III nitride crystal substrate, and light-emitting device and method of its manufacture
Toward making available III nitride crystal substrates advantageously employed in light-emitting devices, and light-emitting devices incorporating the substrates and methods of manufacturing the light-emitting devices, a III nitride crystal substrate has a major face whose surface area is not less than 10 cm 2 and, in a major-face principal region excluding the peripheral margin of the major face from its outer periphery to a 5 mm separation from its outer periphery, the total dislocation density is from 1×10 4 cm −2 to 3×10 6 cm −2 , and the ratio of screw-dislocation density to the total dislocation density is 0.5 or greater.
1. A III-nitride crystal substrate manufacturing method, comprising:
a step of preparing a starting undersubstrate including a III nitride crystal layer having a major face, with the major face having a predetermined angle of inclination of from 0.5° to 10° with respect to a {0001} plane of the III nitride crystal layer;
a step of forming on the major face of the starting undersubstrate a plurality of micro-steps consisting of a plurality of terraced faces paralleling the {0001} plane, and of a plurality of stepped planes having a predetermined angle with respect to the {0001} plane;
a step of initially growing III nitride crystal to a predetermined thickness by a liquid-phase technique onto the major face of the starting undersubstrate;
a step of additionally growing III nitride crystal onto the liquid-phase grown III-nitride crystal; and
a step of slicing the additionally grown III-nitride crystal through a plane paralleling the {0001} plane to produce a III-nitride crystal substrate; wherein
said inclination of, and the form of said micro-steps on, the starting undersubstrate major face are predetermined such that in a major-face principal region of the III-nitride crystal substrate excluding the peripheral margin from the outer periphery of the major face to a 5 mm separation from the outer periphery, the substrate has a total density of screw dislocations, edge dislocations, and mixed screw-and-edge dislocations of between 1×10 4 cm −2 and 5×10 5 cm −2 inclusive, and has a ratio of screw-dislocation density to said total dislocation density of not less than 0.5.
2. A III-nitride crystal substrate manufacturing method, comprising:
a step of preparing a starting undersubstrate including a III nitride crystal layer having a major face, with the major face having a predetermined angle of inclination of from 0.5° to 10° with respect to a {0001} plane of the III nitride crystal layer;
a step of forming on the major face of the starting undersubstrate a plurality of micro-steps consisting of a plurality of terraced faces paralleling the {0001} plane, and of a plurality of stepped planes having a predetermined angle with respect to the {0001} plane; and
a step of initially growing III nitride crystal to a predetermined thickness by a liquid-phase technique onto the major face of the starting undersubstrate;
a step of additionally growing III nitride crystal onto the liquid-phase grown III-nitride crystal; and
a step of slicing the additionally grown III-nitride crystal through a plane paralleling the {0001} plane to produce a III-nitride crystal substrate; wherein
said inclination of, and the form of said micro-steps on, the starting undersubstrate major face are predetermined such that in a major-face principal region of the III-nitride crystal substrate excluding the peripheral margin from the outer periphery of the major face to a 5 mm separation from the outer periphery, the substrate has a total density of screw dislocations, edge dislocations, and mixed screw-and-edge dislocations of between 1×10 4 cm −2 and 5×10 5 cm −2 inclusive, and has a ratio of screw-dislocation density to said total dislocation density of not less than 0.9.
3. A light-emitting device manufacturing method, comprising:
the III-nitride crystal substrate manufacturing method of claim 1 ; and
a step of forming an at least single-lamina III nitride layer onto the III nitride crystal substrate.
4. A light-emitting device manufacturing method, comprising:
the III-nitride crystal substrate manufacturing method of claim 2 ; and
a step of forming an at least single-lamina III nitride layer onto the III nitride crystal substrate.
5. The III-nitride crystal substrate manufacturing method as set forth in claim 1 , further comprising a step in between said steps of initially and additionally growing III-nitride crystal, of planarizing the liquid-phase grown III-nitride crystal to form thereon a major face paralleling the {0001} plane of the III nitride crystal layer on the starting undersubstrate; wherein
in said step of additionally growing III nitride crystal, the growth is by a vapor-phase technique.
6. The III-nitride crystal substrate manufacturing method as set forth in claim 2 , further comprising a step in between said steps of initially and additionally growing III-nitride crystal, of planarizing the liquid-phase grown III-nitride crystal to form thereon a major face paralleling the {0001} plane of the III nitride crystal layer on the starting undersubstrate; wherein
in said step of additionally growing III nitride crystal, the growth is by a vapor-phase technique.