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. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim