Theoretical And Experimental Study On N-doped Ga₂O₃Films

With the development of semiconductor optoelectronic technology, wide band-gaptransparent conductive oxide gallium oxide （Ga₂O₃） thin films have been one of theresearched focuses in semiconductor material fields. The monoclinic β-Ga₂O₃is the moststable structure at room temperature. β-Ga₂O₃crystallizes in a monoclinic （C2/m）. The doublechains of octahedron [GaO₆] that are parallel to the b-axis of the lattice and the chains areconnected by tetrahedron [GaO₄] to one another. This structure is conductive to the movementof the electrons.In this paper, we used the theoretical and experimental method to study the preparationand properties, and discuss the widely applications of β-Ga₂O₃thin films in the moderntechnology. The electronic structure and optical properties of N-doped β-Ga₂O₃, differentconcentrations of N-doped β-Ga₂O₃and N-Zn co-doped β-Ga₂O₃have been studied byfirst-principles. The results indicate the acceptor impurity levels in the three kinds of dopingare introduced above the valence band and intersected with the Fermi level. All the kinds ofdoping are holp to get P-types materials. The impurity absorption edges of N-doped β-Ga₂O₃and different N concentrations of N-doped β-Ga₂O₃are red-shifted. However, the mainabsorption peak is red-shifted and the impurity absorption edge is blue-shifted in N-Znco-doped β-Ga₂O₃.The intrinsic β-Ga₂O₃and N-doped β-Ga₂O₃thin films were successfully fabricated bythe radio frequency （RF） magnetron sputtering method on Si substrates and ultraviolet （UV）transparent quartz substrates. The effects of N-doping and post-annealing on the optical andstructural properties of β-Ga₂O₃films were studied. The structure, optical and surfacemorphology properties of the samples were characterized using X-ray diffraction, scanningelectron microscope, fluorescence spectrometer and ultraviolet spectrophotometer. Theexperimental results show the crystalline quality of the thin films has no obvious differencewith the increasing of N doping concentrations. But the crystalline quality of the thin filmsdecreases after annealing in vacuum. The transmittance is largely decreased and theabsorption is increased with the increasing of N impurity concentration. Comparing withas-deposited β-Ga₂O₃films of the same ammonia partial ratios, the transmittance of N-dopedβ-Ga₂O₃obviously deteriorates after annealing, and the corresponding absorption is increased.