Intersubband absorption of silicon-based quantum wells for infrared imaging

We have calculated the 10-μm intersubband absorptoin in quantum wells made of the silicon-based system, Si/Si1−xGex. The necessary details of the effective-mass anisotropy are included in our analysis. We find that it is readily possible to achieve an absorption constant of order of 104 cm−1 in Si quantum wells with current doping technology. For [110] and [111] growth directions, a further advantage of Si quantum wells is pointed out, namely, an allowed absorption at normal incidence due to the anisotropic effective mass in Si.