Contact failings

26 02 2011

The SIMS results are back from Loughborough Surface Analysis, who have been investigating the contacts of our long term JFETs. The results indicate that the predominant wear out mechanism in our devices is linked to the failure of the contacts, which is caused by oxidation at the NiSi surface. This should be an interesting problem to fix! Increasing the resistance of the contacts in our Finite Element simulations indicates that we can describe this accurately.

Elsewhere, our success with measuring noise in SiC JFETs has hit the buffers, as we can’t link up the existing kit to a hot plate and so would be stuck to measurements at just 25C. Obviously this is of no interest to us, so we are having to go out and build a new rig, based around a Stanford Research SRS760 we got from a second hand dealer. This could yet be a blessing in disguise as the software with our existing Agilent unit is very inflexible when it comes to deciding on the measurements you need, however it does have the ability to automatically extract noise parameters from the data.

The next challenge is the funding opportunity released from the Innovative Electronics Manufacturing Research Centre, who are looking to award around £1.5M to projects looking to sustain and develop high value manufacturing in the field of electronics. This would seem like an ideal opportunity for silicon carbide, as it has the potential to enable a wide range of possibilities which are not possible with conventional silicon.

Curious conductance

13 02 2011

The conductance data from the aged capacitors is throwing up a number of interesting surprises. It’s strange, but it is often considered to be the poor cousin of the capacitance – voltage characteristic, however it would appear that there’s plenty to discover in here and not all of it appears to be described in the literature. The first observation is that the amplitude of the peak can be used to describe the interface trap density, Dit, using the HIll – Coleman technique. (although this generally underestimates Dit, this is the technique everyone uses in SiC) That for most people is the end of the story …

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