Polaronic effects on donor states in III-V and II-VI quantum wells under electric fields

Polaronic effects on the ground state of a donor in GaAs/Al1-xGaxAs and ZnSe/Zn1-xCdxSe quantum wells under the influence of an external electric field are investigated for the impurity atom doped at various positions. The confined electron interacts with the interface as well as confined phonon modes that exist in such structures. It is found that such effects in II-VI compounds are in general much more significant than in III-V compounds, reflecting the stronger electron-phonon coupling in more ionic II-VI materials. The ground state energy of the impurity is calculated by means of the Lee, Low and Pines transformation. Contributions from confined and interface phonon modes are considered separately and results calculated for various well widths, field strengths and different impurity positions are presented and discussed.