Germanium n+/p Shallow Junction With Record Rectification Ratio Formed by Low-Temperature Preannealing and Excimer Laser Annealing

A germanium n⁺/p shallow junction formed by a combination of low-temperature preannealing (LTPA) and excimer laser annealing at a low fluence of 150 mJ/cm² for phosphorus-implanted germanium is demonstrated. The LTPA step plays a critical role in annihilating the implantation damages and significantly suppressing phosphorus diffusion during laser annealing process, resulting in a very small dopant diffusion length with high activation level of phosphorus. A well-behaved Ge n⁺/p shallow junction diode with a record rectification ratio of ~10⁷ and low leakage current density of 8.3 × 10^-5 A/cm² is achieved, which is greatly beneficial to the scaled Ge MOSFET technology.