Development of III-V photodetectors for SWIR and MWIR

Photodetectors for the infrared spectral range are vital for security, defense and space as well as industrial and scientific applications. The research activities at Fraunhofer IAF contribute to Europe’s non-dependence on critical components for sensor technologies. A broad range of III-V material systems is developed to address high-performance photodetection in various parts of the infrared spectral region. Active imaging techniques utilizing LiDAR (light detection and ranging) sensors with laser wavelengths such as 1550nm in the eye-safe short-wavelength infrared (SWIR) spectral range give access to the time-of-flight information and can be utilized for 3D-scene reconstructions and non-line-of-sight (NLOS) imaging. The lattice-matched InGaAs/InP material system is the SWIR detector material of choice and enables the fabrication of avalanche photodiodes with single-photon detection capabilities (SPADs). For photodetectors sensitive in the thermal infrared, InAs/(In,Ga)(As,Sb) type-II superlattices (T2SLs) can be tailored via the choice of appropriate compositions and layer thickness. Here, especially InAs/InAsSb T2SLs have recently gained great interest for achieving high-performance mid-wavelength infrared (MWIR, 3-5 µm) detectors. Due to the combination of bandgap tunability and high minority-carrier lifetime, these Ga-free T2SL permit a substantial increase of operating temperature without performance loss as compared to InAs/GaSb T2SL or bulk InSb. In this contribution, we present the current status of the research activities at Fraunhofer IAF for the epitaxy, process technology, and electro-optical characterization of InGaAs/InP SPADs for the SWIR and Ga-free T2SL detectors for the MWIR, respectively.