  We present InP-based evanescently-coupled waveguide modified uni-traveling
carrier photodiodes (MUTC-PDs) exhibiting a breakthrough in bandwidth. The
optimization of carrier transport and optical coupling is achieved through a
detailed 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 bandwidth
bottleneck associated with the RC time constant. Devices with sizes of 2 * 7
um2 and 2 * 10 um2 achieve 3-dB bandwidths over 220 GHz, along with external
responsivities of 0.161 A/W and 0.237 A/W, respectively. Notably, the RF output
power reaches a peak of -1.69 dBm at 215 GHz for 2 * 15 um2 PDs.
