Recently, based on the results of previous optical simulation research (DOI: 10.1364/OE.389880), the research group of Liu Jianping from Suzhou Institute of Nanotechnology, Chinese Academy of Sciences proposed to use AlInGaN quaternary material whose lattice constant and refractive index can be adjusted at the same time as the optical confinement layer. The emergence of the substrate mold, the related results were published in the Fundamental Research journal, which is directed and sponsored by the National Natural Science Foundation of China. In the research, the experimenters firstly optimized the epitaxial growth process parameters to heteroepitaxially grow high-quality AlInGaN thin layers with step flow morphology on the GaN/Sapphire template. Subsequently, the homoepitaxial time-lapse of AlInGaN thick layer on the GaN self-supporting substrate shows that the surface will appear disordered ridge morphology, which will lead to the increase of surface roughness, thus affecting the epitaxial growth of other laser structures. By analyzing the relationship between stress and morphology of epitaxial growth, the researchers proposed that the compressive stress accumulated in the AlInGaN thick layer is the main reason for such morphology, and confirmed the conjecture by growing AlInGaN thick layers in different stress states. Finally, by applying the optimized AlInGaN thick layer in the optical confinement layer of the green laser, the occurrence of the substrate mode was successfully suppressed (Fig. 1).
Figure 1. Green laser with no leakage mode, (α) far-field distribution of light field in vertical direction, (b) spot diagram.
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