MONOLITHIC GAAS LIGHT-EMITTING DIODES ON SILICON VLSI CIRCUITS ELEMENTS

OPTOELECTRONIC SOURCES, INTEGRATED AS MONOLITHIC ELEMENTS ON SILICON VLSI CHIPS, OFFER IMPORTANT ADVANTAGES IN THE TRANSMISSION OF INFORMATION WITHIN THE CHIP OR BETWEEN CHIPS IN ADVANCED COMPUTER SYSTEMS. THE SPEED OF OPTICAL-INTEGRATED VLSI DEVICES IS EXPECTED TO BE CONSIDERABLY HIGHER THAN EQUIVALENT VLSI WITH METALLIC INTERCONNECTS, DUE TO ABSENCE OF THE RC DELAY INHERENT IN THE METALLIC CONDUCTOR SYSTEM. A KEY OPPORTUNITY, AT THIS TIME, THEREFORE, IS TO INTEGRATE GAAS LED'S ONTO SILICON VLSI CIRCUITS AND TO USE GAAS LED'S TO COMMUNICATE EITHER BY DIRECT OPTICAL INTERACTION WITH A SILICON DETECTOR,OR BY LIGHT-GUIDED OR HOLOGRAPHIC TECHNIQUES. WE PROPOSE TO DEVELOP METHODS OF NUCLEATION AND ISLAND GROWTH OF GAAS ON SINGLE CRYSTAL SILICON WAFERS THROUGH THE USE OF A NOVEL STRUCTURE WHICH MINIMIZES THE CONTACT AREA BETWEEN THE GAAS AND THE SILICON. THIS STRUCTURE WILL BE PREPARED USING SELECTIVE LIQUID-PHASE EPITAXY THROUGH VIAS IN A SILICON DIOXIDE LAYER ON THE SILICON WAFER. AN INTERMEDIATE NUCLEATION INTERLAYER WILL BE UTILIZED TO ACCOMMODATE THE LATTICE MISMATCH BETWEEN THE SILICON SUBSTRATE AND THE GAAS OVERGROWTH. DIRECT CONTACT BETWEEN THE SILICON AND GAAS WILL BE LESS THAN ONE PERCENT OF THE OVERALL AREA, WHICH WILL LIMIT STRAIN AND DISLOCATIONS WITHIN THE GAAS FILM. LIGHT-EMITTING DIODES WILL BE FABRICATED DIRECTLY ON SILICON VLSI CIRCUIT ELEMENTS, NAMELY, ON A N-MOS DRIVER. THE DEMONSTRATION OF A MONOLITHIC GAAS LED INTEGRATED ON A SILICON N-MOS DRIVER REPRESENTS A MAJOR ADVANCE IN THE PROGRESS TOWARD OPTICALLY INTERCONNECTED CIRCUITS FOR THE NEW GENERATION OF ULTRAHIGH SPEED COMPUTER SYSTEMS.