Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing
01 Pubblicazione su rivista
Frigerio J., Ballabio A., Gallacher K., Gilberti V., Baldassarre Leonetta, Millar R., Milazzo R., Maiolo L., Minotti A., Bottegoni F., Biagioni P., Paul Douglas J., Ortolani Michele, Pecora A., Napolitani E., Isella G.
ISSN: 0022-3727
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. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved.