Patent ID: 6936868

Claim:
A sequential mesa type avalanche photodiode comprising: an n-type semiconductor substrate; and a sequential mesa portion formed on an upper part of the n-type semiconductor substrate, said sequential mesa portion comprising a plurality of semiconductor layers which include: an n-type multiplying layer, an p-type electric field concentration layer formed on the n-type multiplying layer, a p-type electric field relaxation layer formed on an upper part of the p-type electric field concentration layer, and a p-type light absorbing layer formed on an upper part of the p-type electric field relaxation layer and laminated by epitaxial growth, wherein the p-type electric field concentration layer and the n-type multiplying layer form a pn junction, wherein a carrier density of the n-type multiplying layer is larger than a carrier density of the p-type electric field concentration layer, and wherein when light is incident from the n-type semiconductor substrate toward the p-type light absorbing layer, electrons and positive holes are generated in the sequential mesa portion and electrons are a main carrier, and there is a single-peaked characteristic in which light-receiving current based on movement of the electrons and the positive holes is larger at a central portion of the sequential mesa portion than at a peripheral portion of the sequential mesa portion.