High efficiency 1.55 μm Geiger-mode single photon counting avalanche photodiodes operating near 0°C

Recent developments in three-dimension imaging, quantum cryptography, and time-resolved spectroscopy have stimulated interest in single-photon counting avalanche photodiodes (APD) operating in the short wavelength infrared region. For visible and near infrared wavelengths, Silicon Geiger-mode APDs have demonstrated excellent photon detection efficiency (PDE) and low dark current rate (DCR)(1). Recently, MIT Lincoln Laboratories, Boeing Spectrolab, and Boeing SVS have demonstrated Geiger-mode (GM) APD focal plane arrays (FPA) operating at 1.06 gm. However for longer wavelength sensitivity around 1.55 mu m, GM-APDs have to be cooled to 180 similar to 240 K to achieve a usable DCR. Power consumption, package weight and size and APD PDE all suffer with this cooling requirement. In this paper we report the development of an InP/InGaAs GM-APD structure with high PDE and low DCR at 273K. The photon collection efficiency was optimized with a single step-graded quaternary layer and a 3.5 jam InGaAs absorption layer, which provides a broadband coverage from 0.95 mu m to 1.62 mu m. The InP multiplication layer and the charge layer are carefully tailored to minimize the DCR and maximize the PDE. Despite having a low bandgap absorber layer InGaAs, these APDs demonstrated excellent dark cur-rent, optical responsivity, and superior DCR and PDE at 1.55 mu m. The DCR and PDE were evaluated on 25 Pm diameter APDs at 273 K. DCRs as low as 20 kHz have been measured at a 2 V overbias, while PDEs at 1.55 mu m exceed 30% at 2 V overbias.