MONOLITHICALLY INTEGRATED INP-BASED FRONT-END PHOTORECEIVERS

The performance characteristics of a monolithically integrated front-end photoreceivers, consisting of a photodiode and a MODFET amplifier, have been analyzed and measured. A vertical scheme of integration was initially used to realize a photoreceiver circuit on InP consisting of a InGaAs p-i-n diode, an InGaAs/InAlAs pseudomorphic MODFET, and passive circuit elements. The device structures were grown by single-step molecular beam expitaxy with an isolating layer in between. The microwave performance of 1-mu-m gate MODFET's in the circuit is characterized by f(T) = 9 GHz, although identical discrete devices have f(T) = 30-35 GHz. The degradation is due to additional parasitic capacitances present in this scheme of integration. In spite of this disadvantage the band-width of the circuit is 2.1 GHz. Integration of the p-i-n diode with 1.0- and 0.25-mu-m gate MODFET's has also been done in a planar scheme, using regrowth, and receiver bandwidths of 6.5 GHz are measured. This value is comparable to hybrid circuits with InP-based devices.