Optical vibration modes in multi-layer quantum dots of polar ternary mixed crystals

Abstract

Within the framework of the dielectric continuum approach and the modified random-element isodisplacement model, the optical vibration modes as well as the corresponding electron-phonon interactions in spherical multi-layer quantum dots (QDs) consisting of ternary mixed crystals (TMCs) are investigated in detail. The dispersion relation and electron-phonon interaction Hamiltonian are obtained. As applications of the present theory, the numerical calculations for the ZnS/ZnxCd1-xS/ZnS and GaAs/AlxGa1-xAs/GaAs QDs are performed and discussed. Considering the “one-mode” and “two-mode” behaviors of the TMCs, the results show that there are 5 and 7 branches of interface/surface optical (IO/SO) phonon modes in the two systems, respectively. It is found that the effects of TMCs have a remarkable influence on the optical phonon frequencies and the electron-phonon interactions. The results also reveal that the presence of the cap layer introduces significant influence on the TMCs effects of optical phonon in multi-layer QDs. We hope that our theoretical results can stimulate further investigations of related photoelectric properties, as well as device applications in multi-layer QDs consisting of TMCs.