Semiconductor materials and devices play a crucial role in nuclear reactor instrumentation, where extreme conditions such as high temperatures and intense radiation fluxes demand robust and reliable performance. Among the most promising materials for these applications are silicon carbide (SiC), diamond, and radiation-hardened silicon. These materials exhibit superior thermal stability, radiation tolerance, and electronic properties, making them indispensable for sensors, detectors, and control systems in next-generation reactors.

Silicon carbide stands out due to its wide bandgap (3.2 eV for 4H-SiC), high thermal conductivity (up to 490 W/m·K), and exceptional radiation resistance. Its covalent bonding and strong atomic lattice minimize displacement damage from high-energy particles, a common issue in nuclear environments. SiC-based devices, such as Schottky diodes and MOSFETs, have demonstrated stable operation at temperatures exceeding 600°C and under neutron fluences beyond 10^15 n/cm². Displacement damage in SiC primarily manifests as lattice defects, including vacancies and interstitials, which can trap charge carriers and degrade carrier lifetime. However, the material’s high displacement energy threshold (approximately 20–35 eV for silicon and carbon atoms) reduces defect generation rates compared to silicon. Mitigation strategies include defect engineering through doping (e.g., nitrogen or aluminum) and post-irradiation annealing at temperatures above 800°C to recover electrical properties.

Diamond, with its ultra-wide bandgap (5.5 eV) and the highest known thermal conductivity (2200 W/m·K), is another exceptional candidate for reactor instrumentation. Its radiation hardness stems from the strong carbon-carbon bonds, requiring approximately 43 eV to displace an atom, making it highly resistant to neutron-induced damage. Diamond-based neutron detectors leverage the material’s ability to generate electron-hole pairs when exposed to ionizing radiation. These detectors exhibit high sensitivity and fast response times due to diamond’s high carrier mobility (4500 cm²/V·s for electrons). However, carrier lifetime degradation remains a challenge, as radiation-induced defects create deep-level traps that reduce charge collection efficiency. Hydrogen termination and boron doping have been explored to passivate defects and enhance radiation tolerance.

Radiation-hardened silicon, while less thermally robust than SiC or diamond, remains relevant for certain reactor applications due to its mature fabrication technology and cost-effectiveness. Advanced hardening techniques, such as silicon-on-insulator (SOI) designs and epitaxial silicon layers, mitigate single-event effects and total ionizing dose (TID) damage. SOI structures reduce parasitic leakage currents by isolating active device regions from the substrate, while epitaxial silicon with low defect densities minimizes displacement damage effects. Silicon neutron detectors often employ enriched boron-10 or lithium-6 converters to enhance sensitivity, though long-term exposure to neutron flux can degrade performance due to boron depletion and lattice disorder.

Displacement damage in semiconductors arises when high-energy particles (neutrons, protons, or gamma rays) collide with lattice atoms, creating vacancies and interstitials. These defects act as recombination centers, reducing minority carrier lifetime and increasing leakage currents. In SiC and diamond, the impact is less severe due to their higher displacement thresholds, but carrier lifetime degradation still occurs at high fluences. Techniques such as pulsed annealing and optimized doping profiles help restore device performance.

Applications in nuclear reactor instrumentation include neutron detectors, temperature sensors, and control electronics. SiC-based neutron detectors utilize the (n,α) reaction with boron-10 coatings, offering high-temperature stability and radiation resistance. Diamond detectors, with their fast response and low noise, are ideal for real-time neutron flux monitoring. Temperature sensors based on SiC Schottky diodes or pn junctions provide accurate readings in harsh environments, leveraging the material’s thermal stability. Control electronics, such as SiC MOSFETs and gate drivers, enable reliable operation of reactor systems under high radiation and temperature conditions.

In summary, SiC, diamond, and radiation-hardened silicon technologies are critical for advancing nuclear reactor instrumentation. Their unique properties address the challenges of displacement damage and carrier lifetime degradation, ensuring reliable performance in extreme conditions. Continued research into defect mitigation and material optimization will further enhance their applicability in next-generation reactors.