Solid State Scientific Corporation

William Clark

An avalanche photodiode comprises, in various implementations, a p-doped absorption region fabricated from a first material and joined along a hetero-junction with one side of an intrinsic charge-carrier multiplication region fabricated from a second material. Situated on an opposite side of the multiplication region is an n-doped diode cathode. Under reverse bias, the p-doped and n-doped regions assume, respectively, a negative charge and a positive charge and an electric field is present in the multiplication region. The first and second materials are selected to one of (i) minimize and (ii) render non-existent any conduction-band-dependent potential barrier opposing the diffusion of electrons from the absorption region into the multiplication region. Additionally, in various implementations, the first and second materials are furthermore selected to one of (i) minimize and (ii) render non-existent any valence-band-dependent potential barrier opposing the movement of holes from the multiplication region into the absorption region. The thickness of the absorption region in alternative implementations is indicated by the diffusion-length characteristics of the first material.

Avalanche photodiode having an extrinsic absorption region

An avalanche photodiode charge-carrier multiplication region comprises a first region fabricated from a first material having a first impact ionization threshold and a second region joined to the first region at an interface and fabricated from a second material having a second impact ionization threshold lower than the first impact ionization threshold. The first region includes, in the presence of an applied reverse-bias, first and second oppositely charged layers to establish an elevated, localized electric field within a sub-region of the first region. The first and second charged layers are arranged such that preferred charge carriers are accelerated by the localized electric field just prior to being injected into the second material where they impact ionize at predetermined statistical rate. Conversely, non-preferred charge carriers are accelerated by the localized electric field into the first material where, due to the higher impact ionization threshold of the first material, the non-preferred charge carriers impact ionize at a statistical rate lower than the statistical rate at which preferred charge carriers impact ionize in the second material.

Growing community of inventors

Chelmsford, MA, United States of America

William Clark