Patent ID: 8076740

Claim:
A photo detector, comprising: a plurality of quantum dot layers being stacked, each of the plurality of quantum dot layers including a plurality of quantum dots and a buried layer which buries the plurality of quantum dots, the buried layer being a first conductive type semiconductor layer; and first conductive type contact layers provided to sandwich the plurality of quantum dot layers on opposite sides, wherein a second conductive type impurity being different from a first conductive type impurity is doped in a first semiconductor layer formed between one of the first conductive type contact layers and a first quantum dot layer closest to the one of the first conductive type contact layers to form a barrier against carriers positioned in the one of the first conductive type contact layers; the first semiconductor layer is formed of a material consisting of a single material composition; the first semiconductor layer and the buried layer comprise the material and one face of the first semiconductor layer is in contact with the first quantum dot layer closest to the one of the first conductive type contact layers, and another face of the first semiconductor layer is in contact with the one of the first conductive type contact layers.