Effect of lateral electric field on the transition energies of neutral and charged excitons in In 0.5 Ga 0.5 As/GaAs quantum dots
Effect of lateral electric field on the transition energies of neutral and charged excitons in In 0.5 Ga 0.5 As/GaAs quantum dots
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横向电场对In 0.5 Ga 0.5 As/GaAs量子点中性和带电激子跃迁能的影响
DOI：
10.1103/physrevb.91.115306
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发表时间：
2015
影响因子：
3.7
通讯作者：
and Yasuhiko Arakawa,
中科院分区：
文献类型：
--
作者：
Toshio Saito;Toshihiro Nakaoka;and Yasuhiko Arakawa,
我们计算了在高达40 kV/cm的横向电场作用下/GaAs量子点（QDs）中中性和带电激子的跃迁能。首先，利用8波段理论计算了横向场下的单粒子电子态和空穴态。包括线性和二次压电。其次，从电子-空穴、电子-电子和空穴-空穴库仑能计算跃迁能。对于碱基长度为15 nm的量子点，在横向电场作用下，正电荷激子的跃迁能量随着电场的增加呈现蓝移，最高可达28 kV/cm，在更高的电场作用下呈现红移。相比之下，那些中性和带负电荷的激子只表现出红移，伴随着两个激子能级的交叉。带正电的激子的计算结果再现了Nakaokaet al.在我们的实验中观察到的非常规的“M”形激子能量位移。理论物理。科学通报，1999,181109 (2011):APPLAB0003-695110.1063/1.3658639]。计算出带正电的激子蓝移的来源是由于侧向电场对压电势的改变，使得QD基角的空穴密度增加，导致空穴-空穴库仑能增加。我们发现蓝移的数量随着量子点的大小而增加。为了了解侧向电场方向的影响，我们计算了在20 kV/cm的侧向电场作用下，沿两个方向的跃迁能。对于带正电的激子，跃迁能在方向上表现出红移，在两个方向上表现出不同量的蓝移，表明横向场的作用在两个方向上是不等效的。结果表明，跃迁能的方向依赖性反映了量子点中由于压电性引起的约束势的对称性。
We have calculated the transition energies of neutral and charged excitons in/GaAs quantum dots (QDs) under a lateral electric field up to 40 kV/cm. First, the single-particle electron and hole states under the lateral field are calculated using the 8-bandtheory. The linear and quadratic piezoelectricity is included. Next, the transition energies are calculated from the electron-hole, electron-electron, and hole-hole Coulomb energies. For a QD with 15-nm base length under a lateral electric field along thedirection, the transition energy of the positively charged exciton exhibits a blueshift with increasing field up to 28 kV/cm, followed by a redshift under higher field. In contrast, those of the neutral and negatively charged excitons exhibit only redshifts accompanied by a crossing of the two exciton levels. The calculated result for the positively charged exciton reproduces the unconventional “M”-shaped exciton energy shift observed in our experiment by Nakaokaet al.[Appl. Phys. Lett. 99, 181109 (2011)APPLAB0003-695110.1063/1.3658639]. The origin of the blueshift calculated for the positively charged exciton is the enhanced hole density in the QD base corner due to the modification of the piezoelectric potential by the lateral electric field, which causes an increase in the hole-hole Coulomb energy. We found that the amount of the blueshift increases with the QD size. In order to understand the effect of the lateral field direction, we calculate the transition energies under a lateral electric field of 20 kV/cm along the, anddirections. For the positively charged exciton, the transition energy exhibits a redshift for thedirection, and blueshifts of different amounts for theanddirections, indicating that the effects of the lateral field are not equivalent for theanddirections. It is demonstrated that the direction dependence of the transition energy reflects the symmetry of the confinement potential in the QDs due to piezoelectricity.