The doping level in Cadmium Telluride (CdTe) is of the utmost importance for many applications. In this work, we have characterized CdTe crystals doped with Tl, Bi, or Yb as well as a crystal co-doped with Ge and Yb. The crystals were characterized using low-temperature Photoluminescence (PL), Positron Lifetime Spectroscopy (PLS), resistivity and a terahertz pump-probe technique that can determine carrier lifetimes. The properties of the crystals were also studied before and after a rapid thermal anneal (RTA) as well as after a longer conventional anneal. The results obtained using the various dopants vary widely. It will be shown, however, that the above mentioned dopants can form complexes with Cd vacancies (vacancy-impurity pairs). As a result, these Cd vacancies can play a key role in determining the resistivity and carrier lifetimes.

A new analysis method using the photoelectron emission yield spectra near threshold has been developed to characterize solid surfaces exposed to ambient air. The application of the analysis method to the yield spectra for a Si (100) wafer surface covered with a native oxide film revealed that three emission peaks are cumulated on the basic yield spectrum line for the silicon. It was indicated that these peaks have a Gaussian-shaped density distribution and the energy levels are located at 5.37, 5.68, and 6.02 eV below the vacuum level, respectively.

The growth of ZnO films deposited by Closed Space Vapor Transport (CSVT) on sapphire substrates has been investigated. Deposition on R oriented sapphire substrates gives rise to a-(11-20) oriented ZnO films. Under optimised conditions, flat surfaces can be achieved and rocking curves with full half width below 500 arcsec are observed. The electrical properties of the films were studied. Hall measurements reveal that the measured n-carrier concentration decreases linearly upon the thickness of the sample. This is interpreted as interface conduction probably related to diffusion of aluminium from the substrate. On thinnest films, the n-carrier concentration can be dramatically decreased with thermal annealing under oxygen. Furthermore, the effect of this annealing under oxygen is found to be completely reversible after a further thermal annealing under oxygen free atmosphere.

The stress depth distribution in the silicon substrate under thin thermal oxide layers has been measured using the photoelastic technique. With the high sensitivity and improved spatial resolution of a newly developed low level birefringence detection system, it is confirmed that the stress distribution deviates significantly from the linear distribution predicted by classical bi-metallic strip theory. The deviation can be attributed to arising from Si self-interstitial injection during the thermal oxidation process. Long term changes in the stress distribution with time have also been observed and the changes can be understood in terms of point defect movements under the stress field in the substrate. Our preliminary results have demonstrated how we can probe microscopic point defect processes in thin film SiO2/Si substrate systems using a macroscopic photoelastic stress measurement technique.

The structural properties of GaN epitaxial layers grown on patterned sapphire substrates by MOCVD have been investigated using HRXRD(high-resolution X-ray diffraction), GIXRD(grazing incidence X-ray diffraction) and PL(photoluminescence). For X-ray characterizations rocking curves for GaN (10·5), (00·2), (11·4) and (11·0) reflections for which incidence angles of X-rays are 32.0°, 17.3°, 11.0° and 0.34°, respectively, were measured. For (10·5), (00·2) and (11·4) reflections FWHMs of the rocking curves for a patterned substrate were broader than those for a unpatterned substrate, for (11·0) reflection, however, FWHM for a patterned substrate was much narrower than that for a unpatterned substrate. The normalized FWHM for all reflections decreases as the incidence angle of X-ray decreases. The results indicate that the crystalline quality in the surface region of the epilayer on a patterned substrate was especially improved because the penetration depth of X-ray depends on the incidence angle. The intensity of PL peak of the epilayer for a patterned substrate increased compared to that for a unpatterned substrate, and the increase in PL intensity is attributed to the reduction in dislocation density at the surface region revealed the by X-ray results.

Change in dopant diffusion was observed for Arsenic source drain extension (SDE) implants when they were performed at various dose rates. The high dose SDE implant amorphizes the surface of the silicon substrate and the thickness of the amorphous layer is strongly influenced by the rate of dopant bombardment. It is well known that the ion implantation process introduces excess interstitials. While the amorphous region is completely re-grown into single crystal during subsequent anneal without leaving behind extended defects, interstitials that are injected beyond the amorphous layer lead to formation of {311} defects or dislocation loops in the end of range region. During thermal processing, these extended defects dissolve, release interstitials, which in turn lead to transient enhanced diffusion of underlying Boron halo dopant. Dopant depth profiles measured by SIMS revealed different amount of Boron pile-up in the near surface region, corresponding to different SDE implant dose rates. In CMOS devices, this surface pile-up would correlate with a Boron pile-up in the channel region that would lead to a shift in transistor characteristics. Through this investigation, we were able to explain the mechanism causing device characteristics shift resulted from SDE implant with the same dose and energy but different dose rates.

Arsenic doped Si:C films were grown epitaxially using Silcore® (Si3H8), methylsilane and arsine as source gases with growth rates up to 90 nm/min at 550°C. We observed a strong dependence of C and As incorporation on growth rate, caused by a growth rate dependent surface segregation behavior of C and As. High-resolution x-ray diffraction measurements of the epi layers reveal a perpendicular lattice constant as low as 5.323 Å. This corresponds to a biaxial stress of more than 2 GPa. Grazing exit (224) x-ray diffraction reciprocal space maps show the full tetragonal strain expected from the C content, suggesting that no relaxation of the films has occurred. Spectroscopic ellipsometry (SE) spectra were acquired in the 0.74 to 6.6 eV photon energy range. For intrinsic Si:C alloys, the E1 critical point shows the expected blueshift due to the alloying. For Si:C:As, a strong broadening of the E1 and E2 transitions exists, due to scattering of Bloch electrons in the crystal by As atoms. Additionally, free carrier effects lead to a decrease (increase) of the real (imaginary) part of the dielectric function in the near-infrared, consistent with a free carrier concentration in excess of 5×1020 cm-3. Transmission electron microscopy (TEM) of As doped Si:C films confirmed single-crystal epitaxial growth.

Zinc oxide (ZnO) has shown great promise as a wide-bandgap semiconductor with a range of optical, electronic, and mechanical applications. The presence of compensating donors, however, is a major roadblock to achieving p-type conductivity. Recent first-principles calculations and experimental studies have shown that hydrogen acts as a shallow donor in ZnO, in contrast to hydrogen's usual role as a passivating impurity. Given the omnipresence of hydrogen during growth and processing, it is important to determine the structure and stability of hydrogen donors in ZnO.

To address these issues, we performed vibrational spectroscopy on bulk, single-crystal ZnO samples annealed in hydrogen (H2) or deuterium (D2) gas. Using infrared (IR) spectroscopy, we observed O-H and O-D stretch modes at 3326.3 cm-1 and 2470.3 cm-1 respectively, at a sample temperature of 10 K. These frequencies indicate that hydrogen forms a bond with a host oxygen atom, consistent with either an antibonding or bond-centered model. In the antibonding configuration, hydrogen attaches to a host oxygen and points away from the Zn-O bond. In the bond-centered configuration, hydrogen sits between the Zn and O. To discriminate between these two models, we measured the shift of the stretch-mode frequency as a function of hydrostatic pressure. By comparing with first-principles calculations, we conclude that the antibonding model is the correct one.

Surprisingly, we found that the O-H complex is unstable at room temperature. After a few weeks, the peak intensity decreases substantially. It is possible that the hydrogen forms H2 molecules, which have essentially no IR signature. Electrical measurements show a corresponding decrease in electron concentration, which is consistent with the formation of neutral H2 molecules. The correlation between the electrical and spectroscopic measurements, however, is not perfect. We therefore speculate that there may be a second “hidden” hydrogen donor. One candidate for such a donor is a hydrogen-decorated oxygen vacancy.

Today's CCD image sensors can provide very high image quality. However, used as a tool, they can also provide a sensitive window into defects in silicon, either intrinsic to the starting wafers or introduced during fabrication. In this paper, we examine some cases of known silicon defects and show how they can appear in, and be studied by, CCD imagers. As examples, we discuss epi-layer defects, slip defects, and dark-current rings.

Self-diffusivity of Si has been obtained over a wide temperature range (867°C-1300°C) using highly isotopically enriched 30Si epi-layers (99.88%) as a diffusion source into natural Si substrates. 30Si epi-layers were grown on both CZ-Si substrates and non-doped epi-layers grown on CZ-Si substrates using low pressure CVD with 30SiH4. Diffusion was performed in resistance-heated furnaces under a pure Ar atmosphere. After annealing, the concentrations of the respective Si isotopes were measured with secondary ion mass spectroscopy (SIMS). Diffusivity of 30Si (called Si self-diffusivity, DSD) was determined using a numerical fitting process with 30Si SIMS profiles. We found no major differences in self-diffusivity between bulk Si and epi-Si. Within the 867°C -1300°C range investigated, DSD can be described by an Arrhenius equation with one single activation enthalpy: DSD =14 exp (—4.37 eV/kT) cm2/s. The present result is in good agreement with that of Bracht et. al.

Diffusivity and thermal equilibrium concentration of Si self-interstitials have been determined using multi-30Si epi-layers consisting of alternative layers with isotopically pure 30Si and natural Si. The sample surface was oxidized and the Si self-interstitials were introduced from the surface. Spreading of 30Si spikes of each layer due to the diffusion of Si self-interstitials generated at the surface was measured with SIMS analysis. The diffusivity of Si self-interstitials, DI, is obtained by fitting with experimental results. In the temperature range between 820 -920°C, DI and thermal equilibrium concentration of Si self-interstitials, CIi, are described by the Arrhenius equations DI3.48×104 exp (—3.82eV/KT) cm2/s and CIi= 9.62×1018 exp (—0.475eV/KT) cm-3, respectively.

A new post annealing method employing excimer laser pulses is proposed to improve the transfer characteristics and the breakdown voltage of the unpassivated AlGaN/GaN heterostructure field-effect transistor (HFET) and the passivated one. The XeCl excimer laser pulses with wavelength of 308 nm anneal the AlGaN/GaN HFET after the Schottky gate metallization. The interface defects between the Schottky gate metal and a GaN layer is decreased by the lateral heat diffusion of the laser pulses. Our experimental results show that the drain current and the maximum transconductance of the unpassivated AlGaN/GaN HFET after laser pulses annealing are 496 mA/mm and 134 mS/mm while a virgin device shows 434 mA/mm and 113 mS/mm, respectively. The proposed method anneals effectively the SiO2 passivated AlGaN/GaN HFET and the leakage current of the passivated device is decreased from 483 nA to 29 nA.

The ability to controllably position individual phosphorus dopant atoms in silicon sur-faces is a critical first step in creating nanoscale electronic devices in silicon, for example a phosphorus in silicon quantum computer. While individual P atom placement in Si(001) has been achieved, the ability to routinely position P atoms in Si for large-scale device fabrication requires a more detailed understanding of the physical and chemical processes leading to P atom incorporation. Here we present an atomic-resolution scanning tunneling microscopy study of the interaction of the P precursor molecule phosphine (PH3) with the Si(001) surface. In particular, we present the direct observation of PH3 dissociation and diffusion on Si(001) at room temperature and show that this dissociation is occasionally complete, leaving a P monomer bound to the surface. Such surface bound P monomers are important because they are the most likely entry point for P atoms to incorporate into the substrate surface at elevated temperature.

The ability to activate greater amounts of dopants is a significant challenge for the realization of shallow junctions in device scaling for Si CMOS technology. Dopant activation is difficult to achieve in shallow junctions due to higher concentrations of dopants and possible formation of dopant clusters. The high temperatures currently used to activate dopants result in increased junction depth and process integration issues with high-k dielectrics. However, lowering the annealing temperature results in lesser dopant activation and problems with transient enhanced diffusion. Our previous work reported on the enhancement of activation in boron implanted at a dose of 5E14/cm2 and annealed at temperatures of 450 °C and below, by the incorporation of atomic hydrogen introduced by exposing the substrate to a hydrogen plasma at 250 °C. In this work, further experiments have been carried out to get a better understanding of the mechanisms responsible for boron activation enhancement. Hydrogen-related activation was studied in boron, phosphorus and antimony implanted samples. The experimental results shed new light on the interactions among atomic hydrogen, point defects and dopants.

In this pioneering study, we have extended noble-gas implant-induced cavity generation in Si and other semiconductors to a dielectric, viz., SiO2 by implanting a variety of inert gas species. It has been seen that helium and neon do not induce bubbles/cavities in SiO2, regardless of implantation parameters and nature of the sample. Krypton and xenon implantation however result in bubbles/cavities formation in the oxide layer. In the case of Xe a minimum threshold dose of about 1016 cm-2 is needed for their formation. Characterization by cross-section transmission electron microscopy (XTEM) and Rutherford backscattering spectrometry (RBS) showed that bubbles/cavities remain even after a 1100°C anneal, while Xe strongly desorbs out at that temperature. C-V measurements reveal that the effective dielectric constant K is reduced from 3.9 SiO2 for bulk SiO2 to < 2.6, thus making this technique very attractive for low-k applications in Si technology.

Silicon carbide PIN diodes have been fabricated using a direct write laser doping and metallization technique. Trimethyaluminum (TMA) and nitrogen are precursors used to laser dope p-type and n-type regions, respectively, and μ4.3 mm p-type doped junction and 4 mm ntype doped junction are fabricated in semi-insulating 6H-SiC wafers. Rutherford backscattering studies show that no amorphization occurred during the laser doping process. A planar edge termination is fabricated by laser metallization in argon ambient to form a high resistivity layer. With this termination, the leakage current of the PIN diodes can be suppressed effectively compared to that of diodes without edge termination. The performance of the diodes can also be tailored by shrinking the active area of the diode and by conventional annealing.

A2B6 semiconductors and their solid solutions (ZnSe, ZnTe, CdTe, ZnCdHgTe) are matter of choice for near- and far-infrared optoelectronics. The importance of maximally reduced degree of defectness for these materials is not subjected to discussion. However, preparation of high quality barrier structures based on these compounds by means of MBE, laser technology or liquid phase technique is not always successful due to lattice parameters mismatch. At the same time, good selection of a proper buffer layer may also pose some unavoidable problems. From this point of view the nanoindentation as a tool of defect engineering can be effective for fabrication of surface barrier structures. The first experimental results and numerical simulation of experimental data obtained under investigation of nanoindentation effect on electric characteristics (in particular, current – voltage (I-V) and capacitance – voltage (C-V)) of ZnCdHgTe thin films and ZnCdHgTe/Cd(Zn)Te heterostructures at the room temperature are presented.

Tantalum oxide has attracted world-wide interest for DRAM (dynamic random access memory) capacitor applications because of its relative high dielectric constant compared to silicon dioxide or nitride. We would like to point out that tantalum oxide behaves very much like a large bandgap n-type semiconductor with 3 main types of donors responsible for leakage current. Native oxygen vacancies are very deep double donors with Ec – Ed = 0.8 eV approximately, where Ec is the bottom of the conduction band and Ed is the energy leVel of the defect state. Si-O vacancy complexes are relatively shallow single donors with Ec – Ed = 0.2-0.4 eV. C-O vacancy complexes are relatively shallow single donors with Ec – Ed = 0.5-0.6 eV. The key points regarding how to suppress these 3 types of donor defects will be discussed for the purpose of leakage current reduction.

Silicon samples were implanted with He+ ions at energies varying from 10keV to 1.55MeV using doses ranging from 1.45×1016 cm-2 to 5×1016cm-2 to obtain similar He concentration at each projection range (Rp). In few samples, gold, platinum, nickel or silver was introduced prior to He+ implantation by diffusion at temperatures ranging from 870°C to 1050°C. All samples were annealed in the 400°C–1050°C temperature range to determine the equilibrium stage of the growth of the cavity. The cavity characteristics (distribution, shape and size) were studied by cross section transmission electron microscopy (XTEM). Their morphology demonstrates the validity of the chemisorption hypothesis when they grow in silicon intentionally contaminated by metal. A consequence of the surface proximity on the cavity characteristics was verified and allows stepping forward two regimes of cavity growth: one, very fast, taking place in a He-free environment and another one, slower, occurring in a He-rich atmosphere.

We have investigated the structural and electrical behavior of Fe centers introduced in InP by high temperature ion implantation. The lattice location of the Fe atoms and the effect of postimplantation annealing treatments have been studied by PIXE-channeling measurements. I-V, CV and DLTS analyses have been used to characterize the electrical properties related to the presence Fe2+/3+ deep traps. The results show that the background n-doping density play a crucial role in controlling the annealing behavior and the electrical activation of the Fe centers. The same effect has been observed in samples containing Fe concentrations both above and below the Fe solubility threshold in InP.

Thin ZnO films deposited on silicon and glass substrates by DC reactive magnetron sputtering were exposed to a sequence of thermal treatments at 400°C in vacuum, then in air, then in vacuum again. Photoluminescence studies of these ZnO films exited at 325 nm by He-Cd laser revealed an appearance of a photoluminescence band around 380 nm upon the annealing in vacuum.

Thin SnOx films were deposited on glass substrates by ion-beam sputtering using pure oxygen as a working gas. X-ray diffraction analysis showed that as-deposited films consist of textured SnO2- and Sn2O3-crystallites which are transformed into polycrystalline SnO2 phase at a moderate temperature near 200°C. It is shown that the growth of the SnO2 crystallite size upon the annealing is mainly due to the disappearance of an amorphous phase at 400°C and coalescence of crystallites at 600°C.