Polycrystalline gallium-nitride self-supporting substrate and light-emitting element using same

Abstract

This invention provides a polycrystalline gallium-nitride self-supporting substrate comprising a plurality of gallium-nitride-based single-crystal grains aligned to a specific crystal orientation in a direction that is substantially parallel to the normal direction. The crystal orientations of said gallium-nitride-based single-crystal grains, as measured by subjecting the surface of the self-supporting substrate to electron backscatter diffraction (EBSD) and performing inverse-pole-figure mapping, form a variety of angles with the aforementioned specific crystal orientation, and the mean value of the distribution of said angles is between 1degrees and 10 degrees, inclusive. This light-emitting element comprises the abovementioned self-supporting substrate and a light-emitting functional layer that is formed on top of the substrate and contains one or more layers each comprising a plurality of semiconductor single-crystal grains each exhibiting a single-crystal structure that is substantially parallel to the normal direction. This invention makes it possible to provide a polycrystalline gallium-nitride self-supporting substrate with a reduced defect density in the surface thereof. A light-emitting element that uses said polycrystalline gallium-nitride self-supporting substrate and exhibits a high luminous efficacy can also be obtained.

Description

technical field [0001] The present invention relates to a polycrystalline gallium nitride self-supporting substrate and a light emitting element using the polycrystalline gallium nitride self-supporting substrate. Background technique [0002] As a light-emitting device such as a light-emitting diode (LED) using a single crystal substrate, a light-emitting device in which various gallium nitride (GaN) layers are formed on sapphire (α-alumina single crystal) is known. For example, mass production of products having a structure in which an n-type GaN layer, a multi-quantum well layer (MQW), and a p-type GaN layer are sequentially stacked on a sapphire substrate has begun. Layered quantum well layers and barrier layers including GaN layers are stacked alternately. In addition, laminated substrates suitable for such applications have also been proposed. For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2012-184144) proposes a gallium nitrid...

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Problems solved by technology

[0003] However, when a GaN layer is formed on a sapphire substrate, dislocations tend to occur because the lattice constant and thermal expansion coefficient of the GaN layer and sapphire, which is a different substrate, do not match.

In addition, since sapphire is an insulating material, electrodes cannot be formed on its surface, so it is impossible to construct a light-emitting element with a vertical structure including electrodes on both the front and back of the element.

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