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首页> 外文会议>Optical Materials in Defence Systems Technology III; Proceedings of SPIE-The International Society for Optical Engineering; vol.6401 >Enhanced Luminescence from InAs/GaAs Quantum Dots
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Enhanced Luminescence from InAs/GaAs Quantum Dots

机译：InAs / GaAs量子点增强的发光

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Single quantum dots (QDs), based on the InAs/GaAs material system have been characterized by micro-photoluminescence (μPL). The self-organized quantum dots studied are fabricated by the Stransky-Krastanov method, taking advantage of the strain caused by the lattice mismatch between InAs and GaAs. Well-defined narrow excitonic features from individual QDs are monitored in the μPL spectra, upon single or dual tunable laser excitation. The charge state of the quantum dot is revealed from these excitonic lines in the μPL spectra. However, by tuning the laser excitation energy, it is demonstrated that the charge state of the dot can be altered: The distribution of neutral and charged excitons is demonstrated to be extremely sensitive on the laser energy. In addition, with an additional infrared laser, striking changes are induced in the μPL spectra. The results achieved demonstrate the existence of two well-defined excitation energy regions for the main laser, in which the presence of the infrared laser will decrease or increase, respectively, the integrated dot μPL intensity. For excitation above the critical threshold energy of the main laser, the addition of the infrared laser will induce a considerable increase, by up to a factor 5, in the QD emission intensity. At laser excitation below the threshold energy, on the other hand, the QD emission intensity will decrease. This fact is due to reduced carrier capture efficiency into the dot as determined by the internal electric field driven carrier transport. In order to getrnfurther insight into the carrier capture process due to the electric field in the vicinity of the QD, the dots have also been subjected to an external electric fieldrnIn most optical experiments with QDs, electrically injected or photoexcited carriers are primarily created somewhere in the sample outside the QDs, e.g. in the barriers or in the wetting layer. Consequently, excited carriers undergo a transport in the wetting layer and/or barriers prior to the capture into the QDs. This circumstance highlights the crucial role of the carrier transport and capture processes into the dot for the performance and operation of the dot based devices such as QD lasers, QD infrared detectors and QD memory devices. This transport effect on the optical response of the quantum dots has been investigated by subjecting the carriers to an external electric field in μPL measurements. This external field is formed by application of a lateral field between two top contacts. It is demonstrated that the QD PL signal intensity could be increased several times ( > 5 times) by optimizing the magnitude of this external field.
机译：基于InAs / GaAs材料系统的单量子点（QD）已通过微光致发光（μPL）进行了表征。利用InAs和GaAs之间晶格失配所引起的应变，通过Stransky-Krastanov方法制造了研究的自组织量子点。在单个或双重可调谐激光激发后，可在μPL光谱中监测各个QD定义的窄激子特征。从μPL光谱中的这些激子线揭示了量子点的电荷状态。但是，通过调整激光激发能，可以证明可以改变点的电荷状态：中性和带电激子的分布对激光能量非常敏感。此外，使用附加的红外激光，可在μPL光谱中引起明显变化。所获得的结果证明了主激光器存在两个明确定义的激发能量区域，其中红外激光器的存在将分别降低或增加积分点μPL强度。对于高于主激光器的临界阈值能量的激发，红外激光器的加入将引起QD发射强度的显着增加，最高达5倍。另一方面，在低于阈值能量的激光激发下，QD发射强度将降低。这是由于内部电场驱动的载流子传输所决定的，载流子进入点的捕获效率降低。为了进一步了解由于QD附近的电场引起的载流子俘获过程，点还受到了外部电场的作用。在大多数使用QD的光学实验中，电注入或光激发载流子主要是在量子点中的某个位置创建的。 QD之外的样本，例如在阻隔层或润湿层中。因此，受激的载流子在被捕获到QD中之前，先在润湿层和/或势垒中经历传输。这种情况突显了载流子传输和捕获过程到点中对于基于点的设备（例如QD激光器，QD红外探测器和QD存储设备）的性能和操作的关键作用。通过在μPL测量中使载流子受到外部电场，已经研究了这种对量子点光学响应的​​传输效应。该外部场是通过在两个顶部触点之间施加横向场而形成的。已经证明，通过优化该外部场的大小，可以将QD PL信号强度提高几倍（> 5倍）。

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