Fabrication and Electrophysical–Spectrometric Characterization of a Large-Area Si(Li) Detector for Alpha-Particle Detection

Abstract A large-area Al/n-Si/i-Si(Li)/Ni radiation detector was fabricated and experimentally investigated for α-particle spectrometry under near room-temperature conditions. The structure was formed by lithium compensation of high-resistivity p-type silicon, creating a wide intrinsic region with a nearly uniform electric field for efficient charge collection. Surface preparation included mechanical polishing and chemical treatment, while atomic force microscopy confirmed a smooth morphology with low nanoscale roughness. Electrical characterization using current–voltage (I–V) and capacitance–voltage (C–V) measurements showed stable reverse-bias operation with leakage currents of 0.5–6 µA and capacitance of 40–180 pF, indicating controlled depletion and low defect density. Spectrometric performance was evaluated using ²²⁶Ra, ²³⁸Pu, and ²³⁹Pu sources. Well-defined spectra were obtained at room temperature; for the 7.65 MeV α-line of ²²⁶Ra the energy resolution was 60–65 keV (FWHM). The dead layer thickness was estimated at ∼1–1.5 µm. The detector exhibited uniform response across a large sensitive area (∼490 mm²) and demonstration of operation without cooling over the duration of the measurement session. These results demonstrate the potential of the Si(Li) detector for reliable and cost-effective α-particle detection systems.