Electrical effect of titanium diffusion on amorphous indium gallium zinc oxide

The authors investigated trap generation by substrate hot-electron injection for MOS devices in which hydrogen was intentionally incorporated by forming gas anneal. It was found that the high-temperature forming gas anneal significantly enhances both interface and oxide trap generation at oxide fields during injection above 4 MV/cm, while no enhancement has been observed below 3 MV/cm. It was also found from secondary ion mass spectroscopy (SIMS) measurements that the forming gas anneal increases the hydrogen concentration at the poly-Si/SiO/sub 2/ interface but not in the gate oxide nor at the SiO/sub 2//Si interface. Based on these experimental results, a novel trap generation model, in which hydrogen released from Si-H at the poly-Si/SiO/sub 2/ interface by hot electrons causes the enhanced trap generation, is proposed. >

Drain bias effect on the instability of amorphous indium gallium zinc oxide thin film transistor

This chapter describes the creation of an Intermediate Band (IB) on single crystal silicon substrates by means of high-dose Ti implantation and subsequent Pulsed Laser Melting (PLM). The Ti concentration over the Mott limit is confirmed by Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) measurements and the recovery of the crystallinity after annealing by means of Glancing Incidence X Ray Diffraction (GIXRD) and Transmission Electron Microscopy (TEM). Rutherford Backscattering Spectroscopy (RBS) measurements show that most of the atoms are located interstitially. Analysis of the sheet resistance and mobility measured using the van der Pauw geometry shows a temperature-dependent decoupling between the implanted layer and the substrate. This decoupling and the high laminated conductivity of the implanted layer could not be explained except if we assume that an IB has been formed in the semiconductor. A specific model for the bilayer electrical behaviour has been developed. The fitting of this model and also the simulation of the sheet resistance with the ATLAS code allow to determine that the IB energetic position is located around 0.36–0.38 eV below the conduction band. Carriers at the IB have a density very similar to the Ti concentration and behave as holes with mobilities as low as 0.4 cm2 Vs− 1.

Chemical bonding states and dopant redistribution of heavily phosphorus-doped epitaxial silicon films: Effects of millisecond laser annealing and doping concentration

Depth profiles of Si nanocrystals formed in sapphire by ion implantation and the effect of charging during X-ray Photoelectron Spectroscopy (XPS) and Secondary Ion Mass Spectrometry (SIMS) measurements have been studied. Atomic concentration and the chemical environment of Si, Al, and O have been measured as a function of depth from the sample surface by SIMS and XPS. Both as-implanted and annealed samples have been analyzed to understand the effect of nanocrystal formation on the depth distribution, chemical structure, and the charging effect before and after the formation process. SIMS measurements have revealed that the peak position of the Si concentration shifts to deeper values with implantation dose. This is explained by the fact that the structure of the matrix undergoes a phase transformation from pure sapphire to a Si rich amorphous Al2O3 with heavy dose implantation. Formation of Si nanocrystals has been observed by XPS by an increase in the Si-Si signal and a decrease in Si-O bond concentrations after the annealing. Variation in binding energies of Si and O with Si concentration (i.e., with depth) has been studied in terms of chemical environments and charging effects. It is found that binding energy of these elements shifts to lower values with increasing Si content. This is a result of less charging due to the presence of easy discharge paths in the Si rich regions of the matrix. Nanocrystal formation leads to even less charging which is probably due to the further increase in conductivity with the formation.

High energy N+ ion implantation in 4H–SiC

This study investigates various tests on AlGaN/GaN high electron mobility transistor (HEMT) wafers, including photoluminescence spectroscopy, secondary ion mass spectroscopy, X‐ray diffraction (XRD), and Hall measurement. The AlGaN/GaN HEMT wafers are grown on low‐resistivity Si substrates with various growth conditions for the buffer and channel layers. Characteristics of AlGaN/GaN HEMTs including drain lag, dynamic RON, and current transients were measured and correlated with the results from the wafer level tests. Results indicate that epitaxial wafers with low yellow luminescence (YL) to band edge (BE) and blue luminescence (BL) to BE ratios as well as a low carbon concentration but a similar low full width at half maximum of XRD profiles can result in devices with significant suppression of current collapse and the same on‐state device characteristics. Therefore, both YL/BE and BL/BE values combined with the carbon concentration in wafer level tests are suitable indicators for estimating device performance.

In this study room temperature vulcanized (RTV) silicone surfaces with designed surface microstructure and well-defined surface chemistry were prepared. Their resistance to marine macrofouling by barnacles Balanus improvisus was tested in field experiments for deducing optimal surface topography dimensions together with a better understanding of macrofouling mechanisms. Polydimethylsiloxane (PDMS) surfaces were microstructured by casting the PDMS pre-polymer on microfabricated molds. The master molds were made by utilizing photolithography and anisotropic etching of monocrystalline silicon wafers. Several iterative casting steps of PDMS and epoxy were used to produce large quantities of microstructured PDMS samples for field studies. The microstructured PDMS surface consisted of arrays of pyramids or riblets creating a surface arithmetic mean roughness ranging from 5 to 17 μm for different microstructure sizes and geometries, as determined by scanning electron microscopy. Chemophysical properties of the microstructured films were investigated by electron spectroscopy for chemical analysis, time-of-flight secondary ion mass spectroscopy and dynamic contact angle measurements. Films were chemically homogeneous down to the submicron level. Hydrophobicity and contact angle hysteresis increased with increased surface roughness. Field tests on the west coast of Sweden revealed that the microstructure containing the largest riblets (profile height 69 μm) reduced the settling of barnacles by 67%, whereas the smallest pyramids had no significant influence on settling compared to smooth PDMS surfaces. The effect of dimensions and geometry of the surface microstructures on the B. improvisus larvae settling is discussed.

Rapid thermal chemical vapor deposition was utilized to deposit silicon-based dielectrics on III-V materials at high temperature. Silicon oxynitride films can be deposited on InP at 750 °C with compositions varying between silicon dioxide and silicon nitride. Secondary ion mass spectroscopy and nuclear reaction analysis measurements show that the oxygen concentration in the layers varies continuously with the oxidant gas flow rate. The overall stoichiometry of the films can be controlled with this parameter. The composition of the layers has a direct incidence on the mechanical tension of the insulator/semiconductor structures. A highly sensitive optical setup has been developed to measure the tension on these samples in order to determine the stoichiometry of the silicon oxynitride (SiOxNy) film that leaves the structure unstressed. The stress-free film composition is shown to depend also strongly on the thickness of the layer. A study of the overall stress introduced in a structure during its fabrication is presented.

Simple organic molecules such as 1‐octadecene, 1‐tetradecene, 1‐dodecyne and 1,13‐tetradecadiene have been grafted to hydrogenated B‐doped silicon (100) surfaces. Such substrate has been obtained by etching commercial native oxide‐capped flat crystal silicon wafers with procedures involving dilute HF aqueous solutions, but also by hydrogenation with a new method involving treatment of the wafer in an oven with H 2 gas. The functionalization of such a surface has been done by using described wet methodologies involving pure liquids or solutions with thermal activation of the hydride. Contact angle, ESCA, atomic force microscopy (AFM) and time‐of‐flight secondary ion mass spectroscopy (ToF‐SIMS) measurements have been carried out to characterize the above systems. Particular emphasis is devoted to the interpretation of the ToF‐SIMS spectra, seldom used until now to characterize organic monolayers. Copyright © 2002 John Wiley & Sons, Ltd.

ABSTRACTThree types of electrical contacts on natural type lib single crystal diamonds have been studied by current-voltage (IV) and capacitance-voltage (CV) measurements. Vertical structures were fabricated with the metal-diamond (MS), metal-undoped diamond-doped diamond (MiS), or metal-SiO2-doped diamond (MOS) contacts and ohmic contacts on the opposite face of the diamond. The MS contact was rectifying and both the MiS and MOS were blocking contacts. While very high leakage currents were measured on the MiS structure in forward bias (MO6times the reverse bias), an accumulation region was observed in the MiS CV data. The uncompensated acceptor concentration values calculated from the CV data were in good agreement for different structures fabricated on the same samples and with the secondary ion mass spectroscopy (SIMS) measurements of the bulk boron concentration. Extreme stretch out was observed in the CV of the MiS and MOS due to interface traps. The density of interface traps was estimated to be in the 1012 cm-2 eV-1 range for these structures.

The reflow properties of tetraethylorthosilicate‐ (TEOS‐) borophosphosilicate glass (BPSG) under furnace and rapid thermal processing conditions that we have studied show good void‐free, subquarter micron gapfill, and planarization. Thick BPSG films on reflow exhibit positive charge buildup at the oxide/Si interface that cause a shift in the flatband voltage. The amount of phosphorous in the BPSG film, the BPSG film thickness, and the BPSG deposition temperature determine the extent of this flatband shift. We observed a linear correlation of the flatband shift and the amount of carbon migration and pileup at the oxide/Si interface during reflow. Using current‐voltage, triangular voltage sweep, and secondary ion mass spectroscopy and field threshold voltage measurements, we demonstrate that under appropriate deposition conditions the flatband shift can be brought to negligible levels.

Strong luminescence from the nitrogen–nitrogen (N–N) interstitials had been observed in GaAsN epilayers grown by metal organic chemical vapour deposition (MOCVD) using nitrogen as the carrier gas. These N–N interstitials in the GaAsN films were thoroughly studied through photoluminescence (PL) and secondary ion mass spectroscopy (SIMS) measurement combined with X-ray diffraction (XRD) measurement. The N–N interstitial emission peak resided at deep level of 0.2–0.23 eV below the inter-band gap transition energy of the GaAsN epilayer. The N–N interstitial PL intensity decreased after the GaAsN samples were thermal annealed. It had also been found that the N–N interstitials contribute to the substitutional nitrogen composition of the GaAsN epilayer after rapid thermal annealing were carried out on the GaAsN epilayer.

GaN thin films have been doped with varying Er concentrations (0.01–10 at. %) during molecular-beam-epitaxy growth. As expected, the visible and infrared (IR) emissions, from photoluminescence (PL) and electroluminescence (EL), are a strong function of Er concentration. We report on the determination of an optimum Er doping level for PL and EL intensity. Secondary ion mass spectroscopy and Rutherford backscattering measurements showed that the Er concentration in GaN increased exponentially with Er cell temperature. PL and EL intensity of green emission at 537 and 558 nm, due to Er 4f–4f inner shell transitions, exhibited a maximum at ∼1 at. % Er. IR PL intensity at 1.54 μm, due to another Er transition, revealed the same maximum for ∼1 at. % Er concentration. PL lifetime measurements at 537 nm showed that samples with Er concentration <1 at. % had a lifetime of ∼5 μs. For Er concentration ⩾1 at. %, the lifetime decreased rapidly to values below 1 μs. This concentration quenching is believed to be due to a combination of Er cross relaxation and energy transfer to GaN defects, eventually followed by precipitation. This conclusion is supported by x-ray diffraction measurements. As a result, we have determined that the optimum Er doping concentration into GaN is ∼1 at. %.

To improve the doping efficiency of boron (B)-doped hydrogenated amorphous silicon [a-Si:H(p)] films, a three-step post-B-doping method was developed. This post-treatment method presents the potential to enhance not only the B content but also the hydrogen content in a-Si:H(p) films by increasing the number of treatment times. Based on secondary ion mass spectroscopy and dark conductivity measurements, the B concentration and efficiency of B-doping in a-Si:H(p) films were effectively improved by the three-step B-doping treatment. Furthermore, it was demonstrated that the atomic hydrogen generated during the B-doping process could diffuse into the a-Si:H(p) film and the underlying a-Si:H(i) layers, which is beneficial for suppressing the carrier recombination in the a-Si:H(p/i) passivation layers. There was an absolute increase of 600 μs in the effective minority carrier lifetime in the standard a-Si:H(n)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(p) structure by the 3× three-step treatment on the emitter side. Consequently, enhancements in both the open circuit voltage and the fill factor were observed, resulting in a 0.28% absolute gain (approximately) in the conversion efficiency of silicon heterojunction cells.