Time resolved photoluminescence (PL) decays have been measured for Si nanocrystals embedded in silicon dioxide. The nanocrystals were formed by implanting 40 keV Si ions into a 1000 Å thick film of thermally grown ${\mathrm{SiO}}_2,$ followed by thermal annealing at 1000–1200 °C. The observed luminescence, peaking at 700–850 nm, is compared to similar measurements performed on porous Si emitting in the same wavelength range. The results show that the PL from the nanocrystals exhibits a stretched exponential decay with characteristic decay time τ in the range 10–150 μs and dispersion factor β in the range 0.7–0.8. Both parameters are, however, higher for the nanocrystals compared to those of porous Si indicating superior passivation of the nanocrystals in the ${\mathrm{SiO}}_{\mathrm{2}}$ matrix. Evidence is also presented for a single exponential behavior at the decay end suggesting a remaining fraction of excitons in isolated nanocrystals. We attribute the highly nonlinear dose dependence of the PL yield to a nucleation process for the nanocrystals and a more curved decay line shape for higher ion doses to a higher crystal density, promoting excitonic migration to nearby nanocrystals. These observations provide strong evidence that the origin of the stretched exponential line shape of the PL decay results from migration and trapping of excitons in a system of randomly distributed and interconnected nanocrystals with a dispersion in size.

The extension of stacking faults in a forward-biased 4H-SiC PiN diodes by the recombination-enhanced motion of leading partial dislocations has been investigated by the technique of optical emission microscopy. From the temperature dependence of the measured velocity of the partials, an activation energy of 0.27 eV is obtained. Based on this and analysis of the emission spectra, a radiative recombination level of 2.8 eV for the stacking fault, and two energy levels for the partial dislocation, a radiative one at 1.8 eV and a nonradiative at 2.2 eV, have been determined.

By combining results from positron annihilation and photoluminescence spectroscopy with data from Hall effect measurements, the characteristic deep level emission centered at $\sim${}1.75 eV and exhibiting an activation energy of thermal quenching of 11.5 meV is associated with the zinc vacancy. Further, a strong indication that oxygen interstitials act as a dominating acceptor is derived from the analysis of charge carrier losses induced by electron irradiation with variable energy below and above the threshold for Zn-atom displacement. We also demonstrate that the commonly observed green emission is related to an extrinsic acceptorlike impurity, which may be readily passivated by oxygen vacancies.

The band-to-band Auger recombination in 4H-SiC material is studied using a time-resolved photoinduced absorption technique. The Auger recombination coefficient is derived from the kinetics of electron-hole plasma in heavily doped n-type 4H-SiC and in low-doped 4H-SiC epitaxial layers in the temperature interval 300–565 K. Within this range, its value decreases from ${\gamma }_3{\text{=(7±1)×10}}^{\text{−31}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{6}}{\mathrm{\hspace{0.17em}s}}^{\mathrm{-1}}$ to ${\gamma }_3{\text{=(4±1)×10}}^{\text{−32}}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{6}}{\mathrm{\hspace{0.17em}s}}^{\mathrm{-1}}.$ The observed pronounced reduction of Auger recombination rate with temperature is correlated to temperature dependent threshold energy of Auger process.

We report on optically induced nucleation and expansion of stacking faults in hexagonal SiC structures. The activation energy for partial dislocation glide under optical excitation is found to reduce to $0.25\pm 0.05\mathrm{eV}$, which is about 2 eV lower than for pure thermal activation. From the measurements of thermal activation and below-gap excitation spectroscopy of dislocation glide, we conclude that the elementary process controlling expansion of stacking faults is kink pair nucleation aided by the phonon-kick mechanism. We propose that solitons on 30° Si(g) partials with a silicon core act as deep $2.4\mathrm{eV}+E_V$ trap sites, readily providing electron-hole recombination energy to enhance the motion of dislocations. Our results suggest that this is a general mechanism of structural degradation in hexagonal SiC.

Reliable single-photon emission is crucial for realizing efficient spin-photon entanglement and scalable quantum information systems. The silicon vacancy ( $${V}_{{\rm{Si}}}$$VSi ) in 4H-SiC is a promising single-photon emitter exhibiting millisecond spin coherence times, but suffers from low photon counts, and only one charge state retains the desired spin and optical properties. Here, we demonstrate that emission from $${V}_{{\rm{Si}}}$$VSi defect ensembles can be enhanced by an order of magnitude via fabrication of Schottky barrier diodes, and sequentially modulated by almost $$50 \%$$50% via application of external bias. Furthermore, we identify charge state transitions of $${V}_{{\rm{Si}}}$$VSi by correlating optical and electrical measurements, and realize selective population of the bright state. Finally, we reveal a pronounced Stark shift of 55 GHz for the V1′ emission line state of $${V}_{{\rm{Si}}}$$VSi at larger electric fields, providing a means to modify the single-photon emission. The approach presented herein paves the way towards obtaining complete control of, and drastically enhanced emission from, $${V}_{{\rm{Si}}}$$VSi defect ensembles in 4H-SiC highly suitable for quantum applications.