极性半导体膜中的束缚极化子

摘要

Taking into account the interaction of an electron with bulk longitudinal-optical (LO) and surface longitudinal-optical (SO) phonons, we study the ground state energy and self-trapping energy of the bound polaron in a polar slab by using the Huybrecht's linear combination operator method. The ground state energy and the self-trapping energy are all derived as function of slab thickness. Etre-ph includes two parts, one is Etre-LO, the other is Etre-SO, and Etre-SO also includes two parts, Etre-SO(+) and Etre-SO(-);taking KCl as an example, Etre-LO increases with the increase of the slab thickness, but Etre-SO,Etre-ph and λ all reduce with the increase of the slab thickness, and when the slab thickness d is more than 5 nm, Etre-ph is about to a stable number. Especially, vibration frequency (λ) increases when there is the Coulomb potential, because of the interactions are strengthened between the electrons and phonons.%采用线性组合算符法和幺正变换方法,研究极性晶体膜中束缚极化子的基态能量、自陷能随膜厚d的变化关系.得出束缚极化子的自陷能由两部分组成:第一部分是由于电子-体LO声子相互作用所引起的(Etre-LO)极化子效应;第二部分则是电子-SO声子相互作用引起的.后者又包含两部分,分别是电子与极性膜中两支表面声子相互作用的贡献(Etre-SO(+),Etre-SO(-)).通过对KCl半导体膜的数值计算表明,Etre-LO随膜厚d的增加而增加;但是Etre-SO、极化子的振动频率以及电子-声子相互作用所产生的总自陷能Etre-ph随膜厚d的增加而减少,当膜厚大于5 nm时,总自陷能Etre-ph趋于一稳定值.另外,由于束缚势的存在,使极化子的振动频率增大,这主要是由于束缚势的存在,使电子-声子间的相互作用增强,极化子效应增大而引起的.