Light-receiving element and optical integrated circuit
A light-receiving element ( 10 ) according to the present invention includes a semiconductor layer ( 100 ) including a p-type semiconductor region ( 101 ), an n-type semiconductor region ( 102 ), and a multiplication region ( 103 ), and a p-type light absorption layer ( 104 ) formed on the multiplication region. The p-type semiconductor region and the n-type semiconductor region are formed to sandwich the multiplication region in a planar direction of the semiconductor layer. This allows an easy implementation of a light-receiving element that serves as an avalanche photodiode by a monolithic manufacturing process.
1. A light-receiving element comprising:
a semiconductor layer including a p-type semiconductor region, an n-type semiconductor region, and a multiplication region, the p-type semiconductor region, the n-type semiconductor region, and the multiplication region being arranged along a planar direction of the semiconductor layer; and
a p-type light absorption layer being in contact with the multiplication region and formed in a direction perpendicular to the planar direction with respect to the multiplication region,
wherein the p-type semiconductor region and the n-type semiconductor region are formed to sandwich the multiplication region, and the light absorption layer has a band gap that decreases toward the multiplication region.
2. The light-receiving element according to claim 1 , further comprising:
a barrier layer that is formed on the light absorption layer and has a conduction band edge energy higher than that of the light absorption layer.
3. The light-receiving element according to claim 1 , wherein the light absorption layer has a p-type impurity concentration that decreases toward the multiplication region.
4. The light-receiving element according to claim 1 , wherein
the multiplication region includes Si,
the light absorption layer includes Ge x Si 1-x , and
the light absorption layer has a composition ratio x of Ge x Si 1-x that increases toward the multiplication region.
5. The light-receiving element according to claim 1 , wherein
the multiplication region includes Si,
the light absorption layer includes Ge x Si 1-x , and
the light absorption layer has a composition ratio x of Ge x Si 1-x that decreases toward the multiplication region.
6. The light-receiving element according to claim 3 , wherein
the multiplication region includes a compound semiconductor,
the light absorption layer includes a compound semiconductor, and
a composition ratio of the compound semiconductor forming the light absorption layer decreases toward the multiplication region.
7. The light-receiving element according to claim 1 , wherein
the multiplication region includes Si, and
the light absorption layer includes a compound semiconductor.
8. An optical integrated circuit comprising:
the light-receiving element defined in claim 1 ;
a core that is formed on the semiconductor layer and optically coupled to a light absorption layer; and
a clad layer formed on the core.