| In this paper,we studied the performance of graphene/GaAs Schottky junction photodetectors.By changing the number of graphene layers,utilizing the plasmonic enhancement effect of metal nanoparticles,and combining interface passivation and plasmonic effect,we fabricated different types of graphene/GaAs photodetectors.Meanwhile,the effects of these methods on the performance of graphene/GaAs photodetectors were investigated.Firstly,a single-layer graphene(SLG)/GaAs photodetector and a bilayer graphene(BLG)/GaAs photodetector were fabricated.Due to the higher light absorption of the BLG in the near-infrared band,the BLG/GaAs photodetector exhibits better performance under near-infrared light at 808 nm.Compared with the SLG/GaAs photodetector,the responsivity of the BLG/GaAs device is increased from 60.19 mA/W to 76.86 mA/W,and its detection rate is 2.38×1011 cm Hz1/2W-1,the rise time is decreased from 25.33 μs to 19.46 μs.Secondly,based on the far-field enhancement effect of the Ag nanoparticles(NPs),plasmon-enhanced SLG/GaAs photodetector was fabricated,and the effect of 30 nm and 100 nm Ag NPs on the device performance was investigated.The results show that the farfield enhancement effect of Ag NPs with larger size can improve the device performance more significantly.The plasmon-enhanced SLG/GaAs photodetector based on 100 nm Ag NPs has a responsivity of 101.84 mA/W and a maximum detection rate of 1.12×1012 cm Hz1/2 W-1,the rise time and fall time are 8.98 μs/110.34 μs.Finally,an interface passivated and plasmon-enhanced BLG/GaAs photodetector was fabricated.The Al2O3 passivation layer inhibits the tunneling of electrons in BLG,which reduces the dark current of the device.On the one hand,the improvement of the photocurrent of the device is due to the Al2O3 passivation layer reduces the recombination probability of carriers at the Schottky junction interface,so that more photogenerated carriers are separated.On the other hand,the absorption of near-infrared light by the device is enhanced by the plasmon enhancement effect of Ag NPs.Under the 808 nm laser,the responsivity of device is enhanced to 119.55 mA/W,the detection rate is 4.72×1011 cm Hz1/2W-1,and the response time is 8.16 μs,98.43 μs,respectively,the performance is much higher than that of traditional graphene/GaAs photodetectors.The method of combining interface passivation and plasmon enhancement greatly improves the device performance,which provides a new idea for improving the performance of graphene/GaAs Schottky junction photodetectors. |
