Rare-earth impurities in III-V semiconductors and their alloys: dependence on doping site and charge state

Rare-earth (RE) impurities in semiconductors have attracted great attention due to the theoretical understanding they provide and their technological applications. One prominent example is Er-doped GaAs, which exhibit sharp, temperature-insensitive 4f-intrashell emission near 1.55 μm, perfectly matching the optimal transmission wavelength for silica optical fibers. Earlier research has shown that some RE can be substitutional while other REs occupy interstitial sites. The positioning of RE elements within the host lattice plays a crucial role in altering the electronic and optical characteristics of the semiconductor. In this study, we investigate the effects of rare-earth doping on III-V semiconductors, including AlAs, GaAs, and InAs, as well as their alloys. Using hybrid density functional theory and first-principles calculations, we analyze the incorporation of all lanthanide elements (from La to Lu) at both substitutional and interstitial lattice sites, considering multiple charge states beyond the neutral condition. We examine the thermodynamic stability of various RE configurations by calculating their formation energies and migration barriers. Our results shed new light on the behavior of rare-earth elements as dopants, offering valuable insights into their potential to improve the performance of III-V semiconductor devices through strategic manipulation of doping sites and charge states.