Si process compatible near-infrared photodetector using AU/SI nano-pillar array

We report on a near-infrared photodetector constructed on an n-typed Si wafer. Vertically oriented Au nano-pillars formed on the n-typed Si performed as optical antennas which absorb the infrared light effectively. Each nano-pillar had several hundred nm of diameter, 2.7-μm-height, and 1-μm-pitch. The nano-pillar exhibited low reflectance of 20% for the wavelength ranging from 1.25 μm (near-infrared) to 4μm (mid-infrared), indicating large absorbance. The absorbed energy is then transduced into photocurrent by the Schottky barrier diode formed on the Au/n-Si interface. The photocurrent sensitivity (responsivity) of the nano-pillar photodetector exhibited around 10-times increase compared with a control Schottky typed photodetector with a flat Au surface. The detectable wavelength limit was thus extended up to 1650 nm. Because this method is compatible with a Si fabrication process, it will serve as a fundamental way to construct a photodetector for multi-wavelength imaging.