High-energy particles in nuclear and space environments induce displacement damage in semiconductors, fundamentally altering their electrical and structural properties. This damage arises when particles such as protons, neutrons, or heavy ions collide with the semiconductor lattice, displacing atoms from their equilibrium positions. The resulting lattice defects, carrier trapping, and mobility degradation critically impact device performance and reliability. Silicon (Si), silicon carbide (SiC), and gallium nitride (GaN) exhibit varying degrees of tolerance to displacement damage, making them suitable for different applications in harsh environments.

Displacement damage begins when an incident particle transfers sufficient energy to a lattice atom, ejecting it from its site and creating a primary defect. The displaced atom may come to rest in an interstitial position, leaving behind a vacancy. These primary defects can further interact, forming complex defect clusters or secondary defects such as divacancies or antisite defects. In compound semiconductors like SiC and GaN, the displacement thresholds for constituent atoms differ, leading to non-stoichiometric damage. For instance, in GaN, nitrogen vacancies form more readily than gallium vacancies due to the lower displacement energy of nitrogen atoms.

The introduction of defects significantly alters carrier dynamics. Defect states within the bandgap act as trapping centers, capturing free carriers and reducing the majority and minority carrier lifetimes. Carrier trapping increases recombination rates, degrading the performance of optoelectronic and high-frequency devices. Mobility degradation occurs due to increased scattering from charged defects and lattice disorder. In Si, carrier removal rates are pronounced due to the formation of deep-level defects like the A-center (vacancy-oxygen complex) or E-center (vacancy-phosphorus complex). In contrast, SiC and GaN exhibit higher displacement thresholds and more stable defect configurations, leading to slower carrier removal rates under equivalent fluence.

Characterization techniques such as deep-level transient spectroscopy (DLTS) and transmission electron microscopy (TEM) are essential for studying displacement damage. DLTS identifies defect energy levels within the bandgap by analyzing capacitance transients induced by carrier emission from traps. For example, in irradiated Si, DLTS reveals prominent peaks corresponding to vacancy-related defects. In SiC, DLTS detects Z1/2 centers (carbon vacancy-related) and EH6/7 centers (silicon vacancy-related), which influence carrier lifetimes. TEM provides direct imaging of defect clusters and amorphized regions. High-resolution TEM can resolve interstitial loops in GaN or stacking faults in SiC, correlating structural damage with electrical degradation.

Comparing the displacement damage tolerance of Si, SiC, and GaN reveals stark differences. Silicon, despite its mature technology, suffers from rapid degradation under high fluences due to its relatively low displacement threshold energy (approximately 15 eV for Si atoms). High-energy particle exposure leads to swift amorphization and severe mobility reduction. Silicon carbide, with a displacement threshold energy around 35 eV for silicon atoms and 20 eV for carbon atoms, demonstrates superior resistance. The strong covalent bonding in SiC reduces defect mobility, limiting the growth of extended defects. GaN exhibits even higher resilience, with displacement thresholds of approximately 19 eV for gallium and 9 eV for nitrogen. While nitrogen vacancies form readily, GaN’s high bond strength and defect annealing at room temperature mitigate long-term damage accumulation.

In nuclear environments, where neutron fluences exceed 10^15 cm^-2, Si devices degrade rapidly, while SiC and GaN maintain functionality. SiC power devices, for instance, show stable operation up to neutron fluences of 10^16 cm^-2, making them suitable for reactor instrumentation. GaN-based high-electron-mobility transistors (HEMTs) excel in space applications due to their resistance to proton-induced displacement damage, critical for satellite electronics exposed to solar particle events.

The choice of semiconductor material depends on the specific radiation environment and operational requirements. Si remains viable for low-radiation applications due to its cost-effectiveness and processing maturity. SiC offers a balanced solution for moderate to high radiation levels, combining radiation hardness with high-temperature stability. GaN is optimal for extreme environments where both radiation tolerance and high-frequency performance are essential.

Understanding displacement damage mechanisms and employing advanced characterization techniques enable the development of radiation-hardened semiconductors. Continued research into defect engineering and material synthesis will further enhance the performance of SiC and GaN in nuclear and space applications, ensuring reliable operation in the most demanding conditions.