Shi Zhi-Feng, Zhang Yuan-Tao, Cui Xi-Jun, Zhuang Shi-Wei, Wu Bin, Chu Xian-Wei, Dong Xin, Zhang Bao-Lin, Du Guo-Tong
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Qianjin Street 2699, Changchun, 130012, China.
Phys Chem Chem Phys. 2015 Jun 7;17(21):13813-20. doi: 10.1039/c5cp00674k. Epub 2015 Mar 24.
Vertically aligned ZnO/MgO coaxial nanowire (NW) arrays were prepared on sapphire substrates by metal-organic chemical vapor deposition combined with a sputtering system. We present a comparative investigation of the morphological and optical properties of the produced heterostructures with different MgO layer thicknesses. Photoluminescence measurements showed that the optical performances of ZnO/MgO coaxial NWs were strongly dependent on the MgO layer thickness. The intensity of deep-level emission (DLE) decreased monotonously with the increase of MgO thickness, while the enhancement of ultraviolet (UV) emission showed a critical thickness of 15 nm, achieving a maximum intensity ratio (∼226) of IUV/IDLE at the same time. The significantly improved exciton emission efficiency of the coaxial NW structures allows us to study the surface passivation effect, photogenerated carrier confinement and transfer in terms of energy band theory. More importantly, we achieved an ultralow threshold (4.5 mA, 0.58 A cm(-2)) electrically driven UV lasing action based on the ZnO/MgO NW structures by constructing an Au/MgO/ZnO metal/insulator/semiconductor diode, and the continuous-current-driven diode shows a good temperature tolerance. The results obtained on the unique optical properties of ZnO/MgO coaxial NWs shed light on the design and development of ZnO-based UV laser diodes assembled with nanoscale building blocks.
通过金属有机化学气相沉积结合溅射系统，在蓝宝石衬底上制备了垂直排列的ZnO/MgO同轴纳米线（NW）阵列。我们对不同MgO层厚度的异质结构的形态和光学性质进行了对比研究。光致发光测量表明，ZnO/MgO同轴纳米线的光学性能强烈依赖于MgO层的厚度。随着MgO厚度的增加，深能级发射（DLE）强度单调下降，而紫外（UV）发射增强呈现出15nm的临界厚度，同时实现了IUV/IDLE的最大强度比（约226）。同轴纳米线结构中显著提高的激子发射效率使我们能够根据能带理论研究表面钝化效应、光生载流子限制和转移。更重要的是，通过构建Au/MgO/ZnO金属/绝缘体/半导体二极管，我们基于ZnO/MgO纳米线结构实现了超低阈值（4.5mA，0.58A cm(-2)）的电驱动紫外激光作用，并且连续电流驱动的二极管表现出良好的温度耐受性。关于ZnO/MgO同轴纳米线独特光学性质的研究结果为基于纳米级构建块组装的ZnO基紫外激光二极管的设计和开发提供了启示。
