Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing
High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8??×??1019 cm?3 has been achieved starting from an incorporated phosphorous concentration of 1.1??×??1020 cm?3. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350?nm thick layer.