Nanosecond pulsed laser-induced damage characteristics and mechanisms of 4H-SiC crystals

Background As a representative third-generation semiconductor, silicon carbide (SiC) exhibits excellent physical properties, including a wide bandgap, high thermal conductivity, and high breakdown field strength, and has been widely applied in emerging fields such as aerospace and new energy vehicles. However, the ultrahigh hardness of SiC poses substantial challenges to conventional contact-based mechanical processing. Nanosecond laser processing techniques, such as laser cutting and drilling, featuring high precision and high efficiency, have therefore become important approaches for SiC machining.

Purpose This work aims to systematically investigate the laser damage characteristics and physical mechanisms of high-purity SiC (HP-SiC) and nitrogen-doped SiC (N-SiC) under nanosecond multi-pulse laser irradiation.

Methods The laser-induced damage thresholds (LIDTs) of HP-SiC and N-SiC were systematically measured using the internationally standardized 1-on-1, S-on-1, and R-on-1 testing protocols. The influences of pulse number and repetition frequency during the S-on-1 test were further analyzed. Weak photothermal absorption measurements and damage morphology characterization were combined to investigate the physical origin of the differences in damage thresholds between the two SiC crystals under various irradiation conditions.

Results Comparative experiments showed that, under the internationally standardized 1-on-1, S-on-1, and R-on-1 testing protocols, the LIDTs of N-SiC crystals were consistently lower than those of HP-SiC crystals. However, the differences in damage thresholds between the two types of SiC crystals varied significantly among the three testing protocols.

Conclusions The higher absorption coefficient and stronger defect-related absorption of N-SiC at 1064 nm contribute to its lower laser-induced damage threshold than HP-SiC. Under multi-pulse irradiation, its weaker thermal diffusion capability enhances thermal accumulation, leading to a more pronounced reduction in the damage threshold.