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

Abstract

We have demonstrated an infrared photodetector based on intersubband transitions in doped (In, Ga)As quantum wells in which the excited state is confined by the minigap between two minibands in a surrounding superlattice. Sharp peaks were observed at 78 K in the infrared photocurrent spectra in the 2.7-3.6 μm wavelength region corresponding to transitions in which the excited state energy is substantially above the (In, Al)As conduction-band edge. Broader, longer-wavelength photocurrent features corresponding to transitions 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.