Fast response and high responsivity realization of microcavity enhanced graphene photodetector using subwavelength grating electrodes

摘要

Graphene photodetectors (GPD) have been studied since the first discovery of graphene, and microcavity enhanced graphene photodetector (MEGPD) is one of the structure of GPDs with many advantages. Additionally, MEGPDs can reach fast response with well-designed electrode structure. Subwavelength grating (SWG) shows extraordinary optical transmission (EOT) phenomenon, making it a potential structure for MEGPD electrodes. Responsivity of MEGPD can be kept at its origin value due to high transmittance of SWG structure while response time of MEGPD could be significantly reduced. In this paper, a design and analysis of MEGPD with SWG electrodes is presented. Theoretical analysis shows that structure parameters including period, height and width of slits are the key factors to influence both the transmittance and response time. Silver is selected as the material of electrodes to obtain high conductivity. Transmittance is determined through a transmission model of SWG structure. SWG structure is confirmed through optimization, and the result is presented below: The period is 730 nm, the height is 580 nm and the width of slits is 330 nm. At a nominal operating wavelength of 1.55 mu m, the transmittance can reach 0.9927 to maintain the responsivity at 1.23A/W and the response time can reach picoseconds. This design may provide an idea to gain high response speed when fabricating high responsivity GPD.