Germanium-tin p-i-n photodetectors integrated on silicon grown by molecular beam epitaxy

GeSn heterojunction p-i-n diodes with a Sn content of 0.5% are grown with a special low temperature molecular beam epitaxy. The Sn incorporation in Ge is facilitated by a very low temperature growth step in order to suppress Sn surface segregation. Diodes with sharp doping transitions are realized as double mesa structures with a diameter from 1.5 up to 80 mu m. An optical responsivity of these GeSn diodes of 0.1 A/W at a wavelength of lambda = 1.55 mu m is measured. In comparison with a pure Ge detector the optical responsivity is increased by factor of 3 as a result f Sn caused band gap reduction. (C) 2011 American Institute of Physics. [doi:10.1063/1.3555439]