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Abstract: ZnO/ZnS bilayer antireflection coatings have been prepared by spray pyrolysis using aqueous solutions of zinc acetate and thiourea or zinc chloride and thiourea. The structure, surface morphology, chemical composition and optical transmittance of the bilayer have been examined as a function of the composition of the initial solution. X-ray photoelectron spectroscopy analysis and Ar ion-beam sputter etching was carried out to obtain a depth profile of bilayer. Neither carbon nor other by-products, which could alter the optical transmittance of the bilayer were found in either the interface or bulk. The differences between the bilayers arise from the annealing of the ZnS underlayer, as well as the precursor used to prepare it. [Copyright &y& Elsevier]

Abstract: Influence of the applied electric field (AEF) on the intersubband transitions (ISBTs) in symmetric Al x Ga1− x N/GaN double quantum wells (DQWs) is investigated by self-consistent calculation. It is found that three- and four-energy-level DQWs can be realized when suitable electric field is applied. When the AEF is 0.93 MV/cm, the 1odd–2even ISBT has a comparable absorption coefficient with the 1even–2odd ISBT, and the four-energy-level DQWs are realized. The wavelengths of the 1odd–2even and 1even–2odd ISBTs are located at 1.31 and 1.62 μm, respectively. When the AEF is 1.10 MV/cm, the 1odd–2even and 1odd–2odd ISBTs have comparable absorption coefficients, and the three-energy-level DQWs are realized. The wavelengths of the 1odd–2even and 1odd–2odd ISBTs are located at 1.30 and 1.55 μm, respectively. The results suggest promising application to two-color optoelectronic devices operating within optical communication wavelength band, and this study also provides a method for realizing the two-color optoelectronic devices by using the AEF. [Copyright &y& Elsevier]

Abstract: Quantum wells of GaSb were grown by molecular beam epitaxy on GaAs substrates. The buffer layer and barrier layers consisted of relaxed AlAs x Sb1− x . The composition of the AlAs x Sb1− x was varied to produce compressive biaxial strains in the GaSb. The confinement and strain in the GaSb quantum wells lift the degeneracy in the valence band, resulting in lower in-plane effective mass and higher mobility. A three-fold enhancement of mobility was achieved, with room-temperature mobilities as high as 1350cm2/Vs and 77K values as high as 10,400cm2/Vs for strains near 1%. These quantum wells should be suitable for high-performance p-channel field-effect transistors for complementary circuits operating at extremely low power. [Copyright &y& Elsevier]

The growth striation of impurity segregation and electrical properties of Ga0.03In0.97Sb single crystals grown by the Czochralski method in an ultrasonic field have been investigated. It is established that ultrasonic irradiation of the melt during growth significantly decreases the growth striation (in particular, it eliminates striations spaced at a distance of more than 14 μm). The Ga0.03In0.97Sb single crystals grown in an ultrasonic field had a higher charge-carrier mobility and thermoelectric power in comparison with the single crystals grown without ultrasound. [ABSTRACT FROM AUTHOR]

Abstract: c-Axis-oriented Al x In1− x N (AlInN) films (0.12⩽x⩽0.87) were grown on AlN/glass substrates by pulsed-dc reactive sputtering. The deposited AlInN films have excellent crystal quality without oxygen contamination. The electron concentrations of sputtered In-rich films are lower than 3×1018 cm−3 for x⩾0.36. The composition dependence of the bandgap is discussed and compared with previous reports. The bandgap discrepancy of In-rich films grown by different methods can be explained by Burstein–Moss effect. The bowing parameter for bandgaps of AlInN films is calculated as 4.1eV by polynomial fitting. The extrapolated bandgap from bowing equation is 6.0eV for AlN. [Copyright &y& Elsevier]

Abstract: Thin films of Cd1−x Mn x S (0≤ x ≤0.5) were deposited on glass substrates by thermal evaporation. All the films were deposited at 300K and annealed at 573K. The as-deposited and the annealed films were characterized for composition, structure and microstructure by using energy-dispersive analysis for X-rays, X-ray diffraction, scanning electron microscopy and atomic force microscopy. Electrical conductivity was studied in the temperature range 190–450K. All the films exhibited wurtzite structure of the host material with the grain size varying in the range between 36 and 82nm. Resistivity of all the films is strongly dependent on Mn content and annealing temperature and lies in the range 13–160Ωcm. [Copyright &y& Elsevier]

Abstract: Electronic and optical properties of aluminum nitride nanotubes are studied in the framework of density-functional theory. It is found that the surface atoms attribute their electronic states near the upper valence band edge as well as the lower conduction band edge as defect states. Moreover, the absorption spectrum of a AlN nanotube is shown to be correlated with the ratios of the surface atoms to the bulk atoms. As tube thickness increases, a AlN tube is observed to have an increased tendency to show an optical absorption of bulk wurtzite AlN. Therefore, we predict that for realistic AlN nanotubes with large thicknesses (30–80nm), the absorption spectra are most probably originating from the electronic states arising from the bulk portion. [Copyright &y& Elsevier]

Abstract: Ga4Se3S layered crystals were studied through the dark electrical conductivity, and illumination- and temperature-dependent photoconductivity in the temperature region of 100–350K. The dark electrical conductivity reflected the existence of two energy states located at 310 and 60meV being dominant above and below 170K, respectively. The photoconductivity measurements revealed the existence of another two energy levels located at 209 and 91meV above and below 230K. The photoconductivity was observed to increase with increasing temperature. The illumination dependence of photoconductivity was found to exhibit linear and supralinear recombination above and below 280K, respectively. The change in recombination mechanism was attributed to the exchange in the behavior of sensitizing and recombination centers. [Copyright &y& Elsevier]

We report the magnetic and magnetotransport properties of Ga1− x Mn x Sb crystals grown with different Mn doping concentrations ( x=0.01, 0.02, 0.03 and 0.04) by the horizontal Bridgman technique. A systematic reduction in lattice parameter with increase in Mn concentration is observed through X-ray diffraction studies. The crystals show negative magnetoresistance and anomalous Hall effect below 10 K. Anomalous Hall coefficient is negative and decreases with increasing Mn concentration. Temperature dependence on magnetization measurement shows a magnetic ordering below 10 K which could arise from GaMnSb alloy formation. Also, ferromagnetism is observed till room temperature due to the presence of MnSb clusters. Existence of MnSb clusters is verified through scanning electron microscopy. The carrier concentration increases with Mn doping and this results in decrease of resistivity. The observed magnetic and transport properties indicate the presence of ferromagnetic phase below 10 K in the studied system. [ABSTRACT FROM AUTHOR]

Electrical and photoelectric properties and also low-temperature photoluminescence of coarsegrained p-ZnTe with a resistivity of 3.3 × 1010Ω cm at 77 K have been studied. The coarse-grained ZnTe sample in the shape of a pipe was synthesized at 730°C from vapor phase in cocurrent flows of components. X-ray structure analysis showed that there are single-crystalline grains in both the [111] and [100] directions. In spite of nonequilibrium conditions of rapid crystallization, X-ray diffractometry measurements showed that the ZnTe crystallinity is good. The results of low-temperature photoluminescence confirm that there is an ordered distribution of impurities in the lattice. The set of impurities is limited to Cu, Ag, Li, and O. The photoconductivity and photoluminescence spectra indicate that there are poorly studied centers with levels deep m the band gap. In the regions with a low density of twins, there is observed a high quantum yield of photoluminescence, the absence of transitions related to complex defects, the presence of intrinsic emission with pronounced polaritonic structure, and manifestation of an ample structure of two-hole transitions that are absent in the crystals obtained under conditions of slow growth. [ABSTRACT FROM AUTHOR]

Abstract: Sb-doped ZnO nanostructures have been deposited onto glass substrates by a sol–gel method. The structural, optical and electrical properties of the Sb-doped ZnO films were characterized by various techniques including scanning electron microscopy, X-ray diffraction, UV–vis absorption, photoluminescence , and electrical transport measurements. The surface morphology of the nanostructure films is found to depend on the concentration of Sb in the source materials. Band-edge emission at 376nm and a broad defect band around 530nm were shown in the photoluminescence spectra. An emission band at 400nm was also observed, which is likely associated with the interstitial Zn in ZnO. The current–voltage characteristics of the films indicate a non-linear behavior. The conductivity type of the films changes from n-type to p-type with increasing Sb-dopant. [Copyright &y& Elsevier]

Abstract: The present paper reports the application of Meyer–Neldel Rule to the observed spread in activation energy in electrical conduction of sol–gel derived ZnO:Al polycrystalline thin films deposited on corning 7059 glass substrate. The experimental results obtained on electrical conductivity over a wide range of temperature (150–600 K) have been analyzed in the light of theory corresponding to the two different transport paths. The conduction mechanism in the high temperature range (400–600 K) is found to be thermally activated whereas at low temperature it is attributed to variable range hopping. The variation in activation energy with Al doping concentration in ZnO has been studied in order to estimate the characteristic MNR temperature where the conductivity process is independent of the activation energy. [Copyright &y& Elsevier]

Abstract: Electronic structure of zinc-blende and wurtzite InN using linear combination of atomic orbitals and the latest approach of generalised gradient approximation within full potential linearised augmented plane wave schemes is reported. An unusual small band gap and real space analysis of our first ever experimental Compton profile are discussed. [Copyright &y& Elsevier]

Nanocrystalline films of zinc oxide deposited by rf magnetron sputtering are used as a working material of UV detectors. The photoelectric performance of UV detectors versus ZnO deposition conditions is studied. The influence of the surface topology of the UV detectors on their efficiency is examined with an atomic force microscope. [ABSTRACT FROM AUTHOR]

Abstract: ZnO films were prepared on (111) YSZ and (0001) sapphire by pulsed laser deposition method. Effect of lattice mismatch on the carrier transport properties of ZnO epitaxial thin films was investigated. The carrier mobility of the ZnO films on YSZ was larger than that of ZnO/sapphire due to smaller lattice mismatch when the thickness was below 150nm. The effect of electrically degenerated layer on the carrier transport property increased with decreasing the film thickness of ZnO film. The carrier density and electron mobility of 20nm-thick-ZnO film on either substrate were regardless of the temperature. We concluded that the dominant carrier scattering mechanism in ZnO ultra thin films is double Schottky barriers at the grain boundary and that their height depends on the carrier concentration. [Copyright &y& Elsevier]

Abstract: Ga-doped ZnO (GZO) thin films were prepared on glass substrates via pulsed laser deposition for window heater applications in the automobile industry. The structural, electrical, and optical properties of these films were investigated for their dependencies on Ga2O3 content and substrate temperature. GZO films with a resistivity of 2.14×10−4 Ωcm and transparency above 90% in the visible range were obtained. GZO line heaters were patterned on glass substrates, and they heated rapidly from room temperature to 88.2°C in 48s at an applied voltage of 12V. These results demonstrate the possibility of using GZO thin films as effective transparent heaters. [Copyright &y& Elsevier]

CdTe/Hg1 − x Cd x Te heterostructures are studied. In the structures, CdTe is used as a passivating layer deposited as a polycrystal or single crystal on a single-crystal Hg1 − x Cd x Te film. The film and a passivating layer were obtained in a single technological process of molecular beam epitaxy. The structure of passivating layers was studied by reflection high-energy electron diffraction, and the effect of the structure of the passivating layer on the properties of the active layer was studied by X-ray diffractometry. Mechanical properties of heterostructures were studied by the microhardness method. Electrical and photoelectrical parameters of the Hg1 − x Cd x Te films are reported. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we concentrate on the study of the role of ohmic electrode metallization of radiation imaging detectors based on bulk semi-insulating (SI) GaAs. We fabricated SI GaAs radiation detectors with Ti/Pt/Au Schottky contact on one side and In/Au, Mg/Au and Gd/Au contacts on the other side of bulk material with the aim to form hole barrier Schottky contact with non-injecting effect. Current–voltage and noise characteristics and also detection performance of detectors are measured and evaluated. Observed results are discussed and compared with detector using standard AuGeNi non-alloyed ohmic metallization. [Copyright &y& Elsevier]

Abstract: Optical properties of InAsN/InGaAs quantum wells on InP grown by gas source molecular beam epitaxy have been investigated by photoconductivity measurements. It is found that the persistent photoconductivity (PPC) does exist in this nitrogen compound material. Through a detailed study of the dependence of the PPC effect on excitation photon energy, temperature, decay kinetics and nitrogen composition, we point out that the origin of the PPC effect arises from the metastability of deep level centers. In different charge states, the defect centers can undergo a large lattice relaxation which creates an energy barrier to prevent the photoexcited carriers from returning to the original states, and thus the PPC occurs. We find that the obtained energy barrier increases with nitrogen composition. [Copyright &y& Elsevier]

Abstract: Top-contact thin film transistors with ZnO as the channel layer and thermally grown SiO2 as the gate dielectric were fabricated by using rf sputtering. The performances of ZnO-TFTs with different thicknesses of the active layer were investigated and the optimized condition was obtained. With the active layer thickness from 25 to 70 nm, the leakage current of devices increased from 10−10 to 10−8 A, and the on/off ratio decreased from 1.2×107 to 2×104. Atomic force microscope research indicated that with the thickness increased, the surface morphology of the active layer improved noticeably at first and then deteriorated. The 25-nm-thick ZnO TFT had the best surface morphology, and showed the best performance with a field effect mobility of 5.1 cm2/V S, on/off ratio of 1.2×107 and threshold voltage of 20 V. This indicates that the surface properties of the channel layer have crucial affects on the performances of ZnO-TFTs. [Copyright &y& Elsevier]

Cd x Hg1 − x Te films with x ≈ 0.22 and thickness of ∼10 µm have been grown by molecular-beam epitaxy on gallium arsenide substrates and doped in situ with arsenic. Activation annealing of doped films provided p-type conduction with a hole density of up to 1017 cm−3. The influence exerted by the arsenic cracking zone temperature on the efficiency of arsenic incorporation into the CdHgTe film was studied. A model describing the dependence of the arsenic concentration in the films on the arsenic cracking zone temperature was suggested. A comparison of the model and the experimental data demonstrated that the incorporation efficiency of diatomic arsenic is approximately two orders of magnitude higher than that of tetratomic arsenic. [ABSTRACT FROM AUTHOR]

n-Hg3In2Te6 single crystals with resistivity of 1–2 Ω cm used in photodiodes for the wavelength 1.55 μm are studied. It is shown that electrical conductivity of the material is controlled by donors of two types with ionization energies of 0.063 and 0.18 eV, while the mobility of charge carriers is predominantly controlled by scattering at charged centers. On the basis of the electroneutrality equation, a quantitative description of the observed temperature dependence of the electron concentration in the temperature range from 100 to 370 K is obtained. [ABSTRACT FROM AUTHOR]

Abstract: Lattice constants, elasticity, band structure and piezoelectricity of hexagonal wide band gap Be x Zn1−x O ternary alloys are calculated using first-principles methods. The alloys'' lattice constants obey Vegard''s law well. As Be concentration increases, the bulk modulus and Young''s modulus of the alloys increase, whereas the piezoelectricity decreases. We predict that Be x Zn1−x O/GaN/substrate () multilayer structure can be suitable for high-frequency surface acoustic wave device applications. Our calculated results are in good agreement with experimental data and other theoretical calculations. [Copyright &y& Elsevier]

The behavior of a longitudinal autosolitons created in excited nonequilibrium electron-hole plasma in compensated p-InSb in crossed magnetic and electric fields is studied experimentally. It is shown that, in magnetic fields ranging from 6.7 × 102 to 3.2 × 104 A/m, a longitudinal autosoliton is in a state of motion with the average velocity 2 × 102−3 × 103 cm/s towards the sample periphery, where the temperature is reduced and the autosoliton is unstable, making the process cyclic and giving rise to oscillations of the current in the external circuit of the sample. In this case, the amplitude and frequency of the oscillations (2144-26855 Hz) depend on the magnetic field. With increasing electric and magnetic fields, the instability of the longitudinal autosoliton current takes on synergetic properties. [ABSTRACT FROM AUTHOR]

The effect of laser radiation on the impurity energy spectrum of intercalated structures is studied by the example of 〈Co〉0.015GaSe. By the variations in frequency dependences of resistivity measured normally to the layers of the obtained structure and by the transformation of the Nyquist diagrams consisting of two connected in series parallel R | C units, a conclusion is made on the laser-stimulated compensation of the intercalant. The obtained values of the real part of permittivity are characteristic of doped semiconductors or their alloys in the radio-frequency range. The experimental results showed that the pulsed laser irradiation is an effective method to affect the energy impurity spectrum of intercalated compounds. [ABSTRACT FROM AUTHOR]

Abstract: The far-infrared (FIR) photoconductivity (PC) of a two-dimensional electron gas in the quantum Hall regime is investigated. We use a novel sample structure which is topologically equivalent to a Corbino-geometry; however, the circumference is greatly enlarged by a meander-like patterning. The geometry allows us to directly study the FIR-induced transport between edge states, which are separated by the insulating bulk region. Due to the high sensitivity of our sample structure it is possible to investigate the PC of our sample in a Fourier spectrometer using a broad band, black-body source with a very low spectral intensity compared to FIR-Lasers used in other experiments. Additionally, we present PC-measurements on a sample with gate tunable carrier density, which allows us to tune the resonance frequency. [Copyright &y& Elsevier]

The selective interaction of the iodine and cesium atoms with the GaAs(001) surface, which leads to a decrease in the bond energy of the Ga and As surface atoms, respectively, owing to the redistribution of the electron density in the near-surface region under the effect of electronegative and electropositive adsorbates, has been experimentally investigated. This selective interaction makes it possible to remove alternately the Ga and As monolayers in the iodine and cesium adsorption followed by heating at T ≤ 450°C and, thus, to implement reversible low-temperature transitions between the Ga-and As-stabilized superstructures, as well as the atomic layer etching of the semiconductor with the physically ultimate monolayer accuracy. [ABSTRACT FROM AUTHOR]

Abstract: Resistivity and Hall effect measurements on nominally undoped Al0.25Ga0.75N/GaN/AlN heterostructures grown on sapphire substrates prepared by metal organic chemical vapor deposition have been carried out as a function of temperature (20–300 K) and magnetic field (0–1.4 T). Variable magnetic field Hall data have been analyzed using the improved quantitative mobility spectrum analysis technique. The mobility and density of the two-dimensional electron gas at the AlGaN/GaN interface and the two-dimensional hole gas at the GaN/AlN interface are separated by quantitative mobility spectrum analysis. The analysis shows that two-channel conduction is present in nominally undoped Al0.25Ga0.75N/GaN/AlN heterostructures grown on sapphire substrate. [Copyright &y& Elsevier]

Abstract: The aim of the present work is to investigate defects that are introduced to Gallium Phosphide (GaP) by electron irradiation as well as their dependence on the background doping. Undoped and Te doped n-type GaP have been irradiated with 1.5 MeV electrons at fluences of 5×1016 e/cm2. Deep level transient spectroscopy assessment revealed the dependence of the trap characteristics on background doping. [Copyright &y& Elsevier]

Abstract: The hydride vapor phase epitaxy (HVPE) of {0001} AlN films on {111} Si substrates covered with epitaxial {111} cubic SiC (3C-SiC intermediate layers) was carried out. 3C-SiC intermediate layers are essential to obtain high-quality AlN films on Si substrates, because specular AlN films are obtained with 3C-SiC intermediate layers, whereas rough AlN films are obtained without 3C-SiC intermediate layers. We determined the polarities of AlN films and the underlying 3C-SiC intermediate layers by convergent beam electron diffraction (CBED) using transmission electron microscopy. For the first time, the polarities of the AlN films and the 3C-SiC intermediate layers were determined as Al and Si polarities, respectively. The AlN films were hardly etched by aqueous KOH solution, thereby indicating Al polarity. This supports the results obtained by CBED. The result is also consistent with electrostatic arguments. An interfacial structure was proposed. The 3C-SiC intermediate layers are promising for the HVPE of AlN films on Si substrates. [Copyright &y& Elsevier]

Abstract: We report the first ever isotropic Compton profiles of mercury chalcogenides using our 740GBq 137Cs Compton spectrometer. To analyze our measurements, theoretical Compton profiles, energy bands, density of states and Mulliken''s populations are computed using pseudopotentials within the Hartree–Fock and density functional theories. A comparison of Compton data on equal-valence-electron-density scale shows the decrease of ionicity from HgS to HgTe. It is seen that these semiconductors have narrow band gap and exhibit inverted-type band structure. [Copyright &y& Elsevier]

A strip-slot guiding structure (GS) containing a distributed semiconductor inclusion with a negative differential conductivity is considered. Instabilities and nonlinear effects observed during propagation of electromagnetic waves in such a structure are investigated via numerical analysis of branching points of solutions to the nonlinear Maxwell equations. The method of universal autonomous blocks with Floquet channels is applied to solve the 3D problem of diffraction of electromagnetic waves by a nonlinear semiconductor irregularity in a strip-slot GS. The solutions obtained describe frequency multiplication and generation of the GS fundamental mode near a branching point. The generation process is described as a function of the incident-wave amplitude. The bifurcation points of the nonlinear Maxwell operator are found numerically with allowance for bounding geometries. These points specify the self-oscillation frequencies in planar Gunn effect diodes in a strip-slot GS. [ABSTRACT FROM AUTHOR]

Abstract: Mn2+-doped CdS nanocrystals have been synthesized by adopting an aqueous solution precipitation method. These nanocrystals have been studied using X-ray diffraction (XRD), X-ray fluorescence (XRF), optical absorbance, photoluminescence (PL), DC electrical conductivity measurements and positron annihilation lifetime spectroscopy (PALS). The system has been found to be in the hexagonal phase. PL spectra have been studied on most prominent exciton peaks within the wavelength range (586–731nm). The emission intensity is found to increase on increasing Mn2+ ion concentration (0–5%). Electrical conductivity lies within 0.819×10−6 to 1.69×10−6 Ω−1 m−1 and the system shows power law dependence for n=3–3.77. The Cd vacancies concentration has been found to decrease on increasing Mn%. [Copyright &y& Elsevier]

A method is developed for simulation of nonlinear propagation and diffraction of electromagnetic waves in guiding structures containing highly nonlinear distributed semiconductor inclusions. A planar Gunn effect diode located in a strip-slot guiding structure is considered, and the nonlinear effect of frequency multiplication in such a diode is simulated. The simulation is performed with the use of a computational algorithm based on universal autonomous blocks with Floquet channels. [ABSTRACT FROM AUTHOR]

Abstract: Zinc selenide (ZnSe) thin films (d =0.11–0.93μm) were deposited onto glass substrates by the quasi-closed volume technique under vacuum. Their structural characteristics were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). The experiments showed that the films are polycrystalline and have a zinc blende (cubic) structure. The film crystallites are preferentially oriented with the (111) planes parallel to the substrate surface. AFM images showed that the films have a grain like surface morphology. The average roughness, R a =3.3–6.4nm, and the root mean square roughness, R rms =5.4–11.9nm, were calculated and found to depend on the film thickness and post-deposition heat treatment. The spectral dependence of the absorption coefficient was determined from transmission spectra, in the range 300–1400nm. The values of optical bandgap were calculated from the absorption spectra, E g =2.6–2.7 eV. The effect of the deposition conditions and post-deposition heat treatment on the structural and optical characteristics was investigated. [Copyright &y& Elsevier]

Abstract: Undoped and Cl-doped CdTe crystals were grown by the modified PVT technique in a vertical configuration. Their structural quality as well as electrical and transport characteristics as a function of a doping concentration was analyzed by means of infrared (IR) spectroscopy, optical microscopy, secondary ion mass spectrometry (SIMS), photoelectrical and Hall effect measurements. In the investigated semi-insulating crystals with resistivity ρ>108 Ω×cm doped in the chlorine concentration range N Cl=1018−1019 cm−3 the best transport and structural characteristics were observed. The formation of precipitates and inclusions at higher values of N Cl results in worsening of crystalline quality as well as a decrease of resistivity in the doped samples. The IR transmission spectra in heavily doped samples are determined by the light scattering on these structural imperfections, whereas optical transitions between the heavy hole and light hole valence bands dominate spectra in undoped ones. The absorption peak caused by these transitions seems to be observed for the first time in undoped CdTe. [Copyright &y& Elsevier]

Abstract: The paper reviews the basic aspects of sublimation growth of wide-bandgap semiconductors such as SiC and group-III nitrides. The most significant physical and chemical phenomena underlying the growth are considered: heat and mass transport, sublimation and condensation, heterogeneous chemical reactions, flow through reacting porous medium, thermoelastic stress, and defect generation. State of the art in numerical modeling of sublimation growth is discussed. Modeling is shown to be effective for solving of practically important problems of the process study and optimization. [Copyright &y& Elsevier]

Abstract: We report on the formation of low-resistance and highly transparent indium tin oxide (ITO) ohmic contacts to p-GaN using a Sn–Ag alloy interlayer. Although the as-deposited Sn–Ag(6nm)/ITO(200nm) contacts show non-ohmic behaviors, the scheme becomes ohmic with specific contact resistance of 4.72×10−4 Ωcm2 and produce transmittance of ∼91% at wavelength of 460nm when annealed at 530°C. Blue light-emitting diodes (LEDs) fabricated with the Sn–Ag/ITO contacts give forward-bias voltage of 3.31V at injection current of 20mA. LEDs with the Sn–Ag/ITO contacts show the improvement of the output power by 62% (at 20mA) compared with LEDs with Ni/Au contacts. [Copyright &y& Elsevier]

Abstract: The Ga1− x Mn x N epitaxial films were grown by metalorganic chemical vapor deposition (MOCVD) with tricarbonyl (methycyclopentadienyl) manganese ((MCP)2Mn) as dopant source. Magnetic measurements indicate that the films are n-type conductivity (x=0.01), ferromagnetic ordering with Curie temperature above room temperature. The magnetic moment per Mn atom decreases when the Mn concentration changes from 0.01 to 0.03. Magneto-transport properties were performed in the temperature range of 2–300K. The magneto-resistance (MR) changes from negative effect to positive effect with increasing temperature. The negative MR effect at low temperature is due to the reduction of the magnetic scattering of the Mn ions under the applied magnetic field. Furthermore, the zero-field-cooled (ZFC)/field-cooled (FC) and MR behavior at low temperature confirm that the ferromagnetism and paramagnetism coexist in Ga1− x Mn x N films. [Copyright &y& Elsevier]

Abstract: The mobility of undoped CdZnTe (CZT) crystals grown by vertical Bridgman method is improved by growing crystals without wall contact. Among the different factors playing an important role for appearance of detached growth, we have chosen the freezing rate as an effective factor for investigation with other factors were held constant. After growing a set of samples we have measured the dislocation densities for the grown samples by Warren–Averbach method. Unique results were obtained when we compared the dislocation densities and mobility, together with the freezing rate. This work and the included relations are published for the first time. [Copyright &y& Elsevier]

Abstract: The growth of dilute nitride alloys of GaInSb by plasma-assisted molecular beam epitaxy is reported. The principle of lattice matching GaInNSb alloys to GaSb(001) substrates is demonstrated. High resolution X-ray diffraction rocking curves and reciprocal space maps indicate the high crystalline quality of the GaInNSb layers and illustrate a lattice match to GaSb with nitrogen and indium incorporations of 1.8% and 8.4%, respectively. The rms roughness of a nominally lattice matched GaInNSb/GaSb(001) layer was determined from atomic force microscopy to be . [Copyright &y& Elsevier]

Abstract: Impurities in three cadmium zinc telluride (Cd1− x Zn x Te or CZT) ingots grown by the modified vertical Bridgman (MVB) method were examined by using inductively coupled plasma mass spectrometry (ICP-MS). The distribution and segregation of impurities along the CZT ingots were found to vary with the concentration and the growth conditions. Photoluminescence (PL) and voltage–current measurements were performed to evaluate the effects of the impurities on the optical and electrical properties. The red shift of the (D 0, X) and DAP positions and the broadening of the DAP band in PL spectrum were observed in the high-impurity CZT ingot. The voltage–current measurement shows a higher resistivity when the impurity concentration was increased. The above results imply that the high-impurity CZT ingot was highly compensated. [Copyright &y& Elsevier]

Abstract: ZnO films were deposited on glass substrates by sputtering a Zn3As2/ZnO target using radio frequency (rf) magnetron sputtering. XRD was used to analyze the crystal orientation of ZnO films. Energy dispersive spectroscopy result shows that As content in ZnO:As films is nearly uniform. Room temperature Hall and resistivity measurements indicate that the substrate temperature is an important factor to determine conduction type of ZnO films and proper thermal treatment for the films may change their electrical behavior from n type to p-type. As-doped ZnO film shows p type conductivity with mobility as high as 4.07cm2/Vs after annealing in Ar ambient at 400°C for 60min. [Copyright &y& Elsevier]

Abstract: This work deals with the study of three different electrode metallizations with the aim to form a Schottky barrier contact. Electrode geometry corresponds to the requirements of digital radiography systems. As substrates bulk Liquid Encapsulated Czochralski (LEC) SI InP wafers doped with Fe and Fe+Zn are used. Results of this study show that no one of the used metallization performs as a blocking contact. However, detectors with Ti/Pt/Au metallization attained a relatively good energy resolution of 7.0keV in full-width at half-maximum (FWHM) and the charge collection efficiency (CCE) higher than 83% for 122keV γ-photons at 255K. The development of SI InP radiation detectors and in particular their electrode technology is discussed in the light of observed results. [Copyright &y& Elsevier]

Abstract: In this work, the requirements of detector-grade semiconductor materials for radiation detectors, applicable in X-ray digital radiology, are identified. The study includes 12 various bulk semi-insulating (SI) GaAs single crystals grown by LEC and VGF methods, undoped and Cr-doped, obtained from 8 different suppliers. Conductivity, Hall, glow discharge mass spectrometry (GDMS), etch pit density (EPD), scanning electron beam induced current (S-EBIC), X-ray and laser scattering tomography (LST) techniques are used for the bulk SI GaAs material evaluation. The radiation detectors fabricated on these SI GaAs single crystals have been characterized by capacitance methods and their performances have been evaluated from detected pulse height spectra of 57Co. The correlation between the physical characteristics of the base materials and the performance of the detectors is demonstrated and discussed. Key detector-grade SI GaAs parameters, useful for material evaluation, are identified. [Copyright &y& Elsevier]

Abstract: Polycrystalline Cadmium Telluride samples were electrically characterized using two high resolution imaging techniques: Electron and Ion Beam Induced Current. Using different probes, electrons and protons, both surface and bulk transport properties were obtained. The grain structure was observed and grain boundaries effects were studied. The material tends to have a homogeneous response under low excitation, with only few weakly responding grains and no dead areas. Under higher excitation, the material exhibits some particular behavior, like grain sub-structures. The IBIC experiment gives a measure of Charge Collection Efficiency under different sample bias voltages. In addition to the measurement of the response dispersion, it leads to a discussion of the charge transport properties and a mobility-lifetime product calculation. [Copyright &y& Elsevier]

Transport properties of undoped high-resistivity n-CdTe polycrystals grown by a new technique have been studied. Characteristic features of the temperature dependences of conductivity, photoconductivity, and carrier drift in these polycrystals have been determined. The results obtained can only partly be understood in terms of the commonly accepted concepts. [ABSTRACT FROM AUTHOR]

Abstract: A novel rare-earth chloride seed was employed as a catalyst for growth of GaN nano- and micro-crystals on c-, a- and r-plane sapphire. The ErCl3 seed on the substrate surface enhanced the growth rate and density of the GaN crystals. Distinctive green photoluminescence was measured, confirming that Er3+ ions were active in the GaN matrix. This technique can be adapted to selectively grow GaN crystals with emission tailored to the particular optical transitions of the rare-earth seed. [Copyright &y& Elsevier]

The results of measurements of frequency dependences of conductivity and electron spin resonance (ESR) of the Cd1 − x FexTe alloys (0.01 ≤ x ≤ 0.05) at room temperature are presented. It is found that, in the composition range 0.003 ≤ x ≤ 0.05, a new asymmetric ESR absorption line with g ≈ 3.9 emerges, and its hysteresis manifests itself while the samples are magnetized. The line with g ≈ 3.9 is attributed to the charge state 3+ of the Fe atoms, which occurs in tetrahedra with three Fe atoms. [ABSTRACT FROM AUTHOR]

Abstract: After Cd0.8Zn0.2Te (CZT) crystals were prepared by a special design based on Bridgman technique, the transport properties were investigated. The dependence of electrical conductivity, Hall effect, Hall mobility, charge carriers concentration and thermoelectric power on temperatures was carried out in the temperature range (228–500K). The relaxation time for both majority and minority carriers was estimated. The scattering mechanism for carrier transport was discussed in the same temperature range. [Copyright &y& Elsevier]