Resonant Energy Transfer Based Electrically Pumped Hybrid Lasers

实现具有低阈值电流密度和可调谐发射波长的电泵浦紧凑和可靠的激光器，这些激光器由廉价的溶液可加工材料制成，将对包括光子学，化学传感和医学诊断在内的许多学科产生革命性的影响。胶体半导体量子点（CQD）是实现这一目标的有吸引力的纳米材料，因为它们可以使用易于扩展的化学技术制造，并且它们的光学性质可以通过量子限制效应直接控制。与其他方法相比，CQD通过使用表面改性和形成CD异质结构提供了几乎无与伦比的高度可控的结构性质的灵活性。然而，CQD薄膜的低载流子迁移率和差的热导率是目前其在电泵浦激光器中应用的主要挑战。拟议的项目专门解决这些挑战，并提供了有前途的解决方案，为开发新的相干光源的基础上，在混合纳米结构的外延硅/硅锗纳米层和铅基CQD薄膜的共振能量转移（RET）。该研究项目的进展将通过出版物、会议报告、学术课程、本科生和研究生研究经验以及当地高中生暑期课程广泛传播。RET是通过偶极-偶极相互作用从能量供体到受体的短程非辐射共振能量转移过程。通常情况下，RET与不期望的能量反向转移（EBT）共存，但本项目中提出的器件设计和纳米材料的选择应抑制EBT。此外，在外延Si/SiGe纳米结构的电荷载流子迁移率和热导率是数量级更好的CQD薄膜相比，和载流子注入的水平，预计将足以实现粒子数反转。此外，所提出的方法是专门集中在混合纳米结构设计，使RET率的数量级更大的竞争过程的能量弛豫，如俄歇和缺陷相关的载流子复合。为了实现这一目标，新型的铅基核-壳CQD具有高度可控的界面组合物将开发利用合成化学的进步，并允许外延覆盖的量子点核的厚度为一个原子单层的壳。在这些组成控制的核-壳CQD中，俄歇复合有望被抑制，并且可以实现光学放大的有利条件。此外，提出的研究解决其他关键问题的电泵浦CQD激光器，包括设计的载流子注入器，控制激子位置和低缺陷密度界面的形成。预期的结果将有助于实现电泵浦CQD基激光器与不同成分的量子点，并提供了一个有前途的路线，为开发新的相干光源的多种应用。该奖项反映了NSF的法定使命，并已被认为是值得支持的评估使用基金会的智力价值和更广泛的影响审查标准。

Realization of electrically pumped compact and reliable lasers with low-threshold current densities and tunable emission wavelengths made from inexpensive, solution processable materials will have a revolutionary impact on many disciplines including photonics, chemical sensing, and medical diagnostics. Colloidal semiconductor quantum dots (CQDs) are attractive nanomaterials for achieving this goal because they can be fabricated using easily scalable chemical techniques, and their optical properties can be directly controlled via the quantum confinement effect. Compared to other approaches, CQDs offer practically unmatched flexibility of highly controllable structural properties by using surface modifications and formation of CD heterostructures. However, low carrier mobilities and poor thermal conductivity of CQD thin films are currently the major challenges for their applications in electrically pumped lasers. The proposed project specifically addresses these challenges and offers promising solution for the development of novel coherent light sources based on resonant energy transfer (RET) in hybrid nanostructures comprised of epitaxial Si/SiGe nanolayers and Pb-based CQD thin films. Advances from this research project will be disseminated widely through publications, conference presentations, academic courses, undergraduate and graduate student research experience and summer programs for local high school students. RET is a short-range non-radiative resonant energy transfer process from an energy donor to acceptor via dipole-dipole interaction. Normally, RET co-exists with the undesirable energy back transfer (EBT), but the proposed in this project device design and choice of nanomaterials should suppress EBT. In addition, charge carrier mobility and thermal conductivity in epitaxial Si/SiGe nanostructures are orders of magnitudes better compared to that in CQD thin films, and the level of carrier injection is expected to be sufficient to achieve population inversion. Also, the proposed approach is specifically focused on hybrid nanostructures designed to make the RET rate orders of magnitudes greater compared to competing processes of energy relaxation, such as Auger and defect related carrier recombination. To achieve this goal, novel Pb-based core-shell CQDs with highly controllable interface composition will be developed using advances in synthetic chemistry and allowing epitaxial coverage of a QD core by a shell with a thickness of an atomic monolayer. In these composition-controlled core-shell CQDs Auger recombination is expected to be suppressed and favorable conditions for optical amplification can be achieved. In addition, the proposed research addresses other key issues for electrically pumped CQD lasers including design of carrier injectors, control over exiton locations and formation of low-defect density interfaces. The anticipated results will contribute to realization of electrically pumped CQD-based lasers with QDs of different compositions and provide a promising route for the development of novel coherent light sources for multiple applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.