Identification of Slow States at the SiO₂/SiC Interface through Sub-Bandgap Illumination

We show that it is possible to obtain information relating to deep level interface traps, or so called 'slow states', by using the photo-CV characterisation method. Sub-bandgap illumination has been chosen in order to avoid band-to-band excitation for the creation of minority carriers. This enables information to be extracted from trapping states at the SiO₂/SiC interface that are energetically deep within the band gap. Empirical observations of deep level trapping states with life times in the order of tens of hours are reported and the interface trap density as a function of energy has been extracted using the Terman method. Characterisation of these interface states will aid the development of new fabrication processes, with the aim of reducing the interface trap density to the same level as that of the SiO₂/Si interface and facilitating the production of higher quality SiC based devices.