Quantum dot infrared photodetector

A quantum dot infrared photodetector, comprising:

• a first contact layer and a second contact layer disposed opposite to each other;
• a quantum dot layer, disposed between the first and second contact layers;
• and
• a n-doped layer cladded by two undoped spacer layers, and a quantum well stack is composed of the n-doped layer and the two undoped spacer layers, the conduction energy band edge alignment of the n-doped layer is lower than the conduction energy band edge alignments of the neighboring undoped spacer layers, the conduction energy band edge alignment of the n-doped layer is higher than the conduction energy band edge alignment of the quantum dot layer;
• two spacer layers disposed inside the first and second contact layers;
• the quantum dot layer disposed inside the spacer layers;
• wherein the n-doped layer is disposed between the first contact layer and the quantum dot layer or between the second contact layer and the quantum dot layer;
• wherein when the first and second contact layers are applied with two bias voltages, the n-doped layer supplies carriers to the quantum dot layer;
• wherein the two undoped spacer layers comprise undoped GaAs or InGaAs, and the two spacer layers comprise GaAs or InGaAs.