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Abstract：
Strain-free GaAs cone-shell quantum dots have a unique shape, which allows a wide tunability of the charge-carrier probability densities by external electric and magnetic fields. Here, the influence of a lateral electric field on the optical emission is studied experimentally using simulations. The simulations predict that the electron and hole form a lateral dipole when subjected to a lateral electric field. To evaluate this prediction experimentally, we integrate the dots in a lateral gate geometry and measure the Stark-shift of the exciton energy, the exciton intensity, the radiative lifetime, and the fine-structure splitting (FSS) using single-dot photoluminescence spectroscopy. The respective gate voltage dependencies show nontrivial trends with three pronounced regimes. We assume that the respective dominant processes are charge-carrier deformation at a low gate voltage U, a vertical charge-carrier shift at medium U, and a lateral charge-carrier polarization at high U. The lateral polarization forms a dipole, which can either enhance or compensate the intrinsic FSS induced by the QD shape anisotropy, dependent on the in-plane orientation of the electric field. Furthermore, the data show that the biexciton peak can be suppressed by a lateral gate voltage, and we assume the presence of an additional vertical electric field induced by surface charges.
摘要：
无应变GaAs锥壳量子点具有独特的形状,它允许通过外部电场和磁场对电荷载流子概率密度进行广泛的可调性。这里,使用仿真实验研究了横向电场对光发射的影响。模拟预测当受到横向电场时,电子和空穴形成横向偶极子。为了通过实验评估这一预测，我们将这些点整合在横向栅极几何形状中，并测量激子能量的斯塔克位移，激子强度,辐射寿命，和使用单点光致发光光谱的精细结构分裂（FSS）。相应的栅极电压依赖性显示出具有三个明显状态的非平凡趋势。我们假设各个主要过程是在低栅极电压U下的电荷载流子变形，介质U处的垂直电荷载流子位移，和高U的横向电荷载流子极化。横向极化形成偶极子，可以增强或补偿由QD形状各向异性引起的固有FSS，取决于电场的平面内方向。此外，数据表明，双激子峰可以被横向栅极电压抑制，我们假设表面电荷引起的额外垂直电场的存在。
