Engineering Strain-Free Epitaxial Ternary Lead Salt Films for Ambient Temperature Infrared Detectors

Physical Sciences Inc. (PSI) and the PARADIM Center at Cornell University will develop photoconductive infrared detectors capable of achieving a detectivity of 2 x 10^11 cm*Hz^1/2/W and a noise-equivalent power (NEP) of less than 0.5 pW/Hz^1/2 at ambient temperature. These gains will be realized by creating fully encapsulated epitaxial films of ternary lead salts. Using vapor-phase deposition techniques, PSI and team members will grow strain-free epitaxial heterostructures consisting of a ternary lead salt photoconductive layer, custom-grown single-crystal substrates engineered to match the lattice constant of the absorber, and an epitaxial capping layer. This approach/architecture will enable quantum efficiencies of greater than 30% by eliminating structural defects such as misfit dislocations and unpassivated surface states that compromise carrier extraction. During Phase I, PSI will demonstrate growth of single-crystal substrates and strain-free ternary lead salt epilayers. PSI will also submit a complete design for a photoconductive detector. In a Phase I option, PSI and partners will demonstrate growth of epitaxial passivation layers lattice-matched to the growth substrate and measure the photoresponse of test devices. During Phase II, PSI will create and test complete detectors meeting the above specifications for detectivity, NEP, and quantum efficiency.