WAVELENGTH TUNING AND ABSORPTION-LINE SHAPE OF QUANTUM-WELL INFRARED PHOTODETECTORS

We have conducted a systematic theoretical and experimental study on wavelength tuning and absorption lineshape of single-bound-state quantum well infrared photodetectors. By computing the oscillator strength using the exact quantum well eigen functions, we show that an intersubband transition is from the ground state to the first resonant state in one extreme when the ground state is totally localized in the well, or to the second miniband in another extreme when the ground state wave function is delocalized. In the intermediate cases, the absorption wavelength is determined by the energy of a final state with which the oscillator strength is maximum. We also calculated the absorption lineshape and show that it depends sensitively on the position of the final state relative to the global band structure of the detector.