NORTHROP RESEARCH AND TECHNOLOGY CENTERPALOS VERDES PENINSULA CA
This report describes results of an investigation of radiation effects on semiconductor devices used in electro-optical sensor applications. Emphasis is placed on determining the basic mechanisms of the interaction of radiation with such devices with a view toward gaining understanding of benefit to developers of radiation-tolerant devices. A study of ionizing radiation effects on silicon MOS devices was performed at temperatures ranging from 4 to 77 degrees K. Charge buildup in the SiO2 layer was observed to be identical at 4 and 77 degrees K after a steady-state exposure to ionizing radiation, which indicates that electron trapping is not important at 4 degrees K. Results at both temperatures can be accounted for quite well in terms of hole trapping and hole transport. An investigation of the basic mechanisms of radiation effects on extrinsic silicon detector material was initiated. Carrier removal produced by neutron bombardment of such material was studied and it was found that the introduction rate of compensating defects depends strongly on the depth within the forbidden gap of the intentional dopant level. A detailed study of radiation effects on charge-coupled devices was performed, with emphasis placed on examining changes in dark current density produced by bombardment with neutrons and with ionizing radiation. The rate of increase in dark current density was found to be very similar for neutron-irradiated buried-channel CCDs obtained from two sources. Results of short-term annealing measurements on CCDs following pulsed neutron bombardment are also presented. A damage coefficient appropriate for describing the introduction of damage in silicon depletion regions was experimentally determined.