Solid state photomultiplier

Abstract

A solid state photon detector includes a semiconducting blocking layer with sufficiently low donor and acceptor concentrations that substantially no charge transport can occur by an impurity conduction mechanism. A semiconducting buffered layer is provided with a sufficiently high donor impurity concentration to create an impurity energy band and with a sufficiently high acceptor impurity concentration that an electron cannot be injected into and drift through the layer without recombining with ionized donors. A semiconducting active layer is positioned between the blocking and buffered layers with a sufficiently high donor concentration to create an impurity energy band. The acitve layer also includes a sufficiently low acceptor impurity concentration that a photogenerated electron can drift through the active layer without recombining with ionized donors. A first electrical contact with the blocking layer collects electrons without injecting D+ charge carriers, while a second electrical contact with the buffered layer collects carriers from the impurity band. The detector is designed to operate with a sufficient electrical bias applied between the first and second contacts to raise the field at some point in the active layer to the threshold for impact ionization of donor impurities. Under appropriate conditions, such detectors are capable of detecting single photons.