Research on neutron irradiation damage in GaAs-based IR LEDs

GaAs has become an indispensable material in semiconductor devices due to its exceptional electron mobility, high photoelectric conversion efficiency, and direct bandgap structure. However, in environments exposed to neutron radiation-such as space exploration, particle physics experiments, and nuclear technology applications-the performance of GaAs may be significantly compromised. To thoroughly investigate the damage mechanisms of GaAs under neutron irradiation, this paper employs the Geant4 Monte Carlo toolkit to simulate and calculate the transport processes of neutrons in centimeter-scale GaAs materials within the energy range of 1 to 20 MeV. Additionally, a detailed analysis of the spatial distribution and energy spectrum of the generated primary knock-on atom (PKA) is conducted. The non-ionizing energy loss (NIEL) of neutrons at various energies in GaAs is calculated concurrently. The research results indicate that, along the direction of neutron incidence, PKAs are generally uniformly distributed. As they diffuse outward, they approximately exhibit a Gaussian distribution with sharp peaks, with the majority of PKAs concentrated at the low-energy end. With an increase in incident neutron energy, the types and energy spectra of PKAs become more varied, and the PKAs generated by nuclear reactions gradually increases. The scattering angles of PKAs are primarily distributed around 20°, 50°, and 80°. As the neutron energy rises, the scattering angles gradually converge towards larger values. The NIEL calculation results demonstrate that, at lower energies, elastic scattering is the predominant source of the irradiation effects in GaAs. As the energy of the incident neutrons continues to increase, the PKAs produced by nuclear reactions will result in more significant NIEL. At the centimeter scale, increasing the thickness of the target material does not substantially alter the NIEL value, indicating that the damage caused by monoenergetic neutrons has good penetration. Furthermore, this study revealed the specific contributions of various PKA types, such as H, He, Ga, and As, along with their energy spectra at different energy levels. Notably, the NIEL reached its maximum value around 10 MeV, indicating that neutrons at this energy cause the most significant structural damage to GaAs. These results provide microscopic physical insights into the displacement damage mechanisms, offering crucial guidance for radiation-resistant design and advanced defect modeling of GaAs-based devices in neutron environments.