Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea.
ACS Nano. 2017 Apr 25;11(4):3832-3840. doi: 10.1021/acsnano.7b00021. Epub 2017 Mar 20.
Despite numerous studies on two-dimensional van der Waals heterostructures, a full understanding of the charge transport and photoinduced current mechanisms in these structures, in particular, associated with charge depletion/inversion layers at the interface remains elusive. Here, we investigate transport properties of a prototype multilayer MoS/WSe heterojunction via a tunable charge inversion/depletion layer. A charge inversion layer was constructed at the surface of WSe due to its relatively low doping concentration compared to that of MoS, which can be tuned by the back-gate bias. The depletion region was limited within a few nanometers in the MoS side, while charges are fully depleted on the whole WSe side, which are determined by Raman spectroscopy and transport measurements. Charge transport through the heterojunction was influenced by the presence of the inversion layer and involves two regimes of tunneling and recombination. Furthermore, photocurrent measurements clearly revealed recombination and space-charge-limited behaviors, similar to those of the heterostructures built from organic semiconductors. This contributes to research of various other types of heterostructures and can be further applied for electronic and optoelectronic devices.
尽管已经有许多关于二维范德华异质结构的研究，但对于这些结构中的电荷输运和光电流机制，特别是与界面处的电荷耗尽/反转层有关的机制，仍未完全理解。在这里，我们通过可调谐的电荷反转/耗尽层研究了原型多层 MoS/WSe 异质结的输运性质。由于 WSe 的掺杂浓度相对较低，与 MoS 相比，在其表面形成了一个电荷反转层，该反转层可以通过背栅偏压进行调节。耗尽区在 MoS 侧限制在几纳米内，而在整个 WSe 侧，电荷完全耗尽，这由拉曼光谱和输运测量确定。通过异质结的电荷输运受到反转层的存在的影响，涉及隧穿和复合两个区域。此外，光电流测量清楚地揭示了复合和空间电荷限制行为，类似于由有机半导体构建的异质结构。这有助于研究各种其他类型的异质结构，并可进一步应用于电子和光电设备。
