Lopez-Sanchez Oriol, Alarcon Llado Esther, Koman Volodymyr, Fontcuberta i Morral Anna, Radenovic Aleksandra, Kis Andras
Electrical Engineering Institute, Ecole Polytechnique Federale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland.
ACS Nano. 2014 Mar 25;8(3):3042-8. doi: 10.1021/nn500480u. Epub 2014 Mar 6.
Two-dimensional (2D) materials are a new type of materials under intense study because of their interesting physical properties and wide range of potential applications from nanoelectronics to sensing and photonics. Monolayers of semiconducting transition metal dichalcogenides MoS2 or WSe2 have been proposed as promising channel materials for field-effect transistors. Their high mechanical flexibility, stability, and quality coupled with potentially inexpensive production methods offer potential advantages compared to organic and crystalline bulk semiconductors. Due to quantum mechanical confinement, the band gap in monolayer MoS2 is direct in nature, leading to a strong interaction with light that can be exploited for building phototransistors and ultrasensitive photodetectors. Here, we report on the realization of light-emitting diodes based on vertical heterojunctions composed of n-type monolayer MoS2 and p-type silicon. Careful interface engineering allows us to realize diodes showing rectification and light emission from the entire surface of the heterojunction. Electroluminescence spectra show clear signs of direct excitons related to the optical transitions between the conduction and valence bands. Our p-n diodes can also operate as solar cells, with typical external quantum efficiency exceeding 4%. Our work opens up the way to more sophisticated optoelectronic devices such as lasers and heterostructure solar cells based on hybrids of 2D semiconductors and silicon.
二维（2D）材料是一类正在深入研究的新型材料，因其具有有趣的物理特性以及从纳米电子学到传感和光子学等广泛的潜在应用领域。半导体过渡金属二硫属化物MoS2或WSe2的单分子层已被提议作为场效应晶体管的有前途的沟道材料。与有机和晶体块状半导体相比，它们具有高机械柔韧性、稳定性和质量，再加上潜在的低成本生产方法，具有潜在优势。由于量子力学限制，单分子层MoS2中的带隙本质上是直接带隙，导致与光的强相互作用，可用于制造光电晶体管和超灵敏光电探测器。在此，我们报告基于由n型单分子层MoS2和p型硅组成的垂直异质结实现发光二极管。精心的界面工程使我们能够实现从异质结整个表面显示整流和发光的二极管。电致发光光谱显示出与导带和价带之间的光学跃迁相关的直接激子的明显迹象。我们的p-n二极管还可以用作太阳能电池，典型的外部量子效率超过4%。我们的工作为基于二维半导体和硅的混合体的更复杂光电器件（如激光器和异质结构太阳能电池）开辟了道路。
