Photon-counting solid-state photomultiplier

Abstract

The solid state photomultiplier is a silicon device capable of continuous detection of individual photons in the wavelength range from 0.4 to 28 mu m. Operated with an applied bias near 7 V the device responds to the absorption of an incident photon with a submicrosecond-risetime current pulse with a narrow amplitude distribution well above the electronic readout noise levels. Optimal photon-counting performance occurs between 6 and 10 K and for count rates less than 10/sup 10/ counts/s/cm/sup 2/ of detector area. A 60% counting quantum efficiency has been demonstrated at 20 mu m, and near 60% was observed in the visible light region. The underlying mechanism involves extremely fast internal charge amplification by impact ionization of impurity-band electrons and results in a pulse for each photoelectrically or thermally induced free carrier. The thermally induced dark pulse rate at 7 K is sufficiently low that background-limited detector performance is obtained at a background of less than 10/sup 6/ photons/cm/sup 2/ s.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>