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Homoepitaxial growth of 4H-SiC at 1400℃ was explored. The growth rate, surface morphology and defects of the epi-layers were studied. Raman characterization combined with KOH etching indicated that the epi-layers were 4H-SiC single crystal without 3C-SiC polycrystalline. In addition, low growth rate and high C/Si ratio were beneficial to convert the basal plane dislocations (BPDs) in substrate surface to threading edge disloca- tions (TEDs) at the sub-epi interface. Furthermore, the low growth rate was also favorable to reduce the defects generated during the growth process. With the growth rate increasing, the surface triangle defects and dislocations of the epilayers significantly increased. Most of these defects and dislocations were considered to be generated at the sub-epi interface at the beginning of the growth. By optimizing the interface layer at initial stage, a smooth transition from surface etching to epi-layer deposition can be achieved while the surface morphological defects and crystal defects are greatly reduced at high growth rate.

Nitrogen-doped 6H-SiC crystal with the diameter of 2-inch was grown along (0001) direction by physical vapor transport method. The spatial distribution of different polytypes such as 6H-SiC, 4H-SiC and 15R-SiC was characterized by mapping Raman spectra. The formation and evolution of different polytypes were investigated during the growth progress. 15R-SiC and 4H-SiC were observed in the as-grown 6H-SiC single crystal. Two different polytype regions are observed from the spatial distribution of different polytypes. One region originates from the growth interface of different polytypes. This region has higher nitrogen doping level and carrier concentration, and the area can become large during the growth process. The other region is dominated by 15R-SiC which appears in the main 6H-SiC due to the perturbation in growth temperature, pressure, etc. This region has less effect on the crystal quality, which could be inhibited by increasing the growth temperature.

A high-power photoconductive semiconductor switch(PCSS) has been fabricated by semi-insulating silicon carbide crystal. The width of the output voltage pulse was about 40 ns and the rise-time was 9.6 ns, when a KrF excimer laser was adopted as the excitation source. Two different steps were observed in the rising edge. With the input voltage rising from 1 kV to 11 kV, the on-state resistance remained about 12 Ω. The peak current through the PCSS came to be 159 A with the 11 kV input voltage, while the peak power reached 1.4 MW. No carrier saturation has been observed in the experiment.

A series of Mn-doped ZnO films have been prepared in different sputtering plasmas by using the inductively coupled plasma enhanced physical vapour deposition. The films show paramagnetic behaviour when they are deposited in an argon plasma. The Hall measurement indicates that ferromagnetism cannot be realized by increasing the electron concentration. However, the room-temperature ferromagnetism is obtained when the films are deposited in a mixed argon-nitrogen plasma. The first-principles calculations reveal that antiferromagnetic ordering is favoured in the case of the substitution of Mn2+ for Zn2+ without additional acceptor doping. The substitution of N for O (NO−) is necessary to induce ferromagnetic couplings in the Zn-Mn-O system. The hybridization between N 2p and Mn 3d provides an empty orbit around the Fermi level. The hopping of Mn 3d electrons through the empty orbit can induce the ferromagnetic coupling. The ferromagnetism in the N-doped Zn-Mn-O system possibly originates from the charge transfer between Mn2+ and Mn3+ via NO−. The key factor is the empty orbit provided by substituting N for O, rather than the conductivity type or the carrier concentration.

Fluorescent 4H-SiC, co-doped with donor and acceptor impurities, can work as phosphor for visible light emission by recombination. Donor concentration and acceptor impurities are two important factors which influence luminescent properties of fluorescent 4H-SiC. In this study, 3 inch N-B-Al co-doped 4H-SiC crystals were prepared by physical vapor transport method. Crystalline type and N-B-Al concentration of the doped 4H-SiC were measured by Raman spectrum and secondary ion mass spectra. Influences of doping concentrations on the photoluminescence were studied by photoluminescence excitation and emission spectra, luminescence decay curves, and internal and external quantum efficiencies. It is found that p-type fluorescent 4H-SiC with low Al doping concentration shows intensive yellow-green fluorescence at room temperature. Heavily doped N and B and lightly doped Al in 4H-SiC produce enough electron hole pairs for the recombination. This sufficient recombination enhances internal quantum efficiency of fluorescent 4H-SiC. Furthermore, the recombination is also helpful to increase their photoluminescence intensity and average fluorescence lifetime.