Advanced Photonix manufactures the largest avalanche photodiodes (> 200 mm2) available in production quantities. Operating gain is 200, with the lowest noise per unit area of any silicon APD. Prototype monolithic 2D arrays have been fabricated from these large devices. However, the junction is located relatively close to the optical surface, and infrared photons are converted in the deeper N-type region where the carriers experience no or little gain. Although these Large Area APDs (LAAPDs) collect more light and are more sensitive from 300 to 800 nm than other APDs, quantum efficiency at 1.06 mm is only 5%. Advanced Photonix proposes an innovative LAAPD design to create a deeper junction and longer drift region. The QE is expected to approach 20%, with response times of about 1 ns, without sacrificing the high gain or low noise presently achieved. This improved QE at longer wavelengths is critical to advanced lidar systems requiring better detectivity at 1.06 microns, such as in airborne or space-based mapping, ranging and altimetry applications. LAAPD arrays fabricated with this "infrared" design will achieve higher QE and faster speed, and still offer imaging capability, high dynamic range, no dead time, ruggedness, and magnetic field immunity.Commercial Applications:Exciting dual-use applications now emerging that employ infrared sources are also expected to benefit from the innovation. These include pollution monitoring, meteorological lidar, and atmospheric chemical analysis. And because the proposed design increases infrared response while preserving ultraviolet and visible sensitivity, the new LAAPD is expected to attract commercial applications that require broadband, multiple wavelength detection, such as fluorescent and absorption spectroscopy, and chemical analysis instrumentation.
