Abstract
Planar InGaAs/InP avalanche photo diodes (APDs) are preferred single-photon detectors in the near-infrared region. They are usually fabricated using the double-diffusion method to avoid edge breakdown. However, this effect cannot be avoided completely as the bias voltage increases in the Geiger mode (GM). In this study, the influence of the deep diffusion window diameter on the premature edge breakdown of GM APDs was quantitatively analyzed using optical probe scanning method. Both numerical simulations and experimental measurements were performed. The electric field and dark current distribution, and the photon current under different optical input positions were numerically simulated. APDs with different deep diffusion window diameters were fabricated and tested to measure the photon current response. According to the normalized scanning photo current, we find that premature edge breakdown diminishes as the diffusion diameter of the device decreases. The position of the maximum electric field gradually shifted to the center as the diameter of the device decreased, and this shift gradually increased as the diameter decreased. The influence of edge breakdown was found to be avoided on the APD with a diameter of 10 μm, indicated by the avalanche gain reaching the maximum at the center, and the overlapping of optical and maximum electric gain regions is realized, which is crucial for high detection efficiency and low dark count of single photon detection.
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