Ultra-Fast Waveguide MUTC Photodiodes over 220 GHz

We present InP-based evanescently-coupled waveguide modified uni-travelingcarrier photodiodes (MUTC-PDs) exhibiting a breakthrough in bandwidth. Theoptimization of carrier transport and optical coupling is achieved through adetailed discussion on the design of the cliff layer and waveguide layer.Addressing the parasitic capacitance challenge, we introduce benzocyclobutene(BCB) beneath the PD electrodes, effectively overcoming the bandwidthbottleneck associated with the RC time constant. Devices with sizes of 2 * 7um2 and 2 * 10 um2 achieve 3-dB bandwidths over 220 GHz, along with externalresponsivities of 0.161 A/W and 0.237 A/W, respectively. Notably, the RF outputpower reaches a peak of -1.69 dBm at 215 GHz for 2 * 15 um2 PDs.