A high-density real-time 1024-pixel terahertz near-field imager in 130-nm SiGe BiCMOS

Abstract

Terahertz near-field imaging enables high-resolution biomedical and material characterization by combining the non-ionizing nature of terahertz radiation with sub-wavelength spatial resolution. However, the scalability of existing solid-state near-field imagers is fundamentally limited by shared illumination schemes and laterally arranged imaging components, restricting pixel miniaturization and array density. This work overcomes these limitations by introducing a novel pixel architecture that vertically integrates the illumination source, near-field sensing element, and power detector within each pixel, replacing conventional lateral implementations. The proposed architecture reduces the pixel footprint while enabling every pixel to operate as an independent terahertz near-field sensor. Based on this concept, a fully monolithic 32 × 32 (1024-pixel) near-field imager was implemented in a 130-nm SiGe BiCMOS HBT technology. The sensor operates in rolling-shutter mode and achieves real-time imaging at up to 40 fps. The chip consumes 280 mW, corresponding to 273 μW per pixel, and achieves a pixel density of 200 pixels/mm ² , the highest reported for monolithically integrated terahertz near-field imaging systems above 100 GHz. The paper presents the scalable architecture together with the design, characterization, and performance analysis of the individual imaging components and discusses the trade-offs introduced by vertical integration.