Intersubband transitions and IR hot-electron transistors

We present a systematic theoretical and experimental study on wavelength tuning and absorption lineshape of single bound state quantum well infrared photodetectors. We found that the absorption energy is determined by the energy level structure above the barriers as well as the shape of the quantum well ground state wave function. We 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. Using a quantum barrier as an electron energy high pass filter to discriminate against the lower energy dark current, we are able to increase the detectivity of the detector. The new device is referred as an IR hot-electron transistor. Its potential advantages in focal plane array applications will be discussed.