Using μ-Raman spectroscopy (μRS) and cathodoluminescence (CL) analyses, the impact of hydrogen plasma treatments on sintered zinc oxide (ZnO) samples was studied. 1 hour H-plasma treatments (150 W, 13.56 MHz) were applied at substrate temperatures between 250 °C and 500 °C. μRS and CL analyses show that plasma hydrogenation causes significant defects in ZnO samples; i) non-specified defect species are established with a maximal density upon H-plasma exposure at 350 °C substrate temperature, and ii) the formation of oxygen vacancies (VO) can be traced. Moreover, μRS reveals vibration modes of H2 molecules trapped in nano-voids. The experimental results indicate that those nano-voids are created by a coalescence of the VO defects.

Electron-hole recombination enhanced glide of Shockley partial dislocations bounding expanding stacking faults and their interactions with threading dislocations in 4H silicon carbide epitaxial layers have been studied using synchrotron white beam X-ray topography and in situ electroluminescence. The mobile silicon-core Shockley partial dislocations bounding the stacking faults are able to cut through threading edge dislocations leaving no trailing dislocation segments in their wake. However, when the Shockley partial dislocations interact with threading screw dislocations, trailing 30o partial dislocation dipoles are initially deposited in their wake due to the pinning effect of the threading screw dislocations. These dipoles spontaneously snap into their screw orientation, regardless the normally immobile carbon-core Shockley partial dislocation components in the dipoles. They subsequently cross slip and annihilate, leaving a prismatic stacking fault in (2-1-10) plane with the displacement vector 1/3[01-10].

Spray pyrolysis was used for the deposition of lead iodide (PbI2) thin films using N.N-dimethylformamide (DMF) as an alternative solvent under varying deposition parameters. Final thickness of 60 μm was obtained for a total deposition time of 2.5 hours. The films were characterized mainly by using Raman and photoluminescence, but additional techniques such as X-ray diffraction, scanning electron microscopy and dark conductivity as a function of temperature were also employed. Thick PbI2 films deposited by spray pyrolysis using DMF as a solvent are promising to be used in medical systems as X-ray imaging.

The photoelectrical properties of p-GaSe(Cu)/n-GaAs heterojunctions obtained by optically contacting the components and by thermal evaporation of GaSe, have been studied. The rectification factor for optically contacted heterojunctions is ∼2·102 at 5 V, and the current flow is determined by diffusion mechanism. The diffusion and recombination through the interface defects mechanisms determine de current flow for heterojunctions formed by GaSe evaporation.

High resolution transmission electron microscopy observations show for the first time the presence of two orientations of pure silver precipitates in nanocavities induced in bulk silicon by implantation at 1.6 MeV with a dose of 5×1016 He+ cm−2 and a two hour annealing at 1050°C. These precipitates were called A and B to refer to the two well-known nickel silicide (NiSi2) precipitates or Ag films on a {111} silicon surface. Thus, the A precipitate corresponds to a growth of silver nanocrystal on {111} cavity walls in epitaxy with the Si matrix with an orientation relationship Ag(-111)[211]||Si(-111)[211]. The B precipitate develops on a {111} plane parallel to a {111} cavity wall as well, but in a twin orientation with respect to the Si matrix defined by Ag(-111)[211]||Si(-111)[-2-1-1]. The Ag nanocrystals have a size ranging from a few nm to 50 nm. Most of them have the faceted-shape characteristic of “clean” cavities. They are either A precipitates or they contain alternatively A and B bands in good agreement with both the low stacking fault energy of silver and the two types of nanocrystal orientations obtained by Ag deposition on (111) Si substrate at room temperature. Some Ag precipitates were also found at dislocations located at the He+ projection range, but these trapping sites were found thermally unstable as compared to the cavity ones. Indeed, during a second identical annealing, the precipitates grow in cavities whereas they fade at dislocations.

The impact of metallic impurities on the carrier lifetime in n-Ge is studied using microwave reflection and absorption techniques. Co, Fe, Ti, Ni and Cr are introduced by ion implantation followed by a thermal anneal and quenching to room temperature. Excess carrier decay transients are examined by microwave reflection and absorption probing after pulsed light excitation. A detailed analysis allows to evaluate the ratio of the capture cross-sections for minority and majority carriers revealing an acceptor-like character of the metal induced traps. Cross-sectional lifetime measurements show an U-shaped depth distribution with the lowest lifetimes in the bulk of the wafer. The lifetime results are correlated with those of deep level transient spectroscopy in order to clarify the properties of the dominant metal related recombination centres. Fe and Co are the most effective lifetime killers in n-Ge while Cr has the least influence.

Carbon co-implantation after pre-amorphization implantation (PAI) has been studied for Boron shallow implants and can be also used to reduce Phosphorus diffusion. The expected role of Carbon is to trap Si interstitials responsible of Phosphorus diffusion. A known drawback of this kind of co-implantation is junction leakage caused by Carbon deep levels. To find a compromise between diffusion reduction and leakages, it is necessary to optimize the location and the amount of Carbon with respect to Si interstitials.

In this work, we present full sheet experiments optimizing Carbon implanted energy and dose in order to minimize Phosphorus diffusion. First, we performed a PAI with Germanium. Then Carbon was implanted at several energies and doses to locate its projected range (Rp) at various locations with respect to the Phosphorus peak and the amorphous/crystalline interface. Finally the Phosphorus implant was placed completely within the amorphized area. Dopants were activated by a spike anneal at 1080°C, 1055°C or 1000°C. SIMS analysis and Rs measurements were used to understand Carbon action on Phosphorus diffusion and activation. The role of C in suppressing P diffusion is discussed in regards of the specificities of P diffusion mechanism.

Results are presented of the simulation of the properties of vacancy clusters in single crystal germanium. Classical molecular dynamics calculations based on a Stillinger and Weber potential were used in a theoretical investigation of different growth patterns of vacancy clusters Vi . The formation and binding energies of vacancy clusters have been studied in the range 1 ≤ i ≤ 35. The energetically favourable growth mode and an estimate of the effective surface energy was determined for a vacancy clusters containing up to 35 vacancies

Defect-free germanium has been demonstrated in SiO2 trenches on silicon via aspect ratio trapping, whereby defects arising from lattice mismatch are trapped by laterally confining sidewalls.Results were achieved through a combination of conventional photolithography, reactive ion etching of SiO2, and selective growth of Ge as thin as 450 nm.It was revealed that facets, when formed early on in the growth process, play a dominant role in determining the configurations of threading dislocations in the films.This approach shows great promise for the integration of Ge and/or III-V materials, sufficiently large for key device applications, onto silicon substrates.

High-power semiconductor lasers are required to be more and more powerful, efficient and reliable for applications such as solid-state lasers pumping, materials processing, and thermal printing among others. The understanding of the degradation mechanisms is essential to improve the high power laser reliability. The highest power emission is achieved with multi-emitter laser cm-bars, which present problems related to packaging induced stress. A very harmful defect in this type of devices is the so-called V defect. We present herein a study of these defects using cathodoluminescence imaging, the role of packaging is discussed.

To weight the importance of a nanocavity buffer in a SiGe deposition substrate, some P type (001) FZ Si wafers are implanted (A samples) or not (B samples) at room temperature with 5×1016 He+ cm–2 at 10keV. They are annealed at 700°C for one hour to form a nanocavity layer close to the Si surface. Then, the wafers are carefully chemically cleaned in a clean room to remove both organic and metallic impurities from the surface. They are coated either by 210 nm (A) or 430 nm (B) Si1−xGex (x=0.20±0.02) alloy grown at 575°C for 0.42 hour by low pressure chemical vapor deposition (LP-CVD) with a growth rate of 8 to 17 nm.mn−1. Both kinds of samples are studied by cross section transmission electron microscopy, X-rays diffraction, Rutherford backscattering, atomic force microscopy and etch pit counts. The association of these techniques demonstrates that the thin SiGe layer which is deposited on sample A is fully relaxed and that the threading dislocation density (estimated to hardly reach 4×103cm−2) is at least one order of magnitude lower than what is obtained so far using ion implantation assistance in SiGe layer growth on Silicon. The roughness of the SiGe surface is low enough to stand a further Si epitaxy. Nevertheless, the mechanism involved responsible for the threading dislocation annihilation and/or confinement is still unclear.

The techniques of small angle X-ray scattering and transmission electron microscopy are applied to characterize the size distribution of nanocavities in a (111) Si wafer multi-implanted with He+ in the Mev range energy. The comparison between both methods shows that they all give access to the same structural information but small angle X-ray scattering additionally offers the possibility to monitor the cavity size distribution during a thermal treatment. Moreover, providing that the collected data are of good quality, the former method also allows the knowledge of the porosity of the implanted Si wafer.

Modifying the properties of ZnO and GaN by means of incorporating arsenic impurities is of interest in both of these semiconductors, although for different reasons. In the case of ZnO, the group V element As has been reported in the literature as one of the few p-type dopants in this technologically promising II-VI compound. However, there is an ongoing debate whether the p-type character is due to As simply replacing O atoms or to the formation of more complicated defect complexes, possibly involving As on Zn sites [1]. In the case of GaN, the incorporation of high concentrations of As has been studied with respect to the formation of GaAs(x)N(1-x) alloys and the related modification of the GaN band gap and its luminescence behaviour. It has been suggested that As in GaN is amphoteric, with its lattice site preference depending on the doping character of the material, i.e. mostly substitutional Ga in p-type but also substitutional N in n-type [2].

We have determined the lattice location of implanted As in ZnO and GaN by means of conversion electron emission channeling from radioactive 73As. In contrast to what one might expect from its nature as a group V element, we find that As does not occupy substitutional O sites in ZnO but in its large majority substitutional Zn sites [3]. Arsenic in ZnO is thus an interesting example for an impurity in a semiconductor where the major impurity lattice site is determined by atomic size and electronegativity rather than its position in the periodic system. The results are different in the case of As implanted into GaN, where we found roughly half of the implanted As atoms occupying Ga and the other half N sites. The amphoteric character of As therefore certainly plays a role in explaining the extreme difficulties in growing high quality GaAs(x)N(1-x) alloys with values of x above a few percent.

A preliminary report will also be given on ongoing emission channeling lattice location experiments using radioactive 124Sb in ZnO and GaN.

We theoretically model the transport of holes across graded wurtzite Indium Gallium Nitride layers with large barriers to metals of the order of 2 electron volts. The effect of continuous strain grading and the resulting piezoelectric grading is explicitly taken into account. As data about critical thicknesses for dislocation creation are scarce for these materials, the grading widths considered for the calculations are deliberately kept small to ensure that the layers are below theoretically predicted critical thickness limits. The spatial variation of spontaneous and piezoelectric polarization creates bulk bound polarization charges that have a strong effect on the electrostatics of the layers, and creates the optimum conditions for efficient tunneling of holes. We also explicitly model the effect of the different hole masses for the valence band. Three orders of magnitude increase of tunneling intensity is seen for split-off holes with effective masses of 0.15 for the case of moderate grading from 30 % Indium to 0% Indium over 30 angstroms, compared to the case without grading. The case of very aggressive grading of the same change in composition over 10 angstroms does not lead to any extra benefits and leads to a decrease in tunneling intensity. The electric field for more aggressive grading dominates the electric field for the moderate grading both near the top and the bottom of the barrier. However, the effective barrier width at the valence band edge becomes higher for the case of aggressive grading, and most of the carriers see a damped tunneling amplitude.

The influence of oxygen treatment on carrier transport properties of pure ZnO and ZnO:Cl thin films grown by MOCVD were studied. The experimentally obtained values of carrier concentrations after oxyden treatment at different temperatures,were compared with the the results obtained fromthermodynemical analysis of the system: ZnO:Cl-Oxyen vapour pressure, using method ofquasi-chemical reactions (QCR).

GaN-based heterostructure devices are of interest for pressure and stress sensing applications due to their potential for use at high temperatures and in caustic environments.We have grown n-GaN/u-AlGaN/n-GaN heterostructure devices on sapphire substrates by organometallic vapor phase epitaxy (OMVPE) using the epitaxial layer overgrowth (ELO) method.The devices were fabricated with varying AlGaN layer thickness and composition.Current-voltage (I-V) characteristics were obtained to characterize the performance of these devices under hydrostatic pressures up to 500 MPa.For a fixed bias, the current was observed to decrease in magnitude with increasing hydrostatic pressure for all devices tested.The current modulation is attributed to piezoelectric effects.Specifically, the polarization charge densities at both GaN/AlGaN interfaces are sensitive to changes in the hydrostatic pressure, and these charges affect the shape of the potential barrier and the current.Changes in the AlGaN layer thickness and composition modify the interfacial polarization, with thicker AlGaN layers and higher Al content increasing the effect of pressure on the observed I-V characteristics.The decreases in current magnitude with increasing pressure are linear over the pressure range tested.In order to quantify the performance of these devices, we calculate a pressure gauge factor based on a normalized change in current divided by the change in pressure.Values obtained range from 0.1–1.0 GPa−1, consistent with our previously published results for a single device.In addition, the turn-on voltages under both forward and reverse bias conditions are observed to increase with increasing AlGaN layer thickness and composition, a result that agrees with our device model.These turn-on voltages are governed by different mechanisms in the forward and reverse bias directions.Under forward bias, the mechanism is a transition from a thermionic to a tunneling process.However, under reverse bias, the turn-on occurs when the total electric field changes sign in the AlGaN layer.

We have examined environmental radiation sources for digital cameras to find the origins of bright-pixel defects known to accumulate with time.We show that beta and gamma emissions from camera parts and lenses cause image transients, but permanent damage can occur with alpha particles from the CCD cover glass.Our experiments with 14-MeV- and thermal-neutron beams confirm that cosmic rays are the primary cause of new imager bright points.

(100)–oriented Czochralski germanium (Cz Ge) wafers were implanted with hydrogen at en-ergies up to 100 keV (related to H+) at a doses of D = 4·106 H+/cm2. Post-hydrogen annealing in normal air atmosphere on a hotplate was employed for 10 min at various temperatures between 350 °C and 600 °C to investigate the samples with regard to blistering and layer exfoliation having in mind the Smart-Cut™ technology for GOI structure formation. The generation and evolution of blisters and craters (“exploded” blisters demonstrating layer exfoliation) were investigated in dependence on the annealing temperature by atomic force microscopy and μ-Raman spectroscopy. The latter method points out the appearance of strong tensile stress upon H+ implantation and subsequent annealing. If the tensile stress exceeds about 1.2 GPa layer exfoliation occurs.

Minority-carrier lifetime in silicon directly relates to defect- and impurity-related recombination, and thus gives a measure of material quality.Lifetime measurements are useful in research laboratories and commercial production environments as an indicator for process development and quality control.While photoconductivity (PCD) techniques for measuring lifetime are commercially available, there has recently been interest in using photoluminescence (PL) to characterize lifetime in silicon because of the measurement speed to image an entire wafer and higher mapping resolution. The intensity of band-to-band PL is theoretically proportional to the effective bulk lifetime in low-injection conditions if carrier diffusion and re-absorption are neglected, surface recombination is small, and silicon properties, such as carrier concentration and the radiative recombination coefficient, are constant.We show data that compare lifetimes from PCD techniques to PL intensity for varying-resistivity, single-crystal silicon. Surface conditions are also varied (native oxide, thermal oxide, and HF etch/methyl-iodine solution), and the measured lifetimes are compared to corresponding PL intensity.

An evaluation of an algorithm used to extract Threading Screw Dislocation defect data from Synchrotron White Beam X-Ray Topographical images of SiC wafers is reported.This extraction involves a two-fold process; firstly the algorithm highlights the appropriate defect and secondly updates the counter to provide a final result of defect count.The result of the automated algorithm is compared to hand counts in all cases, this allowing a critical analysis of the technique.Improvements to this algorithm have been made since last reported by the same authors, which are discussed. The analysis herein was also performed on a much larger sample of SiC wafer images than previously used by the same authors [1] allowing a better judgment of performance and critical evaluation.The algorithm is also compared with a previous algorithm that was used.Advantages and deficiencies in the algorithm are outlined and other potential avenues for extraction of the data are also discussed.