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

主要研究者提出在第三族氮化物材料体系中研究量子点。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改善材料的质量; 2）生产具有较低阈值并且比现有氮化物激光器更有效的QD激光器;以及3）生产有效的氮化物发光二极管（LED），其跨越从蓝色到红色的电磁光谱并且可以被制成发射白光。这两个PI都在氮化物方面进行广泛的研究，这个项目可能是他们计划的一部分。这项活动将主要是晶体生长的性质，但结构和设备处理和材料表征的工作也将进行。分子束外延（MBE）和金属有机化学气相沉积（MOCVD）都将被使用。这是世界上少数几个项目之一，其中两种技术都被一个研究小组用于氮化物，并将使研究人员能够灵活地选择生长过程中每个部分的最佳方法。PI建议通过两种新颖的技术来产生点，他们期望产生更均匀的点。第一种是晶体生长技术，其中点层在足够低的温度下在较小晶格常数的氮化物层上假晶生长，从而发生二维生长。然后将该层退火以形成自组装点层。在第二种技术中，生长停止在点形成层的正下方。然后从生长装置中取出样品。它是在纳米尺度上以均匀间隔排列的凹坑或小丘形成的图案。然后将样品返回到生长装置中，继续生长。图案作为一个模板来形成点，并有助于使它们更均匀。部分激光器结构将从两种方法制成的样品中制造出来，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，改进的激光。将进行包括光致发光、阴极发光、原子力显微镜（AFM）和透射电子显微镜（TEM）在内的微结构表征测量。将制作并表征从蓝色到红色和白色LED的单色LED。

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.