Comparison of InGaAs pin photodiodes with Ti/Pt/Au and Au reflectors

The authors have fabricated planar InGaAs pin photodiodes designed for high -speed operation with rear metallic reflectors. The effectiveness of both T i/Pt/Au and Au reflectors for enhancing the photoresponse of InCaAs pin pho todiodes is evaluated. The experimental results show that an InGaAs pin pho todiode with a 1 mu m absorption layer can achieve a responsivity > 0.9A/W (similar to 86% quantum efficiency) at 1.3 mu m wavelength with an Au refle ctor but can achieve only similar to 0.8A/W (similar to 76% quantum efficie ncy) with a Ti/Pt/Au reflector. Furthermore, the reflectivity of both metal lic mirrors (similar to 0.9 for Au and similar to 0.4 for Ti/Pt/Au) is extr acted using a simple theoretical model.