Andrew Edwards

Vertical power diodes in bulk GaN

Vertical diodes with breakdown voltages up to 2.6kV have been fabricated on bulk GaN substrates. The measured figures-of-merit of these devices show performance near the theoretical limit of GaN. These vertical GaN diodes exhibit robust avalanche breakdown behavior with a positive temperature coefficient. System-level performance advantages have been demonstrated in power conversion applications. Statistical data have been collected from thousands of devices. Initial reliability tests have been completed.

Cycloadditions and nucleophilic attack on Z-2H-heptafluorobut-2-ene

Abstract Chemistry of Z-2H-Heptafluorobut-2-ene 1 is surveyed; cycloaddition reactions occur with a variety of benzenoid compounds, in some cases leading directly to aromatics. Addition to cyclopentadiene, followed by eliminations of hydrogen fluoride and ethyne, lead to isomeric bistrifluoromethylcyclopentadienes. Nucleophilic reactions occur readily with oxygen, nitrogen and sulphur nucleophiles and aniline provides a quinoline synthesis.

A broadband low cost GaN-on-silicon MMIC amplifier

The design and performance of a 0.1 to 5 GHz medium power distributed amplifier is described. The circuit is realized using a low-cost GaN-on-silicon MMIC process featuring 0.5 mum gate length GaN HFETs on a 150 mum thick high resistivity silicon substrate. The circuit was designed using a non-linear FET model and standard passive component models. The first pass circuit demonstrates a saturated output power of 2 W and a maximum efficiency of greater than 30% at 1 GHz at a drain bias of 15 V, and a saturated output power of 3 W and maximum efficiency of 23% at 2.5 GHz with a drain bias of 28 V.

AMBIDENT NUCLEOPHILIC ADDITION TO ETHYL TRIFLUOROMETHYLACETOACETATE

Abstract Reaction between hydroxylamine (1) and ethyl trifluoromethylacetoacetate (2) is reported. A crystal structure of the resultant isoxazolidin-3-one (3) was obtained.

Perfluorocarbon fluids as solvent replacements

Perfluoroperhydrophenanthrene 1 may be used as a ‘bulking agent’ to minimise the problem of solvent recovery in halogen exchange (‘Halex’) reactions for the preparation of octafluorocyclopentene 8, and chlorofluoro-pyridine, -pyrimidine and -benzene derivatives. New ‘one-pot’ procedures for the syntheses of hexafluorobut-2-yne 3, octafluorobut-2-ene 11 and hexafluorocyclobutene 7 are described.

A Comparison of AlGaN/GaN HFETs on Si Substrates in Ceramic Air Cavity and Plastic Overmold Packages

AlGaN/GaN HFETs on Si substrates have been assembled in ceramic air cavity and plastic overmold packages. Thermal, DC, small and large signal RF and reliability characterization have been performed on both types of devices. Thermal characterization shows that the thermal resistance of the plastic overmolded parts is higher resulting in higher operating temperatures. The higher operating temperature causes parameters such as the peak CW power to be lower than that seen in the ceramic air cavity package. The advantage of the plastic packaging resides in its >10x lower package assembly cost.

High-Power and High-Voltage AlGaN/GaN HEMTs-on-Si

GaN-on-Silicon technology is a highly manufacturable, reliable, and cost effective AlGaN/GaN HEMT platform. Maximum RF performance (power and efficiency) can be achieved by addressing two main areas related to the silicon substrate: the RF loss to the silicon substrate and the thermal resistance of the device to the heat sink. In this paper, we will report on how the two areas can be addressed in a realistic environment to enable high power, high voltage operation. This device technology can be used to develop high power amplifiers that are significantly smaller, lighter, and operate over a broad bandwidth.