研究目的
Investigating the influence of sapphire off-cut angles on the morphology and local defect distribution in epitaxially laterally overgrown AlN for optically pumped UVC lasers.
研究成果
The study found a transition in surface morphology from step flow growth to step bunching at a critical off-cut angle of 0.14°. Smooth surface morphologies at low off-cut angles resulted in lower threshold power densities for optically pumped UVC laser structures. The defect distribution was influenced by the ELO patterning but not significantly by the off-cut angles.
研究不足
The study is limited to the specific growth conditions and off-cut angles used. The transition from smooth morphologies to step bunching is not fully understood and requires further investigation.
1：Experimental Design and Method Selection:
The study involved precise measurements of off-cut angles using optical alignment and X-ray diffraction. ELO AlN was grown on c-plane sapphire substrates with varying off-cut angles.
2：Sample Selection and Data Sources:
Two batches of c-oriented sapphire wafers with nominal off-cut angles of
3：1° and 2° were examined. List of Experimental Equipment and Materials:
A Philips X‘Pert MRD Pro X-ray diffractometer, atomic force microscopy (AFM), and scanning transmission electron microscopy (STEM) were used.
4：Experimental Procedures and Operational Workflow:
The wafers were overgrown with AlN, patterned, and analyzed for surface morphology and defect distribution.
5：Data Analysis Methods:
The surface morphology and defect distribution were analyzed using AFM and STEM. The threshold excitation power density for optically pumped lasers was measured.
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