| Metadata | Details |
|---|
| Publication Date | 2021-11-27 |
| Journal | Sensors |
| Authors | Zhongming Zhang, Michael D. Aspinall |
| Institutions | Lancaster University |
| Citations | 5 |
| Analysis | Full AI Review Included |
- Core Value Proposition: This research validates the use of four Wide Band Gap (WBG) semiconductors (Diamond, SiC, Ga2O3, GaN) for thin-film solid-state neutron detectors, demonstrating their suitability for extreme environments (high temperature, high radiation).
- Optimal Performance: Diamond combined with a B4C converter layer showed the best overall performance, achieving the thinnest optimal semiconductor thickness (0.7 ”m at 300 keV LLD) and superior gamma rejection capability.
- Radiation Hardness Leader: GaN exhibited the highest radiation hardness, registering the lowest Displacement Per Atom (DPA) value (1.01 x 10-20 DPA·cm2/incident particle) under 1 MeV neutron flux.
- Commercial Viability: SiC paired with B4C is recommended as the most commercially viable option due to its thin optimal thickness, good performance metrics, and relatively mature manufacturing technology.
- Gamma Rejection: All four optimized materials successfully met the intrinsic gamma detection efficiency requirement of less than 10-6 pulses/incident neutrons, ensuring minimal false-positive counts.
- Charge Collection Efficiency (ECE): Diamond and SiC demonstrated high ECE (greater than 99.9%) even at low applied voltages (5 V), making them ideal for low-bias or zero-bias detector designs.
| Parameter | Value | Unit | Context |
|---|
| Simulation Tool | Geant4 10.7 | N/A | Used with FTFP_BERT_HP physics list |
| Neutron Source Energy (Optimization) | 0.025 | eV | Thermal neutron energy |
| Neutron Source Energy (Radiation Hardness) | 1 | MeV | Fast neutron flux simulation |
| Gamma Rejection Target | < 10-6 | Pulses/incident neutrons | Intrinsic detection efficiency |
| Optimal Thickness (Diamond + B4C, 300 keV LLD) | 0.7 | ”m | Thinnest semiconductor layer achieved |
| Optimal Thickness (Ga2O3 + LiF, 300 keV LLD) | 3.2 | ”m | Thinnest layer using LiF converter |
| Optimal Thickness (SiC + LiF, 900 keV LLD) | 13.2 | ”m | Thickest optimized layer simulated |
| DPA (GaN) | 1.01 x 10-20 | DPA·cm2/incident particle | Best radiation hardness performance |
| DPA (Diamond) | 1.30 x 10-20 | DPA·cm2/incident particle | Second best radiation hardness |
| Electron Mobility (Diamond) | ~2000 | cm2/V·s | Highest electron mobility |
| Electron Lifetime (SiC) | ~19 | ”s | Longest electron lifetime |
| Minimum ECE Operating Voltage (GaN/Ga2O3) | 45 | V | Voltage required for stable high ECE |
| Threshold Displacement Energy (Diamond) | 35 | eV | |
| Threshold Displacement Energy (GaN) | Ga:18, N:22 | eV | |
- Simulation Platform: All detector responses were modeled using Geant4 (version 10.7) utilizing the FTFP_BERT_HP physics list, which includes high-precision models for neutron interactions (elastic/inelastic scattering, capture, fission).
- Detector Geometry: A two-layer structure was simulated: an upper converter layer (B4C or LiF) and a bottom i-type semiconductor diode (Diamond, SiC, Ga2O3, or GaN). The active area was fixed at 1 cm2.
- Thickness Optimization: The optimal converter layer thicknesses were fixed based on prior work (e.g., B4C: 2.6 ”m for 300 keV LLD). Semiconductor thickness was then varied until the intrinsic neutron detection efficiency reached an asymptote, indicating full charged particle energy deposition.
- Low-Level Discriminator (LLD): Simulations were performed using two LLD settings (300 keV and 900 keV) to observe the influence of background rejection on optimal thickness and efficiency.
- Radiation Hardness Analysis (PKA/DPA): Detectors were simulated without a converter layer under a 1 MeV neutron flux. The Primary Knock-on Atom (PKA) energy spectrum was generated, and the Displacement Per Atom (DPA) was calculated using an early atomic displacement model (based on kinetic energy transfer and threshold displacement energy, Ed).
- Gamma Rejection Testing: The neutron source was replaced with 511 keV and 1460 keV gamma sources. The intrinsic gamma detection efficiency was calculated to assess the detectorâs ability to reject photon background.
- Electron Collection Efficiency (ECE): ECE was calculated using the single carrier Hecht Equation, incorporating published electron mobility (”) and lifetime (Ï) data for each material, across applied bias voltages from 5 V to 100 V.
- Nuclear Fission and Fusion: Essential for monitoring neutron flux in next-generation nuclear fission reactors and high-intensity environments required for nuclear fusion research.
- High-Temperature Electronics: WBG materials (Diamond, SiC) enable detector operation in high-temperature environments (Diamond tested up to 240 °C), where traditional Si detectors fail.
- Radiation-Hard Systems: Deployment in extreme radiation fields (e.g., near-core monitoring, high-energy physics experiments) where long service life and resistance to displacement damage (DPA) are critical.
- Space Nuclear Technology: Utilizing the high chemical stability and radiation resistance of WBG materials for reliable neutron detection in corrosive or high-radiation space environments.
- Commercial Neutron Detectors: SiC + B4C offers a high-performance, cost-effective alternative to diamond for commercial applications, benefiting from mature SiC manufacturing processes (MOCVD, MBE).
- Low-Bias/Zero-Bias Operation: Diamond and SiC detectors can be fabricated for low-power applications due to their high ECE at minimal applied voltages (as low as 5 V).
View Original Abstract
Third-generation semiconductor materials have a wide band gap, high thermal conductivity, high chemical stability and strong radiation resistance. These materials have broad application prospects in optoelectronics, high-temperature and high-power equipment and radiation detectors. In this work, thin-film solid state neutron detectors made of four third-generation semiconductor materials are studied. Geant4 10.7 was used to analyze and optimize detectors. The optimal thicknesses required to achieve the highest detection efficiency for the four materials are studied. The optimized materials include diamond, silicon carbide (SiC), gallium oxide (Ga2O3) and gallium nitride (GaN), and the converter layer materials are boron carbide (B4C) and lithium fluoride (LiF) with a natural enrichment of boron and lithium. With optimal thickness, the primary knock-on atom (PKA) energy spectrum and displacements per atom (DPA) are studied to provide an indication of the radiation hardness of the four materials. The gamma rejection capabilities and electron collection efficiency (ECE) of these materials have also been studied. This work will contribute to manufacturing radiation-resistant, high-temperature-resistant and fast response neutron detectors. It will facilitate reactor monitoring, high-energy physics experiments and nuclear fusion research.
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