Gallium oxide (Ga2O3), a wide-bandgap semiconductor, possesses the potential to perform well in a wide range of devices, including transparent conducting electrodes, photoelectrochemical water splitting and ultraviolet optoelectronic devices. For certain classes of power electronics, Ga2O3 could even outperform current state-of-the-art materials.
But first, researchers must be able to control the electrical and optical properties of Ga2O3, which means understanding its impurities. To learn more about these impurities, Stehr et al. identified the previously unknown electron paramagnetic resonance (EPR) signatures of cobalt (Co) and copper (Cu) in β-Ga2O3, a stable crystalline phase of Ga2O3. These transition metals are both impurities often found or used as dopants in Ga2O3.
EPR spectroscopy identifies impurities in semiconductors without destroying the material. The authors used this technique to determine the electronic signatures and geometric arrangement of Co and Cu in β-Ga2O3 bulk crystals and powder. They found that both Co and Cu are present in undoped β-Ga2O3 in the 2+ charge state and prefer to reside on the octahedral gallium lattice site.
“Cobalt can have a profound effect on the electrical properties by altering the Fermi level and, thus, device performance,” said author Jan Stehr. Copper can also alter device performance: Used as a dopant, it may introduce a shallow acceptor level, which might make Ga2O3 more suited for application in bipolar devices.
These obtained parameters can act as signatures of cobalt and copper and be used for their identification.
Source: “Electron paramagnetic resonance signatures of Co2+ and Cu2+ in β-Ga2O3,” by Jan E. Stehr, Detlev M. Hofmann, Jörg Schörmann, Martin Becker, Weimin M. Chen, and Irina A. Buyanova, Applied Physics Letters (2019). The article can be accessed at https://doi.org/10.1063/1.5127651.
