Radiation detectors have been fabricated from lead iodide (PbIJ crystals grown by two methods: zone melting and Bridgman methods. In response characteristics of the detector fabricated from crystals grown by the zone melting method, a photopeak for y-rays from an v"Am source (59.5 kev) has been clearly observed with applied detector bias of 500 V at room temperature. The hole drift mobility is estimated to be about 5.5 cm2/Vs from measurement of pulse rise time for 5.48 MeV a-rays from "Am. By comparing the detector bias versus saturated peak position of the PbI, detector with that of the W e detector, the average energy for producing electronhole pairs is estimated to be about 8.4 eV for the PbI, crystal.A radiation detector fabricated from PbI, crystals grown by the Bridgman method, however, exhibited no response for y-rays.

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Annealing effects on CdTe crystals and CdTe/GaAs films in Hg have been investigated through the spectral changes of PL (photoluminescence) at 4.2 K. Before annealing, the PL spectrum of CdTe crystals or films is dominated by the excitonic-emission lines, the edge-emission band and two broad bands. After annealing, a marked decrease in intensity of the broad and edge-emission bands in the bulk crystals is observed, while an increase in intensity of the broad bands in the MOCVD-grown CdTe is significant. We will point out from the PL investigations that the Hg annealing plays an important role in the improvement of both the surface and bulk properties.

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