Ultra-Sensitive Infrared and Visible Photon Detector

Abstract

The Solid State Photomultiplier (SSPM) is a photon detector based on impurity band conduction (IBC) in semiconductors. The high internal gain (over 50,000) in the device and its fast response (rise time less than 10 ns) combine to permit the detection of single photons over a wide spectrum. The SSPM is a two-terminal device that can operate continuously with a dc bias, yielding an output current pulse for each detected photon. Quantum efficiencies of over 5036 have already been achieved at wavelengths of 0.45 and 20 micrometers using arsenic-doped silicon (Si:As) for the IBC region; even higher values are possible, not only through the addition of anti-reflection coatings but also by the design of device structures optimized for specific wavelength ranges. Currently available Si:As SSPMs operate best at temperatures between 6 and 10K. Pulse count rate densities in excess of 109 per cm2−s have been achieved when an SSPM of typical size (10−4 to 10−2 cm2) is used in conjunction with suitable readout electronics. As the amplitude of the output pulses is large compared to the noise of the readout electronics and the pulse height distribution is quite tight, processing of the output signals can be handled rather conveniently by digital computers without the need for analog-to-digital converters.