Extraction of dipolar coupling constants from low-frequency electrically detected magnetic resonance and near-zero field magnetoresistance spectra via least squares fitting to models developed from the stochastic quantum Liouville equation

We report low-frequency electrically detected magnetic resonance (EDMR) and near-zero field magnetoresistance (NZFMR) measurements observed through spin-dependent trap-assisted tunneling on unpassivated Si-28/(SiO2)-Si-28 metal-insulator-semiconductor (MIS) capacitors. This study both experimentally and theoretically explores the effects of the low-frequency EDMR response and the mechanisms responsible for spin-mixing, which leads to the NZFMR response in the absence of electron-nuclear hyperfine interactions. Previous reports that utilized high-frequency EDMR and NZFMR on these devices indicated that the observed trap-assisted tunneling spectra are dominated by silicon dangling bonds back bonded to silicon at the Si/SiO2 interface, P-b0 and P-b1 centers. These previous results also suggest that the rate limiting step in trap-assisted tunneling is the interface to an oxide trapping event. In this work, we extend the theory to show the explicit connection of the defects observed between the NZFMR response and the EDMR, which has not yet been demonstrated. We also extend a theoretical approach to the analysis of both the EDMR and NZFMR spectra and match the theory to experimental observations made in Si-28/(SiO2)-Si-28 MIS capacitors. The method utilizes a least squares fitting algorithm of models developed from the stochastic quantum Liouville equation. We find that we can extract a dipolar coupling constant by fitting both the NZFMR and EDMR spectra. Our experimental results and resulting fitted spectra from our quantitative model suggest the mechanism responsible for spin-mixing, which leads to the NZFMR response in the absence of electron-nuclear hyperfine interactions, is predominately magnetic dipolar interactions between P-b centers at the interface.