Enhanced photoanode properties of epitaxial Ti doped α-Fe2O3 (0001) thin films Appl. Phys. Lett. 101, 133908 (2012) Structure and optical band gap of ZnO1−xSx thin films synthesized by chemical spray pyrolysis for application in solar cells J. Appl. Phys. 112, 063708 (2012) Roto-flexoelectric coupling impact on the phase diagrams and pyroelectricity of thin SrTiO3 films J. Appl. Phys. 112, 064111 (2012) Plasmonic effects of ultra-thin Mo films on hydrogenated amorphous Si photovoltaic cells

The crystalline structure near the substrate interface has been studied for AlGaN films grown on (0001) sapphire substrates by metalorganic chemical vapor deposition, using AlN buffer layers. Transmission electron lattice images show that the sapphire/AlN interface is coherent, with misfit dislocations separated by 2.0 nm, corresponding to relaxed bulk lattice parameters. The interface between the buffer layer and the AlGaN film is discussed. The defect structure of the epilayer near the substrate interface consists mostly of dislocations and stacking faults lying on basal planes.

The effects of background doping, surface encapsulation, and As4 overpressure on carbon diffusion have been studied by annealing samples with 1000 Å p-type carbon doping spikes grown within 1 μm layers of undoped (n−), Se-doped (n+), and Mg-doped (p+) GaAs. The layers were grown by low-pressure metalorganic chemical vapor deposition using CCl4 as the carbon doping source. Two different As4 overpressure conditions were investigated: (1) the equilibrium pAs4 over GaAs (no excess As), and (2) pAs4 ∼2.5 atm. For each As4 overpressure condition, both capless and Si3N4-capped samples of the n−-, n+-, and p+-GaAs crystals were annealed simultaneously (825 °C, 24 h). Secondary-ion mass spectroscopy was used to measure the atomic carbon depth profiles. The carbon diffusion coefficient is always low, but depends on the background doping, being highest in Mg-doped (p+) GaAs and lowest in Se-doped (n+) GaAs. The influence of surface encapsulation (Si3N4) and pAs4 on carbon diffusion is minimal.

High-resolution X-ray diffraction measurements can be performed at variable temperatures and pressures. The usefulness of such experiments is shown when taking gallium nitride, which is a wide-band semiconductor, as an example. The GaN samples were grown at high pressures (bulk crystals) and as epitaxial layers on silicon carbide and sapphire. The X-ray examinations were done at temperatures of 293-750 K and at pressures of up to 8 kbar. The results served for an evaluation of the basic physical properties of gallium nitride; namely lattice constants, thermal expansion and compressibility. The comparison of monocrystals with epitaxial layers grown on highly mismatched substrates provided important information about the influence of the substrate on the crystallographic perfection of the layers.

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