论文标题
几层TMD设备的超快速光电流和吸收显微镜分离速率限制动力学驱动快速有效的光响应
Ultrafast photocurrent and absorption microscopy of few-layer TMD devices isolate rate-limiting dynamics driving fast and efficient photoresponse
论文作者
论文摘要
尽管固有的层间电导率固有较差，但由2D过渡金属二甲植物（TMD）（例如WSE $ _2 $和MOS $ _2 $）制成的光电探测器仍然可以产生令人期待的快速（$ \ leq $ 90 ps）和高效（$ε$ $ $ $ $ $ $ $ qubud> $ 40 \％\％\％）。通过将超快光电流（U-PC）和瞬时吸收（TA）显微镜相结合，在原本复杂的动力学中明确鉴定了竞争的电子逃生和重组速率。 WSE $ _2 $的U-PC和TA响应均可匹配匹配的层间逃生时间，该时间从1.6 ns加速到86 ns，使用了$ e $ field，以预测实现的最大设备PC效率为$ \ sim $ 44 \％。逃生率与$ e $ $ field的坡度表明，平面外电子和0.129的漏洞迁移率和0.031 cm $^2 $/v $ s $。以上$ \ sim $ 10 $^{11} $ photons/cm $^{2} $入射通量，缺陷辅助螺旋钻散射可通过在空缺缺陷处捕获载体，从而大大降低了效率。 TA和PC光谱都识别出金属胶囊子峰峰，$ \ sim $ 5.6 ns寿命作为主要的陷阱捕获载体，它们会在层之间跳跃。同步TA和U-PC显微镜表明，收集的\ Net PC是由电子逃生的动力学率与线性和非线性螺旋螺旋螺旋体重组率竞争的。这种简单的速率模型进一步预测了基于PC的动力学，非线性振幅和效率，$ε$在10 $^5 $范围的入射光子通量范围内，以几层WSE WSE $ _2 $和MOS $ _2 $设备。
Despite inherently poor interlayer conductivity, photodetectors made from few-layer devices of 2D transition metal dichalcogenides (TMDs) such as WSe$_2$ and MoS$_2$ can still yield a desirably fast ($\leq$90 ps) and efficient ($ε$$>$40\%) photoresponse. By combining ultrafast photocurrent (U-PC) and transient absorption (TA) microscopy, the competing electronic escape and recombination rates are unambiguously identified in otherwise complex kinetics. Both the U-PC and TA response of WSe$_2$ yield matching interlayer electronic escape times that accelerate from 1.6 ns to 86 ns with applied $E$-field to predict the maximum device PC-efficiency realized of $\sim$44\%. The slope of the escape rates versus $E$-field suggests out-of-plane electron and hole mobilities of 0.129 and 0.031 cm$^2$/V$s$ respectively. Above $\sim$10$^{11}$ photons/cm$^{2}$ incident flux, defect-assisted Auger scattering greatly decreases efficiency by trapping carriers at vacancy defects. Both TA and PC spectra identify a metal-vacancy sub-gap peak with $\sim$5.6 ns lifetime as a primary trap capturing carriers as they hop between layers. Synchronous TA and U-PC microscopy show the\ net PC collected is modelled by a kinetic rate-law of electronic escape competing against the linear and nonlinear Auger recombination rates. This simple rate-model further predicts the PC-based dynamics, nonlinear amplitude and efficiency, $ε$ over a 10$^5$ range of incident photon flux in few-layer WSe$_2$ and MoS$_2$ devices.
