Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA novel intrinsic interface state controlled by atomic stacking sequence at interfaces of SiC/SiO$_2$
132
0
0.0
(
0
)
Added by
Yu-ichiro Matsushita
Publication date
2017
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
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.
rate research
Read More
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.
The structural, electronic, and adhesive properties of Cu/SiO$_2$ interfaces are investigated using first-principles density-functional theory within the local density approximation. Interfaces between fcc Cu and $alpha$-cristobalite(001) surfaces with different surface stoichiometries are considered. Interfacial properties are found to be sensitive to the choice of the termination, and the oxygen density at the substrate surface is the most important factor influencing the strength of adhesion. For oxygen-rich interfaces, the O atoms at the interface substantially rearrange after the deposition of Cu layers, suggesting the formation of Cu-O bonds. Significant hybridization between Cu$-d$ and O$-p$ states is evident in site-projected density of states at the interface. As oxygen is systematically removed from the interface, less rearrangement is observed, implying weaker adhesion. Computed adhesion energies for each of the interfaces are found to reflect these observed structural and bonding trends, leading to the largest adhesion energy in the oxygen rich cases. The adhesion energy is also calculated between Cu and SiO$_2$ substrates terminated with hydroxyl groups, and adhesion of Cu to these substrates is found to be considerably reduced. This work supports the notion that Cu films can adhere well to hydroxyl-free SiO$_2$ substrates should oxygen be present in sufficient amounts at the interface.
Despite its interest for CMOS applications, Atomic Layer Deposition (ALD) of GeO$_{2}$ thin films, by itself or in combination with SiO$_{2}$, has not been widely investigated yet. Here we report the ALD growth of SiO$_{2}$/GeO$_{2}$ multilayers on Silicon substrates using a so far unreported Ge precursor. The characterization of multilayers with various periodicities reveals successful layer-by-layer growth with electron density contrast and absence of chemical intermixing, down to a periodicity of 2 atomic layers.
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.
SiC is set to enable a new era in power electronics impacting a wide range of energy technologies, from electric vehicles to renewable energy. Its physical characteristics outperform silicon in many aspects, including band gap, breakdown field, and thermal conductivity. The main challenge for further development of SiC-based power semiconductor devices is the quality of the interface between SiC and its native dielectric SiO$_2$. High temperature nitridation processes can improve the interface quality and ultimately the device performance immensely, but the underlying chemical processes are still poorly understood. Here, we present an energy-dependent hard X-ray photoelectron spectroscopy (HAXPES) study probing non-destructively SiC and SiO$_2$ and their interface in device stacks treated in varying atmospheres. We successfully combine laboratory- and synchrotron-based HAXPES to provide unique insights into the chemistry of interface defects and their passivation through nitridation processes.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
