The Effect of Interfaces in Increasing the Radiation Damage Tolerance Demonstrated in GaAs/AlAs Superlattice

Recent studies have shown that heterostructures in oxide composite systems exhibit high radiation tolerance, which is hypothesized to be caused by defect annihilation/segregation at interfaces. We tested this hypothesis by studying Ga(Al)As heterostructures, consisting of GaAs bulk substrate, GaAlAs alloy, and GaAs/AlAs superlattice with varying interface densities. We grew the samples using molecular beam epitaxy (MBE), where the interfaces are defined with atomic precision. The samples were then irradiated with energetic protons to fluences of 10¹³ ions/cm² and 10¹⁴ ions/cm² to introduce lattice defects without amorphizing the samples. The positron annihilation spectroscopy (PAS) measurements demonstrated that the superlattice samples exhibit higher radiation tolerance compared to its bulk counterpart. In addition to PAS, we also did transient reflectivity measurement, where we observed a mechanism that suggests a photo-doping modification of defects in the samples with interfaces. This observation is supported by density functional theory calculations of the migration energy of charged and neutral lattice defects in the superlattices. Through this photo-doping mechanism, we might be able to find a new way to detect/characterize small defects, that are undetectable in transmission electron microscopy (TEM), in various materials.