Nitride underlayer and fabrication method thereof
A fabrication method of a nitride underlayer structure includes, during AlN layer sputtering with PVD, a small amount of non-Al material is doped to form nitride with decomposition temperature lower than that of AlN. A high-temperature annealing is then performed. After annealing, the AlN layer has a rough surface with microscopic ups and downs instead of a flat surface. By continuing AlGaN growth via MOCVD over this surface, the stress can be released via 3D-2D mode conversion, thus improving AlN cracks.
1. A fabrication method of a nitride underlayer, the method comprising:
1) providing a substrate;
2) sputtering an AlN layer over a surface of the substrate; during the sputtering, doping non-Al material with a decomposition temperature lower than that of AlN when Al source is input to form nitride, wherein the non-Al material comprises Ga;
3) annealing the AlN layer at an annealing temperature of 1080° C.-1200° C. to facilitate desorption of the Ga to thereby form a rough surface; and
4) depositing an Al x Ga 1-x N layer (0≤x≤1) over the AlN layer via MOCVD.
2. The fabrication method of claim 1 , wherein the fabricated nitride underlayer comprises, from bottom up:
the substrate;
the AlN layer over a surface of the substrate with the rough surface; and
the Al x Ga 1-x N layer (0≤x≤1).
3. The fabrication method of claim 1 , wherein in step 4), the Al x Ga 1-x N layer grown via MOCVD releases stress via 3D-2D mode conversion over the rough surface.
4. The fabrication method of claim 1 , wherein the doped non-Al material is not more than 10% of Al source.
5. A fabrication method of a light-emitting diode, the method comprising:
1) providing a substrate;
2) sputtering an AlN layer over a surface of the substrate; during sputtering, doping non-Al material with decomposition temperature lower than that of AlN when Al source is input to form nitride, wherein the non-Al material comprises Ga;
3) annealing the AlN layer at an annealing temperature of 1080° C.-1200° C. to facilitate desorption of the Ga to thereby form a rough surface;
4) depositing an Al x Ga 1-x N layer (0≤x≤1) over the AlN layer via MOCVD; and
5) depositing an n-type nitride layer, an active layer and a p-type nitride layer over the Al x Ga 1-x N layer.
6. The fabrication method of claim 5 , wherein, in step 4), the Al x Ga 1-x N layer grown via MOCVD releases stress via 3D-2D mode conversion over the rough surface.
7. The fabrication method of claim 5 , wherein, a light-emitting wavelength of the active layer is 365 nm-210 nm.
8. The fabrication method of claim 5 , wherein, the doped non-Al material is not more than 10% of Al source.
9. A light-emitting diode fabricated with a fabrication method comprising:
1) providing a substrate;
2) sputtering an AlN layer over a surface of the substrate; during the sputtering, doping non-Al material with decomposition temperature lower than that of AlN when Al source is input to form nitride, wherein the non-Al material comprises Ga;
3) annealing the AlN layer at an annealing temperature of 1080° C.-1200° C. to facilitate desorption of the Ga to thereby form a rough surface;
4) depositing an Al x Ga 1-x N layer (0≤x≤1) over the AlN layer via MOCVD; and
5) depositing an n-type nitride layer, an active layer and a p-type nitride layer over the Al x Ga 1-x N layer;
The light-emitting diode comprising, from bottom to up:
the substrate;
the AlN layer over a surface of the substrate with a rough surface;
the Al x Ga 1-x N layer (0≤x≤1);
the n-type nitride layer;
the active layer; and
the p-type nitride layer.