Throwing some light on interface traps

14 06 2011

We’ve been looking to put some more data in preparation for our abstract being accepted for ICSCRM. Chris, one of our third year undergraduate students has been looking at the behaviour of the SiO2/SiC interface under illumination and we sent this off as an abstract. Since then, he’s finished his exams and called in for the day to run some more tests, with a view to understanding the data he took before. The data shows that using sub bandgap illumination, you can photoexcite a trap level in the bandgap, which shows as a second peak in the conductance data.

Conductance trap SiC MOS illumination

Conductance data under illumination

The capacitance data also shows an effect on illumination

Capacitance MOS data trap SiC

Capacitance data under illumination

Whilst none of this data is corrected for the artefacts from the measurement system, it appears that we are causing a big change in DIT with this illumination and the next job is to extract this using the Terman method to find out what we are looking at.

Having photoexcited these traps, we have gone to look at their decay rate, as one of the critical issues in SiC MOS interfaces is the existence of so called ‘slow states’ By looking at the decay of the capacitance and conductance with time, we found that these traps are still releasing carriers some 24 hours after the illumination is removed. It looks like we need to set the system up to run for longer this weekend in the hope that we can get back to the un-illuminated condition!

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