研究目的
To improve the excitation efficiency of silicon, an indirect bandgap material, by using optical near-field excitation confined in a nano-scale, thereby directly exciting the carrier in the indirect bandgap without phonon assistance.
研究成果
The study demonstrated an enhancement in photo-excitation efficiency by introducing Au nanoparticles as ONF sources, achieving up to a 47.0% increase in photo-sensitivity rate. The results suggest the possibility of large Δk generation by field confinement by ONF sources, with potential applications in photodetectors and solar cells.
研究不足
The small coverage of Au nanoparticles (1.8%) might limit the increase in photo-sensitivity rate. The study also notes the contradiction between the size dependence of Au nanoparticles and the theory of direct optical transition by the ONF based on the uncertainty principle.
1：Experimental Design and Method Selection:
The study involved fabricating a lateral Si p–n junction with Au nanoparticles to generate field confinement and evaluating the photo-sensitivity with and without Au nanoparticles.
2：Sample Selection and Data Sources:
The samples included thick and thin lateral p–n junctions fabricated from n-type Si wafers, with Au nanoparticles dispersed on the junction surface.
3：List of Experimental Equipment and Materials:
Equipment included a white light source (halogen lamp) for photo-sensitivity measurement, Au nanoparticles (Tanaka Kikinzoku Kogyo), and a finite difference time domain (FDTD) method for numerical calculations.
4：Experimental Procedures and Operational Workflow:
The photo-sensitivity was measured by comparing the sensitivity of the lateral p–n junction with and without Au nanoparticles, using a white light source. The increased photo-sensitivity rate was calculated and compared for different dispersion numbers of Au nanoparticles.
5：Data Analysis Methods:
The increased photo-sensitivity rate was analyzed using a formula considering the ratios of direct and indirect transitions, with the band gap energy set based on fitting the photo-sensitivity data.
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