Effectiveness of metallic mirror for promoting the photoresponse of InGaAs PIN photodiode

The effectiveness of metallic mirror for raising the photoresponse of vertical-illuminated InGaAs PIN photodiode was calculated and experimentally verified. The preliminary results show that an InGaAs PIN photodiode with a 1-μm absorption layer and Ti/Pt/Au backside metallization can reach a responsivity of ∼0.8 A/W or a quantum efficiency of ∼76% at 1.3 μm wavelength. Such values indicate that the incident light travels the absorption region more than 1 μm and in turn provide the evidence for light reflection. From the comparison with the calculated responsivity spectra, the reflectivity of Ti/Pt/Au can be derived with a value of ∼0.4, which agrees reasonably well with the calculated metallic reflectivity.