【作者】 温淑敏；

【导师】 班士良；

【作者基本信息】 内蒙古大学 ， 凝聚态物理， 2006， 硕士

【摘要】 本文考虑压力及准二维电子气对杂质库仑势屏蔽的影响，计及各向同性电子有效质量，材料介电常数及禁带宽度随流体静压力的变化，利用变分法讨论有限深量子阱中的施主杂质态能级。 对GaAs／Al_xGa_1-xAs量子阱中的杂质态结合能进行了数值计算，给出结合能随铝组份，阱宽和压力的变化关系，并讨论了有无屏蔽时的区别。结果显示，屏蔽效应随压力而增加，且显著降低杂质态的结合能。 计算结果表明，杂质态结合能随压力明显增大。一方面，屏蔽使结合能明显下降，另一方面，屏蔽使结合能对压力的敏感程度降低。结合能在有、无屏蔽时均随阱宽的增加先增后减，在中间阱宽时出现极值，屏蔽使极值峰更为尖锐，在宽阱和窄阱时，屏蔽的影响更加明显。 在铝组份取0≤x≤0.4的范围内，结合能随铝组份单调非线性增加，屏蔽效应使结合能降低，其变化趋势大致与无屏蔽时一致。 进而，考虑压力及屏蔽效应，同时计入量子阱结构中三类光学声子模（局域类体光学声子、半空间类体光学声子和界面光学声子）的作用，利用改进的LLP中间耦合方法处理电子-声子相互作用，讨论有限深量子阱中极化子效应对杂质态结合能的影响。结果表明，极化子效应使杂质态结合能明显降低，但压力使极化子效应减弱，屏蔽对极化子效应的影响不明显。更多还原

【Abstract】 In this thesis, the impurity states in quantum wells with finite barriers are investigated by considering the influence of hydrostatic pressure and screening effect from the quasi-2D electronic gas on the coulombic potential of an impurity. A variational method is adopted to discuss donor binding energies by considering the variations of isotropic effective band masses of an electron, dielectric constants and band gaps with hydrostatic pressure.The numerical calculation is performed for the binding energies of impurity states in GaAs/Al_xGa_1-xAs quantum wells. The relations between the binding energies of donors and Al concentration, well width and hydrostatic pressure are given. The difference between the cases with and without screening is also discussed. The result indicates that the screening increases with pressure and decreases the binding energies of impurity states obviously.The numerical results show that the binding energies of impurity states increase with pressure. Not only does the screening decrease the binding energies but also decrease their sentibility to pressure. The binding energy first increases, then reaches a maximum value at the middle well width, finally decreases slowly with increasing the well width for both with and without screening. The screening effect sharpens the maximum peak. Its influence on the binding energy becomes more obvious when the well width is either small or large.The results indicate that the binding energies increase nonlinearly and monotonously with increasing Al concentration from 0 to 0.4. Screening decreases the binding energies and its property is similar to that without screening.更多还原