Highly (00l)-textured antimony telluride films were fabricated using molecular beam epitaxy (MBE) on Si (111) substrate at 280 °C. X-ray diffraction analysis implying the samples have good crystalline quality, simultaneously, the grain sizes coarsening with increasing thickness. The results of Hall coefficient measurement demonstrated that the carrier concentration and mobility are strongly affected by grain boundaries and microcrystalline internal defects. It was found that the grain boundaries play a primary factor influencing the carrier concentration in thinner film. At room temperature, the results in a maximum mobility value of 305 cm2/Vs for 121-nm-thick film, and the electrical conductivity increased from 425.7 S/cm to 1036 S/cm as the thickness varied from 28 nm to 121 nm. In the range of room temperature to 150 °C, the resistivity almost linearly increased with increasing temperature. This may be explained by low concentration of impurities or defects and shallow impurity band. For difference thickness films, temperature coefficients of resistivity are substantially equal, and the values are about 3 ∼ 4 μΩ⋅cm/K.
We have characterized an InGaP/InGaAsN/GaAs NpN double-heterojunction bipolar transistor structure using polarized photoreflectance (PR) spectroscopy. The ordering parameter of the InGaP is deduced from the polarization {[110] and [11̄0]} dependence of the PR signals from the emitter region. The ordering related piezoelectric field is also found to influence the electric field, as evaluated from observed Franz–Keldysh oscillations, in the InGaP emitter region. The field in the emitter region is found to be about 25 kV/cm smaller than the theoretical value that does not take into account the possible ordering induced screening effect, while the field in the collector region agrees well with the theoretical value. In addition, the InGaAsN band gap is also determined by analyzing the PR spectrum of the base region.
The variations of the electrical resistivity, the magnetization, and the grain-boundary precipitates of a Ni-rich Ni-In alloy system with In concentration up to 7.5 at. % have been investigated as functions of annealing time at 773 K. For samples homogenized at 1225 K, clear grain boundaries are,observed. However, for these aged samples, we observed both grain-boundary precipitates and variations of the electrical resistivity and the magnetization; and the binary alloy with higher In concentration has the higher variation rate in the decrease of the electrical resistivity, the increase of the magnetization, and the growth of the grain-boundary precipitates.
We report a detailed temperature dependent study of polarized piezoreflectance (PzR) for two AlInP2 epilayers that exhibit different degree of ordering in the range between 23 and 500 K. The polarized PzR measurements showed anisotropic character along the [110] and [110] directions for the partially ordered sample. The PzR spectra were fitted using the first-derivative of a Lorentzian line shape functional form. The direct band-, crystal field splitting- and spin-orbit splitting to conduction band transition energies which are denoted as E
g, E
g+ΔE
12 and E
g+ΔE
13 respectively, at various temperatures were accurately determined. The temperature dependence of these near direct band-edge critical points transition energies were analyzed by the Varshni expression and an expression containing the Bose-Einstein occupation factor for phonons. The parameters that describe the temperature variation of transition energies were evaluated and discussed.
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