Effective mass of the ground state of the strong-coupling exciton in a quantum well

Abstract

The properties of the effective mass of the ground state of the exciton, for which the electron (hole) is strongly coupled with interface-optical (IO) phonons but weakly coupled with bulk-longitudinal-optical (LO) phonons in a quantum well, are studied by means of Tokuda's improved linear combination operator and a modified second Lee-Low-Pines transformation method. The results indicate that the contributions of the interaction between the electron (hole) and the different phonon branches to the effective mass are greatly different, and change with the well width and the relative position between the electron and the hole.Semiconductor quantum wells (QWs) are widely applied in active and passive optoelectronic devices for the reason of the large exciton binding energy, the large optical nonlinearity and fast non-linear response speed [1,2] . QW is a quasi-twodimensional (Q-2D) system, and the exciton-phonon coupling is a main interaction in it. Therefore, the properties of the exciton-phonon system of Q-2D system have been studied deeply [3][4][5][6][7] . However, so far, most of the works on the Q-2D exciton are limited to the weak and intermediate couplings between exciton and phonons. The theory of the weak coupling is undoubtedly correct for the group III-V compound materials. In recent years, with the development of the molecule extension technique, the group II-VI compounds have been of great interests. In fact, the band gaps of the group II-VI and I-VII compound semiconductor materials cover the region from the ultraviolet to the far-infrared, and the exciton binding energy of them is larger than that of the group III-V compound semiconductor materials. So the devices made from this kind of material may work effectively at room temperature [1] . Generally, the carrier-phonons coupling constant of the material is an order of magnitude larger than that of the group III-