高密度硅量子点的表面修饰与光增益特性研究

The realization of high luminescence efficiency and stimulated emission is of great significance for the development of the monolithic integration of optoelectronic devices on mass-produced Si chips, which is one of the research hot topics at the forefront. In our project, we would fabricate three-dimensional constrained, size-controlled and well-resulated dense Si quantum dots (QDs) embedded in SiOxNy system based on constrained crystallization principle with the purpose of enhancing the carrier concentration in this system. Furthermore, we would modificate the surface of Si QDs by N and O atoms. We would study the energy level distribution by using photoluminescence as well as electroluminescence spectra, and understand the role of the surface states and size of Si QDs on the carrier transport and recombination process, and then in turn control the surface states. Meanwhile, we would study its electronic band structure by using first-principles calculations and explore the way to realize the multiple-level luminescence model based on quantum confinement effect. On the basis of these, we would systematically investigate the optical gain from the Si QDs system by using the variable-stripe-length methods combined with the shifting-excitation-spot (SES) technique. We would reveal the mechanism of net optical gain and explore the way to obtain high optical-gain Si-based materials. Finally, we would design optical microcavity by using dense Si QDs as active layer and investigate the stimulated emission from this system so as to lay a good foundation for the realization of the monolithic integration of Si-based optoelectronic devices.

硅基材料的高效发光和受激发射是实现硅基单片光电集成的关键，是当前国际上的研究热点与前沿课题。本项目提出利用限制晶化原理，构建基于SiOxNy体系的三维量子限制、尺寸可控、有序分布的高密度硅量子点，提高对光的吸收与转换，以增加载流子注入浓度；并利用N与O对硅量子点表面进行修饰，通过光致发光与电致发光两种手段相结合，研究发光能级分布，理解量子点表面态与尺寸在电子和空穴输运、复合过程中的作用，以调控表面电子态；同时，结合第一性原理计算，深入研究其能带结构，探索基于量子限制发光中心的多能级发光系统的实现途径；在此基础上，基于一维光放大模型，利用变条长及移动激发点方法，研究其光学增益特性，从物理上深入理解量子点尺寸、密度及表面态在其中的行为，揭示净光学增益的形成机制，探索获取高增益硅基介质的途径；进一步地，设计光学微腔，在获得Si量子点光增益基础上争取实现光激射，为最终实现硅基电泵激光打下良好基础。

硅基材料的高效发光是实现硅基单片光电集成的关键所在。本课题完成了基于N、O表面修饰的高密度硅量子点的制备、微结构表征、发光特性与发光机制、以及光增益特性的研究，成功探索获取高增益硅基介质的实现途径，并拓宽了新的研究内容，对了C、O表面修饰的高密度硅量子点、稀土离子掺杂发光材料、以及高质量石墨烯的制备与光电特性进行了研究。四年来，得到了如下一些主要成果：1）成功在Si-rich SiOxNy系统构建基于N、O修饰的高密度硅量子点，获得强近红外光发射；2）进一步利用Si-rich SiOxNy/SiOxNy多层膜调制结构，调控硅量子点及其表面态，获得增强的红外光发射，并阐明发光增强机制；3）成功探索获取高增益硅基介质的实现途径，并揭示净光学增益的形成机制，在紫外光泵浦下,基于Si-rich SiOxNy/SiOxNy多层膜结构构建的N、O表面修饰的硅量子点在900 nm 峰值波长处净增益系数高达172 cm-1，此为目前国际上最高的硅基介质净增益系数；4）在高密度硅量子点发光器件中引入超薄纳米硅层作为空穴阻挡层，有效地抑制载流子的非平衡注入，将器件发光效率提高2倍。项目完成了预期目标，现已发表SCI收录学术论文16篇, 其中影响因子大于2的论文13篇、封面论文1篇；做邀请报告1次；获授权国家发明专利1项；培养硕士研究生5名，其中3名已毕业。