Gallium nitride self-supported substrate, light-emitting device and manufacturing method therefor

A method for manufacturing a self-supporting gallium nitride substrate, comprising the steps of:

• providing an oriented polycrystalline sintered body;
• forming a seed crystal layer composed of gallium nitride on the oriented polycrystalline sintered body so that the seed crystal layer has crystal orientation mostly in conformity with crystal orientation of the oriented polycrystalline sintered body;
• forming a layer with a thickness of 20 μm or greater composed of gallium nitride-based crystals on the seed crystal layer so that the layer has crystal orientation mostly in conformity with crystal orientation of the seed crystal layer;
• and
• removing the oriented polycrystalline sintered body to obtain the self-supporting gallium nitride substrate, wherein gallium nitride-based single crystal grains exposed at a o surface of the self-supporting gallium nitride substrate connect to a bottom surface of the self-supporting gallium nitride substrate without intervention of a grain boundary, and wherein a ratio DT/DB, which is a ratio of a cross-sectional average diameter DT at an outermost surface of the gallium nitride-based single crystal grains exposed at a top surface of the self-supporting gallium nitride substrate to a cross-sectional average diameter DB at an outermost surface of the gallium nitride-based single crystal grains exposed at a bottom surface of the self-supporting gallium nitride substrate, is greater than 1.0.

A method for manufacturing a self-supporting gallium nitride substrate, comprising the steps of:

• providing an oriented polycrystalline sintered body;
• forming a seed crystal layer composed of gallium nitride on the oriented polycrystalline sintered body so that the seed crystal layer has crystal orientation mostly in conformity with crystal orientation of the oriented polycrystalline sintered body;
• forming a layer with a thickness of 20 μm or greater composed of gallium nitride-based crystals on the seed crystal layer so that the layer has crystal orientation mostly in conformity with crystal orientation of the seed crystal layer;
• and
• removing the oriented polycrystalline sintered body to obtain the self-supporting gallium nitride substrate, wherein gallium nitride-based single crystal grains exposed at a top surface of the self-supporting gallium nitride substrate connect to a bottom surface of the self-supporting gallium nitride substrate without intervention of a grain boundary, and wherein a cross-sectional average diameter of the gallium nitride-based single crystal grains at an outermost surface of the substrate is from 20 μm to 1000 μm.