研究目的
Investigating the effects of 6H-SiC substrate polarity on the morphology and microstructure of AlN films grown by HVPE with varied V/III ratio.
研究成果
The best AlN layer quality was obtained on the Si-face 6H-SiC at V/III ratio of 10. The samples on Si-face 6H-SiC have smoother surface morphology than on C-polar. High density of nanotubes only generate at samples on C-polar substrates.
研究不足
The study is limited to the effects of substrate polarity and V/III ratio on the morphology and microstructure of AlN films. The potential for optimizing growth conditions to further improve film quality is not explored.
1：Experimental Design and Method Selection:
AlN films were grown on 2-in diameter c-oriented 6H-SiC substrates by HVPE at atmospheric pressure in a home-made high-temperature HVPE system with a horizontal quartz reactor. HCl and ammonia were used as input active gases, and the mixture of N2 and H2 as carrier gas.
2：Sample Selection and Data Sources:
The substrates polarity of sample A and B were Si-polar and grown at V/III ratio of 5 and 10, respectively. The substrates polarity of sample C and D were C-polar and grown at V/III ratio of 10 and 20, respectively.
3：List of Experimental Equipment and Materials:
Digital Instruments Nano Scope III tapping-mode atomic force microscope (AFM), Labram HR 800 Raman spectroscopy, Bruker D8 Discover X-ray diffraction (XRD), 200 kV Tecnai G2 F20 S-Twin TEM.
4：Experimental Procedures and Operational Workflow:
Thermal cleaning of the substrate was carried out at 1100℃ for 10 mins, afterwards, the substrate was rapidly raised to 1400℃ in the mixture atmosphere of H2 and N2 for 2 hours growth.
5：Data Analysis Methods:
The surface morphology of the AlN films was characterized by AFM. The residual stress of the films was measured by Raman spectroscopy. The crystalline quality of the layers was examined by XRD. Cross-section and plane-view TEM analyses were carried out to clarify dislocations and other defects characteristics.
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