Fabrication method of nitride light emitting diodes
A fabrication method of a nitride semiconductor LED includes, an Al x In y Ga 1-x-y N material layer is deposited by CVD between an AlN thin film layer by PVD and a gallium nitride series layer by CVD, to reduce the stress effect between the AlN thin film layer and the nitride layer, improve the overall quality of the LED and efficiency. An AlN thin film layer is deposited on a patterned substrate having a larger depth by PVD, and a thin nitrogen epitaxial layer is deposited on the AIN thin film layer by CVD, which reduces the stress by reducing the thickness of the epitaxial layer and improves warpage of the wafer and electric uniformity of the single wafer; the light extraction efficiency is improved by using the large depth patterned substrate; further, the doping of high-concentration impurity in the active layer effectively reduces voltage characteristics without affecting leakage, thereby improving the overall yield.
1. A fabrication method of a nitride light emitting diode, the method comprising:
step 1: providing and placing a substrate in a physical vapor deposition (PVD) chamber;
step 2: depositing an AlN material layer over the substrate by PVD;
step 3: moving the substrate, over which the AlN material layer is deposited, to a chemical vapor deposition (CVD) chamber;
step 4: depositing a nitride material layer over a surface of the AlN material layer by CVD;
step 5: depositing over a surface of the nitride material layer a highly-doped active layer with sufficient impurity to improve a voltage characteristics of the light emitting diode; and
step 6: depositing a p-type layer over a surface of the highly-doped active layer.
2. The method of claim 1 , wherein: said depositing in step 4 through step 6 is a metal-organic chemical vapor deposition (MOCVD).
3. The method of claim 1 , wherein: the substrate is a patterned substrate with a height of pattern of 2-20 μm.
4. The method of claim 1 , wherein: the highly-doped active layer deposited in step 5 is doped with n-type impurity, with a doping concentration higher than 6×10 18 /cm 3 .
5. The method of claim 1 , wherein: the nitride material layer in step 4 is a combined layer of a high-temperature undoped gallium nitride layer and an n-type gallium nitride material layer.
6. The method of claim 1 , wherein: the nitride material layer in step 4 is a combined layer of a low-temperature gallium nitride layer, a high-temperature undoped gallium nitride layer and an n-type gallium nitride material layer.
7. The method of claim 6 , wherein: a growth temperature of the low-temperature gallium nitride layer ranges from 200° C. to 900° C.
8. The method of claim 6 , wherein: a thickness of said low-temperature gallium nitride layer is 5 Å-1500 Å.
9. The method of claim 6 , wherein: a thickness of the nitride material layer ranges from 1.0 μm to 3.5 μm.
10. The method of claim 1 , wherein: a thickness of a complete epitaxial layer of the nitride light emitting diode is less than or equal to 4 μm.
11. The method of claim 1 , wherein: a temperature of the chamber in step 2 is 350-550° C.
12. The method of claim 1 , wherein: a pressure of the chamber in step 2 is 2-10 mtorr.
13. The method of claim 1 , wherein: a thickness of the A1N material layer deposited in step 2 is 5-350 Å.