抛物阱中极化子效应对D^-心的影响

Polaron Effects on D^- Center in a Parabolic Quantum Well

采用改进的LLP方法在考虑体声子影响的情况下研究了抛物量子阱中电子-LO声子相互作用对D-心能量的影响。研究结果表明,阱宽较小时,D-心的基态能量和结合能随着阱宽L的增大而急剧减小;阱宽较大时,能量的减小比较缓慢,最后接近体材料中的三维值。并且得出了电子-LO声子相互作用可使D-心的结合能有显著的提高。

A negative-donor center （ D^- ） in a semiconductor heterostructure or quantum well is formed by a neutral center （ D^0 ） trapping an extra electron. This system has attracted considerable attention since the earlydays of quantum mechanics. D^- centers are one of the simplest many-body electronic systems which can be used as a test for theoretical descriptions of e-e correlation. In previous experimental and theoretical studies, the dependence of the binding energy of D^- on the magnetic-field strength and on the dimension of the quantum well have been investigated the D^- centers in Q2D systems, of the D^- center in a parabolic . Ahhougli there have been great efforts toward understanding the behavior of very little information is available concerning polaron effects on the properties quantum well （POW）. The polarization potential and the binding energy of the D^- center in a parabolic quantum well are investigated. The study has taken the effect of bulk longitudinal optical （LO） phonons into account. In order to simplify the calculation, we use the simple trial function for both electrons. By using the method of modified Lee-Low-Pines（LLP） variational method, the polarization potential and the ground state energy of D^- center in the GaAs/Alx,Ga1-xAs PQW are obtained. The contribution of the impurity and LO phonon interaction to the total electron energy can be eliminated by the first canonical transformation, and the effect of this displacement on the lattice polarization leads to the polarization potential which .partially compensates the electron-impurity Coulomb interaction. By the second canonical transformation, the ground state energy of the D^- center in the infinite parabolic quantum well is worked out, and then the binding energy of D^- center can be gained by further calculations. The research results indicate that, the ground state energy and binding energy of the D^- center decreases rapidly with increasing L at the beginning, then decreases very slowly with increasing L and finally closes to the three-dimensional value in GaAs. Polaron effects on the properties of the D^- center in a PQW were found to be important. Because the binding energy of the D^- center is much smaller than that of a shallow donor, the relative contribution of the polaron correction is larger.