New avalanche multiplication phenomenon in quantum well superlattices: Evidence of impact ionization across the band-edge discontinuity

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Abstract
In suitably designed superlattice structures hot carriers in the barrier layers can collide with carriers confined or dynamically stored in the wells and impact ionize them out, across the band‐edge discontinuity. Photomultiplication and spectral response measurements as a function of temperature and chopping frequency in Al0.48 In0.52 As/Ga0.47 In0.53As and AlSb/GaSb superlattices provide strong evidence of this effect. The observed phenomenon is characterized by a large ratio of the multiplication factors for holes and electrons implying that β≫α and can be the basis for a new class of very low noise avalanche photodiodes and solid‐state photomultipliers.