Collaborative Research: Synthesis and Investigation of Gallium Nitride Based Quantum Dots

主要研究者提出在iii族氮化材料体系中研究量子点（QDs）。目标有三个方面：1)通过使用点层将结构的有源层与衬底解耦来提高材料的质量；2)生产一种比现有氮化激光器具有更低阈值且效率更高的QD激光器；3)生产高效的氮化发光二极管（led），它可以跨越从蓝色到红色的电磁波谱，并且可以发出白光。这两个项目都在进行氮化物的广泛研究，该项目将成为他们项目的组成部分。活动将主要是晶体生长，但也将进行结构和器件加工以及材料表征的工作。分子束外延（MBE）和金属有机化学气相沉积（MOCVD）都将被采用。这是世界上为数不多的将两种技术都应用于氮化物研究小组的项目之一，这将使研究人员能够灵活地为生长过程的每个部分选择最佳方法。pi提出了两种新技术，他们希望能产生更均匀的点。第一种是晶体生长技术，在足够低的温度下，点层在晶格常数较小的氮化物层上以伪晶方式生长，从而实现二维生长。然后将该层退火形成自组装点层。在第二种技术中，生长停止在刚好低于点形成层的地方。然后将样品从生长装置中取出。它在纳米尺度上以均匀间隔的凹窝或小山排列成图案。然后将样品送回生长装置，继续生长。这些图案可以作为形成点的模板，并使它们更均匀。部分激光结构将由两种方法制成的样品制成，这将允许确定点尺寸是否足够均匀，以产生更窄的自发线宽，从而产生更低的阈值，改进激光。其他表征测量，包括光致发光，阴极发光，原子力显微镜（AFM）和透射电子显微镜（TEM）将进行。从蓝色到红色和白色的单色led将被制造和表征。

The principal investigators propose to study quantum dots (QDs) in the group III-nitridematerials system. The objectives are three-fold: 1) to improve the quality of the materialby using the dot layers to decouple the active layers of structure from the substrate; 2) toproduce a QD laser that has a lower threshold and is more efficient than present nitridelasers; and 3) to produce efficient nitride light emitting diodes (LEDs) that span theelectromagnetic spectrum from the blue to the red and that can be made to emit whitelight. Both of the PIs are carrying out extensive research in the nitrides, and this projectwill be integral part of their programs. The activity will be largely crystal growth innature, but work on structure and device processing and materials characterization willalso be carried out. Both molecular beam epitaxy (MBE) and metal organic chemicalvapor deposition (MOCVD) will be used. This is one of the few projects in the worldwhere both techniques are employed by one research group for the nitrides and will givethe researchers the flexibility to choose to best method for each part of the growthprocess. The PIs propose to produce the dots by two novel techniques which they expectwill produce more uniform dots. The first is a crystal growth technique whereby the dotlayer is grown pseudomorphically on a nitride layer of smaller lattice constant at lowenough temperature so that two dimensional growth occurs. The layer is then annealed toform a layer of self-assembled dots. In the second technique, the growth is stopped justbelow the dot-forming layer. The sample is then removed from the growth apparatus. Itis patterned on a nanoscale with a uniformly spaced array of dimples or hillocks. Thesample is then returned to the growth apparatus, and the growth is continued. The patternserves as a template to form the dots and helps make them more uniform. Partial laserstructures will be fabricated from samples made by both methods that will permit thedetermination of whether the dot size is uniform enough to produce a narrowerspontaneous linewidth and, hence, a lower threshold, improved laser. Othercharacterization measurements, including photoluminescence, cathodoluminescence,atomic force microscopy (AFM), and transmission electron microscopy (TEM) will becarried out. Single color LEDs from blue to red and white LEDs will fabricated andcharacterized.