[论文解读] Gate-tunable and high responsivity graphene phototransistors on undoped semiconductor substrates

Biddut K. Sarker, Isaac Childres+3 more|arXiv (Cornell University)|Sep 19, 2014

Graphene research and applications参考文献 3被引用 5

一句话总结

本文提出了一种在本征4H-SiC衬底上制备的栅压可调、高响应度石墨烯光电晶体管，利用衬底中光激发载流子产生的电场诱导光电响应。通过背栅和源漏偏压调控，该器件在室温下实现了约7.4 A/W的响应度——远超实际应用需求——实现了无需掺杂衬底的可调谐、高性能光电探测。

ABSTRACT

Due to its high charge carrier mobility, broadband light absorption, and ultrafast carrier dynamics, graphene is a promising material for the development of high-performance photodetectors. Graphene-based photodetectors have been demonstrated to date using monolayer graphene operating in conjunction with either metals or semiconductors. Most graphene devices are fabricated on doped Si substrates with SiO2 dielectric used for back gating. Here, we demonstrate photodetection in graphene field effect phototransistors fabricated on undoped semiconductor (SiC) substrates. The photodetection mechanism relies on the high sensitivity of the graphene conductivity to the local change of the electric field that can result from the photo-excited charge carriers produced in the back-gated semiconductor substrate. We also modeled the device and simulated its operation using the finite element method to validate the existence of the field induced photoresponse mechanism and study its properties. Our graphene phototransistor possesses a room-temperature photoresponsivity as high as ~ 7.4 A/W, higher than the required photoresponsivity (1 A/W) in most practical applications. The light power-dependent photocurrent and photoresponsivity can be tuned by the source-drain bias voltage and back-gate voltage. Graphene phototransistors based on this simple and generic architecture can be fabricated by depositing graphene on a variety of undoped substrates, and are attractive for many applications in which photodetection or radiation detection is sought.

研究动机与目标

• 开发不依赖掺杂衬底的高性能石墨烯光电探测器，以避免引入不必要的掺杂和载流子散射。
• 通过利用本征半导体衬底中光激发载流子产生的电场调制，实现石墨烯的栅压可调光电探测。
• 在环境条件下，通过简单且可扩展的结构实现石墨烯光电晶体管的高响应度。
• 通过有限元建模与仿真验证电场诱导光电响应机制。

提出的方法

• 在本征4H-SiC衬底上制备石墨烯场效应晶体管，以消除衬底掺杂效应。
• 通过本征半导体衬底实现背栅调控，调节石墨烯的电导率并控制光电响应。
• 采用有限元法（FEM）仿真模拟电场分布，验证电场诱导光电响应机制。
• 在不同源漏偏压和背栅电压下测量光功率依赖的光电流和响应度，以展示其可调性。
• 利用石墨烯的宽带吸收特性和高载流子迁移率，提升光电响应效率。
• 在室温下表征器件性能，以确保其实际应用可行性。

实验结果

研究问题

• RQ1 能否在使用本征半导体衬底（而非掺杂Si/SiO2）的情况下，实现石墨烯光电晶体管的高响应度光电探测？
• RQ2 衬底中光激发载流子产生的电场在石墨烯中产生可测量光电流的过程中起什么作用？
• RQ3 通过栅压和源漏偏压，光电流和响应度的可调范围有多大？
• RQ4 有限元模型如何支持所提出的电场诱导光电响应机制？
• RQ5 该结构能否实现超过1 A/W的响应度，即大多数实际光电探测应用的阈值？

主要发现

• 石墨烯光电晶体管在室温下实现了约7.4 A/W的光电响应度，显著超过大多数实际应用所需的1 A/W阈值。
• 通过独立调控源漏偏压和背栅电压，光电流和响应度实现了宽范围可调。
• 有限元仿真证实了由本征SiC衬底中光激发载流子驱动的电场诱导光电响应机制的存在。
• 该器件在室温下有效工作，证明了其在真实光电探测系统中的实际可行性。
• 该结构具有通用性和可扩展性，可适用于除SiC以外的多种本征半导体衬底。
• 衬底中无掺杂显著减少了载流子散射，与传统掺杂Si基器件相比提升了器件性能。