LIGHT-EMITTING DEVICE AND MANUFACTURING METHOD THEREOF
A light-emitting device comprises a substrate; a first semiconductor layer formed on the substrate; a light-emitting layer on the first semiconductor layer; and a second semiconductor layer having a rough surface formed on the light-emitting layer, wherein the rough surface comprises a plurality of cavities randomly distributed on the rough surface, and one of the plurality of cavities has a substantially hexagonal shape viewed from top and a curved sidewall viewed from cross-section.
1 . A manufacturing method of a light-emitting device, comprising:
providing a substrate;
growing a first semiconductor layer comprising a first semiconductor material on the substrate and forming a first rough surface with a plurality of cavities during growing the first semiconductor layer; and
treating the first rough surface of the first semiconductor layer with a reducing gas to form a second rough surface.
2 . The manufacturing method according to claim 1 , further comprising nitrogenizing the first semiconductor layer after treating the first rough surface of the first semiconductor layer by introducing a nitrogen-containing gas.
3 . The manufacturing method according to claim 1 , wherein the second rough surface comprises a crystal plane less reactive with the reducing gas than c-plane is.
4 . The manufacturing method according to claim 1 , wherein the substrate comprises sapphire, GaN, AlN, SiC, GaAs, GaP, Si, ZnO, MgO, MgAl 2 O 4 , or glass.
5 . The manufacturing method according to claim 2 , wherein the first semiconductor material comprises p-type group III A-nitride semiconductor material.
6 . The manufacturing method according to claim 1 , further comprising forming a second semiconductor layer between the substrate and the first semiconductor layer, and forming a light-emitting layer between the first semiconductor layer and the second semiconductor layer, wherein a polarity of the second semiconductor layer is opposite to a polarity of the first semiconductor layer.
7 . The manufacturing method according to claim 6 , further comprising forming a stop layer between the first semiconductor layer and the light-emitting layer, wherein the stop layer is less reactive with the reducing gas than the first semiconductor layer, and the material of the stop layer comprises Al x Ga 1-x N, wherein 0<x<1.
8 . The manufacturing method according to claim 7 , wherein a thickness of the stop layer is between 50 Å and 500 Å.
9 . The manufacturing method according to claim 1 , wherein the reducing gas comprises hydrogen gas.
10 . The manufacturing method according to claim 5 , wherein the reducing gas decomposes a material of the first semiconductor layer to a group IIIA element.
11 . The manufacturing method according to claim 10 , wherein the group III A element reacts with the nitrogen-containing gas to form the first semiconductor material during the nitrogenizing step.
12 . A light-emitting device, comprising:
a substrate;
a first semiconductor layer formed on the substrate;
a light-emitting layer on the first semiconductor layer; and
a second semiconductor layer having a rough surface formed on the light-emitting layer, wherein the rough surface comprises a plurality of cavities randomly distributed on the rough surface, and one of the plurality of cavities has a substantially hexagonal shape viewed from top and a curved sidewall viewed from cross-section.
13 . The light-emitting device according to claim 12 , wherein each of the plurality of cavities comprises a deepest point and the deepest points are randomly distributed in the second semiconductor layer.
14 . The light-emitting device according to claim 12 , further comprising a stop layer formed between the light-emitting layer and the second semiconductor layer, wherein the stop layer comprises a chemical property less reactive with a reducing gas than the second semiconductor layer, wherein the material of the stop layer comprises Al x Ga 1-x N, wherein 0<x<1.
15 . The light-emitting device according to claim 14 , wherein a thickness of the stop layer is between 50 Å and 500 Å.
16 . The light-emitting device according to claim 12 , wherein the substrate comprising an epitaxial growth plane, and the rough surface is substantially devoid of a flat plane parallel to the epitaxial growth plane of the substrate.
17 . The light-emitting device according to claim 12 , wherein one of the plurality of cavities comprises a cone shape, and an angle between a tangent line of the curved sidewall and c-plane is between 10 and 75 degrees.
18 . The light-emitting device according to claim 12 , wherein the rough surface comprises a crystal plane less reactive with a reducing gas than c-plane.
19 . The light-emitting device according to claim 12 , wherein part of the plurality of cavities are spaced apart from one another with a gap, another part of the plurality of cavities are directly connected with one another, wherein the gap comprises a curved surface.
20 . The light-emitting device according to claim 12 , wherein a bottom portion of one of the plurality of cavities comprises a curved surface, and/or a sidewall of one of the plurality of cavities comprises different inclined surfaces.