Development of material quality and structural design for high performance Type II InAs/GaSb superlattice photodiodes and focal plane arrays

Recent progress made in the structure design, growth and processing of Type-II InAs/GaSb superlattice photo-detectors lifted both the quantum efficiency and the R₀A product of the detectors. Type-II superlattice demonstrated its ability to perform imaging in the Mid-Wave Infrared (MWIR) and Long-Wave Infrared (LWIR) ranges, becoming a potential competitor for technologies such as Quantum Well Infrared Photo-detectors (QWIP) and Mercury Cadmium Telluride (MCT). Using an empirical tight-binding model, we developed superlattices designs that were nearly lattice-matched to the GaSb substrates and presented cutoff wavelengths of 5 and 11 μm. We demonstrated high quality material growth with X-ray FWHM below 30 arcsec and an AFM rms roughness of 1.5 Å over an area of 20×20 μm². The detectors with a 5 μm cutoff, capable of operating at room temperature, showed a R₀A of 1.25 10⁶ Ω.cm² at 77K, and a quantum efficiency of 32%. In the long wavelength infrared, we demonstrated high quantum efficiencies above 50% with high R₀A products of 12 Ω.cm ² by increasing the thickness of the active region. Using the novel M-structure superlattice design, more than one order of magnitude improvement has been observed for electrical performance of the devices. Focal plane arrays in the middle and long infrared range, hybridized to an Indigo read out integrated circuit, exhibited high quality imaging.