A HYDROGENATED AMORPHOUS SILICON PARTICLE DETECTOR

HYDROGENATED AMORPHOUS SILICON HAS GREAT POTENTIAL FOR APPLICATIONS REQUIRING LARGE TOTAL AREAS OF LOW COST IONIZED PARTICLE DETECTORS, SUCH AS IN CALORIMETERS AT THE SUPERCONDUCTING SUPER COLLIDER (SSC) OR IN MEDICAL IMAGING. AMORPHOUS SILICON IS MORE RESISTANT TO RADIATION DAMAGE THAN CRYSTALLINE SILICON, MAKING IT ATTRACTIVE FOR USE IN HIGH RADIATION ENVIRONMENTS. TO BE USEFUL FOR SSC APPLICATIONS, THE SIGNAL-TO-NOISE RATIO FROM AMORPHOUS SILICON DIODES MUST BE IMPROVED. THE MAJOR PROBLEM IS A RELATIVELY HIGH MIDGAP DENSITY OF STATES WITHIN THE INTRINSIC MATERIAL. THIS DENSITY LIMITS THE DEPLETION WIDTH TO ABOUT 50 MUM USING EXISTING TECHNOLOGY. PRELIMINARY RESULTS SUGGEST THAT A NOVEL TECHNIQUE TO CHEMICALLY MODIFY INTRINSIC AMORPHOUS SILICON CAN SIGNIFICANTLY REDUCE THE MIDGAP DENSITY OF STATES. THIS PHASE I PROJECT WILL ATTEMPT TO VERIFY THIS RESULT BY USING THE NEW TECHNIQUE IN CONJUNCTION WITH STANDARD PLASMA-ENHANCED CHEMICAL VAPOR DEPOSITION TO GROW FULLY DEPLETED, LOW NOISE, AMORPHOUS SILICON P-I-N DIODES. THESE DIODES WOULD EXHIBIT INTRINSIC LAYER THICKNESSES UP TO 75 MUM, WELL IN EXCESS OF THE CURRENT 50 MUM RECORD DEPLETION WIDTH FOR AN AMORPHOUS SILICON DEVICE. THINNER DEVICES ARE BEING MADE USING BOTH THE NEW TECHNIQUE AND STANDARD PROCESSING FOR DETAILED COMPARISON OF THE MATERIAL PROPERTIES.