High dopant activation of phosphorus in Ge crystal with high-temperature implantation and two-step microwave annealing

In this letter, high-temperature ion implantation and low-temperature microwave annealing were employed to achieve high n-type active concentrations, approaching the solid solubility limit, in germanium. To use the characteristics of microwave annealing more effectively, a two-step microwave annealing process was employed. In the first annealing step, a high-power (1200 W; 425 °C) microwave was used to achieve solid-state epitaxial regrowth and to enhance microwave absorption. In the second annealing step, contrary to the usual process of thermal annealing with higher temperature, a lower-power (900 W; 375 °C) microwave process was used to achieve a low sheet resistance, 78Ω/□, and a high carrier concentration, 1.025 × 10²⁰ P/cm³, which is close to the solid solubility limit of 2 × 10²⁰ P/cm³.