Silicon photomultipliers and single-photon avalanche diodes with enhanced NIR detection efficiency at FBK

Silicon photomultipliers (SiPMs) have recently obtained a growing attention as an alternative to traditional photomultiplier tubes for detecting low photon fluxes. SiPMs are currently used in many medical and physics applications, but they are also emerging as a valuable option in single-photon or few-photon applications, like light detection and ranging, optical spectroscopy, and bio-medical instrumentation. During last years at Fondazione Bruno Kessler (Trento, Italy) we developed two different SiPM technologies, with peak sensitivity in the green wavelength region and in the blue one. Recently, we also started to develop a new technology with increased sensitivity in the red and near infra-red (NIR) wavelength region. This development poses several technological and design challenges since the single-photon avalanche diode (SPAD) internal structure has to be modified in order to collect carriers generated by photons absorbed at a depth of several microns. In this paper we will describe the first NIR-SiPMs and NIR-SPADs produced in FBK and we will present and discuss their experimental characterization. These devices show promising performance: SiPMs with 35 μm cell reach a PDE of about 18% at 850 nm and of more than 10% at 900 nm. These values are mainly limited by the SPAD border effect, which will be discussed in the paper by means of TCAD simulations. The full potentiality of these devices, in terms of PDE, will also be demonstrated by PDE measurements on a single SPAD with shielded active-area border.