Semiconductor light emitting device with protrusions to improve external efficiency and crystal growth
First Claim
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1. A semiconductor light emitting device comprising:
- a transparent substrate including a surface for growing semiconductor layers including an active layer, said surface having protrusions, with a side face of each of said protrusions defining a first inclination angle on a lower portion of said side face and a second inclination angle on an upper portion of said side face, said first inclination angle being greater than said second inclination angle; and
semiconductor layers, of material different from a material of said transparent substrate, on said surface of said transparent substrate, said semiconductor layers covering said protrusions,wherein either(i) said upper portion of said side face of each of said protrusions is flat and said lower portion of said side face of each of said protrusions is rough, or(ii) said upper portion of said side face of each of said protrusions has a surface roughness that is smaller than a surface roughness of said lower portion of said side face of each of said protrusions,wherein light is reflected at an interface between said protrusions and said semiconductor layers, andwherein a groove is formed at a bottom periphery of each of said protrusions.
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Abstract
A substrate has at least one recess and/or protrusion formed in and/or on a surface thereof so as to scatter or diffract light generated in an active layer. The recess and/or protrusion is formed in such a shape that can reduce crystalline defects in semiconductor layers.
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Citations
24 Claims
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1. A semiconductor light emitting device comprising:
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a transparent substrate including a surface for growing semiconductor layers including an active layer, said surface having protrusions, with a side face of each of said protrusions defining a first inclination angle on a lower portion of said side face and a second inclination angle on an upper portion of said side face, said first inclination angle being greater than said second inclination angle; and semiconductor layers, of material different from a material of said transparent substrate, on said surface of said transparent substrate, said semiconductor layers covering said protrusions, wherein either (i) said upper portion of said side face of each of said protrusions is flat and said lower portion of said side face of each of said protrusions is rough, or (ii) said upper portion of said side face of each of said protrusions has a surface roughness that is smaller than a surface roughness of said lower portion of said side face of each of said protrusions, wherein light is reflected at an interface between said protrusions and said semiconductor layers, and wherein a groove is formed at a bottom periphery of each of said protrusions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A semiconductor light emitting device comprising:
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a transparent substrate including a surface for growing semiconductor layers including an active layer, said surface having protrusions, with a side face of each of said protrusions defining a first inclination angle on a lower portion of said side face and a second inclination angle on an upper portion of said side face, said first inclination angle being greater than said second inclination angle; and semiconductor layers, of material different from a material of said transparent substrate, on said surface of said transparent substrate, said semiconductor layers covering said protrusions, wherein said lower portion of said side face of each of said protrusions has notches, said notches being oriented longitudinally, and said upper portion of said side face of each of said protrusions has either no substantial notches or has notches of at least one of a smaller width and a smaller number than a width and a number, respectively, of said notches in said lower portion of said side face of each of said protrusions, and wherein light is reflected at an interface between said protrusions and said semiconductor layers. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A light emitting device comprising:
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a transparent substrate having a surface for growing semiconductor layers including an active layer, said surface having protrusions spaced apart from one another, a semiconductor light emitting element including semiconductor layers formed on said surface of said transparent substrate, said semiconductor light emitting element covering said protrusions, wherein a width of a cross section of said protrusions at a base of each of said protrusions is greater than a width of a cross section of each of said protrusions at a top of each of said protrusions, such that (i) circumscribed by side faces of two closest ones of said protrusions at the bases of these two protrusions is a first circle that is co-planar with said surface of said transparent substrate, (ii) circumscribed by side faces of at least three adjacent ones of said protrusions at the bases of these at least three protrusions, with two of these at least three protrusions being said two closest ones of said protrusions, is a second circle that is co-planar with said surface of said transparent substrate, and (iii) circumscribed by the side faces of said two closest ones of said protrusions at the tops of these two protrusions is a third circle that is co-planar with top surfaces of these two protrusions, with a diameter of said second circle being larger than a diameter of said first circle and smaller than a diameter of said third circle, and with said third circle and said second circle overlapping each other, wherein an inclination angle of the side face of each of said protrusions is smaller near a top of the protrusion than near a base of the protrusion, wherein light is reflected at an interface between said protrusions and said semiconductor layers, and wherein a side face of each of said protrusions has longitudinally-oriented notches. - View Dependent Claims (22, 23, 24)
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Specification