Large area nonpolar or semipolar gallium and nitrogen containing substrate and resulting devices
View Patent ↗A method for fabricating large-area nonpolar or semipolar GaN wafers with high quality, low stacking fault density, and relatively low dislocation density is described. The wafers are useful as seed crystals for subsequent bulk growth or as substrates for LEDs and laser diodes.
1. A method for fabricating a gallium and nitrogen containing substrate comprising:
providing a gallium and arsenic containing substrate having a major surface region of a predetermined area;
forming a plurality of recessed regions within a thickness of the substrate, each of the plurality of recessed regions having a first exposed surface of a first crystallographic orientation and a second exposed surface of a second crystallographic orientation;
depositing masking material over at least the first exposed surface of each of the recessed regions;
depositing nucleation material over the second exposed surface of each of the recessed regions;
forming a thickness of gallium and nitrogen containing material overlying the nucleation material such that the thickness of gallium and nitrogen containing material fills each of the recessed regions to form a plurality of growth structures in each of the recessed regions;
coalescing the plurality of growth structures to form a resulting thickness of a gallium and nitrogen containing material overlying the major surface region of the predetermined area; and
releasing the resulting thickness of the gallium and nitrogen containing material from at least the major surface region.
2. The method of claim 1 wherein the predetermined area is greater than 15 square centimeters and the gallium and arsenic containing substrate is a GaAs wafer.
3. The method of claim 1 wherein the major surface region has an orientation within about 5 degrees of {110}.
4. The method of claim 1 wherein the major surface region has an orientation within about 5 degrees of an orientation chosen from {1 −1 0.7}, {1.22 −0.78 0.22}, {1 −1 2}, {1.43 −0.56 0.43}, {1 −1 3}, and {3 −1 1}.
5. The method of claim 1 wherein the second exposed surface is a non-(111)A surface.
6. The method of claim 1 wherein depositing nucleation material comprises a low-temperature process ranging from about 450 degrees Celsius to about 600 degrees Celsius.
7. The method of claim 1 wherein forming the thickness of gallium and nitrogen containing material comprises a high-temperature GaN epitaxial process selected from metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE).
8. The method of claim 1 wherein the resulting thickness of a gallium and nitrogen containing material is between about 10 microns and about 10 millimeters.
9. The method of claim 1 wherein coalescing comprises forming the resulting gallium and nitrogen containing material by a hydride vapor phase epitaxy (HVPE) process.
10. The method of claim 9 wherein each of growth structures has an edge dislocation density at a coalescence front of less than about 10 4 cm −2 .
11. The method of claim 1 wherein a region of the resulting thickness of the gallium and nitrogen containing material has stacking faults with a concentration of less than about 10 4 cm −1 .
12. The method of claim 1 further comprising depositing at least one active layer on the gallium and nitrogen containing material, the active layer comprising nitrogen and at least one of gallium, aluminum, and indium.
13. The method of claim 12 wherein the plurality of recessed regions comprises a linear array of recessed regions and electrical contacts are configured so as to provide for light emission from the active layer positioned between the coalescence fronts of the growth structure.
14. The method of claim 12 wherein the plurality of recessed regions comprises a two-dimensional array of recessed regions and electrical contacts are positioned to provide for light emission from the active layer between the coalescence fronts of the growth structure.
15. The method of claim 12 wherein electrical contacts are placed on a defective region, wherein the defective region is a seed region or a region having stacking faults at a concentration of at least 10 1 cm −1 .
16. A method for fabricating a light emitting device, comprising:
providing a gallium and nitrogen containing substrate having a wurtzite structure and a nonpolar or semipolar major surface orientation and comprising a one- or two-dimensional array of seed regions and coalescence fronts;
depositing at least one active layer on the gallium and nitrogen containing substrate, the active layer comprising nitrogen and at least one of gallium, aluminum, and indium; and
depositing n-type and p-type contacts capable of conducting electrical current to and from the active layer.
17. The method of claim 16 , wherein the coalescence fronts comprise linear arrays of edge dislocations with a line density of at least about 10 2 cm −1 .
18. The method of claim 16 wherein the seed regions comprise stacking faults with a concentration greater than 1 cm −1 .
19. The method of claim 16 wherein the period of the seed regions and coalescence fronts is between about 2 microns and about 5000 microns.
20. The method of claim 16 wherein electrical contacts are placed on a defective region, wherein the defective region is selected from a seed region, a region having coalescence fronts, and a region having stacking faults at a concentration of at least 10 1 cm −1 .