Random Population of Quantum Dots in InAs–GaAs Laser Structures
Random Population of Quantum Dots in InAs–GaAs Laser Structures
复制标题
InAs-GaAs 激光结构中量子点的随机分布
DOI：
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发表时间：
2010
影响因子：
2.5
通讯作者：
P. Smowton
中科院分区：
文献类型：
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作者：
I. O'Driscoll;P. Blood;P. Smowton
我们已经测量了自发辐射率，吸收和增益光谱的量子点之间的20 K和350 K使用分段接触的方法，利用自组装点的双峰尺寸分布。在20 K，我们发现小的和大的点集的基态的辐射率之间的线性关系，并使用吸收数据，我们显示的斜率对应于在不同的能量具有相同的概率的状态的随机布居。发射光谱表明，在20 K时，同一组点中载流子从激发态到基态的弛豫。我们已经开发了一个速率方程模型来描述从热到随机布居的转变，包括激发态和基态在同一点之间的弛豫。这产生了一个费米-狄拉克占领分布的电子在所有状态在350 K与全球准费米能级。在20 K时，所有基态都具有相同的占据概率，而与它们的能量无关。使用值的自发寿命和增益截面的吸收数据，这些速率方程给出了一个非常好的描述的实验结果作为温度的函数的辐射阈值电流密度，再现在200 K的最小值，从而模拟从高温下的热制度的过渡，在低温下的随机制度。
We have measured the spontaneous emission rates, absorption, and gain spectra of quantum dots between 20 K and 350 K using the segmented contact method, exploiting self assembled dots with a bimodal size distribution. At 20 K, we find a linear relationship between the radiative rates of the ground states of small and large sets of dots, and using absorption data we show the slope corresponds to random population of states at different energy with equal probability. The emission spectra indicate relaxation of carriers from excited to ground states in the same set of dots at 20 K. We have developed a rate equation model to describe the transition from thermal to random population, including relaxation between excited and ground states in the same dot. This produces a Fermi-Dirac occupation distribution of electrons in all states at 350 K with a global quasi Fermi level. At 20 K all ground states have the same occupation probability, irrespective of their energy. Using values for spontaneous lifetime and gain cross section from absorption data, these rate equations give a very good description of the experimental results for radiative threshold current density as a function of temperature, reproducing the minimum at 200 K, and thereby modeling the transition from the thermal regime at high temperature, to the random regime at low temperature.