Patent ID: 6747296
Filing Date: 2004-06-08
Classification: H01L

Abstract:
An avalanche photodiode charge-carrier multiplication region adapted to facilitate (a) the generation, through impact ionization, of charge-carrier pairs, each charge-carrier pair including first and second oppositely charged charge carrier types, and (b) the movement of charge carriers of the first type in a first direction and of charge carriers of the second type in a second direction anti-parallel to the first direction, wherein the impact ionization by one of the first and second charge carrier types is preferred over impact ionization by the opposite charge carrier type and the charge-carrier multiplication region comprises:at least one period of lattice structure comprising a first crystalline region having first and second sides and being fabricated from a first material having a first impact ionization threshold and a second crystalline region having first and second ends and joined, at the first end, to the second side of the first crystalline region at a first region-second region interface, the second crystalline region being fabricated from a second material having a second impact ionization threshold lower than the first impact ionization threshold, the first crystalline region including, at least in the presence of an externally applied electric field, first and second oppositely charged layers separated by an intrinsic sub-region of the first crystalline region such that a localized electric field, is present between the first and second charged layers, the first and second charged layers being arranged such that (i) each charge carrier of a set of charge carriers of the preferred type having a travel path directed toward the second end of the second crystalline region, and extending through the first region-second region interface, encounters a charged layer of the same charge prior to encountering the charged layer of the opposite charge, such that the preferred charge type is accelerated by the localized electric field prior to passing through the first region-second region interface and entering the second crystalline region where, due to the lower impact ionization threshold of the second crystalline material and the increased kinetic energy of the accelerated preferred charge carrier, the preferred charge carrier has a predetermined statistical probability of dissipating energy through impact ionization and generating additional pairs of first and second oppositely charged charge carrier types at a predetermined statistical rate and such that (ii) each charge carrier of a set of charge carriers of the non-preferred type having a travel path directed toward the first side of the first crystalline region, and extending through the first region-second region interface, crosses the second region-first region interface prior to being accelerated by the electric field between the first and second charged layers but, due to higher impact ionization threshold of the first material, has a lower statistical probability of dissipating energy through impact ionization within the first material at as high a statistical rate as does a charge carrier of the preferred type in the second material.