Photoconductive gain greater than unity in CdSe films with Schottky barriers at the contacts

Abstract

Photoconductive gains greater than unity can be obtained by illuminating a homogeneous photoconductor having blocking contacts with band gap radiation. A model is presented, which conceives such a possibility. Au contacts to CdSe form a Schottky barrier at the interface. Upon illumination the photogenerated holes are trapped in the Schottky barrier, shrinking the barrier and allowing injection of electrons in the CdSe. This gives rise to the possibility of gain greater than unity. Experimental evidence supporting the model is presented. Photoconductive gains as large as 300 have been measured when these films were illuminated with a photon flux of 2×1015 photons/cm2/sec.