  We present modeling and simulation of prototypical multi bound state quantum
well infrared photodetectors and show that such a detection design may overcome
the problems arising when the operation frequency is pushed down into the far
infrared spectral region. In particular, after a simplified analysis on a
parabolic-potential design, we propose a fully three-dimensional model based on
a finite difference solution of the Boltzmann transport equation for realistic
potential profiles. The performances of the proposed simulated devices are
encouraging and support the idea that such design strategy may face the
well-known dark-current problem.
