高灵敏度宽谱响应石墨烯光电探测器研究

Graphene, a two dimensional carbon based crystal, owns the highest carrier mobility of 200,000cm2V-1s-1 and the wide light absorption from the visible to mid-infrared. These advantages make graphene become an excellent candidate in high speed light detection in a wide spectum range. However, the quick carrier-phonon scaterring rate which leads to the rapid recombination of photo-generated electron-hole pairs and low absorption (about 2.3%) cause the responsivity of graphene photodetector as low as 0.01A/W. The low responsivity blocks the graphene application in optoelectronic field. The presented proposal aims to improve the performance of graphene photodetector by introducing electron trapping centers. The electron trapping center could trap the photo-generated electrons and then let the photo-generated holes transit in the circuit many times. Then the responsivity of graphene photodetector could increase. Our initial experiment results show that high density defects and bandgap form after a Titanium (Ti) sacrificial layer fabrication process. And the responsivity of graphene photodetector are extraordinarily enhanced in wide range from visible to mid-infrared. The imrpovement could result from the introduction of defect related electron trapping centers and bangap in graphene. Compared to other approaches to enhance the graphene photodetector performance, this method is much simpler, cheaper and has a large scale output. In this project, we will investigate the relation between process parameters and the defects and bandgap formed on graphene. Moreover, the effect of defect and bandgap on the performance of graphene photodetector including the defect types, trapping states density and the value of bandgap will also be studied. This proposal aims at achieving high responsivity and broad spectral response graphene photodetector and open up exciting opportunities for future graphene based optoelectronics.

二维碳族晶体石墨烯具有高达200,000cm2V-1s-1的载流子迁移率以及从可见光到中红外的超宽光谱吸收，使得石墨烯在宽光谱超快光电探测方面具有广阔的发展前景。然而，石墨烯极低的光吸收度（2.3%）和超快的载流子-声子散射时间导致其光电响应度很低（仅为0.01A/W左右）。这严重阻碍了石墨烯在光电领域的应用。本项目拟通过在石墨烯中引入能够捕获光生电子的缺陷态陷阱，从而延长光生电子-空穴的复合时间，进而提高石墨烯的光电响应度。前期的实验结果表明，经过金属Ti处理后，石墨烯上形成了高密度的缺陷态和电子带隙。且其光电响应度明显提高。此方法简便可行，成本低，适合于大面积制备。本项目将在前期实验的基础上进一步研究金属处理参数与石墨烯缺陷态及带隙大小的关系，最终实现可控制备。此外，还将探索缺陷类型，缺陷态密度及带隙大小对探测器性能影响的机理，为设计高性能石墨烯光电探测器提供理论指导和工艺支持。

二维碳族晶体石墨烯具有高达200,000cm2V-1s-1的载流子迁移率以及从可见光到中红外的超宽光谱吸收，使得石墨烯在宽光谱超快光电探测方面具有广阔的发展前景。然而，石墨烯极低的光吸收度（2.3%）和超快的载流子-声子散射时间导致其光电响应度很低（仅为0.01A/W左右）。这严重阻碍了石墨烯在光电领域的应用。本项目拟通过在石墨烯中引入能够捕获光生电子的缺陷态陷阱，从而延长光生电子-空穴的复合时间，进而提高石墨烯的光电响应度。前期的实验结果表明，经过金属Ti处理后，石墨烯上形成了高密度的缺陷态和电子带隙。且其光电响应度明显提高。此方法简便可行，成本低，适合于大面积制备。本项目将在前期实验的基础上进一步研究金属处理参数与石墨烯缺陷态及带隙大小的关系，最终实现可控制备。此外，还将探索缺陷类型，缺陷态密度及带隙大小对探测器性能影响的机理，为设计高性能石墨烯光电探测器提供理论指导和工艺支持。