Low-strain laser structures with group III nitride active layers

A separate-confinement heterostructure laser comprising:

• an aluminum indium gallium nitride active layer;
• upper and lower waveguide layers on said active layer formed from the group consisting of AlGaN, InGaN, and AlInGaN;
• and
• upper and lower cladding layers on said respective upper and lower waveguide layers and formed of AlGaN.

A group III nitride laser structure comprising:

• an active layer that includes at least one layer of a Group III nitride;
• a silicon carbide substrate;
• and
• a coupling structure between said active layer and said substrate, said coupling layer including at least one graded layer of silicon carbide and a group III nitride in which the graded layer is silicon carbide at the interface with said substrate, and the graded layer is the group III nitride at the interface with said active layer.

A group III nitride laser structure comprising:

• an active layer that includes at least one layer of a Group III nitride;
• a silicon carbide substrate;
• a buffer layer between said active layer and said silicon carbide substrate, said buffer layer being selected from the group consisting of gallium nitride, aluminum nitride, indium nitride, ternary Group III nitrides having the formula A.sub.x B.sub.1-x N, where A and B are Group III elements and where x is zero, one, or a fraction between zero and one, and alloys of silicon carbide with such ternary Group III nitrides;
• and
• a strain-minimizing contact layer above said active layer that has a lattice constant substantially the same as said buffer layer.