Doped Silicon and Germanium Photoconductors as Targets for Infrared Television Camera Tubes

Abstract

Several doped germanium and silicon photoconductors have been investigated as targets for an infrared television camera tube. The performance of gold-doped silicon is outstanding. Its properties, sensitivity, speed of response, and freedom from various image retention effects are superior to those of a standard vidicon in the visible. It is within an order of magnitude of the maximum performance to be expected of a tube of the vidicon type. The other silicon dopings investigated were gallium, bismuth, and indium. These materials showed very little extrinsic photoconductivity. Copper-, gold-, silver-, and tellurium-doped germanium were also investigated. Targets prepared with all of these germanium dopings showed the development of an insensitive, nonimaging state in a few minutes’ operation. The original imaging state could be recovered by a short change in operating conditions. This nonimaging state has been demonstrated to be due to an induced surface conductivity.