Heat treatment to prevent image defect occurrence in amorphous Se doped with Te avalanche multiplication photoconductive film

We have been developing an amorphous selenium (a-Se) avalanche multiplication photoconductive film, named HARP (high-gain avalanche rushing amorphous photoconductor), for the purpose of making a high-sensitivity video camera useful for broadcasting, x-ray medical diagnosis, etc. The HARP film used for the red channel in a colour camera is doped with tellurium (Te) to improve its red-light sensitivity. However, doping a-Se with Te generates impurity levels that trap electrons, and the built-in-field formed by these trapped electrons causes image defects. We devised a heat treatment to prevent the occurrence of these defects. We suppose that the thermal energy of the heat treatment releases the originally trapped electrons, and that the energy makes it difficult for moving electrons to be trapped during operation. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)