Wang Ren-Zhi

Stability and electronic structures of the polar diamond/boron-nitride(001) interface

Abstract Structural stability and Electronic structures of polar (001) diamond/cubic-boronitride (c-BN) interface are investigated employing the generalized gradient approximation (GGA) and the first-principles pseudopotential approach. Results for the atomic relaxation at the interface, formation energies, and valence-band offsets are presented for the reconstructed interface with one mixed layer and lateral (1×2) and c(2×2) arrangements. The valence-band offsets of diamond/c-BN(001) depend strongly on the chemical composition of the interface layer but are less sensitive to the type of atomic arrangement at the interface. The calculated formation energies indicate that the diamond/c-BN(001) heterojunction is thermodynamically unstable.

Valence offsets of three series of alloy heterojunctions

Electron structure of three series of alloy heterojunctions (GaAs)x(Ge2)1-x/Ge,(AlAs)x(Ge2)1-x/Ge and AlxG1-xAs/Ge are calculated by linear muffin-tin orbital method with atomic-sphere approximation using the average-bond-energy theory in conjunction with a cluster expansion method. The results indicate the variations of ΔEν(x) at heterojunctions (GeAs)x(Ge2)1-x/Ge and (AlAs)x(Ge2)1-x/Ge are nonlinear, which are very different from that of AlxGa1-xAs/Ge.

Electronic Structure of Beta Silicon Nitride

Electron structure of silicon nitride β-Si3N4 was calculated by LMTO-ASA method cooperated with the use of Lowdin perturbation technique that saved computation time considerably. The results are in good agreement with that of ab initio pseudopotential method and indicate that appropriate setting of empty spheres is especially important for a crystal with a widely open structure.

Band offset and optical property of (ZnS)(n)/(Si-2)(n)(110) superlattice

Supercell self-consistent calculation of band structures of (ZnS)n/(Si2)n (110) (n = 2, 3, 4, 5) has been performed by means of linear muffin-tin orbitals method. The valence-band offset of such systems is calculated by frozen optential method and their Joint density of states has been computed by tetrahedron method. Our results show that the (ZnS)n/(Si2)n (110) superlattices have a large valence-band offset and their optical properties integrate exellent optical properties of bulk ZnS and that of Si.

Electronic Structures of Wurtzite Compounds GaN, AlN and Strained-Layer Superlattice (Ga2N2)1(Al2N2)1 (001)

The electronic structures of wurtzite compounds GaN, AlN and strained-layer super-lattice (SLS) (Ga2N2)1(Al2N2)1 (001) constituted by straining GaN-layer to match the lattice constant of AlN according to the elastic theory are studied with the first-principles Linearized-Muffin-Tin-Orbitals band-structure method. The band offsets at the SLS are determined by the frozen potential approach. The results of the bulk materials are in good agreement with available experimental data.

AB INITIO CALCULATIONS OF OPTICAL PHONON DEFORMATION POTENTIALS IN DIAMOND AND ZINC-BLENDE SEMICONDUCTORS

Ab initio calculations of optical-phonon deformation potentials (ODPs), i. e., d0, d30, d10 (val) and d10 (con) for sixteen semiconductors were carried out systematically. The calculations are based on the LMTO-ASA band-structure method within the framework of the frozen-phonon approximation model, in which the displacement of empty sphere is considered to match its atomic sphere partners. We have compared the d0 values obtained by several different theoretical calculation methods and studied the main factors affecting them. It is pointed out that the two different models (rhombohedral strain model and frozen-phonon model) for calculations will lead to different results of d0.

Optical-Phonon Deformation Potentials in Diamond-Structure Crystals: ab initio LMTO-ASA Calculation

The optical-phonon deformation potentials of C, Si, Ge and Sn are calculated by LMTO-ASA approach within the frosen-phonon approximation. The comparisons between our results and those of several present theoretical calculations and experiments demonstrate that our calculation model is reasonable.