非均匀应变二维半导体中漏斗效率的极限
Limits of funneling efficiency in non-uniformly strained 2D semiconductors
AI总结：
该研究分析非均匀应变二维半导体中激子漏斗效率的极限，发现实际单层TMDC中效率低于5%，而在长寿命异质结构中室温下可达约50%，并指出俄歇复合限制强光下的效率。
摘要：
在过渡金属二硫化物（TMDC）中，当这些材料受到非均匀应变时，光激发电子-空穴对（激子）会感受到一个有效力。对于由尖锐针尖按压悬浮TMDC膜中心所产生的应变情形，激子被输运至膜中心应变最大处。这种效应称为激子漏斗效应，可用于提高TMDC中的光转换效率、探索激子输运以及研究激子在高密度下产生的关联态。在此，我们分析了实际器件几何结构中漏斗效率的极限。研究发现，在实际单层TMDC中，无论是在室温还是低温下，漏斗效率都很低，低于5%。这归因于室温下扩散占主导以及低温下激子寿命短。另一方面，在具有长激子寿命的TMDC异质结构中，当激子密度在漏斗中达到热平衡时，室温下的漏斗效率可达约50%。最后，我们表明，对于强光照源，俄歇复合限制了漏斗效率。
英文摘要：
Photoexcited electron-hole pairs (excitons) in transition metal dichalcogenides (TMDC) experience an effective force when these materials are non-uniformly strained. In the case of strain produced by a sharp tip pressing at the center of a suspended TMDC membrane, the excitons are transported to the point of the highest strain at the center of the membrane. This effect, exciton funneling, can be used to increase photoconversion efficiency in TMDC, to explore exciton transport, and to study correlated states of excitons arising at their high densities. Here, we analyze the limits of funneling efficiency in realistic device geometries. The funneling efficiency in realistic monolayer TMDCs is found to be low, $ <5 \;\%$ both at room and low temperatures. This results from dominant diffusion at room temperature and short exciton lifetimes at low temperatures. On the other hand, in TMDC heterostructures with long exciton lifetimes the funneling efficiency reaches $\sim 50\;\%$ at room temperature, as the exciton density reaches thermal equilibrium in the funnel. Finally, we show that Auger recombination limits funneling efficiency for intense illumination sources.
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