The low responsivity observed in photodetectors based on monolayer transition-metal dichalcogenides has encouraged the pursuit of approaches that can efficiently enhance the external quantum efficiency, which relies predominantly on the light absorption, the lifetime of the excess carriers, and the charge collection efficiency. Here, we demonstrate that phototransistors fabricated on large-area bilayer tungsten disulfide (WS₂) grown by chemical vapor deposition exhibit remarkable performance with photoresponsivity, photogain, and detectivity of up to ∼3 × 10³ A/W, 1.4 × 10⁴, and ∼5 × 10¹² Jones, respectively. These figures of merit of bilayer WS₂ provide a significant advantage over monolayer WS₂ due to the greatly improved carrier mobility and significantly reduced contact resistance. The photoresponsivity of bilayer WS₂ phototransistor can be further improved to up to 1 × 10⁴ A/W upon biasing a gate voltage of 60 V, without evident reduction in detectivity. Moreover, the bilayer WS₂ phototransistor exhibits a high response speed of less than 100 μs, large bandwidth of 4 kHz, high cycling reliability of over 10⁵ cycles, and spatially homogeneous photoresponse. These outstanding figures of merit make WS₂ bilayer a highly promising candidate for the design of high-performance optoelectronics in the visible regime.

中文翻译：

---

基于化学气相沉积生长的原子薄双层二硫化钨构建的超高增益和快速光电探测器

在基于单层过渡金属二卤化物的光电探测器中观察到的低响应性促使人们寻求能够有效提高外部量子效率的方法，这些方法主要取决于光吸收，过量载流子的寿命和电荷收集效率。在此，我们证明了在通过化学气相沉积法生长的大面积双层二硫化钨（WS ₂）上制造的光电晶体管表现出了显着的性能，其光响应性，光增益和检测率高达〜3×10 ³ A / W，1.4×10 ⁴，和〜5×10 ¹²琼斯。双层WS _2的这些品质因数提供了优于单层WS的显着优势_{如图2所示，}由于大大提高了载流子迁移率并大大降低了接触电阻。在偏置60 V的栅极电压时，可以进一步将双层WS ₂光电晶体管的光响应提高到1×10 ⁴ A / W，而不会明显降低检测率。此外，双层WS ₂光电晶体管显示出低于100μs的高响应速度，4 kHz的大带宽，超过10 ⁵个循环的高循环可靠性以及空间均匀的光响应。这些优异的性能使WS ₂双层成为可见光领域高性能光电设计的高度有前途的候选人。