石墨烯/氮化镓基异质外延的界面特性及其光电性能研究

There are some disadvantages of the efficiency droop at high injection levels and the difficult to detachment of substrate for conventional LED structure grown on the sapphire and silicon substrate. The over layer of GaN-Based LED films grown on the graphene substrate can be easily transferred onto other flexible substrates due to weak van der Waals interaction between graphene and overlaying layers. It will promote LED application on flexible device. The interfacial properties of the graphene /gallium nitride heterojunction will be studied as a key point in this project. Based photoelectron spectroscopy and microscopy characterization for the graphene surface, the interface structure of the graphene / gallium nitride heterojunction, and the surface of the epitaxial layer, we can clarify the mechanism of the interfacial formation between two dimensional graphene substrate and three dimensional epitaxial light emitting layers, and reveal the hidden rules of the effect of the interfacial structure on photoelectric properties. It would help the achievement of low cost and high performance LED flexible electrical device, and the research of hybrid systems for various functional device formed by graphene and other semiconductor materials by carrying out this project.

为解决常规衬底如硅、蓝宝石制作的LED结构在应用于大电流密度时光效下降和衬底剥离难的缺点，本研究以二维石墨烯作为衬底，利用其表层范德华力作用，设计生长一种石墨烯/氮化镓基异质外延结构，以探索van der Waals epitaxy结构生长模式和外延结构转移，从而实现柔性LED显示器件。以石墨烯/氮化镓形成的界面特性为研究出发点，依据对石墨烯表面、及其与GaN基外延层的界面结构、外延层表面的光电子谱学和显微学的表征手段，分析影响高质量外延薄膜形成的主要因素，理解二维石墨烯衬底层/氮化镓基异质外延层的界面形成机理，调控并掌握其生长动力学条件，揭示二维石墨烯衬底层/氮化镓基异质外延层的界面特性对柔性LED光电性能的影响机制。本项目的实施不仅对推动低成本、柔性LED器件的实现方面具有重要的理论研究价值，同时对构建二维石墨烯/三维半导体异质外延的功能器件具有指导意义。

本项目通过在二维石墨烯薄膜上生长氮化镓基异质外延，研究了二维石墨烯/氮化镓基异质外延的界面结构，包括厚度、化学成分、原子结构、电子结构和缺陷等，掌握了二维与三维异质界面的生长机理，为实现二维石墨烯衬底上生长其它三维异质结构的可控生长创造了条件，也为实现柔性LED显示奠定了基础。为降低由MOCVD生长GaN基蓝光芯片后激发黄光荧光粉实现白光LED光源的生产成本，进行了三个方面的探索研究：一是采用掩模法在MOCVD中生长金字塔状GaN 微米锥结构，利用其半极性面不同位置发光波长不同的结构特点及光学特性，制备了多波长混合发射白光LED光源；二是采用自制HCVD装置进行了GaN基纳米材料的工艺参数研究为实现源材料低成本高效率生长奠定了基础；三是进行了新无机发光结构（n-ZnO/p-GaN）和有机LED发光材料的开发研究。 In掺杂量达到7%时，n-ZnO纳米棒与p-GaN薄膜构成的发光二极管的电致发光效率最高。合成两种发射峰位于410nm深蓝光的萘和芴基芳香烃异构体荧光材料。