Firstly, the semi-conductor structure in the infrared detector can be designed to form quantum wells such that the energy gap between the ground state and the first excited state match the energy of the photon at expected detection wavelength. Then, when infrared photons get absorbed, the photo-excited carriers can be transported by an external injection current, forming the photocurrent. The peak response wavelength of the quantum well infrared detector can be precisely controlled by changing the width of quantum wells and the barrier height.