Patent ID: 8188559

Claim:
A light-receiving element comprising a group III-V compound semiconductor stacked structure including an absorption layer having a pn-junction therein, the group III-V compound semiconductor stacked structure being formed on a group III-V compound semiconductor substrate, wherein the absorption layer has a multiquantum well structure composed of group III-V compound semiconductors, the pn-junction is formed by selectively diffusing an impurity element into the absorption layer, the concentration of the impurity element in the absorption layer is 5×10 16 /cm 3 or less, a diffusion concentration distribution control layer composed of III-V group semiconductor is disposed in contact with the absorption layer on a side of the absorption layer opposite the side adjacent to the group III-V compound semiconductor substrate, the bandgap of the diffusion concentration distribution control layer is lower than that of the group III-V compound semiconductor substrate, the diffusion concentration distribution control layer has an n-type impurity concentration of 2×10 15 /cm 3 or less before the diffusion, the diffusion concentration distribution control layer having a portion adjacent to the absorption layer, the portion having a low impurity concentration.