Effects of InP crystallographic slope with light-input tapered SiOx facet on InGaAsP–InGaAs–InP waveguide photodetectors

In this paper, the influence of InP crystallographic slope with light-input tapered SiOx facet of InGaAsP–InGaAs–InP waveguide photodiodes (WGPDs) on the light-injected collection efficiency and responsivity are investigated with 3-D ray-tracing simulations and manufacturing implementation. According to our calculation results of the examination of simulations and real situations, we find that the appropriate light-input tapered facet in front of the active region designed here enlarges substantially the light-coupling aperture and therefore assists the light collection of the thin absorption layer outside of its area. The thin absorption layer of WGPDs for high frequency operation with high responsivity will be achieved by InP crystallographic slope through a simple chemical etching. The InP crystallographic slope also provides higher misalignment tolerance for fiber coupling. The anisotropic etching in appropriate processes also makes the designed WGPD have a superior current–voltage characteristic.