The optical properties are investigated by spectroscopic characterizations for bilayer InGaAs/GaAs quantum dot (QD) structures consisting of a layer of surface quantum dots (SQDs) separated from a layer of buried quantum dots (BQDs) by different GaAs spacers with thicknesses of 7 nm, 10.5 nm and 70 nm. The coupling from the BQDs to SQDs leads to carrier transfer for the two samples with thin spacers, 7 nm and 10.5 nm, in which QD pairs are obtained while not for the 70 nm spacer sample. The carrier tunneling time is measured to be 0.145 ns and 0.275 ns from BQDs to SQD through the 7 nm and 10.5 nm spacers, respectively. A weak emission band can be observed at the wavelength of ∼ 960 nm, while the excitation intensity dependent PL and PLE spectra show that this is from the wetting layer (WL) of the SQDs. This WL is very important for carrier dynamics in bilayer structures of BQDs and SQDs, including for carrier generation, capture, relaxation, tunneling, and recombination. These results provide useful information for understanding the optical properties of InGaAs SQDs and for using such hybrid structures as building blocks for surface sensing devices.

中文翻译：

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耦合的InGaAs / GaAs表面量子点对结构的润湿层的光致发光特性和载流子动力学。

通过光谱表征研究了双层InGaAs / GaAs量子点（QD）结构的光学特性，该结构由一层表面量子点（SQDs）和一层埋入量子点（BQDs）通过不同的厚度为7 nm的GaAs隔离层隔开，10.5 nm和70 nm。从BQD到SQD的耦合导致两个带有7nm和10.5nm薄间隔物的样品的载流子转移，其中获得了QD对，而没有获得70nm间隔物样品。从BQD到SQD分别通过7 nm和10.5 nm的间隔物测得的载流子隧穿时间分别为0.145 ns和0.275 ns。在约960 nm的波长处可以观察到弱发射带，而与激发强度相关的PL和PLE光谱表明，这是来自SQD的润湿层（WL）。该WL对于BQD和SQD双层结构中的载流子动力学非常重要，包括载流子的产生，捕获，弛豫，隧穿和重组。这些结果为了解InGaAs SQD的光学特性以及将此类混合结构用作表面传感设备的构建基块提供了有用的信息。