LARGE-AREA PHOTODETECTOR ARRAYS

HYDROGENATED AMORPHOUS SILICON (A-SI:H) IS A REVOLUTIONARY NEW SEMICONDUCTING MATERIAL THAT CAN BE DEPOSITED OVER LARGE AREAS AT RELATIVELY LOW COST, AND IS PARTICULARLY SUITED FOR APPLICATIONS SUCH AS LARGE-VOLUME PHOTODETECTORS IN HIGH ENERGY PHYSICS ACCELERATOR PROJECTS. PEREZ-MENDEZ AND OTHERS AT LAWRENCE BERKELEY LAB REPORTED RECENTLY THAT ALPHA PARTICLES WERE DETECTED WITH TILTED A-SI:H REVERSE-BIASED DIODES 10MUM THICK, BUT THICKER A-SI:H IS DESIRED FOR DETECTING WEAKLY IONIZING PARTICLES. HOWEVER, CONVENTIONAL PARALLEL-PLATE PLASMA REACTORS HAVE HAD LIMITEDSUCCESS IN DEPOSITING THICKER A-SI:H NEEDED FOR WEAKLY IONIZING PARTICLES. USING A NOVEL GRADIENT-FIELD (GF) PLASMA REACTOR, A-SI:H DIODES WERE PLASMA-DEPOSITED WITH GOOD ELECTRONIC PROPERTIES AND THICKNESS EXCEEDING 50MUM. PEREZ-MENDEZ DETECTED X-RAYS WITH 20MUM THICK A-SI:H DIODES DEPOSITED IN A GF REACTOR AND REPORTED AT LEAST A 10MUM DEPLETED ZONE AND A GAIN OF UNITY. THE PRODUCT OF GAIN AND BANDWIDTH OF PLASMA-DEPOSITED A-SI:H DIODES WILL BE MAXIMIZED BY ADJUSTING THE POSITION OF THE FERMI LEVEL IN ACCORDANCE WITH THE ROSE CRITERIA. A 40 X 40 DIODE ARRAY WILL BE FABRICATED. THE A-SI:H WILL BE DEPOSITED CONTINUOUSLY IN A ROTATING-DRUM PLASMA DEPOSITION SYSTEM TO PROVIDE UNIFORM THICKNESS OVER LARGE AREAS FOR DETECTOR ARRAYS.