110-GHZ, 50-PERCENT-EFFICIENCY MUSHROOM MESA WAVE-GUIDE P-I-N PHOTODIODE FOR A 1.55-MU-M WAVELENGTH

A mushroom-mesa structure is proposed to reduce the CR-time constant w hich originates from the waveguide photodiode structure. Experimental results at a 1.55-mum wavelength show that the multimode waveguide p-i -n photodiode with mushroom-mess structure has an electrical 3-dB band width of more than 75 GHz in the frequency domain and an electrical 3- dB bandwidth of 110 GHz in the time domain. The external quantum effic iency is 50% or 0.63 A/W, which leads to a record bandwidth-efficiency product of 55 GHz for long wavelength p-i-n photodetectors.