4H-SiC PIN detector for alpha particles from room temperature to 90 °C

In the field of high-energy particle detection, detectors operating in high-radiation environments primarily face high costs associated with power consumption and cooling systems. Therefore, the development of particle detectors capable of stable operation at room temperature or even elevated temperatures is of great significance. Silicon carbide (SiC) exhibits significant potential for particle detector applications due to its exceptional carrier mobility, radiation hardness, and thermal stability. Over the past decade, significant breakthroughs in silicon carbide epitaxial growth technology and device processing techniques have enabled the development of SiC-based particle detectors, providing a new technological pathway for particle detection in high-temperature environments. In this work, we fabricate a 4H-SiC PIN detector, named SIlicon CARbide (SICAR) and characterize its leakage current, capacitance, and charge collection across varying temperatures. The results indicate that the detector maintains a very low leakage current (< 10 nA) at 90 C, with no degradation in depletion capacitance or charge collection performance. Additionally, it achieves a fast rise time of 333 ps at 90 C, confirming its potential for high-temperature radiation detection applications.

💡 Research Summary

The paper presents the design, fabrication, and comprehensive characterization of a 4H‑silicon carbide (SiC) PIN radiation detector, termed SICAR, intended for operation from room temperature up to 90 °C. Recognizing the limitations of conventional silicon detectors—particularly their reliance on extensive cooling and limited thermal stability—the authors exploit SiC’s wide bandgap (~3.2 eV), high electron mobility, superior radiation hardness, and thermal conductivity to develop a detector capable of high‑temperature operation without performance degradation.

Device fabrication involved a fully epitaxial structure grown on a 4H‑SiC substrate. A heavily doped P++ contact layer (doping >1 × 10¹⁹ cm⁻³, thickness 0.6 µm) was employed to form low‑resistance ohmic contacts. A Ni/Ti/Al multilayer (50/15/80 nm) was deposited on both the P++ layer and the C‑face of the n‑type substrate, followed by rapid thermal annealing at 850 °C for 5 min. Transmission Line Method (TLM) measurements confirmed a contact resistivity of 6.25 × 10⁻⁵ Ω·cm², satisfying the stringent requirements for SiC PIN devices. The active region consists of a lightly doped n‑type layer ~30 µm thick, bounded by an etched termination with a 45°–60° angle and 1.6 µm depth to mitigate edge field crowding. A field‑plate structure made of aluminum and a ring‑shaped electrode layout further homogenize the electric field and raise the breakdown voltage, allowing operation at 300 V bias. The sensor area is 1.2 mm × 1.2 mm, including the field‑plate.

Electrical characterization was performed in a humidity‑controlled chamber (<5 % RH) at five temperature set points: 23 °C, 30 °C, 50 °C, 70 °C, and 90 °C. Leakage current measurements revealed an exceptionally low dark current: <0.1 nA at room temperature and <10 nA at 300 V bias even at 90 °C. Capacitance‑voltage (CV) sweeps at 10 kHz showed a stable depletion capacitance of 4.5 pF for reverse biases above 80 V, with negligible temperature dependence and a consistent depletion width of ~30 µm across the entire temperature range. These results indicate that the detector maintains a high signal‑to‑noise ratio and high‑frequency performance under elevated temperatures.

Charge collection performance was evaluated using an Americium‑241 alpha source positioned ~7 mm from the detector. At 300 V bias and 23 °C, the average collected charge was 55 fC (σ ≈ 4.6 fC), with a Gaussian distribution superimposed on a low‑charge tail attributable to Landau fluctuations in energy deposition. Systematic measurements at 200 V, 250 V, and 300 V bias across the full temperature range demonstrated that the collected charge varied by less than ±10 %, confirming temperature‑independent charge collection efficiency.

Temporal response was examined by recording the voltage pulse from individual alpha events with a 2.5 GHz bandwidth, 50 Ω‑terminated oscilloscope (10 GS/s). The pulse width was <2 ns, and the 10 %–90 % rise time increased modestly from 292.5 ps at 23 °C to 333.4 ps at 90 °C—a 14 % change—demonstrating that the detector’s timing resolution remains robust at high temperature.

The authors conclude that the 4H‑SiC PIN detector exhibits a combination of ultra‑low leakage current, stable depletion capacitance, consistent charge collection, and fast rise time up to 90 °C, making it a strong candidate for demanding applications such as nuclear reactor monitoring, space missions where cooling is impractical, and high‑energy physics experiments requiring radiation‑hard, high‑temperature sensors. The work also highlights the importance of optimized ohmic contact formation and field‑plate electrode design in achieving reliable SiC detector performance, thereby advancing the path toward commercial SiC‑based radiation detection technologies.