Infrared photodetector based on intersubband transitions to minigap-confined states in doped quantum wells

We have demonstrated an infrared photodetector based on intersubband transi tions in doped (In, Ga)As quantum wells in which the excited state is confi ned by the minigap between two minibands in a surrounding superlattice. Sha rp peaks were observed at 78 K in the infrared photocurrent spectra in the 2.7-3.6 mum wavelength region corresponding to transitions in which the exc ited state energy is substantially above the (In, Al)As conduction-band edg e. Broader, longer-wavelength photocurrent features corresponding to transi tions into the lower-lying miniband states were also observed. The spectral features in the photocurrent spectra are well described by calculations of the optical absorption cross section.(C) 2001 American Institute of Physic s.