This promises to transform imaging applications across medicine, security, autonomous driving, and aerospace, setting a new standard for ultra-high-resolution sensors.
KAIST, in collaboration with researchers from Inha University and Yale University, has introduced an ultra-thin broadband photodiode (PD), a major advancement in high-performance image sensor technology. Led by Professor SangHyeon Kim from KAIST’s School of Electrical Engineering, the research addresses the longstanding trade-off between absorption layer thickness and quantum efficiency in traditional photodiodes.
The newly developed photodiode achieves an impressive quantum efficiency exceeding 70%, despite its absorption layer being less than one micrometer thick—around 70% thinner than existing technologies. This achievement simplifies pixel processing and paves the way for higher resolution, enhanced carrier diffusion, and reduced production costs. However, ultra-thin absorption layers traditionally struggle with capturing long-wavelength light. The research team effectively tackled this limitation.
Central to their innovation is integrating a guided-mode resonance (GMR) structure. This design enables efficient absorption across a broad spectrum, from 400 nanometers (nm) to 1700 nm, encompassing visible and shortwave infrared (SWIR) light. This broad-spectrum capability is crucial for applications in medical imaging, security systems, and autonomous driving.
The GMR structure utilizes principles from electromagnetics to enhance absorption efficiency by creating resonant conditions for specific wavelengths. Beyond expanding the absorption spectrum, the design supports hybrid and monolithic 3D integration with CMOS-based readout integrated circuits (ROIC), laying the foundation for next-generation ultra-high-resolution image sensors.
The photodiode’s exceptional performance in the SWIR range positions it as a game-changer for applications in digital cameras, aerospace technologies, autonomous vehicles, and satellite observations. The thinner absorption layer not only reduces manufacturing costs and power consumption but also boosts international competitiveness in imaging technology.
Professor SangHyeon Kim emphasized that this research demonstrates how ultra-thin absorption layers can surpass the performance of conventional technologies, marking a significant leap in image sensor innovation.
