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Register a new userElectrically detected magnetic resonance of carbon dangling bonds at the Si-face 4H-SiC/SiO$_2$ interface
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SiC based metal-oxide-semiconductor field-effect transistors (MOSFETs) have gained a significant importance in power electronics applications. However, electrically active defects at the SiC/SiO$_2$ interface degrade the ideal behavior of the devices. The relevant microscopic defects can be identified by electron paramagnetic resonance (EPR) or electrically detected magnetic resonance (EDMR). This helps to decide which changes to the fabrication process will likely lead to further increases of device performance and reliability. EDMR measurements have shown very similar dominant hyperfine (HF) spectra in differently processed MOSFETs although some discrepancies were observed in the measured $g$-factors. Here, the HF spectra measured of different SiC MOSFETs are compared and it is argued that the same dominant defect is present in all devices. A comparison of the data with simulated spectra of the C dangling bond (P$_textrm{bC}$) center and the silicon vacancy (V$_textrm{Si}$) demonstrates that the P$_textrm{bC}$ center is a more suitable candidate to explain the observed HF spectra.
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We study the coupling of Pb0 dangling bond defects at the Si/SiO2 interface and 31P donors in an epitaxial layer directly underneath using electrically detected double electron-electron resonance (EDDEER). An exponential decay of the EDDEER signal is observed, which is attributed to a broad distribution of exchange coupling strengths J/2pi from 25 kHz to 3 MHz. Comparison of the experimental data with a numerical simulation of the exchange coupling shows that this range of coupling strengths corresponds to 31P-Pb0 distances ranging from 14 nm to 20 nm.
We use many-body perturbation theory, the state-of-the-art method for band gap calculations, to compute the band offsets at the Si/SiO$_2$ interface. We examine the adequacy of the usual approximations in this context. We show that (i) the separate treatment of band-structure and potential lineup contributions, the latter being evaluated within density-functional theory, is justified, (ii) most plasmon-pole models lead to inaccuracies in the absolute quasiparticle corrections, (iii) vertex corrections can be neglected, (iv) eigenenergy self-consistency is adequate. Our theoretical offsets agree with the experimental ones within 0.3 eV.
The authors demonstrate readout of electrically detected magnetic resonance at radio frequencies by means of an LCR tank circuit. Applied to a silicon field-effect transistor at milli-kelvin temperatures, this method shows a 25-fold increased signal-to-noise ratio of the conduction band electron spin resonance and a higher operational bandwidth of > 300 kHz compared to the kHz bandwidth of conventional readout techniques. This increase in temporal resolution provides a method for future direct observations of spin dynamics in the electrical device characteristics.
We report the density-functional calculations that systematically clarify the stable forms of carbon-related defects and their energy levels in amorphous SiO$_2$ using the melt-quench technique in molecular dynamics. Considering the position dependence of the O chemical potential near and far from the SiC/SiO$_2$ interface, we determine the most abundant forms of carbon-related defects: Far from the interface, the CO$_2$ or CO in the internal space in SiO$_2$ is abundant and they are electronically inactive; near the interface, the carbon clustering is likely and a particular mono-carbon defect and a di-carbon defect induce energy levels near the SiC conduction-band bottom, thus being candidates for the carrier traps.
On the basis of ab-initio total-energy electronic-structure calculations, we find that interface localized electron states at the SiC/SiO$_2$ interface emerge in the energy region between 0.3 eV below and 1.2 eV above the bulk conduction-band minimum (CBM) of SiC, being sensitive to the sequence of atomic bilayers in SiC near the interface. These new interface states unrecognized in the past are due to the peculiar characteristics of the CBM states which are distributed along the crystallographic channels. We also find that the electron doping modifies the energetics among the different stacking structures. Implication for performance of electron devices fabricated on different SiC surfaces are discussed.
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