Manufacturing of low defect density free-standing gallium nitride substrates and devices fabricated thereof
The invention relates to a method for manufacturing a single crystal of nitride by epitaxial growth on a support ( 100 ) comprising a growth face ( 105 ), the method comprising the steps of formation of a sacrificial bed ( 101 ) on the support ( 100 ), formation of pillars ( 102 ) on said sacrificial bed, said pillars being made of a material compatible with GaN epitaxial growth, growth of a nitride crystal layer ( 103 ) on the pillars, under growing conditions such that the nitride crystal layer does not extend down to the support in holes ( 107 ) formed between the pillars, and removing the nitride crystal layer from the support.
1. A method for manufacturing a single crystal of nitride by epitaxial growth on a support ( 100 ) comprising a growth face ( 105 ), the method comprising the steps of:
formation of a sacrificial bed ( 101 ) on the support ( 100 ), wherein a plurality of first openings within the sacrificial bed expose portions of the growth face;
epitaxial growth of a layer including a material compatible with GaN epitaxial growth, wherein the layer is grown from the portions of the growth face and extending over the sacrificial bed;
formation of pillars ( 102 ) on said sacrificial bed, said pillars being formed by patterning the layer;
formation of a first mask between the pillars, wherein at least a portion of the mask covers a portion of the growth face;
growth of a nitride crystal layer ( 103 ) on the pillars, under growing conditions such that the nitride crystal layer does not extend down to the support within the holes ( 107 ) formed between the pillars; and
removing the nitride crystal layer from the support.
2. The method according to claim 1 , wherein each pillar of the pillars ( 102 ) comprises walls ( 104 ), said walls being perpendicular to the growth face of the support.
3. The method according to claim 1 , wherein the pillars ( 102 ) have substantially the same height (D).
4. The method according to claim 1 , wherein the pillars ( 102 ) have superior faces defining a growth face, the superior faces being above 20% of an overall surface of a growth face of the support.
5. The method according to claim 4 , wherein the superior faces of the pillars ( 102 ) define a growth face accounting for below 80% of the overall surface of the growth face of the support.
6. The method according to claim 1 , wherein the pillars ( 102 ) define a ratio D/d of a height D of one pillar to a distance d between two adjacent pillars, and wherein the ratio D/d is greater than or equal to 1.5.
7. The method according to claim 6 , wherein the ratio D/d is greater than or equal to 2.
8. The method according to claim 1 , wherein the pillars ( 102 ) are discrete pillars, separated from each other by a distance (d).
9. The method according to claim 1 , wherein the pillars ( 102 ) are uniformly distributed on the support.
10. The method according to claim 1 , wherein the pillars ( 102 ) are made of GaN.
11. The method according to claim 1 , wherein the sacrificial bed ( 101 ) comprises a chemically removable material.
12. The method according to claim 11 , wherein the sacrificial bed ( 101 ) comprises SiO 2 .
13. The method according to claim 1 , wherein the layer including the material compatible with GaN epitaxial growth comprises GaN.
14. The method according to claim 1 , wherein patterning the layer including the material compatible with GaN epitaxial growth comprises:
deposition of a second mask on the layer, said second mask comprising a plurality of second openings; and
etching the layer to form the pillars ( 102 ).
15. The method according to claim 14 , wherein the plurality of the second openings form a same pattern as the plurality of the first openings, and the second mask is placed to match the second openings with the first openings.
16. The method according to claim 1 , wherein removing the nitride crystal layer from the support comprises etching the sacrificial bed.
17. A substrate for manufacturing a single crystal of nitride by epitaxial growth, said substrate comprising a support and a plurality of pillars on the support, wherein said substrate further comprises a sacrificial bed between the support and the pillars as defined in claim 1 , wherein a ratio D/d of a height D of one pillar to a distance d between two adjacent pillars is greater than or equal to 1.5.
18. A semiconductor material comprising a substrate and a single crystal of nitride on the substrate, wherein said substrate comprises a support, a sacrificial bed on the support, and a plurality of pillars on said sacrificial bed as defined in claim 1 , wherein a ratio D/d of a height D of one pillar to a distance d between two adjacent pillars is greater than or equal to 1.5.
19. A single crystal of nitride comprising pillars, said single crystal being obtained by a method according to claim 1 , wherein a ratio D/d of a height D of one pillar to a distance d between two adjacent pillars is greater than or equal to 1.5.