Point Defects in Lithium Gallate and Gallium Oxide
Technical Report,01 Sep 2016,13 Sep 2019
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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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 Ea 1.05 eV and gallium vacancies at Ea 2 eV below the conduction band minimum. Mg and Fe doped Ga2O3 crystals are investigated with EPR and FTIR and concentrations of Ir4 ions greater than 1018 cm3are observed. The source of the unintentional deep iridium donors is the crucible used to grow the crystal. In the Mg-doped crystals, the Ir4 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 Ir4 ions to have a low-spin 5d5, S12 ground state. The Ir4 ions have an infrared absorption band representing a d-d transition within the t2g orbitals. Using these same techniques the Fe2 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 Fe2 ions.
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