IMPROVED FRETTING OF TITANIUM ALLOYS BY ION IMPLANTATION

DEVICE PERFORMANCE OF GAAS METAL-SEMICONDUCTOR FIELD EFFECT TRANSISTORS (MESFETS) ON CONVENTIONAL SEMI-INSULATING GAAS SUBSTRATES HAS BEEN LIMITED BY BACKGATE OR SIDEGATE EFFECTS WHICH CAN LEAD TO UNDESIRABLE CROSS-TALK BETWEEN NEIGHBORINGDEVICES AND THUS IMPOSE LIMITS ON PACKING DENSITIES. RECENTRESEARCH HAS SHOWN THAT INCORPORATION OF A LOW TEMPERATURE BUFFER LAYER GROWN BY MOLECULAR BEAM EPITAXY (MBE) CAN RESULT IN MANY PERFORMANCE IMPROVEMENTS, INCLUDING ELIMINATION OF BACKGATING. BECAUSE OF ITS VERY HIGH PROCESSING COST, MBE IS NOT A COMMERCIALLY VIABLE PRODUCTIONMETHOD. WE PROPOSE TO FORM AN EFFECTIVE BUFFER LAYER USING ION IMPLANTATION, A DEMONSTRATED MANUFACTURABLE PROCESS. ONE OF THE DOMINANT CHARACTERISTICS OF THE MBE-GROWN BUFFER LAYERS IS AN EXCESS OF AS IN THE FILM. ION IMPLANTATION IS WELL SUITED TO SIMULATE THE MBE LAYERS SINCE IMPLANTATION CONDITIONS CAN BE TIGHTLY CONTROLLED TO PRECISELY ENGINEER THE AS PROFILE BY ADJUSTING IMPLANTATION PARAMETERS SUCH AS DOSE, ENERGY, AND DOSE RATE. THE GOAL OF THE PHASE I WORK IS TO USE ION IMPLANTATION TO PRODUCE AS-RICH ISOLATING BUFFER LAYERS IN GAAS. THE STRUCTURAL AND ELECTRICAL PROPERTIES OF THE BUFFER LAYERS WILL BE STUDIED AND COMPAREDTO THOSE OF MBE-GROWN LAYERS. PHASE II WORK WILL OPTIMIZE THE PROCESSES DEVELOPED IN PHASE I AND WILL INCLUDE FABRICATION OF DEVICES SUCH AS MESFETS AND HIGH ELECTRON MOBILITY TRANSISTORS (HEMTS) IN DEVICE LAYERS GROWN ON ION-IMPLANTED BUFFER LAYERS.