采用格林函数的方法,研究极性晶体膜中束缚极化子的有效质量随膜厚d的变化关系。得出电子一体LO声子相互作用以及电子-SO声子相互作用都对束缚极化子的有效质量有贡献。通过对KCl半导体膜的数值计算表明,束缚极化子的有效质量随膜厚d的增加而减少;当膜厚小于5nm时电子-S0声子相互作用对束缚极化子的有效质量起主要贡献,但是当膜厚大于10nm时,电子一体LO声子相互作用对束缚极化子的有效质量起主要贡献,当膜厚大于5nm而小于10nm时,二者共同影响束缚极化子的有效质量;另外,由于束缚势的存在,使束缚极化子的有效质量增大,这主要是由于束缚势的存在,使电子一声子间的相互作用增强,极化子效应增大而引起的。
Taking into account the interaction of an electron with bulk longitudinal-optical (LO) and surface longi- tudinal-optical (SO) phonons, we studied the effective mass of the bound polaron in a polar slab by using the method of Green's function. The effective mass was derived as function of slab thickness, and it reduces with the increase of the slab thickness ; for a very thin slab ( d 〈 5 nm), the effective mass was mainly attributed to the electron-SO pho- non interaction, oppositely, d 〉 10 nm, the effective mass was mainly attributed to the electron-LO phonon interac- tion. But when 5 nm 〈 d 〈 10 nm, all of them must be consider together. Especially, the effective mass increased when there was the Coulomb potential because the interactions between the electrons and phonons was strengthened.