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Threading dislocations that are of a type were observed to form locally in InGaN layers and wells containing 7%-15% indium. Direct correlations between a type dislocations and stacking faults in InGaN layers and wells were observed. The formation of these dislocations is attributed to the dissociation of Shockley partials bounding the stacking faults. [ABSTRACT FROM AUTHOR]

We report the bandgap and electronic properties of wurtzite ZnO doped with elements IIA or/and IIIA, investigated using both theoretical and experimental methods. With wurtzite ZnO co-doped with B and Mg (denoted as ZnO:[B,Mg]) grown via metalorganic chemical vapor deposition, we have observed that both the bandgap and the conductivity can be widely tunable with the doping levels. From first-principles calculations of wurtzite ZnO:Mg, we show that IIA doping elements have a great impact on the widening of the bandgap. Also, from a newly developed calculation method for investigating the electronic properties of wurtzite ZnO:Al, we have found that IIIA doping elements play an important role in tailoring the conductivity. [ABSTRACT FROM AUTHOR]

We investigated the spin-transfer switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar through micromagnetic simulation. A two-step switching hysteresis loop due to the fourfold in-plane magnetocrystalline anisotropy of Co2FeAl0.5Si0.5 layers was obtained. The simulation explains the experimental result of the resistance versus current hysteresis loop and yields good agreement with the measured critical current. Furthermore, the magnetization trajectory and magnetization distribution were shown and analyzed to elucidate the different characters of two-step switching. [ABSTRACT FROM AUTHOR]

Predicting the domain structures and properties in both bulk single crystal and thin film ferroelectrics using the phase-field approach requires the knowledge of fundamental mechanical, electrical, and electromechanical coupling properties of a single-domain state. In this work, the elastic properties and structural parameters of cubic single crystals as well as tetragonal, orthorhombic, and rhombohedral BaTiO3 single domain states are obtained using first-principles calculations under the local density approximation. The calculated lattice constants, bulk modulus, and elastic constants are in good agreement with experiments for both the cubic paraelectric phase and the low-temperature ferroelectric phases. Spontaneous polarizations for all three ferroelectric phases and the electrostrictive coefficients of cubic BaTiO3 are also computed using the Berry’s phase approach, and the results agree well with existing experimentally measured values. [ABSTRACT FROM AUTHOR]

The temperature- and growth-dependent Urbach band-tail characteristics in polysilicon wafers have been investigated both experimentally and theoretically for the improvement of solar cells. The band-tail parameter in polysilicon has been obtained by temperature-dependent transmission spectra, with the aid of a detailed calculation of the transmission profile. The band-tail parameter is in the range of 30-90 meV in polysilicon. A band-tail model based on the calculation of density of occupied states and the carrier-phonon interaction has been employed to analyze the temperature-dependent band-tail characteristics. It is found that the yielded structural information can be well explained by Raman measurements. We have correlated various aspects of the observed structural properties, such as the band-tail parameter, trap concentration, grain-surface charge density, and correlation length, with the conversion efficiency of the polysilicon solar cells. [ABSTRACT FROM AUTHOR]