1] Department of Physics, Columbia University, New York, New York 10027, USA [2] Department of Chemistry, Columbia University, New York, New York 10027, USA [3] KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-701, Korea.
Department of Materials Science and Engineering, Yonsei University, Seoul 120-749, Korea.
Nat Nanotechnol. 2014 Sep;9(9):676-81. doi: 10.1038/nnano.2014.150. Epub 2014 Aug 10.
Semiconductor p-n junctions are essential building blocks for electronic and optoelectronic devices. In conventional p-n junctions, regions depleted of free charge carriers form on either side of the junction, generating built-in potentials associated with uncompensated dopant atoms. Carrier transport across the junction occurs by diffusion and drift processes influenced by the spatial extent of this depletion region. With the advent of atomically thin van der Waals materials and their heterostructures, it is now possible to realize a p-n junction at the ultimate thickness limit. Van der Waals junctions composed of p- and n-type semiconductors--each just one unit cell thick--are predicted to exhibit completely different charge transport characteristics than bulk heterojunctions. Here, we report the characterization of the electronic and optoelectronic properties of atomically thin p-n heterojunctions fabricated using van der Waals assembly of transition-metal dichalcogenides. We observe gate-tunable diode-like current rectification and a photovoltaic response across the p-n interface. We find that the tunnelling-assisted interlayer recombination of the majority carriers is responsible for the tunability of the electronic and optoelectronic processes. Sandwiching an atomic p-n junction between graphene layers enhances the collection of the photoexcited carriers. The atomically scaled van der Waals p-n heterostructures presented here constitute the ultimate functional unit for nanoscale electronic and optoelectronic devices.
半导体 p-n 结是电子和光电子器件的基本组成部分。在传统的 p-n 结中，在结的两侧形成自由电荷载流子耗尽的区域，产生与未补偿掺杂原子相关的内置电势。载流子通过扩散和漂移过程跨越结传输，受该耗尽区域的空间范围影响。随着原子层薄的范德华材料及其异质结构的出现，现在可以在极限厚度下实现 p-n 结。由 p 型和 n 型半导体组成的范德华结（每个仅一个单胞厚）预计将表现出与体异质结完全不同的电荷传输特性。在这里，我们报告了使用范德华组装过渡金属二卤化物来制造原子层薄的 p-n 异质结的电子和光电性质的特征。我们观察到栅极可调谐的类似二极管的电流整流和 p-n 界面的光伏响应。我们发现，多数载流子的隧穿辅助层间复合是电子和光电过程可调谐的原因。在石墨烯层之间夹入原子 p-n 结可以增强光激发载流子的收集。这里呈现的原子级范德华 p-n 异质结构构成了纳米电子和光电子器件的最终功能单元。
