A first-principles model of the photocurrent in quantum well infrared photodetectors ͑QWIPs͒ is derived. The model examines the responsivity, carrier capture probability and quantum efficiency. It is found that the QWIP sensitivity reaches a plateau below the 10 m detection wavelength and remains nearly constant from 10 to 50 m.

A quantum-mechanical scattering theory approach is taken to evaluate the capture probability from the continuum into the quantum wells in quantum-well infrared photodetectors. The calculations show that the capture probability is dependent on the well width, the barrier height, and bias. An additional tunnel barrier is introduced to disturb the continuum levels near the top of the quantum well. It is shown that this can be optimized to reduce the capture probability and thus increase the photoconductive gain of the device.

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