Integrated Optoelectronic Devices For High-Speed Ic Interconnects

GaAs is an ideal material for use in Very-High-Speed Integrated Circuits for two fundamental reasons: (1) such circuits have great potential for high-speed performance because of the high intrinsic mobility and saturation velocity of GaAs, and (2) efficient optical devices can be fabricated in this material, providing the potential for optical interconnects. In this paper, the integration of optoelectronic devices utilizing geometries that lend themselves to inter- and intra-chip interconnects will be discussed. Monolithic integration of active devices parallel to the plane of the epitaxial layers will be described, along with recent schemes developed for output couplers transverse to the layers. For the case of monolithic integration within the epitaxial layers, the development of Distributed Feedback and other devices utilizing periodic corrugations will be reviewed briefly. More attention will be devoted to the formation of Fabry-Perot resonators using both wet and dry etching techniques, and the monolithic integration of these devices into optical circuits. Results in both GaAs and InP-based materials will be reported. Attempts to produce ring lasers or other structures utilizing curved waveguides will also be described, along with investigations of techniques to produce optical circuits directly during the crystal-growth procedure by utilizing various types of masks. Output couplers will also be considered in this paper. The use of gratings can result in coherent, parallel output beams that are easily coupled into optical fibers. Recent attempts to fabricate Fabry-Perot resonators in the direction transverse to the epilayers will also be reviewed.