Correlation between exciton decay time and Stokes shift in digital magnetic heterostructures
Correlation between exciton decay time and Stokes shift in digital magnetic heterostructures
复制标题
数字磁性异质结构中激子衰减时间与斯托克斯位移之间的相关性
DOI：
10.1103/physrevb.65.125306
复制
发表时间：
2002
影响因子：
3.7
通讯作者：
E. Janik
中科院分区：
文献类型：
--
作者：
W. Heiss;G. Prechtl;S. Maćkowski;E. Janik
系统地研究了一组含MnTe层的CdTe/Cd 1 -xMgxTe量子阱样品中激子复合时间和激子光致发光斯托克斯位移。与稀释磁性半导体类似，这些数字磁性异质结构表现出强烈的磁场依赖性光致发光谱线，这些谱线不均匀加宽。研究中的两个量取决于Mn含量、量子威尔斯内Mn分布的细节以及检测能量。三组样品进行了研究：数字磁性异质结构包含四个MnTe层的等距间距和不同厚度的MnTe层，量子威尔斯包含1-ML的MnTe在量子阱中的不同位置，和量子威尔斯包含在总的1-ML的MnTe，但在量子阱中以不同的方式分布。对于所有样品，激子复合时间是强烈相关的斯托克斯位移。这种相关性是由激子局域化引起的，导致具有小动量的辐射衰减态与具有大动量的非辐射态的混合。然而，在我们的实验中，观察到激子衰减时间和斯托克斯位移之间的线性关系，据我们所知，这还不能用理论解释。虽然，在半磁性半导体的发光特性的影响，导致形成磁极化子的交换相互作用，这一过程可以被排除作为所观察到的相关性的起源。
The exciton recombination time and the exciton photoluminescence Stokes shift are systematically investigated in a set of CdTe/Cd 1 - x Mg x Te quantum-well samples containing MnTe layers with the thickness below or equal to 1 ML. Similar to diluted magnetic semiconductors, these digital magnetic heterostructures exhibit strongly magnetic-field-dependent photoluminescence lines which are inhomogeneously broadened. Both quantities under investigation depend on the Mn content, on the details of the Mn distribution within the quantum wells, and on the energy of detection. Three sets of samples are investigated: digital magnetic heterostructures containing four MnTe layers with equidistant spacing and various thickness of the MnTe layers, quantum wells containing 1-ML MnTe at various positions in the quantum well, and quantum wells containing in total 1-ML MnTe but distributed in the quantum well in different ways. For all samples, the exciton recombination time is strongly correlated to the Stokes shift. This correlation is caused by exciton localization, leading to a mixing of radiatively decaying states with small momentum with nonradiative states with large momentum. In our experiment, however, a linear dependence between the exciton decay time and the Stokes shift is observed, which is not yet explained by theory, to our knowledge. Although, the luminescence properties in semimagnetic semiconductors are affected by exchange interactions leading to the formation of magnetic polarons, this process can be ruled out as the origin of the observed correlation.