HARP photoconductive film using CdSe layer with high quantum efficiency

We have been developing high‐gain avalanche rushing amorphous photoconductor (HARP) imaging devices to achieve ultra‐high‐sensitivity television cameras with high picture quality. The HARP photoconductive film, which multiplies signal electric charges through an avalanche multiplication phenomenon, is mainly made of amorphous selenium (a‐Se) that has a band gap width of about 2.0 eV. The film has little sensitivity to light with wavelengths over 620 nm. To solve this problem drastically, we developed a new HARP film with a cadmium selenide (CdSe) layer to improve the quantum efficiency for red light. The new film had a quantum efficiency of over 80% across almost all of the visible light region and a multiplication factor of over 10. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)