Avalanche Photodiodes with Enhanced Ionization Rates Ratio: Towards a Solid State Photomultiplier

Recent results on a new class of low excess noise avalanche photodiodes (APDs) are discussed. A significant enhancement of the ionization rates ratio has been demonstrated in AlGaAs/GaAs superlattice and graded gap APDs. In addition two novel APDs where only electrons ionize (channeling and staircase APDs) have been disclosed. The staircase APD has lower bias voltage (5-10V) than conventional APDs and virtually noise free multiplication similarly to a phototube.