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Microstructural and optical properties of self-assembled quantum dots for optical devices grown by molecular beam epitaxy.

机译：通过分子束外延生长的光学器件的自组装量子点的微观结构和光学性质。

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Low-dimensional semiconductor heterostructures have been extensively studied because of their potential applications and the unique physical phenomena they exhibit. Quantum dots (QDs) represent the latest innovation in the development of these structures. Due to the three-dimensional confinement of the carriers, semiconductor QD structures are expected not only to lead to the improvement of the device performance but also to limit the device degradation of the II-VI semiconductor-based devices. On the other hand, ZnCdMgSe material system shows potential in fabricating interband and intersubband devices with applications from the UV-visible to infrared range due to their widely adjustable bandgaps. For the first time, single and multi-QDs (MQDs) of CdSe with ZnCdMgSe barriers were successfully grown by self-assembling using molecular beam epitaxy and their properties were characterized. Atomic force microscopy (AFM) measurements showed CdSe QDs in uncapped structures. Control and reproducibility of the QD size leading to light emission throughout the entire visible spectrum was obtained by varying the CdSe deposition time. Based on this, stacked QD structures consisting of three QD layers emitting in the red, green and blue regions of the spectrum were grown. Photoluminescence (PL) measurements exhibited bright white emission that was observed by eye, at 77K or at room temperature, because of the mixing of colors. Preliminary light emitting diodes structures designed to obtain white emission were grown and tested.; Size reduction, higher uniformity, higher density and a blue-shifted PL peak of the QD layer, by increasing Mg concentration in the Zn1-x CdxMg1-x-y Se barrier were demonstrated. Results pointed to Mg as chemical factor that induced QD formation, either by increasing the atomic steps or/and by changing the surface energy of the ZnxCdyMg1-x-ySe. Electronic coupling and polarization of the emitted light from the MQD layers were accomplished by changing the spacer thickness and its MgSe composition. Power dependence studies demonstrated the PL peak position associated with coupled QDs depends on the laser excitation power while the one of the uncoupled QDs remains invariable. Polarized studies consistent with AFM images demonstrated the presence of a spontaneous QD organization for the uncoupled MQDs (wire-like structure). No surface organization was obtained for the coupled case.
机译：低维半导体异质结构因其潜在的应用和独特的物理现象而得到了广泛的研究。量子点（QD）代表了这些结构发展中的最新创新。由于载流子的三维限制，期望半导体QD结构不仅导致器件性能的改善，而且还限制了基于II-VI半导体的器件的器件劣化。另一方面，ZnCdMgSe材料系统由于具有可广泛调节的带隙，因此在制造带间和子带间器件方面具有潜力，其应用范围从UV可见到红外。首次使用分子束外延通过自组装成功地生长了具有ZnCdMgSe势垒的CdSe的单量子点和多量子点（MQD），并对其性质进行了表征。原子力显微镜（AFM）测量显示无盖结构中的CdSe QD。通过改变CdSe沉积时间，可以控制和重现导致整个可见光谱范围内发光的QD尺寸。基于此，生长了由在光谱的红色，绿色和蓝色区域中发射的三个QD层组成的堆叠QD结构。由于颜色混合，光致发光（PL）测量显示出在77K或室温下用肉眼观察到的亮白色发射。生长并测试了设计用于获得白光发射的初步发光二极管结构。通过增加Zn1-x CdxMg1-x-y Se势垒中的Mg浓度，证实了QD层的尺寸减小，更高的均匀性，更高的密度和蓝移的PL峰。结果指出，Mg是诱导QD形成的化学因子，可以通过增加原子步长或/和/或通过改变ZnxCdyMg1-x-ySe的表面能来实现。通过改变间隔物的厚度及其MgSe的成分，可以实现MQD层发射光的电子耦合和极化。功率相关性研究表明，与耦合QD相关的PL峰值位置取决于激光激发功率，而未耦合QD之一保持不变。与AFM图像一致的极化研究表明，未耦合的MQD（线状结构）存在自发的QD组织。耦合箱未获得表面组织。

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