Semiconductor photodetector and avalanche photodiode

Abstract

There is provided a semiconductor photodetector which comprises (i) an InP substrate(), (ii) an optical waveguide() having an N-type semiconductor layer() formed on the InP substrate(), an optical waveguide core layer() formed on a partial area of the N-type semiconductor layer(), and an upper cladding layer() formed on the optical waveguide core layer(), and (iii) an avalanche photodiode() constructed by forming a photo absorbing layer(), a heterobarrier relaxing layer(), an underlying layer() of a N-type field dropping layer(), an overlying layer() of the N-type field dropping layer(), a carrier multiplying layer(), and a P-type semiconductor layer() in sequence on another area of the N-type semiconductor layer(), and coupled to the optical waveguide(), wherein a side surface of the underlying layer() of the N-type field dropping layer() comes into contact with a side surface of the optical waveguide core layer(), and a part of the overlying layer() of the N-type field dropping layer() is formed on the optical waveguide core layer().