Microphotoluminescence studies of single quantum dots. I. Time-resolved experiments
Microphotoluminescence studies of single quantum dots. I. Time-resolved experiments
复制标题
单量子点的显微光致发光研究。
DOI：
10.1103/physrevb.55.4456
复制
发表时间：
1997
影响因子：
3.7
通讯作者：
P. Roussignol
中科院分区：
文献类型：
--
作者：
U. Bockelmann;W. Heller;A. Filoramo;P. Roussignol
对单个GaAs/${\mathrm{Ga}}_{\mathrm{x}}$${\mathrm{Al}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As量子点进行了空间、时间和光谱分辨率相结合的光致发光测量。完全的空间量子化导致了一系列离散的发射线。研究了一系列具有不同约束强度的结构随激发波长、激发功率和温度的变化。在所有情况下，都可以观察到发光的快速上升。几个独立的结果表明，库仑散射在能量弛豫的早期阶段起主要作用。在液氦温度下，具有不同侧向势的点具有明显不同的复合动力学。对于弱的侧向限制，在发光光谱的时间依赖关系中直接观察到能量弛豫。相反，在具有最强约束的样品中，离散的线发生独立的复合。随着激发功率的增大，出现高能线，谱权重从最低能线系统地向高能线方向移动。对于这一变化，对应于单点中估计的电子-空穴对的数量从大约1char2 12增加到2 0 0，峰值能量几乎没有变化。我们还对量子点中激子的能谱和弛豫复合时间进行了详细的计算。假设激子气体的形成遵守泡利不相容原理，实验结果得到了令人惊讶的良好解释。
Photoluminescence measurements with combined spatial, temporal, and spectral resolution are performed on single GaAs/${\mathrm{Ga}}_{\mathrm{x}}$${\mathrm{Al}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As quantum dots. The complete spatial quantization leads to a spectrum of discrete emission lines. A series of structures with various confinement strength is investigated, as a function of excitation wavelength, excitation power, and temperature. In all cases, a fast rise of the luminescence is observed. Several independent results show that Coulomb scattering plays a major role within the early stage of energy relaxation. At liquid-helium temperature, a strikingly different recombination dynamics is observed for dots with various lateral potential. For weak lateral confinement, energy relaxation is directly observed in the time dependence of the luminescence spectrum. In contrast, in the sample with strongest confinement, independent recombination of the discrete lines occurs. Increasing the excitation power, higher-energy lines appear and the spectral weight shifts systematically from the lowest to the higher-energy lines. For this variation, which corresponds to an increase in the estimated number of electron-hole pairs in the single dot from about 1\char21{}2 to 200, the peak energies hardly change. We have also performed detailed calculations of the energy spectrum and the relaxation and recombination times of excitons in quantum dots. The experimental results are surprisingly well interpreted assuming the formation of an exciton gas obeying the Pauli exclusion principle.