高Al组分AlGaN量子能级间辐射跃迁轨道工程调控及其应用

The excellent electronic and optical properties of AlGaN have made it an important semiconductor with critical and wide ranging technological applications in ultraviolet optoelectronics devices. With decreasing the scale of AlGaN quantum structure, the quantum energy level orbital at the band edge, especially the orbit constituting the plane two-dimensional electron gas under the strong polarization of AlGaN, plays a role in the optical radiation transition . It is essential to understand the behavior and mechanism of the band-side orbital change and apply orbital engineering to modulate the band-edge energy level, especially by adjusting the quantum confinement degrees of different orientations to study the quantum confinement effect, such as constructing a quantum structure on a polar or non-polar surface. Thereby the orbital symmetry is affected to change the order of the quantum energy levels and to control the quantum confinement effect. The space-resolved scanning electron microscopy-cathodic fluorescence spectroscopy was used to selectively detect the transition radiation characterizing the quantum energy levels of different orientation quantum structures and to establish the corresponding relationship between the orbital characteristics of different orientation quantum structures and the macro-optoelectronic properties. Based on the above design and development of high-efficiency deep-ultraviolet AlGaN optoelectronic devices, it is of great significance to open up new technology applications, including AlGaN based deep ultraviolet LED & LD technology, power electronics technology, ultraviolet detection technology and sensing technology.

AlGaN优异的光电学性能使其成为工作在深紫外光电应用的重要半导体材料。随着AlGaN基量子结构尺度日益减小，带边量子能级能带轨道构成，特别是AlGaN量子结构强极化下形成的平面二维电子气薄层轨道构成，在参与光辐射跃迁上发挥作用凸显。理解带边轨道变化行为和机制，利用轨道工程调制带边能级，特别是通过调整不同取向的量子限制自由度以研究量子限制效应，如在半极性或非极性面上构建量子结构，借此影响轨道对称性以改变量子能级的能量排列和调控量子限制效应。采用空间分辨的扫描电子显微镜-阴极荧光谱选择性地探测表征不同取向量子结构量子能级间跃迁辐射光，建立不同取向量子结构轨道特征与宏观光电性质的对应关系。以此为基础设计开发高效深紫外AlGaN光电器件，对于开拓新技术应用，包括诸如基于深紫外AlGaN的LED、LD发光技术、功率电子技术、紫外探测技术与传感技术具有重要意义。

本项目瞄准高效率深紫外AlGaN光电器件的关键科学问题，兼顾时下深紫外LED器件产业界的技术需求。通过对AlGaN新型量子结构的设计，运用轨道调控工程，突破深紫外AlGaN量子结构材料和器件的关键技术。运用第一性原理计算发现，高Al组分AlGaN量子结构价带顶哑铃形p轨道顶对顶排布时易形成ppσ耦合，轨道耦合能量为正，并排分布时则产生ppπ耦合，其轨道间的耦合能量为负；揭示了轨道耦合引起的能量增益附加至能带带阶上，是高Al组分AlGaN量子阱中CH带非限域现象产生的原因，提出了对AlGaN量子限域机制的新理解。在此基础上，进一步发展出以轨道耦合工程来调控轨道取向的新理论，通过改变轨道耦合作用所形成的附加能量，达到调控量子限域的目的。一方面利用轨道调控的MOVPE分层生长技术，实现阱、垒清晰可辨且异质界面极为陡峭的高Al组分AlGaN量子阱结构；另一方面，开展了MOVPE外延生长金字塔型微米柱研究，利用微米柱几何结构上天然的半极性面和非极性面外延生长不同取向的量子结构。此外，开发了针对量子态微区探测的空间分辨SEM-CL表征技术，通过SEM观测到所生长金字塔倾斜表面主要由倾角分别为30°和60°的半极性面相接；单色CL成像辨别来自不同取向量子结构pz态的发光，CL谱峰强度表明侧面非极性量子结构发射强度更高、非极性面量子阱的跃迁几率更高，为轨道耦合工程提供了有力的证据。