局部静电门控限定的少层黑磷PN结中的光伏效应
Photovoltaic effect in few-layer black phosphorus PN junctions defined by local electrostatic gating
摘要：
光伏效应是光能收集中最基本的光-物质相互作用之一。在常规光伏太阳能电池中，光生载流子由PN结的内置电场提取，该内置电场通常由半导体中的离子掺杂剂限定。在原子级薄的半导体中，掺杂水平可以通过场效应控制，而不需要在晶格中注入掺杂剂，这使得二维半导体成为实现电调谐PN结的有前景的材料。然而，大多数2D半导体材料不显示实现PN结所必需的双极P型和N型场效应输运。少层黑磷是一种新型的二维半导体材料，具有直接带隙、高迁移率、电流开/关比和双极工作等优点。在这里，我们制作了几层黑磷（b-P）场效应晶体管与分裂底栅和结晶六方氮化硼（h-BN）电介质。我们展示了静电控制的本地载流子的类型和密度以上的每个栅极的设备，调整其电气行为从金属整流。照明的栅极定义的PN结，我们观察到零偏置的光电流和显着的开路电压，我们归因于由内部电场驱动的电子-空穴对在结区的分离。由于该材料的小带隙，我们观察到的光电流和光电压的照明波长高达940 nm，有吸引力的能量收集应用在近红外区域
英文摘要：
The photovoltaic effect is one of the fundamental light-matter interactions in light energy harvesting. In conventional photovoltaic solar cells, the photogenerated charge carriers are extracted by the built-in electric field of a PN junction, typically defined by ionic dopants in a semiconductor. In atomically thin semiconductors, the doping level can be controlled by the field-effect without need of implanting dopants in the lattice, which makes 2D semiconductors prospective materials to implement electrically tunable PN junctions. However, most 2D semiconducting materials do not show ambipolar P-type and N-type field-effect transport, necessary to realize PN junctions. Few-layer black phosphorus is a recently isolated 2D semiconductor that presents a direct bandgap, high mobility, current on/off ratio and ambipolar operation. Here, we fabricate few-layer black phosphorus (b-P) field-effect transistors with split bottom gates and crystalline hexagonal boron nitride (h-BN) dielectric. We demonstrate electrostatic control of the local charge carrier type and density above each gate in the device, tuning its electrical behaviour from metallic to rectifying. Illuminating a gate-defined PN junction, we observe zero-bias photocurrents and significant open-circuit voltage, which we attribute to the separation of electron-hole pairs driven by the internal electric field at the junction region. Due to the small bandgap of the material, we observe photocurrents and photovoltages for illumination wavelengths up to 940 nm, attractive for energy harvesting applications in the near-infrared region
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