A systematic density functional theory study of the electronic structure of bulk and (001) surface of transitionmetals carbidesThe effect of in-plane lattice strain on the atomic and electronic properties of low-index transition metal ͑M = Ti, Nb, and Ta͒ carbide surfaces is studied by first-principles molecular dynamics calculations using a pseudopotential plane-wave technique. The most stable cubic rock-salt phase is considered for carbides. The first-principle study of various ͓͑001͒, ͑110͒, and metal-terminated ͑111͔͒ carbide surfaces reveals that both compressive and tensile strains strongly affect surface relaxation and electronic properties ͑work function values and band structures͒. The most stable ͑001͒ carbide surfaces exhibit rumpling between transition metal and carbon atoms in the topmost surface layers, which depends on the applied strain. The work function ͑WF͒ for the metal-terminated ͑111͒ surfaces varies monotonically, rather strongly depending on the applied strain ͑the range of variation reaches about 1 eV͒, while the WF for the ͑001͒ surface varies nonmonotonically with a much smaller resulting variation over the wide range of the applied strains. Surface energy calculations show that surface stability is also governed by the applied strain.

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In this work we report the results of theoretical study based on first‐principles calculations of the polarization properties of semiconductors AlN, GaN and AlGaN with wurtzite structure. The values of the spontaneous and the piezoelectric polarizations and the piezoelectric constants were calculated for these nitride compounds. We study the nonlinear dependence of the spontaneous polarization on AlGaN composition. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The computational scheme of multiscale modeling of semiconductor heterostructures is presented. Three scale levels are taken into account. On the atomic level the system is described using crystallographic information and quantum‐mechanical model. Ab initio modeling allows to determine the electronic structure, define polarization effects and calculate charge densities on the interfaces between layers. Obtained information is used in the nanoscale level model for the calculation of the charge carrier distribution in the heterostructure. At this level mathematical model contains the system of conjugated Schrödinger and Poisson equations. The carrier density distributions over the lateral direction of the multilayered structure and 2DEG localization are of the most interest at this point. This data is used in the next scale level model where electron mobility is calculated. A wide range of electron scattering mechanisms are taken into account during this calculation. This approach was applied to model 2DEG in AlGaN/AlN/GaN heterostructures. The good agreement between calculated values of interface charge density, 2DEG electron concentration, electron mobility and known experimental data was achieved. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)