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2D pn junctions driven out-of-equilibrium
Nanoscale Advances ( IF 4.7 ) Pub Date : 2020-06-08 , DOI: 10.1039/d0na00267d
Ferney A Chaves 1 , Pedro C Feijoo 1 , David Jiménez 1
Affiliation  

The pn junction is a fundamental electrical component in modern electronics and optoelectronics. Currently, there is a great deal of interest in the two-dimensional (2D) pn junction. Although many experiments have demonstrated the working principle, there is a lack of fundamental understanding of its basic properties and expected performances, in particular when the device is driven out-of-equilibrium. To fill the current gap in understanding, we investigate the electrostatics and electronic transport of 2D lateral pn junctions. To do so we implement a physics-based simulator that self-consistently solves the 2D Poisson's equation coupled to the drift-diffusion and continuity equations. Notably, the simulator takes into account the strong influence of the out-of-plane electric field through the surrounding dielectric, capturing the weak screening of charge carriers. Supported by simulations, we propose a Shockley-like equation for the ideal current–voltage (JV) characteristics, in full analogy to the bulk junction after defining an effective depletion layer (EDL). We also discuss the impact of recombination–generation processes inside the EDL, which actually produce a significant deviation with respect to the ideal behavior, consistently with experimental data. Moreover, we analyze the capacitances and conductance of the 2D lateral pn junction. Based on its equivalent circuit we investigate its cut-off frequency targeting RF applications. To gain deeper insight into the role played by material dimensionality, we benchmark the performances of single-layer MoS2 (2D) lateral pn junctions against those of the Si (3D) junction. Finally, a practical discussion on the short length 2D junction case together with the expected impact of interface states has been provided. Given the available list of 2D materials, this work opens the door to a wider exploration of material-dependent performances.

中文翻译:

2D pn 结被驱动失衡

pn结是现代电子和光电子学中的基本电气元件。目前,人们对二维 (2D) pn 结非常感兴趣。尽管许多实验已经证明了其工作原理,但对其基本特性和预期性能缺乏基本的了解,特别是当设备被驱动失衡时。为了填补当前的理解空白,我们研究了二维横向 pn 结的静电学和电子传输。为此,我们实现了一个基于物理的模拟器,该模拟器自洽地求解与漂移扩散和连续性方程耦合的二维泊松方程。值得注意的是,模拟器考虑了平面外电场通过周围电介质的强烈影响,捕获电荷载流子的弱筛选。在模拟的支持下,我们提出了理想电流-电压的类 Shockley 方程(JV ) 特性,完全类似于定义有效耗尽层 (EDL) 后的体结。我们还讨论了 EDL 内部重组生成过程的影响,这实际上与实验数据一致,与理想行为产生了显着偏差。此外,我们分析了二维横向 pn 结的电容和电导。基于其等效电路,我们研究了其针对射频应用的截止频率。为了更深入地了解材料维度所起的作用,我们对单层 MoS 2的性能进行了基准测试(2D) 横向 pn 结相对于 Si (3D) 结的那些。最后,提供了关于短长度二维结情况以及界面态的预期影响的实际讨论。鉴于可用的二维材料列表,这项工作为更广泛地探索材料相关性能打开了大门。
更新日期:2020-08-11
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