Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in a semiconductor industry that is silicon-based and currently faced with diminishing returns of performance versus cost of investment. At a material level, its high electric field strength and electron mobility have already shown tremendous potential for high frequency communications and photonic applications. Advances in growth on commercially viable large area substrates are now at the point where power conversion applications of GaN are at the cusp of commercialisation. The future for building on the work described here in ways driven by specific challenges emerging from entirely new markets and applications is very exciting. This collection of GaN technology developments is therefore not itself a road map but a valuable collection of global state-of-the-art GaN research that will inform the next phase of the technology as market driven requirements evolve. First generation production devices are igniting large new markets and applications that can only be achieved using the advantages of higher speed, low specific resistivity and low saturation switching transistors. Major investments are being made by industrial companies in a wide variety of markets exploring the use of the technology in new circuit topologies, packaging solutions and system architectures that are required to achieve and optimise the system advantages offered by GaN transistors. It is this momentum that will drive priorities for the next stages of device research gathered here.

A comprehensive overview of novel high voltage GaN field effect transistors (FETs) based on the Polarization Superjunction (PSJ) concept and a cost-effective approach towards manufacturing these high performance devices are presented. Current challenges impeding wider adoption of GaN power switching transistors in applications, and latest results of scaled-up PSJ-FETs from POWDEC KK, have also been discussed. The article also presents hard-switching characteristics of 400V-to-800V boost converter constructed using a PSJ-FET grown on sapphire substrate and the future direction of GaN power semiconductor technology based on monolithic integration for advanced power electronics.

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Weight losses of aluminum in hydrochloric acid are diminished in the ranges 16–75 for n-; 40–90 for di-n~ and 50–98percent for tri-n-butylamine. Inhibitor efficiency increases with acid concentration up to 1.25 or 1.5 N, depending on the inhibitor and is practically constant thereafter. Efficiency increases with increased inhibitor concentration up to a certain value, then remains constant. Optimum inhibitor concentration depends on acid concentration and immersion period. Experimental results indicate corrosion of pure aluminum in hydrochloric acid solutions is essentially under cathodic control and inhibition by amines is by adsorption on cathodic areas. A similar mechanism is indicated for aluminum alloyed with manganese.