Lateral carrier crosstalk suppression in pure-boron ultraviolet detector arrays using a novel deep trench isolation process

Abstract

Pure-boron (Pure-B) ultraviolet photodiodes form an ultra-shallow P+ junction at the silicon surface, enabling a nearly ideal entrance window with high quantum efficiency and low dark current for UV/EUV and electron detectors. However, in high-density arrays, lateral carrier transport within lightly doped epitaxial layers induces pronounced pixel-to-pixel crosstalk, which degrades spatial resolution. In this work, a novel deep trench isolation (DTI) scheme compatible with a dual-epitaxial Pure-B planar structure is proposed and experimentally demonstrated to suppress crosstalk in ultraviolet detector arrays. Technology computer aided design simulations reveal that DTI structures leave a residual lateral bypass path beneath the trench bottom, leading to a strong dependence of crosstalk on epitaxial thickness, whereas a 10-μm-deep DTI effectively eliminates this path and reduces simulated crosstalk to the lower level, largely independent of epitaxial thickness. Devices fabricated with the optimized DTI process exhibit low crosstalk of 0.27% under 0–2 V reverse bias, a detector signal of 0.24 A/W at 13.5 nm, dark current below 0.15 nA, and a rise time of approximately 60 ns. The proposed approach provides a scalable isolation strategy for high-pixel-count ultraviolet detector arrays with minimal electrical-performance degradation.