High performance InP Geiger-mode SWIR avalanche photodiodes

LAser Detection And Ranging (LADAR) is a promising tool for precise 3D-imaging, which enables field surveillance and target identification under low-light-level conditions in many military applications. For the time resolution and sensitivity requirements of LADAR applications, InGaAsP/InP Geiger-mode (GM) avalanche photodiodes (APDs) excel in the spectrum band between 1.0~1.6 μm. Previously MIT Lincoln Laboratory has demonstrated 3D LADAR imaging in the visible and near infrared (1.06 μm) wavelengths with InP/InGaAsP GMAPD arrays. In order to relieve the design tradeoffs among dark count rate (DCR), photo detection efficiency (PDE), afterpulsing, and operating temperature, it is essential to reduce the DCR while maintaining a high PDE. In this paper we will report the progress of GM-APD detectors and arrays with low DCR and high PDE at 1.06 μm. In order to improve both DCR and PDE, we optimized the multiplication layer thickness, substrate, and epitaxial growth quality. With an optimized InP multiplier thickness, a DCR as low as 100 kHz has been demonstrated at 4V overbias at 300 C. and at 240 K, less than 1 kHz DCR is measured. A nearly 40% PDE can be achieved at a DCR of 10 kHz at the reduced temperature.