Interference of resonance Raman scattering by optical phonons and electronic-subband excitations in p-type modulation-doped multiple-quantum-well structures

A theory of the scattering spectrum as well as of the resonance enhancement of the Raman scattering by coupled optical phonons and electronic subband excitations in p-type modulation-doped multiple-quantum-well structures is developed without and with applied external magnetic fields. The scattering cross section for the interfering vibronic and electronic excitations is derived by means of a Green’s-function formalism and specified for backscattering, parallel light polarizations, and resonance with the incoming photons. In this limit, we can show that the relevant polar Fröhlich interaction induces a doubly resonant one-phonon Raman process for confined phonons of a particular symmetry, depending on the resonantly excited hole subband. On the other hand, the same interaction is found to be responsible for the resonant decay of these phonons into electron-hole pairs in the heavy-hole subbands and vice versa. Moreover, noncoupling phonons of another symmetry and weaker resonance behavior are observed. Apart from this weak noncoupling phonon line, the spectrum of the coupled elementary excitations is discussed for different parameters, frequencies, and field strengths. We extract conditions for the occurrence of the limiting cases of a pure two-coupled-mode behavior and an antiresonance Fano effect and compare with experimental findings.