5Gb/s Monolithically Integrated GaAs MSM/PHEMT 850nm Optical Receiver Front End

An 850nm monolithically integrated optical receiver front end is developed with a 0.5μm GaAs PHEMT process,which comprises a metal-semiconductor-metal (MSM) photodetector and a distributed amplifier.The photodetector has a photosensitive area and capacitance of 50μm×50μm and 0.17pF,respectively,as well as a dark current of less than 17nA under a bias of 4V.The distributed amplifier has a -3dB bandwidth close to 20GHz,with a transimpedance of 46dBΩ.In the range of 50MHz ~16GHz,both the input and output voltage standing wave ratio are less than 2.The measured noise figure varies form 3.03 to 6.5dB.The output eye diagrams for 2.5Gb/s and 5Gb/s NRZ pseudorandom binary sequence are also obtained.