Photodiode, photodiode array, and solid-state imaging device

Abstract

A photodiode that multiplies a charge generated by photoelectric conversion in an avalanche region includes: a p− type semiconductor layer having interfaces; an n+ type semiconductor region located inside the p− type semiconductor layer and in contact with the interface; an n+ type semiconductor region located inside the p− type semiconductor layer and connected to the n+ type semiconductor region; and a p type semiconductor region located between the n+ type semiconductor region and the interface, wherein the n+ type semiconductor region, the n+ type semiconductor region, and the p type semiconductor region each have a higher impurity concentration than the p− type semiconductor layer, the avalanche region is a region between the n+ type semiconductor region and the p type semiconductor region inside the p− type semiconductor layer, and the n+ type semiconductor region has a smaller area than the n+ type semiconductor region in planar view.