High-sensitivity X-ray imaging based on cost-effective and large-size CZT epitaxial crystal

Cadmium zinc telluride (CZT) is widely regarded as the premier material for large-area X-ray imaging. However, its widespread adoption in X-ray imaging has long been constrained by high production costs, limited wafer dimensions, and insufficient sensitivity under standard primary charge collection regimes. In this work, a high-quality 6-inch CZT epitaxial wafer was synthesized via close-spaced Epitaxy (CSE). By employing an in situ modified two-step growth protocol governed by an engineered step-flow mode, thermal-stress-induced dislocation multiplication was proactively suppressed at the growth wavefront, achieving an exceptionally narrow double-crystal rocking curve FWHM of 10.44 arcsec. Crucially, post-growth binary regulation was implemented to precisely tailor point-defect energetics, completely eradicating lethal deep-level recombination centers while sustaining active shallow donor states. This atomic-level defect engineering prolongs the non-equilibrium carrier lifetime through regulating recombination centers. Under high biases, the coordinated superposition of bulk Poole-Frenkel thermal emission and interfacial energy-band bending compresses the cathode depletion width, driving a massive field-assisted quantum tunneling secondary injection. This mechanism establishes an autonomous bulk-defect-to-interface synergy that unleashes a quantified giant photoconductive gain of 16.52 under a purely dark-field electrical configuration. The resulting detectors exhibit an unprecedented sensitivity of 99 701.39 µC Gy_air^-1 cm^-2, a record-low detection limit of 28.5 nGy_air s^-1, and a spatial resolution of 4.2 lp mm^-1, providing a reliable and scalable single-crystal platform for next-generation high-performance medical digital radiography.