Light emitting devices having dislocation density maintaining buffer layers
First Claim
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1. A method for forming a light emitting device, comprising:
- forming a buffer layer on a substrate at a growth temperature, the buffer layer comprising an aluminum gallium nitride (AlGaN) layer and a gallium nitride (GaN) layer, wherein, at the growth temperature, a tensile strain is generated in the buffer layer; and
forming a light emitting stack on the buffer layer, the light emitting stack including an active layer configured to generate light upon the recombination of electrons and holes,wherein at least one layer of the light emitting stack and the buffer layer has a first coefficient of thermal expansion higher than a second coefficient of thermal expansion of the substrate, anda growth condition for forming the buffer layer is selected to generate a compressive strain in the buffer layer during cool-down to a room temperature to counterbalance the tensile strain generated between the buffer layer and the substrate so that the light emitting device has a radius of curvature (absolute value) that is greater than 50 m.
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Abstract
A method for forming a light emitting device comprises forming a buffer layer having a plurality of layers comprising a substrate, an aluminum gallium nitride layer adjacent to the substrate, and a gallium nitride layer adjacent to the aluminum gallium nitride layer. During the formation of each of the plurality of layers, one or more process parameters are selected such that an individual layer of the plurality of layers is strained.
136 Citations
25 Claims
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1. A method for forming a light emitting device, comprising:
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forming a buffer layer on a substrate at a growth temperature, the buffer layer comprising an aluminum gallium nitride (AlGaN) layer and a gallium nitride (GaN) layer, wherein, at the growth temperature, a tensile strain is generated in the buffer layer; and forming a light emitting stack on the buffer layer, the light emitting stack including an active layer configured to generate light upon the recombination of electrons and holes, wherein at least one layer of the light emitting stack and the buffer layer has a first coefficient of thermal expansion higher than a second coefficient of thermal expansion of the substrate, and a growth condition for forming the buffer layer is selected to generate a compressive strain in the buffer layer during cool-down to a room temperature to counterbalance the tensile strain generated between the buffer layer and the substrate so that the light emitting device has a radius of curvature (absolute value) that is greater than 50 m. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for forming a light emitting device, comprising:
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forming a buffer layer on a substrate at a growth temperature, the buffer layer comprising an aluminum gallium nitride (AlGaN) layer and a gallium nitride (GaN) layer, wherein, at the growth temperature, a tensile strain is generated in the buffer layer; and forming a light emitting stack on the buffer layer, the light emitting stack including an active layer configured to generate light upon the recombination of electrons and holes, wherein at least one layer of the light emitting stack and the buffer layer has a first coefficient of thermal expansion higher than a second coefficient of thermal expansion of the substrate, and a growth condition for forming the buffer layer is selected to generate a compressive strain in the buffer layer during cool-down to a room temperature to counterbalance the tensile strain generated between the buffer layer and the substrate. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method for forming a light emitting device, comprising:
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forming an AlN layer on a substrate at a first growth temperature, wherein, at the first growth temperature, a tensile strain is generated in the AlN layer; forming a first AlxGa1-xN layer on the AlN layer at a second growth temperature, wherein ‘
x’
is a number between 0 and 1, and, at the second growth temperature, a compressive strain is generated in the first AlxGa1-xN layer;forming a GaN layer on the first AlxGa1-xN layer at a third growth temperature, wherein, at the third growth temperature, a compressive strain is generated in the GaN layer; and forming a light emitting stack on the GaN layer, the light emitting stack having an n-type gallium nitride (n-GaN) layer, a p-type gallium nitride (p-GaN) layer, and an active layer between the n-GaN and p-GaN layers, wherein the AlN layer, the first AlxGa1-xN layer and the GaN layer forms a buffer layer, at least one layer of the light emitting stack and the buffer layer has a first coefficient of thermal expansion higher than a second coefficient of thermal expansion of the substrate, and a growth condition for forming the buffer layer is selected to generate a compressive strain in the buffer layer during cool-down to a room temperature to balance the strain generated between the buffer layer and the substrate. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
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Specification