Due to the properties of fast response, high resolution, low volume, low power consumption and non-contact measuring, photodetectors have been widely applied in many aspects of daily life and military field. But own to the limitation of the detection principle, the traditional photodetectors just can detect the intensity of the incident light and can’t detect the wavelength, polarization and angle of the incident light. They must combine with other optical elements, such as polarizers, color filters, or gratings, which impede the development of the photodetector system into the direction of multi-function, miniaturization, integration. So, it is urgent to put forward novel concept, structures, technology and materials to solve those problems in the field of photodetectors. Plasmonics is a new research area mainly focus on the investigation of the interaction between light and sub-wavelength metallic nanostructure. Surface plasmon resonance (SPR) is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity material stimulated by incident light. The resonant wavelength, field enhancement factor, field distribution pattern are strongly dependent on the shape, size, materials and dielectric environment of the nanostrucutrue. Thus the surface plasmon have an extremely wide application in the field of Physics, Chemistry, Biology, and Opti-electric devices, etc.
In this thesis, we aim to explore the work mechanism and potential feasibility of applying the surface plasmon nanostrucuture in the novel wavelength-resolution and polarization-sensitive photodetectors. On the above bases, we studied the optical and electrical properties of the metal /semiconductor nanostructures and metal/dielectric nanostructures.
The thesis mainly focus on two aspects of research: (1) manipulation of the optical absorption or transmission by designing and fabricating different kinds of plasmonic nanostructures;(2)extend the response spectra of the photodetectors by utilizing the surface plamosn resonance induced hot electrons.
The major achievements of the thesis are list as follows:
1. The influence of the shape of grating slit on the transmission spectra and extinction ratio under different polarized-light illumination was investigated. It is found that the convex shaped slit not only possesses high transmission but also have large extinction ratio. The absorption properties of Au grating/Si substrate structure under TM/TE polarized light incident in the near-infrared range were also investigated.
2. Design of several multiple narrowband perfect absorbers based on the “subwavelength metallic grating-dielectric-metallic substrate”. The optical properties, field distribution pattern and its formation mechanism were studied. In addition, a broadband absorbers based on the nanospikes array substrate was also designed and fabricated by the AAO method, the simulated absorption spectra agree well with the experimental results.
3. The photoresponse properties of the Au nanoparticles decorated IGZO TFT were investigated. The hot electron ejection process was demonstrate with a simple way by analyzing the variation of the I-T curve. The effect of backgate voltage on the hot electron ejection efficiency were also studied and find that the ejection efficiency increases with the increasing backgate voltage.
4. Design and fabrication of gold nanostructures/Si micro-pyramid Schottky near-infrared photodetectors based on wet chemical etching and film deposition method. The effect of the Au NPs size and the micro-pyramid structure on the devices performance were analyzed. The absorption and hot electron ejection efficiency both controlled by the Au NPs size and the micro-pyramid structure. Finally, the influence of the illumination direction on the hot electron ejection efficiency were investigated both experimentally and theoretically based on the Au film/Si micro-pyramid Schottky photodetectors.
Keywords: Surface plasmon, hot electrons, photodetection, perfect absorbers, polarization-sensitive