Vaquero Daniel, Clericò Vito, Salvador-Sánchez Juan, Díaz Elena, Domínguez-Adame Francisco, Chico Leonor, Meziani Yahya M, Diez Enrique, Quereda Jorge
Nanotechnology Group, USAL-Nanolab, Universidad de Salamanca, E-37008 Salamanca, Spain.
GISC, Departamento de Física de Materiales, Universidad Complutense, E-28040 Madrid, Spain.
Nanoscale. 2021 Oct 8;13(38):16156-16163. doi: 10.1039/d1nr03896f.
Two-dimensional transition metal dichalcogenide (TMD) phototransistors have been the object of intensive research during the last years due to their potential for photodetection. Photoresponse in these devices is typically caused by a combination of two physical mechanisms: the photoconductive effect (PCE) and photogating effect (PGE). In earlier literature for monolayer (1L) MoS phototransistors, PGE is generally attributed to charge trapping by polar molecules adsorbed to the semiconductor channel, giving rise to a very slow photoresponse. Thus, the photoresponse of 1L-MoS phototransistors at high-frequency light modulation is assigned to PCE alone. Here we investigate the photoresponse of a fully h-BN encapsulated monolayer (1L) MoS phototransistor. In contrast with previous understanding, we identify a rapidly-responding PGE mechanism that becomes the dominant contribution to photoresponse under high-frequency light modulation. Using a Hornbeck-Haynes model for the photocarrier dynamics, we fit the illumination power dependence of this PGE and estimate the energy level of the involved traps. The resulting energies are compatible with shallow traps in MoS caused by the presence of sulfur vacancies.
二维过渡金属二硫属化物（TMD）光电晶体管由于其在光电探测方面的潜力，在过去几年中一直是深入研究的对象。这些器件中的光响应通常由两种物理机制共同引起：光电导效应（PCE）和光门控效应（PGE）。在早期关于单层（1L）MoS光电晶体管的文献中，PGE通常归因于吸附在半导体沟道上的极性分子的电荷俘获，从而导致非常缓慢的光响应。因此，1L-MoS光电晶体管在高频光调制下的光响应仅归因于PCE。在此，我们研究了完全由h-BN封装的单层（1L）MoS光电晶体管的光响应。与先前的认识相反，我们发现了一种快速响应的PGE机制，在高频光调制下，该机制成为光响应的主要贡献因素。使用用于光载流子动力学的Hornbeck-Haynes模型，我们拟合了这种PGE的光照功率依赖性，并估计了相关陷阱的能级。所得能量与由硫空位的存在导致的MoS中的浅陷阱兼容。
