Study On Hot-Electron Photodetection In Nanoholed Metal-Semiconductor-Metal Structure

Because of the local effects of space electromagnetic waves and the light absorption not limited by the band gap of semiconductor materials,the applications of surface plasmons(SPs)in photodetection,optical sensing,light energy conversion,and photocatalysis have attracted extensive attention.Numerous micro-and nano-structures have been proposed to enhance the light-mater interaction,which shows amazing potentials in bio-sensing,medical diagnosing,photodetection and other aspects.However,the SP manipulation for the hot-electron photodetection application is relatively complicated and high-cost in device fabrication;moreover,the performances of hot-electron photodetectors are generally unsatisfactorily low.This thesis proposes the nanoholed metal-semiconductor-metal structure for hot-electron photodetection application,with addressing the device design,fabrication,performance test and analysis.The main contents are as follows:1)By using the finite-difference time-domain(FDTD)method,a hot-electron photodetector based on nanoholed metal-semiconductor-metal structure is designed.The influences of the nanohole period and diameter,the thickness and material of intermediate spacer on the wavelength and intensity of the SPs are systematically studied.It is demonstrated that the structure has tunable narrowband,polarization and incident-angle independent absorption in the near-infrared band,and the absorption peak can be larger than 90%.The responsivity spectrum is calculated under the device configuration of the asymmetric band-bending,which shows that the responsivity peak without a bias is up to 2.82 mA/W.2)The device based on the nanoholed metal-semiconductor-metal structure is prepared by combining the self-assembled nanosphere lithography and lift-off technology.The diameter and period of the nanoholes are controlled through adjusting the original(before self-assembled process)as well as the reduced(after self-assembled process)nanosphere diameters.Our experiments prove that the SP-based system shows a good insensitivity against the incident polarization and angle.In the near-infrared band,there is a narrowband and tunable absorption peak of over 90%.When the nanohole period and diameter are separately 600 nm and 550 nm,the responsivity in the Au-TiO2-Al system,where the TiO2 film is prepared by sol-gel method,shows a peak of 60 nA/W at the wavelength of 700 nm.This work sheds some lights on the fields of optical-resonance manipulation and new-mechanism optoelectronic detectors.