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The development and scaling-up of a process for the growth of large diameter aluminum nitride thick films on 2-in sapphire is described. Optimal growth rates between 10 and 15 μ m/h have been reached by adjustment of the reactor pressure, substrate temperature and gas flows. The layer thickness is determined by in situ laser reflection from the layer surface and ex situ by the curve of reflectivity versus wavelength after growth. The crystal quality is demonstrated by in situ laser reflection, scanning electron microscopy (cross sectional images and thickness) and atomic force microscopy (average roughness before and after polishing in the ranges of 20–50 and 3–8 nm, respectively).

Indium phosphide, gallium arsenide phosphide, and aluminum indium phosphide have been deposited by metalorganic vapor-phase epitaxy using tertiarybutylphosphine and tertiarybutylarsine. The effects of growth temperature and V/III ratio on the amount of silicon, sulfur, carbon, and oxygen in InP have been determined. Minimum incorporation was observed at 565 °C and a V/III ratio of 32. In this case, the material contained a background carrier concentration of 2.7×10 14 cm −3 , and the Hall mobilities were 4970 and 135,000 cm 2 /V s at 300 and 77 K. The oxygen contamination in AlInP was found to be only 9.0×10 15 cm −3 for deposition at 650 °C and a V/III ratio of 35. The relative distribution of arsenic to phosphorus in GaAs y P 1− y was determined at temperatures between 525 and 575 °C. The distribution coefficient [ ( N As / N P ) film / ( P TBAs / P TBP ) gas ] ranged from 25.4 to 8.4, and exhibited an Arrhenius relationship with an apparent activation energy of 1.2 eV.

The reduction in oxygen contamination levels in organometallic precursors has been established as a key requirement in the metal organic vapour-phase epitaxy (MOVPE) of high brightness light emitting diode (LED) and laser devices. A number of different volatile oxygen-containing impurity species have been identified, and both physical and chemical techniques have been developed to eliminate them from a wide range of source materials to produce the next generation grade of high-purity products. In this study conclusive growth results are presented to highlight the significantly improved quality of device structures obtained when higher purity oxygen-free precursors are employed.

We report here a synthetic route to bis(N,N'-aryl)-6-aminofulvene-2-aldimine (AFA) ligand systems, specifically Ph(2)-AFAH and Dip(2)-AFAH. The synthesis and structural characterization of a series of Cu(I) complexes [(Ph(2)-AFA)Cu(CNPh)(2)] (2), [(Ph(2)-AFA)Cu(CN(i)Pr)] (3), and [(Dip(2)-AFA)Cu(CN(i)Pr)] (4), from the reaction of the corresponding lithiated AFA systems with Cu-Cl derivatives are reported; notably in the case of [(Ph(2)-AFA)Cu(CNPh)(2)] studies have revealed the existence of two structural isomers (2a and 2b), both of which can be isolated and structurally characterized. Density functional theory (DFT) calculations suggest that the two crystal forms are comparatively close in energy, and geometry optimization reveals a convergence of these two forms to a geometry that more closely resembles the solid-state structure of isomer 2b, having a CH···π interaction. The reactions of the AFA compounds Ph(2)-AFAH and Dip(2)-AFAH with ZnMe(2) and AlMe(3) have also been investigated, and the results of these reactions are described here.

The reaction of [(eta(5)-C(5)H(5))Cu(CNPh)] with phenyl-isocyanide results in an unprecedented double migratory insertion into two sp(2) C-H bonds of a eta(5)-coordinated cyclopentadienyl group, and formation of the 6-aminofulvene-2-aldimine complexes [(CNPh)Cu{kappa(2)-N,N-C(5)H(3)-1,2-(CHNPh)(2)}] and [(CNPh)(2)Cu{kappa(2)-N,N-C(5)H(3)-1,2-(CHNPh)(2)}], respectively, both of which have been structurally characterised.

Transport of trimethylindium (TMI) must be highly reliable throughout source lifetimes. Bubbler design is a key factor and a number of different designs have been assessed. Significant improvements in output stability are demonstrated.

In the MOVPE process a steady, controllable flux of precursor into the reaction chamber is a key factor when fabricating highly complex device structures employing ternary and quaternary layers. Historically a simple bubbler design has been employed to perform this task with carrier gas flow and source temperature control able to provide a suitably stable system. However, with the increasing volume demands placed on MOVPE equipment, increased flows and larger bubblers have become necessary and the simple dip tube (dip leg) approach is no longer 100% suitable. In this study, an investigation of 3 novel bubbler dip tube designs have been performed and a comparison made with the standard approach. An Epison III ultrasonic analyser was employed to monitor the pick up of the precursor from a variety of bubblers across a range of flow rates and temperatures. Flows up to 10 sclm have been investigated and differences observed between bubbler dip leg designs the results of which highlight the improvements achievable using a new crosspiece dip tube design.

In current times when molecular biology is King attention is generally directed towards protein factors at the expense of perhaps equally important low molecular weight non-protein factors. To a large extent this has been true for angiogenesis. Protein angiogenic factors such as fibroblast growth factors (FGFS) have received disproportionate attention despite being notoriously non-specific for the microvasculature where angiogenesis occurs.