Near single carrier-type multiplication in a multiple graded-well structure for a solid-state photomultiplier

We report the observation of very large ionization rate ratios (β/α) in multiple graded-well Al0.48In0.52As/Ga0.47In0.53As avalanche photodiodes, grown by MBE. Avalanche multiplication occurs when holes heated by the field in the barrier layers impact ionize thermally-generated holes dynamically stored in the wells over the valence band-edge discontinuity. Since electrons are not confined in the graded structure, there is no multiplication of electrons by this process. This is the first observation of near single carrier-type multiplication in a III-V material.