Transparent Metallic Fractal Electrodes for Semiconductor Devices
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- 作者：Farzaneh Afshinmanesh ; Alberto G. Curto ; Kaveh M. Milaninia ; Niek F. van Hulst ; Mark L. Brongersma
- 刊名：Nano Letters
- 出版年：2014
- 出版时间：September 10, 2014
- 年：2014
- 卷：14
- 期：9
- 页码：5068-5074
- 全文大小：464K
- ISSN：1530-6992
文摘
Nanostructured metallic films have the potential to replace metal oxide films as transparent electrodes in optoelectronic devices. An ideal transparent electrode should possess a high, broadband, and polarization-independent transmittance. Conventional metallic gratings and grids with wavelength-scale periodicities, however, do not have all of these qualities. Furthermore, the transmission properties of a nanostructured electrode need to be assessed in the actual dielectric environment provided by a device, where a high-index semiconductor layer can reflect a substantial fraction of the incident light. Here we propose nanostructured aluminum electrodes with space-filling fractal geometries as alternatives to gratings and grids and experimentally demonstrate their superior optoelectronic performance through integration with Si photodetectors. As shown by polarization and spectrally resolved photocurrent measurements, devices with fractal electrodes exhibit both a broadband transmission and a flat polarization response that outperforms both square grids and linear gratings. Finally, we show the benefits of adding a thin silicon nitride film to the nanostructured electrodes to further reduce reflection.