SBIR Phase II: Geiger Mode Avalanche Photodiodes for Photon Counting from 0.9 Micrometers to 2.0 Micrometers

This SBIR Phase II project is to develop an InGaAs/InP avalanche photodiodes for use in Geiger mode photon counting with wavelength response extended from the conventional cutoff wavelength of 1.7 microns to 2.1 microns. Commercial InGaAs/InP avalanche photodiodes developed for linear operation in optical fiber communication systems have limited quantum detection efficiency and relatively high dark count rates when operated in Geiger mode, and are unable to detect radiation from important laser sources such as Tm/Ho near 2 microns. Using our experience as manufacturers of commercial linear-mode avalanche photodiodes and our epitaxial growth facility, we will design and fabricate avalanche photodiodes optimized specifically for Geiger-mode operation. The goal will be to obtain enhanced quantum detection efficiency, reduced dark count rate, and extended wavelength response to 2.1 microns. The two primary impacts of this work will be to enhance the understanding of the physics of Geiger-mode avalanche photodiodes, and to provide the broader research community with improved detectors that will significantly enhance the usefulness of photon-counting techniques in the near-infrared spectral region. Although the basic theory of Geiger-mode operation of avalanche photodiodes is several decades old, there continues to be a significant quantitative discrepancy between the quantum detection efficiency predicted by the theory and the quantum detection efficiency observed experimentally. Part of this study will pursue this discrepancy, not only to design improved devices but also to better understand the fundamental performance limits. By developing improved near infrared photon-counting detectors this study will take a major toward making such detectors commercially available to the larger research community, which will enable photon-counting techniques to be more widely applied in the near-infrared spectral region.