The Study Of InGaAs-based Near-infrared Photodetectors

In this paper,ITO/metal/InGaAs and graphene/Al2O3/InGaAs near-infrared photodetectors are fabricated based on InGaAs.Due to a narrow band gap,InGaAs often gains a high dark current with a Schottky junction structure,which is hard to detect near-infrared light effectively.With a special material system and structure,these structures enable InGaAs based Schottky diodes to work effectively to detect nearinfrared light and improve the performance of the devices.Firstly,ITO/metal/InGaAs Schottky diodes are fabricated and studied.With an increasing Schottky barrier height,the device with an inserting metal layer between ITO and semiconductor can effectively suppress the dark current.InGaAs could expand the light absorption spectrum to 1550 nm.At the same time,the 2μm intrinsic layer also effectively expands the depletion region.The long depletion region reduces the junction capacitance and then the device response speed is enhanced.The response time of the device can reach 703 ns/2.11μs;The responsivity is 73.4 mA/W(1550 nm,1V);The detectivity is 2.55×1010 cm-Hz1/2·W-1(1550 nm,-0.09 V).Then the graphene/InGaAs Schottky photodiode is studied.Through the comparative experiment of inserting Al2O3 thin film,it is found that Al2O3 thin film can enhance the junction barrier to 0.594 eV,which greatly inhibits the dark current of the device.At the same time,the anti-reflection characteristic of Al2O3 thin film and the characteristics of graphene greatly improve the photo response characteristics of the device.The responsivity and detectivity of graphene/Al2O3/InGaAs near-infrared photodiodes were 523.77 mA/W and 4.42×1010 cm·Hz1/2/W(1064 nm,-0.4 V),respectively.In order to obtain more stable and better performance device,a graphene/Al2O3/InGaAs Schottky junction near-infrared photodetector with an InP layer under SiNx was fabricated.The interface state and defect state between the isolation layer and InGaAs were suppressed,and the dark current of the device was more stable.The photo response characteristics was greatly improved.The responsivity reaches 1.32 A/W(1550 nm,0 V).The detectivity can reach 2.3 × 1013 cm·Hz1/2·W-1(1550 nm,0 V).The response time can reach 557 ns/3.22 μs.