Point Defects in Lithium Gallate and Gallium Oxide
Abstract
Electron paramagnetic resonance (EPR), Fourier-Transform Infrared spectroscopy (FTIR), photoluminescence (PL), thermoluminescence (TL), and wavelength-dependent TL are used to identify and characterize point defects in lithium gallate andGa2O3 doped with Mg and Fe acceptor impurities single crystals. EPR investigations of LiGaO2 identify fundamental intrinsiccation defects lithium and gallium vacancies. The defects' principle $g$ values are found through angular dependence studies and atomic-scale models for these new defects are proposed. Thermoluminescence measurements estimate the activation energy of lithium vacancies at E_a = 1.05 eV and gallium vacancies at E_a > 2 eV below the conduction band minimum. Mg and Fe doped Ga2O3 crystals are investigated with EPR and FTIR and concentrations of Ir^4 ions greater than 10^{18} cm^3are observed. The source of the unintentional deep iridium donors is the crucible used to grow the crystal. In the Mg-doped crystals, the Ir^4 ions provide compensation for the singly ionized Mg acceptors contributing to the difficulties in producing p-type behavior in bulk single crystals. A large spin-orbit coupling causes Ir^4 ions to have a low-spin (5d^5, S=1/2) ground state. The Ir^4 ions have an infrared absorption band representing a d-d transition within the t_2g orbitals. Using these same techniques the Fe^2 /3 level in Fe-doped Ga2O3 crystals is determined. With these noncontact spectroscopy methods, a value of 0.83 \pm 0.04 eV below the conduction band is obtained for this level. These results clearly establish that the E2 deep level observed in DLTS experiments is due to the thermal release of electrons from Fe^2 ions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 14, 2019
- Accession Number
- AD1084594
Entities
People
- C. A. Lenyk
Organizations
- Air Force Institute of Technology