A Localized Surface Plasmon Resonance And Light Confinement Enhanced Near Infrared Light Photodetector

Light manipulation is paramountly important to the fabrication of high-performance optoelectronic devices such as solar cells and photodetectors. In this study, a high-performance near infrared light nano-photodetector (NIRPD) was fabricated based on germanium nanoneedles array (GeNNs array) with strong light confining capability, and single layer graphene (SLG) modified with heavily doped tin doped indium oxide nanoparticles (ITONPs), which are capable of inducing localized surface plasmons resonance (LSPR) under NIR irradiation. The specific achievements are as follows:1.In this dissertation, the vertical and uniform GeNNs array was obtained by combining Ag-assisted etching with widely used polystyrene (PS) nanospheres lithography technique, and then SLG film decorated with heavily doped ITONPs. The ITONPs were fabricated by a reflux method in oleylamine and characterized by TEM、XPS and XRD. The absorption curves of as-synthesized ITONPs with different Sn doping levels shows strong absorption peaks due to LSPR are found to depend on the doping level of the NPs. Unlike conventional noble metal nanocrystal normally with tunable LSPR band in visible and UV region, the present heavily doped ITONPs exhibit typical LSPR in NIR region, which is completely compatible for the detection of NIR irradiation.2. Optoelectronic study shows that after modification with ITONPs, the NIRPD displays distinct rectifying behavior with a tiny turn-on voltage of 0.3 V. Further device analysis reveals that the device performance including on/off ratio, responsivity and detectivity of the device were estimated to be 5×104,185 mA/W and 2.28×1013 cmHz1/2W-1, which are much better than other devices with similar geometries. In addition, the ITONPs@SLG/GeNNs array NIRPD is able to monitor high-switching optical signals with frequency as high as 1 MHz, with high response speed (response/recovery time of 450/460 ns) and good reproducibility in a wide range of switching frequencies (1 Hz-1 MHz).Theoretical simulations based on finite element method (FEM) reveals that the observed high performance is not only due to the strong light confining capability of the GeNNs array, but also due to the plasmonic ITONPs induced hot electron injection. The generality of the above results suggests that the present NIRPD will have promising potential in future optoelectronic devices application.