Observation of magnetoresistance effect in charge pumping measurements

We report on a new magnetoresistance effect based on spin dependent trapping events at MOSFET gate/substrate interfaces called near zero field spin dependent charge pumping (NZF SDCP). NZF SDCP involves the application of a trapezoidal gate voltage waveform which cycles the substrate Fermi level between the conduction and valence band edges. Interface defects are cyclically filled and emptied, generating a net substrate recombination current proportional to the number of defects. The change in current is measured as a function of magnetic field. We find that: (1) in most cases the NZF SDCP amplitude appears to saturate as a function of waveform frequency, and (2) the NZF SDCP spectrum broadens with increasing frequency. These observations may allow for experimental exploration of several magnetoresistance theories regarding interaction or exchange times between charge carriers and defect spin centers. (3) The addition of N to the 4H-SiC MOSFET interface can have a profound impact on the NZF SDCP response, and (4) we almost certainly resolve electron-nuclear hyperfine interactions from a H-complexed defect. These observations strongly suggest that NZF SDCP could be a powerful tool to obtain atomic-scale physiochemical information about MOSFET interface defects.