Resonant cavity enhanced InP/InGaAs photodiode on Si using epitaxial liftoff

Epitaxial liftoff (ELO) is used in the fabrication of an InP/InGaAs resonant cavity photodetector on Si. External mirrors were employed with the bottom mirror consisting of an intermediate gold layer between the Si and ELO InP film. A dielectric stack of Si/SiO2 was used as the top mirror instead of a semitransparent metallic mirror to increase the quantum efficiency further. An external quantum efficiency of 0.57 in the spectral region of 1.55 μm was obtained for a 2500-Å-thick InGaAs absorbing layer. This is four times larger than the predicted value for a conventional pin photodiode with the same absorbing layer thickness. The spectral response showed wavelength selectivity. A full width at half-maximum of 150 Å is obtained with the top mirror reflectivity matched for optimum quantum efficiency. Further increase in the top mirror reflectivity improved spectral selectivity but at the expense of reduced quantum efficiency.