On the Choice of Metallic Contacts with Polycrystalline PbSe Films and Its Effect on Carrier Sweepout and Performance in Mid-wave Infrared (MWIR) Photodetectors
Carrier sweepout is one of the many phenomena that limit critical performance metrics of mid-wave infrared (MWIR) photodetectors, such as the photoconductive gain (γ), photoresponsivity (η), specific detectivity (D*), and hence the overall performance of cameras built using these detectors. Preventing carrier sweepout in photoconductors at high applied bias and modulation frequencies can increase the electrical operating bias range and consequently expand the possible read-out integrated circuit design space and capabilities. Polycrystalline PbSe-based MWIR photodetectors have shown great potential for building integrated high-performance devices. We discuss herein the choice of metallic contacts for such detectors built by Northrop Grumman Systems Corp. under this program using the complex physics of carrier trapping and the interface of the contact metal with the photosensitive PbSe film that allows these detectors to be essentially free of carrier sweepout even at high applied electric fields.