First-Principles Study On The Interface Structures Of The Gallium Nitrided Epitaxial Growth On The Silicon Carbide

In the semiconductor industry, the core technology dominating the development of blue light LED is the property of nitrided gallium film, and the substrate material is the primary factor that affects the quality of the epitaxial gallium nitrided film. Choosing a better substrate material can contribute to higher effective of reducing the defects in the film growth. While the silicon carbide as the epitaxial growth gallium nitrided's substrate, has a good performance in chemical stability, electric conductivity and heat conduction, and has the characteristics of nonabsorbing visible light. The mismatch between the silicon carbided and the gallium nitrided is 4.2 %. Therefore the silicon carbided has the enormous superiority than the sapphire or the silicon substrate. In a word, the heoretical study on the interface structure of silicon carbided epitaxial growth gallium nitrided is necessary to understand the influence of the substrate to the epitaxial film.In this work, to study the characteristic of the interface structure in the preliminary stage of epitaxial film growth, the structure of energy bands, the density of states, the electron density difference and the Mulliken population of the SiC, GaN primitive cell and the SiC/GaN interface are calculated and analyzed with the implementation of the ultra soft pseudopotential, based on the first principle computation of the density functional theory, the exchange potential derived from the generalized gradient approximate (GGA) , as well as the arbitrary function derived from PBE,The most stable structures is found along the (001) direction in the interfaces between Si-N and C-N,after the geometry optimization, The fundamental research indicated that the electrons mainly distributes in C, N and Ga atoms periphery in the interface, when the substrate adsorbs the N atomic at the top position with the end surface of silicon. The atomic charge density of C and N mainly increases on the p orbit, which proved that the very strong covalence function between Si-N and Si-C exits. Moreover, the bond population of Si-N has increases when adsorbtion occured at the bridge position, which forms the stable four coordination covalent bonds between N atoms and Si atoms with the bond length staying at 1.852 nm, while the binding energy is -5.5786 eV, lower than -4.7490 eV at the top position. When the substrate take C as an end surface, the C-N duplet bond between the C atom and the N atom is formed, the bottom of conduction band and the top of valence band has few overlapping in the Fermi level, and the pseudogap occurs, which reflected the neighboring two atoms had strong bonding effect. The binding energy is -5.5489 eV, bigger than -5.5786 eV the binding energy of Si surface adsorb N at the top position. However, the structure will tend to be the top position model after the optimal process, when the adsorption occured at the bridge position, it concludes that the lowest energy achieved at the top position.