SELECTIVE-AREA EPITAXY OF GALLIUM ARSENIDE ON SILICON

THERMAL EXPANSION MISMATCH BETWEEN GALLIUM-ARSENIDE (GAAS) AND SILICON(SI) CAUSES SUBSTRATE BOWING AND CRACKING DURING COOLING FROM THE GROWTH TEMPERATURE. THIS IS A MAJOR OBSTACLE TO OVERCOME BEFORE THE FULL POTENTIAL OF THIS MATERIAL CAN BE REALIZED. THE FEASIBILITY IS BEING INVESTIGATED OF USING SELECTIVE-AREA EPITAXY OF GAAS ON SI TO REDUCE THE TENSILE STRESS TO A LEVEL WHERE SUCH SUBSTRATE BOWING AND CRACKING WILL NOT BE A PROBLEM. METALORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD) IS BEING UTILIZED FOR DEPOSITING AREAS OF GAAS, WITH VARYING DIMENSIONS, ON TWO-INCH SI SUBSTRATES THROUGH OPENINGS PATTERNED ON SILICON DIOXIDE (SIO2). THE EFFECTS OF THIS TECHNIQUE ONSUBSTRATE BOWING, FILM CRACKING, CRYSTALLOGRAPHIC PROOPERTIES AND TREADING DISLOCATIONS ARE BEING DETERMINED. SPECIFICALLY THE FOLLOWING ARE BEING ESTABLISHED: BASIC PROCESS FOR PATTERNING THERMALLY GROWN SIO2; MOCVD GROWTH PARAMETERS FOR THE DEPOSITION OF GAAS OVER PATTERNED SIO2 ON SI; AND WORKABLE PROCESS TO REMOVE GAAS AND SIO2 FROM UNWANTED AREAS. THE TECHNIQUES DEVELOPED ARE EXPECTED TO BE INSTRUMENTAL IN REDUCING THREADING DISLOCATIONS TO BE ADDRESSED IN A LATER STUDY. WHEN SUCCESSFUL, THIS TECHNOLOGY WOULD YIELD DEVICE QUALITY GAAS ON SI AND A PROCESS APPLICABLE FOR MONOLITHIC INTEGRATION OF GAAS AND SI DEVICES, GREATLY ENHANCING PRESENT DEVICE CAPABILITIES.