Van Hove singularities in intersubband transitions in multiquantum well photodetectors

High dynamics measurements of spectral response were carried out on quantum well infrared photodetectors (QWIP). Photocurrent spectra were studied over more than three orders of magnitude, revealing the presence of spectral structures which were never observed hitherto. Electric field assisted tunneling and, more surprisingly, Van Hove singularities at the miniband edges, are shown to play an important role in the low and high energy parts of the QWIP photocurrent spectra, respectively. These experimental features motivated us to initiate a theoretical study of the absorption in a multiquantum well structure. Our work is based on the study of the electronic wave function in a periodic structure.