NER: Engineering of InAs Quantum Dot Ensembles Using Interference of Optical Surface Waves

利用光表面波干涉的InAs量子点集成工程本项目解决了通过应力驱动的voler - weber或stranski - krstanov生长机制形成的量子点（QD）外延半导体集成的尺寸分布的不均匀展宽问题。量子点的均匀性和狭窄的尺寸分布是量子点结构在光电器件中应用的主要挑战。本提案的主要目标是评估利用光学表面波的干涉在GaAs表面上纳米尺度控制InAs量子点成核过程的可行性。在分子束外延（MBE）生长量子点的过程中，脉冲紫外激光会在衬底表面产生干涉图样。该模式的典型周期为几百nm，将使用两种不同的光学方案(i)入射波与散射相干表面波的干涉；（ii）入射波与两个表面波耦合到分裂激光束的干涉。光学干涉图案将周期性地调制基片的表面性质100- 200nm水平。量子点的成核可以通过衬底温度调制来控制，从而破坏驻波模式正极的成核簇，或者通过激光烧蚀来控制表面的波动来控制表面能。100-nm的调制尺度有望形成初始QD成核的模板，QD系综的后续演化将在热力学上向更高的点密度（3-10）e10 cm-2方向发展。原位光学冲击的重要特点是它不会在表面留下任何残留物，可以在生长过程中进行，并且可以调整以引入最小缺陷密度。我们将系统地研究提供均匀窄量子分布和高效发光的因素（生长温度、As通量、生长速率、激光功率等）。利用原位RHEED、STM、TEM和光致发光等方法对光控成核的样品进行研究，揭示生长参数与QD体系结构和性能之间的相关性。该研究所的实验室拥有qd表征所需的所有设备。这包括最先进的场发射超高分辨率TEM，聚焦离子束站，表面分析工具，五个STMtools配置不同的成像模式和环境，包括超高真空，和独特的超声力显微镜。这项工作的成功完成将对各种光电元件的性能产生重大影响。该方法将允许生长具有明显尺寸分布和高辐射复合效率的量子点结构。例如，量子点结构将用作激光二极管的有源介质，具有更高的效率、更高的热稳定性、更高的调制频率和更高的可靠性。

Engineering of InAs Quantum Dot Ensembles Using Interference of OpticalSurface WavesThis project addresses the problem of inhomogeneous broadening of the sizedistribution of quantum dot (QD) epitaxial semiconductor ensembles formedvia a stress-driven Volmer-Weber or Stranski-Krastanov growth mechanism. Theuniformity and narrow size distribution of the QDs are the major challengesfor the utilization of QD structures in optoelectronic devices. The primarygoal of this proposal is to evaluate the feasibility of nanoscale control ofthe nucleation process of InAs QDs on a GaAs surface using the interferenceof the optical surface waves. The interference pattern will be generated onthe surface of the substrate using a pulsed UV laser during the growth ofQDs by molecular beam epitaxy (MBE). The pattern, with a typical period offew hundred nm, will be created using two different optical schemes basedon: (i) the interference of the incident wave with the scattered coherentsurface wave; and (ii) the interference of the incident waves with twosurface waves coupled to the split laser beams. The optical interferencepattern will modulate periodically the surface properties of the substrateat 100-200 nm level. The nucleation of QDs will be controlled through eithersubstrate temperature modulation, thereby destroying the nucleation clustersin the antinode of the standing wave pattern, or through undulation of thesurface by laser ablation to control the surface energy. The 100-nmmodulation scale is expected to form a template for initial QD nucleation,and the subsequent evolution of the QD ensemble will be driventhermodynamically towards higher density of dots, (3-10)e10 cm-2. Theimportant features of the in-situ optical impact are that it does not leaveany residues on the surface, can be conducted during the growth process, andcan be adjusted to introduce the minimum defect density.We will systematically investigate the factors (growth temperature, As flux,growth rate, laser power, etc.) that provide uniform and narrow QDdistribution and efficient luminescence. The samples grown using opticallycontrolled nucleation will be studied by the in-situ RHEED, as well as STM,TEM and photoluminescence methods to reveal the correlations between growthparameters, and the structure and properties of the QD systems. Thelaboratories at the Institute have all the necessary equipment for the QDcharacterization. This includes state-of-the-art field-emission ultra-highresolution TEM, focused ion beam station, surface analysis tools, five STMtools configured for different imaging modes and environment includingultra-high vacuum, and unique ultrasonic force microscope.The successful completion of the proposed work would have a significantimpact on the performance of various optoelectronic components. The methodwill allow the growth of QD structures with sharp size distribution and highradiative recombination efficiency. For example, the QD structures will beused as active media for laser diodes with superior performancecharacteristics, such as higher efficiency, higher thermal stability, highermodulation frequency and increased reliability.