Characterization of n-Ge/i-Ge/p-Si PIN photo-diode

A PIN photo-diode was fabricated from the phosphorus doped n-Ge/i-Ge/p-Si hetero-structure grown by rapid thermal chemical vapor deposition (RTCVD). The surface morphology of the n-Ge/i-Ge layer was found to be mirror like and the n-Ge/i-Ge layer was under a tensile strain of ~0.071%. The phosphorus doping concentration and the RMS surface roughness were 2×1019 cm−3 and 2.46 nm, respectively. Current–voltage characteristics of the PIN photo-diode showed a forward saturation current density of 0.63 A/cm2 at 2 V and reverse-biased characteristics behaved similar to forward-biased characteristics of the diode. Roll-off in spectral response was observed at wavelengths greater than 1600 nm which could be attributed to decreased absorption of Ge at room temperature.