Optoelectronic substrate and methods of making same

An improved method of fabricating a device having a Group III nitride layer, in which method an auxiliary substrate is provided having a first Group III nitride layer disposed thereon, and then at least one epitaxial Group III nitride layer is deposited on an exposed face of the first Group III nitride layer, and then a further metal layer is deposited over at least a portion of the epitaxial Group III nitride layer(s), and then a final substrate is bonded on the deposited metal layer, and finally the auxiliary substrate is removed to form the device from the final substrate and deposited layers, wherein the improvement comprises providing the auxiliary substrate by the steps comprising:

• preparing a bonding surface of a free-standing Group III nitride substrate by polishing the N-face of such substrate and then by depositing a dielectric layer onto the polished N-face, wherein the free-standing Group III nitride substrate has a dislocation density that is less than about 106 and an exposed Ga-face opposite to the N-face;
• implanting one or more atomic species through the dielectric layer into the Group III nitride substrate in order to form a splitting area below the N-face of Group III nitride substrate;
• bonding the bonding surface of the dielectric layer of the free-standing Group III nitride substrate to the auxiliary substrate;
• and
• splitting the free-standing Group III nitride substrate at the splitting area to leave the auxiliary substrate with the first Group III nitride layer disposed thereon, the first Group III nitride layer having a nitrogen face that faces the auxiliary substrate and an opposite Ga-face that is exposed.