High speed, low noise, near infrared HgCdTe avalanche photodiodes

High efficiency and speed silicon avalanche photodiodes (APD) are currently available for low-light detection in the 200 to 1150nm range. However, silicon has weak optical absorption beyond 1000 nm. The NASA Surface Topography and Oceanic Measurements programs requires high efficiency, high speed, and low noise detectors in the 1500 to 2200 nm wavelength region. The semiconductor alloy Hg1-xCdxTe, with its wavelength tunability over a broad spectral range, high quantum efficiency, low dielectric constant permitting high speed operation, and low noise in APDs (due to the resonant enhancement of hole ionization coefficient), is an attractive material for meeting NASA's specifications. We propose a new generation of high quantum efficiency, high speed, photon counting, near infrared (1500-2200 nm) avalanche photodiodes with excellent noise and gain-bandwidth performance. They will be an asset to NASA's proposed Earth Science Enterprise program and related space programs as part of three-dimensional imaging systems. The goals will be achieved by i) using the established flexible manufacturing molecular beam epitaxy technology for device quality HgCdTe material growth on silicon substrates, and ii) developing novel APD device architectures including separate absorption and multiplication.