Process for producing an epitaxial layer of gallium nitride
The present invention relates to a process for producing an epitaxial layer of gallium nitride (GaN) as well as to the epitaxial layers of gallium nitride (GaN) which can be obtained by said process. Such a process makes it possible to obtain gallium nitride layers of excellent quality by (i) forming on a surface of a substrate, a film of a silicon nitride of between 5 to 20 monolayers, functioning as a micro-mask, (ii) depositing a continuous gallium nitride layer on the silicon nitride film at a temperature ranging from 400 to 600° C., (iii) after depositing the gallium nitride layer, annealing the gallium nitride layer at a temperature ranging from 950 to 1120° C. and (iv) performing an epitaxial regrowth with gallium nitride at the end of a spontaneous in situ formation of islands of gallium nitride.
1. A process for producing an epitaxial layer of gallium nitride (GaN) comprising:
forming on a surface of a substrate, a film of a silicon nitride of between 5 to 20 monolayers, functioning as a micro-mask;
depositing a continuous gallium nitride layer on the silicon nitride film at a temperature ranging from 400 to 600° C.;
after depositing the gallium nitride layer, annealing the continuous gallium nitride layer at a temperature ranging from 950 to 1120° C.; and
performing an epitaxial regrowth with continuous gallium nitride layer at the end of a spontaneous in situ formation of islands of gallium nitride.
2. A process according to claim 1 , wherein the substrate is selected from the group consisting of sapphire, ZnO, 6H—SiC, 4H—SiC, 3C—SiC, LiAlO 2 , LiGaO 2 , MgAlO 4 , Si, GaAs, AlN, ZrB 2 and GaN.
3. A process according to claim 1 , wherein the silicon nitride film is a layer of the Si x N y type.
4. A process according to claim 1 , wherein the temperature of depositing the continuous gallium nitride layer ranges from 450 to 550° C.
5. A process according to claim 1 , wherein the temperature of annealing the continuous gallium nitride layer ranges from 1050 to 1080° C.
6. A process according to claim 1 , wherein the temperature of depositing the continuous gallium nitride layer ranges from 450 to 550° C. and the temperature of annealing the continuous gallium nitride layer ranges from 1050 to 1080° C.
7. A process according to claim 1 , wherein the deposition of silicon nitride film is carried out with a carrier gas containing H 2 .
8. A process according to claim 1 , wherein the silicon nitride film is a layer of the Si x N y type and wherein forming the film of silicon nitride comprises reacting ammonia and silane.
9. A process according to claim 1 , wherein the temperature of depositing the continuous gallium nitride layer ranges from 450 to 550° C. and the temperature of annealing the continuous gallium nitride layer ranges from 1050 to 1080° C., wherein the deposition of silicon nitride film is carried out with a carrier gas containing H 2 , and wherein the silicon nitride film is a layer of the Si x N y type and wherein forming the film of silicone nitride comprises reacting ammonia and silane.
10. A process according to claim 1 , wherein the epitaxial regrowth is carried out using gallium nitride doped with a dopant chosen from the group consisting in magnesium, zinc, cadmium, beryllium, calcium, silicium, oxygen, tin, germanium and carbon.