Theoretical Study On Element Semiconductor MOSFETs With High ? Perovskite Oxide Gate Dielectric

It is indispensable in miniaturization of electronic components to explore the high ? gate dielectric material for element semiconductor metal-oxide-semiconductor high electron mobility transistor.The continued downscaling of element semiconductor metal-oxide-semiconductor field-effect transistors(MOSFETs)has led to the conventional gate dielectric becoming so thin that the gate leakage current becomes too large.The replacement of traditional gate dielectric with high-? oxides allows the thicker physical thickness of gate oxides to suppress the leskage current to meet the requirements of miniaturization of element semiconductor MOSFETs devices.We will study the microstructure and physical properties of the surface and interface of element semiconductor/perovskite oxide system using the density functional theory.Our study may provide a physical basis and physical insights for the growth and design of element semiconductor optoelectronic devices.Firstly,The replacement of traditional SiO2 with high-k oxides allows the physical thickness of the gate dielectric to be thicker without the tunneling problem in Si-based metal-oxide-semiconductor field-effect transistors.LaAlO3 appears to be a promising high-k materials for use in future ultra large scale integrated devices.The electronic properties of Si/LaAlO3(001)heterojunctions are investigated by first-principles calculations.We studied the Si atomic initial adsorption on the LaAlO3(001)surface,and found that Si adsorption atoms preferentially adsorb at the top sites of oxygen atoms under high coverage.The surface phase diagrams indicate that Si atoms may replace oxygen atoms at La O-terminated surface.The band offsets,electronic density of states,and atomic charges are analyzed for the Si/LaAlO3 heterojunctions.The Si/AlO2 interface is suitable for the design of metal oxide semiconductor devices because the valence and conduction band offsets are both larger than 1 eV.Secondly,Germanium-perovskite oxide heterostructures have a strong potential for next-generation lowvoltage and low-leakage metal-oxide-semiconductor field-effect transistors.We investigated the atomic structure and electric properties of Ge on perfect and defective(001)SrTiO3.The specific adsorption sites at the initial growth stage and the atomic structure of Ge on the SrTiO3(001)substrate have been systematically investigated.Both SrO and TiO2 terminations of STO(001)are considered,because they can be realizd in the theory and the experiment.The stable adsoption sites and electronic properties of Ge on the SrO and TiO2 terminations are calculated.The surface grand potential of Ge on the defective SrTiO3(001)was calculated and compared as function of the relative chemical potential.The complete phase diagram is presented.The ennrgetically favorable interfaces were pointed out among the atomic arrangements of Ge/SrTiO3(001).The atomic structure and electronic properties of the intrinsic point defects were calculated and analyzed for the Ge/SrTiO3(001).The physic properties of Ge/Sr TiO3 interfaces were also studied.Finally,we calculated the atomic structure and electric properties of the perfect and defective Ge/SrTiO3 interface.The substitution of Ge for Ti in the interface induces the occupied states at the upper valence band.They provide further integrating these materials into future complementary metal oxide semiconductor processing.