Modeling of intersubband and free-carrier absorption coefficients in heavily doped conduction-band quantum-well structures

Theoretical modelings of the transition energy for intersubband absorptions, and the intersubband and free-carrier absorption coefficients in heavily doped conduction-band anisotropic semiconductor quantum-well (QW) structures are presented. The transition matrix elements for photon absorption and emission, which are not identical due to the different many-body effects involved in the photon absorption and emission processes, are rigorously derived. We also show that the linewidth broadening effect caused by various scattering processes gives a considerable increase in resonance energy, which explains the relatively large parallel-mode transition energy which cannot be inferred from previous modeling studies. In addition, theoretical modeling of free-carrier absorption in anisotropic semiconductor QW structures is presented for the first time. The calculated results are compared with the experimental values for /spl delta/-doped Si QW's.