Semiconductor strained SL APD apparatus

An avalanche photodiode wherein a first buffer layer, a multiplication layer, an electric field relaxation layer, a light absorbing layer, a second buffer layer, and a contact layer are laminated on a crystalline substrate in this order, and said multiplication layer comprises superlattice layers having a structure in which at least two types of semiconductors with different band gaps are laminated, and a lattice constant of barrier layers of said superlattice layers is smaller than a lattice constant of the crystalline substrate by 0.1% to 3.5%, and the difference between a mean lattice constant of said multiplication layer and the lattice constant of the crystalline substrate is not more than 0.2%.

A front end receiver in a light transmission system comprising a transmitter and a receiver, wherein the front end of said receiver has an avalanche photodiode which has a multiplication layer and a light absorbing layer, said multiplication layer comprising superlattice layers having a structure in which at least two types of semiconductors with different band gaps are laminated, and wherein a tensile stress is applied to barrier layers among said superlattice layers.