New ultra-low-noise avalanche photodiode with separated electron and hole avalanche regions

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Abstract
A new low-excess-noise avalanche detector is proposed. In this structure electrons and holes are spatially separated and impact ionise in regions of different bandgap. The ionisation rates ratio can thus be made extremely high (α/β≥100) by suitably choosing the bandgap difference, so that the device mimics a photomultiplier. This new concept is applicable to most III-V lattice-matched heterojunctions, including long-wavelength materials.