Development of advanced internal gain radiation detector structures based on neutron transmutation doped silicon, High T/sub c/ superconductive compounds and their potential application to detection of ionizing radiation: Annual report, December 1, 1986-November 30, 1987

This report covers the period of work from December 1, 1986 through November 30, 1987. The work on mercuric iodide has now entered a new and more developmental phase with support now being obtained from other agencies (NIH, NASA, JPL, the CalTech President's Fund etc.) for specific, directed applications. These include development of arrays of HgI2 x-ray spectrometers for synchrotron radiation application supported by NIH and for long term space mission use supported by NASA. It has been undertaken during the past year (with some work done in the previous year) to re-examine the technology of high field ''avalanche'' radiation detector structures which use the ''controlled surface'' principle as developed previously under DOE sponsorship. This was undertaken because of the advent of a fundamental advance in silicon single crystal technology -''neutron transmutation doped'' or ''NTD'' single crystal. This new material conceptually solves a basic problem that previously halted the development of these potentially useful radiation detection structures. That problem was the non-uniform, (or ''striated'') distribution of donor impurities which adversely affected electric field distribution and thus attainable avalanche gain in these structures. A new effort started late in the year springs from the development of high critical temperature superconducting ceramic compounds. In essence, the phenomenon of superconductivity can now be achieved at temperatures reached by liquid nitrogen rather than expensive and more complicated cryogenic helium. This, in essence, then brings superconductivity into the same temperature range where lithium drifted silicon and intrinsic germanium already operate. The usefulness of superconductivity in detection and spectroscopy of ionizing radiations based on the narrow superconductive band gap is very appealing and we have begun theoretical (presented herein) and experimental studies investigating these new materials