HIGH RESISTIVITY ION-IMPLANTED GAAS BUFFER LAYERS FOR INTEGRATED PHOTONICS

THE PERFORMANCE OF GAAS-INTEGRATED CIRCUITS HAS BEEN LIMITED BY BACKGATE OR SIDEGATE EFFECTS WHICH CAN LEAD TO UNDESIRABLE CROSS-TALK BETWEEN NEIGHBORING DEVICES AND IMPOSE LIMITS ON DEVICE PACKING DEN- SITY. RECENT RESEARCH HAS SHOWN THAT INCORPOATING A GAAS BUFFER LAYER GROWN AT LOW TEMPERATURES BY MOLECULAR BEAM EXPITAXY (MBE) CAN RESULT IN MANY PERFORMANCE IMPROVEMENTS, INCLUDING ELIMINATION OF BACKGATING. ONE OF THE DOMINANT CHARACTERISTICS OF THE MBE-GROWN BUFFER LAYERS IS AN EXCESS OF AS IN THE FILM. WE PROPOSE THE FORMATION OF AS-RICH BUFFER LAYERS BY ION IMPLANTATION OF AS+ INTO GAAS. ION IMPLANTATION OFFERS MANY BENEFITS INCLUDING REPRODUCIBILITY AND CONTROLLABILITY. THE PROPOSED PROGRAM WILL COMBINE ION IMPLANTATION AND METALORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD) TECHNIQUES TO DEVELOP A METHOD TO ISOLATE ACTIVE GAAS DEVICE REGIONS IN THREE DIMENSIONS. IN PHASE I, WE WILL GROW EPIAXIAL GAAS LAYERS BY MOCVD AND IMPLANT AS UNDER VARIOUS CONDITIONS (INCLUDING MEV IMPLANTATION) TO FORM BURIED BUFFER LAYERS FOR VERTICAL ISOLATION AND AS-RICH WALLS BETWEEN ACTIVE REGIONS FOR HORIZONTAL ISOLATION. TEST PATTERNS WILL BE FABRICATED AND THE ELECTRICAL ISOLATION PROPERTY OF AS+-IMPLANTED LAYERS EVALUATED. PHASE II WORK WILL OPTIMIZE THE PROCESSES DEVELOPED IN THE PHASE I PROGRAM AND WILL INCLUDE FABRICATION OF DEVICES SUCH AS MESFETS AND PHOTODIODES IN ACTIVE GAAS REGIONS ISOLATED BY ION-IMPLANTED BUFFER LAYERS.