Department of Materials Science and Engineering, National Taiwan University , 1, Sec. 4, Roosevelt Road, Taipei 10610, Taiwan.
National Nano Device Laboratories, National Applied Research Laboratories , 26, Prosperity Road I, Hsinchu 30076, Taiwan.
ACS Appl Mater Interfaces. 2016 Mar;8(10):6718-26. doi: 10.1021/acsami.5b11425. Epub 2016 Mar 1.
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.
高像素密度、高效的颜色分离、紧凑的结构、卓越的量子效率和低功耗是现代彩色图像传感器的重要特点。在这项研究中，我们开发了一种基于表面等离激元的彩色图像传感器，具有高光电响应、无微透镜结构和零偏压工作电压。我们的紧凑型传感器仅由(i) 基于单层结构铝（Al）膜的多功能电极和 (ii) 硅（Si）衬底组成。这种方法显著简化了器件结构和制造工艺；例如，红色、绿色和蓝色像素可以在单个光刻步骤中同时制备。此外，这种基于肖特基的等离子体激元电极具有多种功能，包括颜色分离、光电信号转换以及用于彩色图像检测的光生载流子收集。我们的基于多功能电极的器件还可以避免干扰现象，这种干扰现象会降低传统彩色图像传感器中发现的颜色分离光谱。此外，该器件利用 Al-Si 结周围的近场表面等离激元效应来增强 Si 的光吸收，从而即使在低光照环境和零偏压下，也能产生显著的光电电流输出。这些基于等离子体肖特基的彩色图像器件可以将光电流直接转换为光电压，并提供足够的电压输出，即使在仅有几飞瓦每平方微米的光强下也能进行彩色图像检测。与传统的彩色图像设备不同，使用电压作为输出信号可以减少外围读出电路的面积，因为它不需要电流到电压转换电容或其相关电路。因此，这种策略具有与互补金属氧化物半导体（CMOS）兼容的电路设计直接集成的巨大潜力，提高了使用成熟 Si 基技术开发的成像传感器的像素密度。
