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The effects of annealing on epitaxial graphene on SiC substrates with various conditions are investigated. Results show that high pressure hydrogen atmosphere is more effective to decouple the epitaxial graphene from SiC substrate than that of a relative lower pressure process. Besides, the characteristic 2D-peak of graphene in Raman spectra disappeared with an annealing temperature 1000 °C, which means that the epitaxial graphene layer was decomposed in this condition. The study also shows that the decomposition of graphene can be effectively suppressed by increasing carbon vapor partial pressure through introducing ethylene during high pressure hydrogen annealing at 1000 °C. And the epitaxial graphene is successfully transferred to quasi free standing graphene by the annealing with an appropriate flow of ethylene.

The morphology of the in-situ etching process on Si-face and C-face 4H-SiC, by annealing in a hydrogen environment, is studied by atomic force microscopy (AFM). The uniform step-terrace morphology of both the Si-face and C-face 4H-SiC is achieved with the assistance of carbon/silicon flux. The full width at half maximum (FWHM) of Raman 2D peak for the graphene grown on the uniform step-terrace morphology of the Si-face and C-face is 36.2 and 22 cm-1, respectively.

1200V-15A 4H-SiC junction barrier schottky (JBS) diodes were designed and fabricated based on SiC epitaxy and device technology. By adopting the proper SBD metal,optimized structures and fabrication process, we succeeded in achieving good balance between blocking voltage and on-resistance, especially at high temperature to 200°C. Furthermore, the fabricated diode have a fast recovery time of 30ns, and its dynamic characteristics are constant at high temperature.

3.3kV and 4.5kV 4H-SiC junction barrier Schottky (JBS) diodes with floating guard rings edge termination have been fabricated. The 3.3kV device with 33μm 2.7E15 cm-3 epilayer and 5.5Х5.5mm2 schottky contact area has a blocking voltage (Vb ) of 3.9 kV and a specificon-resistance (Ron) of 10.5 mΩ.cm2, with a forward current measured up to 50A at VF=3.0V. The 4.5kV device with 50 um 1.2E15 cm-3 epilayer and 5.5Х5.5mm2 schottky contact area has a blocking voltage (Vb ) of 5.1 kV and a specificon-resistance (Ron) of 22.9 mΩ.cm2, with a forward current of 30A at VF=3.7V.

Results are presented for the silicon carbide (SiC) vertical channel junction field effect transistor (VJFET) fabricated based on in-house SiC epitaxial wafer suitable for power devices. We have demonstrated continuous improvement in blocking voltage, forward drain current under high temperature. The SiC VJFET device’s current density is 360 A/cm2 and current is 11 A at VG= 3 V and VD = 2 V, with related specific on-resistance 5.5 mΩ·cm2. The device exceeds 1200 V at gate bias VG = -10V. The current of the SiC VJFET device is 4 A and the reverse voltage is 1200V at the 200 °C high temperature.

A 100μm silicon carbide epilayer with mean doping concentration 6×1014 cm-3 was achieved on 3 inch silicon carbide substrate using a growh rate of 30 μm/h. Hydrogen gas foil rotation was adopted to improve the doping uniformity. The intra-wafer thickness and doping uniformity was 1.83% and 7.51%, respectively. Schottky diodes fabricated on this epilayer presented a breakdown voltage of 10kV. This is the first report of 10kV schottky diodes fabricated on silicon carbide epilayer made in China.

With the introduction of Be-doped AlxGa1-xAs template, self-assembled In0.79Mn0.21As quantum dots samples were prepared on semi-insulating (001) GaAs substrates by molecular beam epitaxy. High quantum dots density was confirmed by the atomic force microscopy. The ferromagnetism of the samples was revealed by superconducting quantum interference device magnetometer analysis at 10K, and the Curie temperatures ranging from 292 to 314K were able to be regulated by adjusting Al content and Be dopant in Be-doped AlxGa1-xAs templates, implying the feasible application of spintronic devices.