Nitride-based semiconductor light emitting diode

1. A nitride-based semiconductor LED comprising:

a substrate that is formed in a rectangle shape and of which a ratio of the width and the length is equal to or more than 1.5;

an n-type nitride semiconductor layer that is formed on the substrate and is composed of an n-type semiconductor material having a compositional formula of In X Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1);

an active layer and a p-type nitride semiconductor layer that are sequentially formed on a predetermined region of the n-type nitride semiconductor layer, the active layer being composed of a semiconductor material having a compositional formula of In X Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1) and the p-type nitride semiconductor layer being composed of a p-type semiconductor material having a compositional formula of In X Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1);

a transparent electrode that is formed on the p-type nitride semiconductor layer;

a p-electrode pad that is formed on the transparent electrode;

an n-electrode pad that is formed on the n-type nitride semiconductor layer; and

a buffer layer that is formed between the substrate and the n-type nitride semiconductor layer,

wherein the p-electrode pad, devoid of any elongated protrusion or any auxiliary electrode, is spaced at a distance of 50 to 200 μm from an outer edge line of the p-type nitride semiconductor layer such that a uniform luminous effect is obtained in the entire LED, and wherein the center of the outer edge line of the p-type nitride semiconductor layer intersects with a straight line that connects a center of the p-electrode pad and a center of the n-electrode pad, and,

whereby when the p-electrode pad is spaced at a distance in some range of 50 to 200 μm from the outer edge line of the p-type nitride semiconductor layer, optical power increases, and when the p-electrode pad is spaced at a distance in some range of more than 200 μm from the outer edge line of the p-type nitride semiconductor layer, optical power decreases.

2. The nitride-based semiconductor LED according to claim 1 , wherein the n-type nitride semiconductor layer is a GaN layer or GaN/AlGaN layer doped with any one n-type conductive impurity selected from the group consisting of Si, Ge, and Sn,

the p-type nitride semiconductor layer is a GaN layer or GaN/AlGaN layer doped with any one p-type conductive impurity selected from the group consisting of Mg, Zn, and Be, and the active layer is composed of an InGaN/GaN layer with a multi-quantum well structure.

3. The nitride-based semiconductor LED according to claim 2 , wherein the p-electrode pad and the n-electrode pad are formed of Au or Au/Cr.

4. The nitride-based semiconductor LED according to claim 1 , wherein

the distance between the p-electrode and the outer edge line of the p-type nitride semiconductor layer is longer that a distance between the n-electrode and another outer edge line of the p-type nitride semiconductor layer.

5. A nitride-based semiconductor LED comprising:

a substrate that is formed in a rectangle shape and of which a ratio of the width and the length is equal to or more than 1.5;

an n-type nitride semiconductor layer that is formed on the substrate and is composed of an n-type semiconductor material having a compositional formula of In X Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1);

an active layer and a p-type nitride semiconductor layer that are sequentially formed on a predetermined region of the n-type nitride semiconductor layer, the active layer being composed of a semiconductor material having a compositional formula of In X Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1) and the p-type nitride semiconductor layer being composed of a p-type semiconductor material having a compositional formula of In X Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1), the p-type nitride semiconductor layer having a p-electrode pad;

a transparent electrode that is formed on the p-type nitride semiconductor layer;

an n-electrode pad that is formed on the n-type nitride semiconductor layer; and

a buffer layer that is formed between the substrate and the n-type nitride semiconductor layer,

wherein the p-electrode pad, devoid of any elongated protrusion or any auxiliary electrode, is spaced at a distance of 50 to 200 μm from an outer edge line of the p-type nitride semiconductor layer such that a uniform luminous effect is obtained in the entire LED, and wherein the center of the outer edge line of the p-type nitride semiconductor layer intersects with a straight line that connects a center of the p-electrode pad and a center of the n-electrode pad, and

whereby optical power when the p-electrode pad is spaced at a distance of 50 to 200 μm from the outer edge line of the p-type nitride semiconductor layer is higher than optical power when the p-electrode pad is spaced at a distance more than 200 μm from the outer edge line of the p-type nitride semiconductor layer.

6. The nitride-based semiconductor LED according to claim 5 , wherein

the distance between the p-electrode and the outer edge line of the p-type nitride semiconductor layer is longer that a distance between the n-electrode and another outer edge line of the p-type nitride semiconductor layer.

7. A nitride-based semiconductor LED comprising:

a substrate that is formed in a rectangle shape and of which a ratio of the width and the length is equal to or more than 1.5;

an n-type nitride semiconductor layer that is formed on the substrate and is composed of an n-type semiconductor material having a compositional formula of In X Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1);

an active layer and a p-type nitride semiconductor layer that are sequentially formed on a predetermined region of the n-type nitride semiconductor layer, the active layer being composed of a semiconductor material having a compositional formula of In X Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1) and the p-type nitride semiconductor layer being composed of a p-type semiconductor material having a compositional formula of In Al Y Ga 1-X-Y N (0≦X, 0≦Y, and X+Y≦1;

a transparent electrode that is formed on the p-type nitride semiconductor layer;

a p-electrode pad that is formed on the transparent electrode, a center of an outer edge line of a p-type nitride semiconductor layer being intersected by a straight line that connects a center of the p-electrode pad and a center of the n-electrode pad, wherein the p-electrode pad is spaced at a distance of 50 to 200 μm from the outer edge line of the p-type nitride semiconductor layer such that a uniform luminous effect is obtained in the entire LED;

an n-electrode pad that is formed on the n-type nitride semiconductor layer; and

a buffer layer that is formed between the substrate and the n-type nitride semiconductor layer,

whereby optical power when the p-electrode pad is spaced at a distance of 50 to 200 μm from the outer edge line of the p-type nitride semiconductor layer is higher than optical power when the p-electrode pad is spaced at a distance more than 200 μm from the outer edge line of the p-type nitride semiconductor layer.

8. The nitride-based semiconductor LED of claim 1 , 5 or 7 , wherein the buffer layer is composed of AlN/GaN.