In this letter, we describe a novel edge-coupled photodiode (PD) structure, which can greatly relax the dependence of the responsivity on the cleaved length of an evanescently coupled optical waveguide. The integration of a leaky optical waveguide with a distributed Bragg reflector (DBR) and a partially p-doped photoabsorption layer allows the demonstrated device to exhibit a higher saturation current-bandwidth and responsivity than a control sample without the DBR structure. We achieved excellent speed (40-50 GHz), responsivity (0.8 A/W), and saturation current-bandwidth products (720 mA · GHz at 40 GHz), comparable to the high-performance of an evanescently coupled PD, whose variation of responsivity is more sensitive to the cleaved waveguide length (30% versus 7%) than is our demonstrated device.
- Distributed Bragg reflector (DBR)
- High-power photodiode (PD)
- Leaky optical waveguide