Abstracts Physics

The use and design of geiger mode avalanche diodes to count photons

by Sam Patrick Dean

Astronomers need single photon detectors to detect very faint light sources from deep space. An avalanche photodiode in the geiger mode is especially suited for the detection of single photons. Three by three arrays of avalanche photodiodes were fabricated. Breakdown voltages of 200V were measured. Large reverse currents prevented operating the array in the geiger mode. An improved design which minimizes the reverse current is needed. A commercial avalanche photodiode especially made for the geiger mode was tested and compared to a general purpose avalanche photodiode. Using the general purpose avalanche in the geiger mode was found to be unacceptable because when exposed to a weak light source, 90% of the output pulses were dark current pulses. A computer interface circuit was designed to read the time and location where photons were absorbed by the array. The circuit performed its function qualitatively, but it had a false triggering problem.