title: Plasmonics-Based Multifunctional Electrodes for Low-Power-Consumption Compact Color-Image Sensors.
abstract: High pixel density, efficient color splitting, a compact structure, superior quantum efficiency, and low power consumption are all important features for contemporary color-image sensors. In this study, we developed a surface plasmonics-based color-image sensor displaying a high photoelectric response, a microlens-free structure, and a zero-bias working voltage. Our compact sensor comprised only (i) a multifunctional electrode based on a single-layer structured aluminum (Al) film and (ii) an underlying silicon (Si) substrate. This approach significantly simplifies the device structure and fabrication processes; for example, the red, green, and blue color pixels can be prepared simultaneously in a single lithography step. Moreover, such Schottky-based plasmonic electrodes perform multiple functions, including color splitting, optical-to-electrical signal conversion, and photogenerated carrier collection for color-image detection. Our multifunctional, electrode-based device could also avoid the interference phenomenon that degrades the color-splitting spectra found in conventional color-image sensors. Furthermore, the device took advantage of the near-field surface plasmonic effect around the Al-Si junction to enhance the optical absorption of Si, resulting in a significant photoelectric current output even under low-light surroundings and zero bias voltage. These plasmonic Schottky-based color-image devices could convert a photocurrent directly into a photovoltage and provided sufficient voltage output for color-image detection even under a light intensity of only several femtowatts per square micrometer. Unlike conventional color image devices, using voltage as the output signal decreases the area of the periphery read-out circuit because it does not require a current-to-voltage conversion capacitor or its related circuit. Therefore, this strategy has great potential for direct integration with complementary metal-oxide-semiconductor (CMOS)-compatible circuit design, increasing the pixel density of imaging sensors developed using mature Si-based technology.
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei 10610, Taiwan.
authors.forename: Keng-Te
authors.initials: KT
authors.lastname: Lin
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei 10610, Taiwan.
authors.forename: Hsuen-Li
authors.initials: HL
authors.lastname: Chen
authors.affiliation: National Nano Device Laboratories, National Applied Research Laboratories , 26, Prosperity Road I, Hsinchu 30076, Taiwan.
authors.forename: Yu-Sheng
authors.initials: YS
authors.lastname: Lai
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei 10610, Taiwan.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Chi
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei 10610, Taiwan.
authors.forename: Ting-Wei
authors.initials: TW
authors.lastname: Chu
keywords: color image sensors; hole array; low-power-consumption; multifunctional electrode; plasmonics