SEMICONDUCTOR LIGHT EMITTING DEVICE

• US 20080303043A1
• Filed: 01/30/2008
• Published: 12/11/2008
• Est. Priority Date: 07/24/2001
• Status: Active Grant

• Current Assignee: Nichia Corporation
• Original Assignee: Nichia Corporation
• Inventors: Sano, Masahiko, Yamada, Motokazu, Shioji, Shuji, NIKI, Isamu
• Granted Patent: US 7,635,875 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 21/02378 Silicon carbide
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02647 Lateral overgrowth
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/16 with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/26 Materials of the light emitting region
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

At least one recess and/or protruding portion is created on the surface portion of a substrate for scattering or diffracting light generated in a light emitting region. The recess and/or protruding portion has a shape that prevents crystal defects from occurring in semiconductor layers.

Claims

1. A semiconductor light emitting device, comprising:

a substrate;

a plurality of GaN based semiconductor layers stacked on said substrate and made of different materials from that of said substrate; and

an ohmic electrode formed on the top layer of said GaN based semiconductor layers, so that light generated in said GaN-based semiconductor layers is emitted from said ohmic electrode or from said substrate,

wherein a plurality of protruding portions for scattering or diffracting light generated in said GaN based semiconductor layers are created in the surface of said substrate in a repeated pattern with a pitch larger than or equal to λ

/4 and smaller than or equal 10 μ

m, where λ

is the wavelength of a light emitted from said GaN based semiconductor layers.

a planar shape of said protruding portions is approximately triangular or hexagonal,

each component side of the planar shape of said protruding portions is perpendicular to a line segment connecting a center and a vertex of a hexagon whose component sides are defined by A axes of said GaN based semiconductor layers,

wherein a side surface of said protruding portions is inclined so that a taper angle of said side surface is greater than 90 degrees and smaller than or equal 150 degrees, and

wherein the top and side surfaces of said protruding portions and flat portions, where no protruding portions are formed, on the surface of said substrate are continuously covered by said GaN-based semiconductor layers.

2. A semiconductor light emitting device according to claim 1, wherein said ohmic electrode covers substantially the entire surface of the top layer of said GaN based semiconductor layers.

3. A semiconductor light emitting device according to claim 1, wherein said ohmic electrode is transparent.

4. A semiconductor light emitting device according to claim 1, wherein said substrate is selected from the group consisting of a sapphire substrate, an SiC substrate and a spinel substrate.

5. A semiconductor light emitting device according to claim 1, wherein said substrate is a C-plane (0001) sapphire substrate.

6. A semiconductor light emitting device according to claim 1, wherein a size of said protruding portions is greater than or equal to λ

/(4n) and smaller than or equal to 20 μ

m, where λ

is the wavelength of a light emitted from said GaN based semiconductor layers and n is the refractive index of said GaN based semiconductor layers.

7. A semiconductor light emitting device according to claim 1, wherein the taper angle is greater than or equal to 105 degrees and smaller than or equal to 150 degrees.