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Register a new userSecond-harmonic interferometric spectroscopy of the buried Si(111)-SiO$_2$ interface
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The second-harmonic interferometric spectroscopy (SHIS) which combines both amplitude (intensity) and phase spectra of the second-harmonic (SH) radiation is proposed as a new spectroscopic technique being sensitive to the type of critical points (CPs) of combined density of states at semiconductor surfaces. The increased sensitivity of SHIS technique is demonstrated for the buried Si(111)-SiO$_2$ interface for SH photon energies from 3.6 eV to 5 eV and allows to separate the resonant contributions from $E^prime_0/E_1$, $E_2$ and $E^prime_1$ CPs of silicon.
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The mechanism of DC-Electric-Field-Induced Second-Harmonic (EFISH) generation at weakly nonlinear buried Si(001)-SiO$_2$ interfaces is studied experimentally in planar Si(001)-SiO$_2$-Cr MOS structures by optical second-harmonic generation (SHG) spectroscopy with a tunable Ti:sapphire femtosecond laser. The spectral dependence of the EFISH contribution near the direct two-photon $E_1$ transition of silicon is extracted. A systematic phenomenological model of the EFISH phenomenon, including a detailed description of the space charge region (SCR) at the semiconductor-dielectric interface in accumulation, depletion, and inversion regimes, has been developed. The influence of surface quantization effects, interface states, charge traps in the oxide layer, doping concentration and oxide thickness on nonlocal screening of the DC-electric field and on breaking of inversion symmetry in the SCR is considered. The model describes EFISH generation in the SCR using a Green function formalism which takes into account all retardation and absorption effects of the fundamental and second harmonic (SH) waves, optical interference between field-dependent and field-independent contributions to the SH field and multiple reflection interference in the SiO$_2$ layer. Good agreement between the phenomenological model and our recent and new EFISH spectroscopic results is demonstrated. Finally, low-frequency electromodulated EFISH is demonstrated as a useful differential spectroscopic technique for studies of the Si-SiO$_2$ interface in silicon-based MOS structures.
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.
Optical second-harmonic generation is demonstrated to be a sensitive probe of the buried interface between the lattice matched semiconductors gallium phosphide and silicon with (001) orientation. Rotational anisotropy measurements of SHG from GaP/Si show a strong isotropic component of the response not present for pure Si(001) or GaP(001). The strength of the overlaying anisotropic response directly correlates with the quality of the interface as determined by atomically resolved scanning transmission electron microscopy.Optical second-harmonic generation is demonstrated to be a sensitive probe of the buried interface between the lattice matched semiconductors gallium phosphide and silicon with (001) orientation. Rotational anisotropy measurements of SHG from GaP/Si show a strong isotropic component of the response not present for pure Si(001) or GaP(001). The strength of the overlaying anisotropic response directly correlates with the quality of the interface as determined by atomically resolved scanning transmission electron microscopy. Systematic comparison of samples fabricated with different growth modes in metal organic vapor phase epitaxy reveals that the anisotropy for different polarization combinations can be used as a selective fingerprint for the occurrence of anti-phase domains and twins. This all-optical technique can be applied as an {it in-situ} and non-invasive monitor even during growth. Systematic comparison of samples fabricated with different growth modes in metal organic vapor phase epitaxy reveals that the anisotropy for different polarization combinations can be used as a selective fingerprint for the occurrence of anti-phase domains and twins. This all-optical technique can be applied as an {it in-situ} and non-invasive monitor even during growth.
We present a novel spectroscopic technique for second harmonic generation (SHG) using femtosecond laser pulses at 30~kHz repetition rate, which nevertheless provides high spectral resolution limited only by the spectrometer. The potential of this method is demonstrated by applying it to the yellow exciton series of Cu$_2$O. Besides even parity states with $S-$ and $D-$ envelope, we also observe odd parity, $P-$ excitons with linewidths down to 100 $mu$eV, despite of the broad excitation laser spectrum with a full width at half maximum of 14~meV. The underlying light-matter interaction mechanisms of SHG are elaborated by a group theoretical analysis which allows us to determine the linear and circular polarization dependences, in good agreement with experiment.
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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