Gallium nitride wafer substrate for solid state lighting devices, and associated systems and methods
View Patent ↗Gallium nitride wafer substrate for solid state lighting devices, and associated systems and methods. A method for making an SSL device substrate in accordance with one embodiment of the disclosure includes forming multiple crystals carried by a support member, with the crystals having an orientation selected to facilitate formation of gallium nitride. The method can further include forming a volume of gallium nitride carried by the crystals, with the selected orientation of the crystals at least partially controlling a crystal orientation of the gallium nitride, and without bonding the gallium nitride, as a unit, to the support member. In other embodiments, the number of crystals can be increased by a process that includes annealing a region in which the crystals are present, etching the region to remove crystals having an orientation other than the selected orientation, and/or growing the crystals having the selected orientation.
1. A method of making a solid state lighting (“SSL”) device substrate, the method comprising:
forming a region of silicon over a support substrate, the region of silicon including first crystals having a (111) crystal orientation and second crystals not having the (111) crystal orientation;
etching the region of silicon to preferentially remove material from the second crystals relative to material from the first crystals;
forming additional silicon over the region of silicon after etching the region of silicon; and
forming gallium nitride over the region of silicon after forming the additional silicon, the gallium nitride forming with a (0001) crystal orientation.
2. The method of claim 1 , wherein forming the region of silicon over the support substrate includes forming the region of silicon over the support substrate that includes polycrystalline aluminum nitride.
3. The method of claim 1 , further comprising removing the gallium nitride from the region of silicon.
4. The method of claim 1 , further comprising forming a buffer material over the region of silicon, wherein forming the gallium nitride includes forming the gallium nitride over the buffer material.
5. The method of claim 4 wherein forming the buffer material includes forming a buffer material that includes aluminum gallium nitride.
6. The method of claim 1 wherein forming the gallium nitride includes forming gallium nitride using a metal organic chemical vapor deposition (“MOCVD”) process.
7. The method of claim 1 , wherein forming the gallium nitride includes forming gallium nitride having a dislocation density of 10 9 /cm 2 or less.
8. The method of claim 1 wherein:
the method further comprises
growing an intermediate structure over the support substrate, and
disposing a seed material over the intermediate structure; and
forming the region of silicon over the support substrate includes forming the region of silicon over the intermediate structure.
9. The method of claim 8 , further comprising annealing the region of silicon by zone melt recrystallization.
10. The method of claim 8 wherein growing the intermediate structure includes forming a layer having at least one of silicon dioxide, silicon carbide and silicon nitride.
11. The method of claim 8 wherein disposing the seed material includes disposing a seed material comprising aluminum nitride.
12. The method of claim 8 wherein disposing the seed material includes disposing a seed material comprising titanium and nickel.
13. The method of claim 3 , further comprising forming an SSL device from the removed gallium nitride.
14. The method of claim 1 wherein the region of silicon includes a layer containing only silicon.