Wiley

In this paper, we investigate gallium co‐doping during CZ crystallization of boron and phosphorus compensated Si. It is shown that the addition of gallium yields a fully p‐type ingot with high resistivity despite high B and P contents in the silicon. Segregation of doping impurities is consistent with theory. Minority carrier lifetime and majority carrier mobility measurements indicate that this material is suitable for the realization of solar cells with comparable efficiencies to standard material. Significant light‐induced degradation of minority carrier lifetime is however revealed to occur in this material. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Transparent conducting undoped and indium‐doped zinc oxide (ZnO) thin films have been deposited by the spray pyrolysis method at 350 °C substrate temperature. X‐ray diffraction spectra of the films have shown that the films are polycrystalline and hexagonal wurtzite in structure. The average optical transmittance of 1% indium‐doped ZnO thin films was over 84% in the visible range. The direct band gap value of the undoped ZnO film was calculated. Electrical conductivity measurement of Ag‐ZnO:In‐Ag structures have been carried out using the two‐probe method in dark, in the range of temperature from 90 to 320 K. The conductivity of undoped and indium‐doped ZnO films increases with increase in temperature. The incorporation of indium in the ZnO film enhanced the conductivity. The conductivity of 1 at.% In‐doped film is higher than undoped ZnO at room temperature. The activation energies E_a values in the range of 90‐320 K temperatures were also determined. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In this research, the effect of silver doping on Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_y ceramic superconductor has been investigated. The solid‐state reaction method and two different silver doping methods has been used, namely, doping during making processes of samples (batch 1) and doping after making Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_y superconductor (batch 2). We observed that by adding silver to BPSCCO compound, partial melting temperature of the compound is decreased. The critical current density (J_c) in both batches is affected by Ag doping. The investigation of SEM images of samples has shown that the all surfaces of the samples are porous and the grains are plate like. It seems that the BPSCCO grains in batch 1 samples are coated with silver but in the samples of batch 2, the silver also sits between the BPSCCO grains. The XRD patterns studies indicated that the silver peaks form separate phase and also by adding silver to BSCCO, the BPSCCO peaks do not show considerable shift. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We report details about the quantitative analysis of B and P impurities in the concentration range between 1 × 10¹⁴ and 1 × 10¹⁷ cm^–3 by photoluminescence (PL) in solar‐grade Si (SOG‐Si). The intensity ratio of impurity‐bound exciton (BE) to free exciton (FE) at 4.2 K was used as a measure of the impurity concentration in the range between 5 × 10¹⁰ and 1 × 10¹⁵ cm^–3 in the standard PL method. We raised the sample temperature to enhance the FE emission, which enabled us to extend the concentration range higher. The sample temperature was accurately determined from the FE‐line shape. We deduced a formula for the determination of the B and P concentrations in the higher range from the BE/FE ratio and the sample temperature (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Epitaxial growth characteristics of nonpolar (M‐ and A‐plane) ZnO on M‐ and R‐plane sapphire substrates were investigated. The growth of ZnO along the c‐axis direction, which aligns parallel to [2‐1‐10] and [01‐11] directions of M‐ and R‐plane sapphire, is achieved under lower growth temperature and/or VI/II ratio, and this growth direction is preferable for smooth lateral growth. Increasing the growth time, the surface becomes rough on M‐plane, while is significantly improved on R‐plane sapphire. The growth behaviour on R‐plane sapphire can be attributed to the small lattice mismatching along the ZnO c‐axis direction and enhanced lateral growth characteristics. From photoluminescence measurements, the appearance of peak at 3.383 eV, which is at higher energy compared to well‐known impurity‐ and/or defect‐related peaks, at 10 K suggests the residual strain in ZnO films. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

GaN films with thickness up to 3 mm were grown by halide vapour phase epitaxy method. Two growth modes were observed: the high temperature (HT) mode and the low temperature (LT) mode. Films grown in HT mode had smooth surface, however the growth stress was high and caused cracking. Films grown in LT mode had rough surface with high density of V‐defects (pits), however, such films were crack‐free. The influence of growth parameters on the pit shape and evolution was investigated. Origins of pits formation and process of pit overgrowth are discussed. Crack‐free films with smooth surface and reduced density of pits were grown using combination of the LT and HT growth modes. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The variations in surface potential and the Schottky barrier height Φ_B in fluorine‐plasma‐treated Al_xGa_1‐xN/GaN heterotructures are systematically studied by x‐ray photoelectron spectroscopy (XPS), giving insights into the mechanisms underlying the strong threshold voltage shift in Al_xGa_1‐xN/GaN HEMTs by the F plasma treatment technology. It is found that the treatment resulted in a fluorinated surface containing masses of AlF₃, with the surface potential of Al_0.25Ga_0.75N/GaN heterostructure increased by ∼0.38 eV during the first 60 seconds of the treatment. Annealing at 400 °C in N₂ ambient for 10 minutes does not affect the surface potential, but results in quick reduction of AlF₃, consistent with the relative poor thermal stability of AlF₃ reported in literature. Φ_B between Ni and F‐plasma‐treated Al_0.25Ga_0.75N surface was extrapolated from the shift in Ga 2p_3/2 core‐level and exhibits a small increase of 0.20 eV. The enhanced Φ_B is much smaller than the positive shift in V_th observed from HEMTs fabricated with the same treatment conditions, suggesting that the primary factor responsible for the conversion from depletion‐mode to enhancement‐mode Al_xGa_1‐xN/GaN by F plasma treatment is not the surface modifications, but rather the negative fixed charges carried by F ions in Al_xGa_1‐xN/GaN heterostructures. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Samples of doped and undoped a‐Si:H were deposited at temperatures ranging from 100 ºC to 350 ºC and then submitted to different dehydrogenation temperatures (from 350 ºC to 550 ºC) and times (from 1 h to 4 h). a‐Si:H films were characterised after deposition through the measurements of specific material parameters such as: the optical gap, the conductivity at 25 ºC, the thermal activation energy of conductivity and its hydrogen content. Hydrogen content was measured after each thermal treatment. Substrate dopant contamination from phosphorus‐doped a‐Si thin films was evaluated by SIMS after complete dehydrogenation and a junction depth of 0.1 mm was obtained. Dehydrogenation results show a strong dependence of the hydrogen content of the as‐deposited film on the deposition temperature. Nevertheless, the dehydrogenation temperature seems to determine the final H content in a way almost independent from the initial content in the sample. H richer films dehydrogenate faster than films with lower hydrogen concentration (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In this work, the electrical and electroluminescence properties of para‐hexaphenylene (p6P) thin films and nanofibers have been investigated in a field‐effect transistor device configuration with interdigitated source‐drain bottom contact electrodes. P‐type behavior of thin films is observed with a mobility of 1×10^‐6 cm²/Vs and a threshold voltage around ‐30 V. AC gated devices show electroluminescence for both thin films and stamped nanofibers even when the drain electrode is floating. This suggests either hole and electron injection from the same electrode or impact ionization. The highest electroluminescence intensity is observed from thin film FETs with a 2.5 µm source‐drain gap. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)