High and Uniform Phosphorus Doping in Germanium Through a Modified Plasma Assisted Delta Doping Process With H₂ Plasma Treatment

To achieve high and uniform phosphorus (P) dopant concentration (more than $1\times 10^{{20}}$ cm ⁻³ ) near the germanium (Ge) surface, H ₂ plasma treatment and modified plasma-assisted delta doping (MPADD) process are proposed and investigated. Sufficient vacancies are formed on the Ge surface using H ₂ plasma treatment. Consequently, P and vacancies are uniformly included inside during Ge growth through the MPADD process. After the annealing, phosphorus-vacancy-oxygen (PVO) clusters with the lowest binding energy are formed. Therefore, the migration activation energy increases, and the dopant diffusion into the substrate is reduced. As a result, the surface P dopant concentration ( $4\times 10^{{21}}$ cm ⁻³ ) improves, and a uniform P concentration of approximately 5 nm is from the Ge surface. These results show that the MPADD process enables a uniform and high surface doping concentration of recently promising Ge materials and compensates for the disadvantages of conventional delta doping, such as long process time and the need for an ultra-high vacuum system.