A MODFET-BASED OPTOELECTRONIC INTEGRATED-CIRCUIT RECEIVER FOR OPTICAL INTERCONNECTS

The design, fabrication, and characterization of a 0.85-mum sensitive photoreceiver is described. The monolithically integrated optoelectronic receiver is based on pseudomorphic InGaAs on GaAs modulation-doped field-effect transistors (MODFET's) and metal-semiconductor-metal (MSM) photodectectors. High-performance quarter-micrometer MODFET's with f(t)'s of approximately 70 GHz are utilized in a two-stage transimpedance amplifier. An asymmetric and a symmetric amplifier design are compared. The symmetric design is found to provide the desired zero dc offset voltage for a variety of supply voltages. Excess MSM-detector dark current and low-frequency internal gain are greatly reduced through the use of a silicon nitride passivation layer and/or AlGaAs cap layer. Receiver transimpedances between 100 and 5000 OMEGA are obtained by varying the bias on an active feedback resistor. The parasitic capacitances of this common-gate feedback FET are studied. A transimpedance amplifier bandwidth as high as 14 GHz and an overall photoreceiver bandwidth of 11 GHz are measured. These are the highest bandwidths yet reported for any monolithic OEIC receiver.