Papers by Keyword: Cathodoluminescence

Abstract: Analysis of forward bias degradation reduction of 4H-Silicon Carbide (4H-SiC) PiN diodes on bonded substrates was performed. In the analysis, cathodoluminescence (CL), photoluminescence imaging (PL imaging), and transmission electron microscope (TEM) were used. Under high forward bias stress, the Shockley-type stacking fault (SSF) does not expand into the transferred layer of the bonded substrate, while in the monocrystalline substrate, the SSF expands below the epilayer/substrate interface. The basal plane dislocation (BPD) within the transferred layer does not expand to the SSF. The transferred layer has the effect of suppressing the expansion of SSFs. This effect can be caused by hydrogen implantation for wafer splitting to produce bonded SiC substrates.

Abstract: Point defects in silicon carbide (SiC) are well positioned for integration with SiC based quantum photonic devices due to the maturity of SiC material and fabrication technology, the plethora of candidate quantum emitters that can be formed in SiC, and the potential for emission over a wide spectral range from the visible to the infrared. However, for each of the available color centers in SiC, only one of the charge states has displayed quantum emission, meaning that the emission strongly depends on the Fermi level and hence the doping concentration in the material. In this contribution, we discuss the methodology and mechanism for electrical charge-state control over point defects in SiC devices.

Abstract: In-grown stacking faults (IGSFs) generated in 4H-SiC epilayers were characterized. Melted KOH etching, room-temperature cathodoluminescence, low-temperature photoluminescence and cross-section transmission electron microscopy was conducted to investigate the propagation of the IGSFs in the down-stream region of a 3C inclusion. It was found that the SFs could extend, close and convert during the epitaxial growth. The origin of these IGSFs were attributed to the interference introduced by the 3C inclusion to the step-flow growth, and the propagating behaviors of these IGSFs were discussed.

Abstract: Terbium-doped aluminum nitride thin films have been deposited by radio frequency magnetron sputtering. The influence of annealing treatments on structural, morphological and luminescence properties of the films is examined with the aim to optimize post-deposition annealing conditions. Temperatures starting from 500 up to 1000°C using two annealing techniques were investigated: rapid thermal processing and quartz tube furnace. X-ray diffraction analysis revealed the formation of aluminum oxide and aluminum oxynitride phases at temperatures higher than 750°C. The oxygen content in the surface layer was measured with energy dispersive X-ray. The terbium emission was obtained after excitation either by photons or electrons. The films treated with rapid thermal processing at 750°C resulted in the highest emission.

Abstract: The results of the study of spectral and decay kinetic characteristics of the pulse cathodoluminescence (PCL) for the group of industrial “white” LEDs phosphors with different composition of the host and dopants are presented. The quantitative characteristics of the PCL: position and half-width of the luminescence spectra, the luminescence decay times were determined.

Abstract: The luminescence spectra and luminescence excitation spectra have been investigated in the spectral range of 6.5–4.4 eV. Pulsed cathodoluminescence of LiF-WО₃ and LiF-TiО₂ crystals has been studied in the temperature range of 20–300 K. All LiF crystals doped with metal oxides are found to have similar luminescent properties and identical structure of the luminescence centers. It is assumed that photon and electron bombardment induces excitation of different types of О²⁻ oxygen centers perturbed by impurities and Fe₂О₃, WО₃ and TiО₂ included in the oxygen complexes.

Abstract: The influence of structural defects in the active layer of GaN-on-Si substrates on the vertical leakage current was studied. The structural defects were analyzed by analytical scanning electron microscopy by means of cathodoluminescence (CL). The leakage current was determined by vertical I-V measurements.Two possibilities were found, which give potential explanations for the variations of the vertical leakage current: i) Threading dislocations, which may partially form leakage paths, were detected by CL imaging. ii) Variations of the carbon doping, which is used to tune GaN to a semi insulating material were revealed by CL spectroscopy.

Abstract: We measured Fourier transform infrared (FT-IR) and cathodoluminescence (CL) spectra of SiO₂ films with various thicknesses, grown on 4H-SiC substrates. The appearance of broad phonon modes at ~1150–1250 cm^-1 in p-polarized light and their disappearance in s-polarized light confirmed that the phonon modes at ~1150–1250 cm^-1 originated from surface polaritons (SPPs). For the thin SiO₂ film (8-nm thick), the peak frequency of the transverse optical (TO) phonon in the SiO₂ film on the 4H-SiC substrate was observed at ~1080 cm^-1 and was higher than that in SiO₂ films on the Si substrate (1074 cm^-1). This suggested that the thin SiO₂ film (8-nm thick) is under compressive stresses at the interface between the SiO₂ film and SiC substrate. On the other hand, for the thick SiO₂ films (85 and 130-nm thick), the TO phonon peak frequency tended to shift toward lower frequencies with increasing oxide layer thickness. The CL measurement indicated that the CL peak intensity at ~640 nm, attributed to non-bridging oxidation hole centers (NBOHCs), became stronger with increasing oxide layer thickness, relative to that of the CL peaks at ~460 and 490 nm due to oxygen vacancy centers (OVCs). By comparing the FT-IR and CL measurements, we concluded that the TO phonon red-shift with increasing oxide layer thickness can mainly be attributed to an increase in inhomogeneity with increasing oxide layer thickness for the thick SiO₂ films.

Abstract: The present study aims to analyze the corrosion mechanism of Al₂O₃-SiC-C castables for blast furnace main trough. The anti-oxidation and corrosion properties of the castable caused by slag were studied with residual lining investigation and microstructure analysis. A rapid recognition of grain distribution, ingredients, and mineral phases was achieved by using cathodoluminescence (CL) in conjunction with stereo microscopy. Different materials such as brown fused alumina, spinel, and low-melting CaO containing phases etc. can be detected due to their distinct fluorescence. The result indicated that when carbon in the matrix of castables was oxidized, its non-wetting property to slag was reduced, which causes slag penetrate into the castable and formed low-melting CaO containing phases. On the contrary, when the anti-oxidation property of castable was improved, the carbon in the matrix was not easily oxidized and corroded by slag. Furthermore, MgO of slag reacted with Al₂O₃ in the matrix to form a continuous spinel layer, which retarded slag to penetrate and corrode the castable.

Abstract: Transmission electron microscopy and the cathodoluminescence method have been used to study the transition region in 3C-SiC/6H-SiC heterostructures. It is shown that this region is, as a rule, constituted by alternating 3C-SiC and 6H-SiC layers, with possible inclusion of other silicon carbide polytypes. An assumption is made that this structure of the transition region can be explained in terms of the spinodal decomposition model