Rare-earth impurities in III-V semiconductors and their alloys*

Rare-earth impurities in semiconductors have long been studied theoretically and experimentally, with implications for both basic and applied sciences. For example, Er-doped GaAs, known for its sharp and temperature-independent 4f-intrashell emission near 1.55 μm, aligns with the lowest attenuation wavelength of silica-based optical fibers. Early experimental results suggested that Yb substitute on the In in InP, while Er was found to occupy interstitial sites. The location of the rare-earth impurity in the lattice of the semiconductor may well be related to how it modifies the electronic and optical properties of the host material. In this presentation, we discuss the interaction between rare-earth doping and III-V semiconductors, such as AlAs, GaAs, and InAs, and their alloys. Using first-principles calculations based on hybrid density functional theory, we explore the incorporation of La, Gd, Er, and Lu into interstitial and substitutional sites of the zinc blende lattice, considering possible charge states of the impurity other than the neutral state. The choice of rare-earth impurities covers the different occupations of the 4f shell, from completely unoccupied to half occupied, to fully occupied. We analyze the stability of the rare-earth impurity configuration not only through their formation energy but also through their migration barriers. Our calculations provide valuable insights into the behavior and properties of rare-earth elements as dopants in semiconductors, contributing to a better understanding of their potential to enhance the performance of III-V semiconductor devices.