Type-II Superlattice Based Low Dark Current Short-Wavelength Infrared Photodetectors With Optical Response From 0.4 to 2.5um

In recent years, Type-II superlattices have experienced significant development. However, the full potential of Type-II superlattice has not been fully explored and alternate superlattice architectures hold great promise. Despite demonstration of SWIR photodetectors based on this material system, there has been no report about Type-II superlattice-based photodetectors that have been sensitive to visible light. We propose to develop Type-II superlattice-based photodetectors and focal plane arrays for NASA's imaging and spectroscopy applications in the spectral band from visible to extended short-wavelength infrared (0.4 - 2.5 um) with a very low dark current density. In mid- and long-wavelength infrared spectral bands, Type-II superlattice-based photodetectors already offers performance comparable to the state-of-the-art mercury cadmium telluride but at a fraction of the cost due to the leveraging of commercial growth and process equipment. Our goal is to extend that benefit into the short-wavelength infrared. Using the best material currently available and a novel bandgap-engineering design and process, we will fabricate photodetectors and, ultimately, focal plane arrays. In Phase I, we are going to demonstrate photodetector designs based on Type-II superlattices, which can cover spectral range between 0.4 to 2.5 um with a very low dark current density (<10^-11 A/cm2) at temperatures below 100 K.. In Phase II, we are going to continue reduction of the dark current density to <10^-13 A/cm^2 -level at temperatures below 100K. Then, we will use the optimized device design to develop and deliver 1Kx1K imagers to NASA for planetary sciences.