Detection Efficiencies and Generalized Breakdown Probabilities for Nanosecond-Gated Near Infrared Single-Photon Avalanche Photodiodes

A rigorous model is developed for determining single-photon quantum efficiency (SPQE) of single-photon avalanche photodiodes (SPADs) with simple or heterojunction multiplication regions. The analysis assumes nanosecond gated-mode operation of the SPADs and that band-to-band tunneling of carriers is the dominant source of dark current in the multiplication region. The model is then utilized to optimize the SPQE as a function of the applied voltage, for a given operating temperature and multiplication-region structure and material. The model can be applied to SPADs with In/sub 0.52/Al/sub 0.48/As or InP multiplication regions as well as In/sub 0.52/Al/sub 0.48/As--InP heterojunction multiplication regions for wavelengths of 1.3 and 1.55 /spl mu/m. The predictions show that the SPQE generally decreases with decreasing the multiplication-region thickness. Moreover, an InP multiplication region requires a lower breakdown electric field (and, hence, offers a higher SPQE) than that required by an In/sub 0.52/Al/sub 0.48/As layer of the same width. The model also shows that the fractional width of the In/sub 0.52/Al/sub 0.48/As layer in an In/sub 0.52/Al/sub 0.48/As--InP heterojunction multiplication region can be optimized to attain a maximum SPQE that is greater than that offered by an InP multiplication region. This effect becomes more pronounced in thin multiplication regions as a result of the increased significance of dead space

Avalanche photodiodes as single photon detectors

Photodiodes capable of detecting very weak intensities of light, down to single photon levels, have been investigated for a long time. Single photon detectors have numerous applications, including quantum cryptography, three-dimensional imaging, atmospheric monitoring, and time resolved spectroscopy. Conventionally, photomultiplier tubes have been the detectors of choice for low intensity light applications. However, due to their limitations such as high operating voltages, bulkiness, and limited sensitivity in the infrared, alternative solutions are sought. Avalanche photodiodes (APDs) operated above their breakdown voltage, can achieve single photon sensitivity. APDs were fabricated for single photon detection at wavelengths ranging from ultraviolet to infrared. Linear mode characterization experiments such as contact resistance and current-voltage were performed to determine the viability of a detector as a photon counter. Single photon detectors are often operated at low temperatures to minimize the dark noise. The temperature dependence of forward and reverse characteristics of the APDs was studied. A cryogenic system was established and calibrated for characterization of photodetectors at very low levels of illumination. The effect of various experimental parameters such as temperature, excess voltage, and discriminator threshold on Geiger mode APD performance was studied. Single photon detection at 1.54 µm was demonstrated using a separate-absorption-charge-multiplication avalanche photodetector with an In0.52Al0.48As multiplication layer. Various dark count generation mechanisms were modeled to understand the temperature dependence of dark counts in the In0.53Ga0.47As/In0.52Al0.48As APDs. The experimental observations were explained using band-to-band tunneling in the multiplication layer as the dominant dark count mechanism. Based on the modeling and experimental results, design guidelines for single photon counting avalanche diodes are suggested. An APD structure with thicker In0.52Al0.48As multiplication layer and punchthrough voltage close to the breakdown voltage was designed. In addition, SiC and GaAs based APDs were evaluated as photon detectors in the ultraviolet and near infrared regions, respectively. Single photon counting at 325nm was achieved using 4H-SiC APDs. Although MBE grown GaAs/AlGaAs APDs with high quantum efficiencies and low dark currents showed promise for single photon counting at 830nm, further experiments are needed to understand their inability to function as single photon detectors.Electrical and Computer Engineerin

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Detection Efficiencies and Generalized Breakdown Probabilities for Nanosecond-Gated Near Infrared Single-Photon Avalanche Photodiodes

Abstract—A rigorous model is developed for determining single-photon quantum efficiency (SPQE) of single-photon avalanche photodiodes (SPADs) with simple or heterojunction multiplication regions. The analysis assumes nanosecond gated-mode operation of the SPADs and that band-to-band tunneling of carriers is the dominant source of dark current in the multiplication region. The model is then utilized to optimize the SPQE as a function of the applied voltage, for a given operating temperature and multiplication-region structure and material. The model can be applied to SPADs with InH SPAlH RVAs or InP multiplication regions as well as InH SPAlH RVAs–InP heterojunction multiplication regions for wavelengths of 1.3 and 1.55 m. The predictions show that the SPQE generally decreases with decreasing the multiplication-region thickness. Moreover, an InP multiplication region requires a lower breakdown electric field (and, hence, offers a higher SPQE) than that required by an InH SPAlH RVAs layer of the same width. The model also shows that the fractional width of the InH SPAlH RVAs layer in an InH SPAlH RVAs–InP heterojunction multiplication region can be optimized to attain a maximum SPQE that is greater than that offered by an InP multiplication region. This effect becomes more pronounced in thin multiplication regions as a result of the increased significance of dead space. Index Terms—Avalanche photodiodes (APDs), breakdown probability, dark count, dead space, detection efficiency, Geiger mode, heterostructure APDs, impact ionization, InAlAs, InP, single-photon detection