Low-noise UV-to-SWIR broadband photodiodes for large-format focal plane array sensors

Broadband focal plane array sensors, operating in the 0.25 to 2.5 μm wavelength range, are an enabling technology for several imaging applications including atmospheric greenhouse gas monitoring. Currently, hyper-spectral imagers use separate image sensors for different spectral sub-bands, for example GaN for UV, Si for visible, and InGaAs for IR, thus requiring expensive component-level integration. Our approach is to manufacture a single image sensor with 0.25 to 2.5 μm spectral range using GaAs substrates, which are commercially available in diameters as large as 6 inches. The key challenges, namely achieving high UV efficiency, low dark current, and high speed operation, are addressed separately in a lattice-matched GaAs UV-to-Visible photodiode and a lattice-mismatched InGaAs NIR-to-SWIR photodiode. The method for monolithically combining the two structures into a single UV-to-SWIR photodiode / photodiode array is also presented.