Study Of Electronic Structure And Optical Properties Of N-type β-Ga₂O₃

As a wide band-gap material, β-Ga2O3has attracted a wide range of interests due to itspotential applications in ultraviolet optoelectronic devices and conductance-based gas-sensingdevices. Recently, National Institute of Information and Communications Technology inJapan developed β-Ga2O3transistors. They found that β-Ga2O3is a very promising candidatefor power device applications because of its excellent material properties and suitability formass production. The wide band gap and the Baliga’s figure of merit (FOM) of Ga2O3aremuch larger than those of SiC and GaN. If we want to further improve the applications ofβ-Ga2O3, we should control the n-type and p-type doping effectively and accurately. P-typesemiconductors are hard to be fabricated and we studied n-type doping in β-Ga2O3.In this paper, first-principles calculations were performed to investigate electronicstructures and optical properties of Sn/F doped, different concentrations of F-doped and Tidoped β-Ga2O3. The results show that the mono-doping and co-doping of Sn and F lead toFermi energy shift into conduction band and turn β-Ga2O3into n-type semiconductor. Sn/Fco-doped β-Ga2O3is relatively easy to be formed under O-rich conditions with lower defectformation energy and F-doped β-Ga2O3is relatively easy to be formed under Ga-richconditions. Fermi-level in Sn/F co-doped Ga2O3shifts into the conduction band deeply. Theunstable electrons localize around Fermi energy may transit across a much little barrier, whichenhance the optical absorption in visible light region. The results of F-doped β-Ga2O3systemat various concentrations show that the electron effective mass becomes smaller, the relativeelectron number becomes larger and the occupied states become broader with an increase in Fcontent, which increases the conductivity of β-Ga2O3. That is, we can design some electricalproperties of Ga2O3by doping different F concentration. The optical band-gap becomesbroader and absorption edges are blue-shifted with F-doping concentrations. Thus, selecting asuitable doping level is crucial to optimize the photoelectric performance of F-doped β-Ga2O3.The results of Ti-doped β-Ga2O3system demonstrate that impurity bands introduced by Tidopant can act as intermediate bands, which could cause electron transitions from impuritybands to conduction bands and valence bands to impurity bands and then transition probabilitywill be enhanced. The band gap of intrinsic β-Ga2O3calculated by GGA+U method isconsistent with the experimental value.