Iron-doped β-Ga2O3 single crystal: the iron occupying site and optical properties

Abstract

β-Phase gallium oxide (β-Ga₂O₃) is an extra wide-bandgap semiconductor that has garnered significant attention for its immense potential in high-power electronic and optoelectronic applications. However, the high electron concentration due to the intrinsic defects restricts the applications of β-Ga₂O₃. Doping with Fe³⁺ can introduce deep acceptors that compensate background n-type conductivity, resulting in semi-insulating characteristics. Therefore, in this report, low-dose Fe³⁺ ions were doped in a β-Ga₂O₃ single crystal (SC) through the edge-defined film-fed growth method. Although the X-ray diffraction spectrum of the Fe-doped sample showed no distinct difference from that of the unintentionally doped sample, the UV-vis absorption and Fourier transform infrared spectra indicated the successful incorporation of Fe into the lattice of the β-Ga₂O₃ SC. Considering the calculated formation energies of Fe_GaI and Fe_GaII impurities together with the results of the angular-resolved polarization Raman spectra, it was revealed that trace Fe³⁺ ions mainly occupied the Ga_II site and greatly affected the symmetry of the Ga_IO₄ tetrahedra. The temperature-dependent photoluminescence spectra indicated that deep-level defects induced by introducing trace Fe ions greatly reduce the radiative recombination from donor–acceptor pairs. The identification of the site occupied by Fe ions helps to understand the impact of trace Fe on the crystal structure and optical properties, which provides insights for obtaining high-resistance β-Ga₂O₃.