further improvement in activation and recrystallization. In this work, co-implantation of phosphorus (P) and tin (Sn) were performed, followed by KrF laser thermal annealing, to form an np junction in Ge. Laser fluence was varied to achieve np junction with higher activation and recrystallization. It is found that high degree of recrystallization was obtained in higher-fluence annealed sample, with 40% decrease of sheet resistance compare to those of lower-fluence annealed sample. Raman peak shift (≈ 3.5 cm) was also observed in the higher-fluence annealed sample, suggesting increase of localized strain in the sample.