III-nitride light emitting device including porous semiconductor
A semiconductor structure comprising a III-nitride light emitting layer disposed between an n-type region and a p-type region is grown over a porous III-nitride region. A III-nitride layer comprising InN is disposed between the light emitting layer and the porous III-nitride region. Since the III-nitride layer comprising InN is grown on the porous region, the III-nitride layer comprising InN may be at least partially relaxed, i.e. the III-nitride layer comprising InN may have an in-plane lattice constant larger than an in-plane lattice constant of a conventional GaN layer grown on sapphire.
1. A method comprising:
growing a first III-nitride layer directly on a substrate;
making at least a portion of the first III-nitride layer porous;
growing a second III-nitride layer directly on the porous portion, the second layer comprising InGaN; and
growing a device structure directly on the second III-nitride layer, the device structure comprising a III-nitride light emitting layer disposed between an n-type region and a p-type region.
2. The method of claim 1 further comprising:
forming a mask over the first III-nitride layer; and
forming a plurality of openings in the mask;
wherein growing a second III-nitride layer comprises growing by epitaxial lateral overgrowth.
3. The method of claim 2 wherein making at least a portion of the first III-nitride layer porous comprises making regions of the first III-nitride layer aligned with the plurality of openings porous.
4. The method of claim 1 wherein the second III-nitride layer has an in-plane lattice constant of at least 3.189 Å.
5. The method of claim 1 further comprising:
forming n- and p-contacts electrically connected to the n- and p-type region, wherein the n- and p-contacts are both formed on a same side of the device structure;
connecting the device structure to a mount; and
removing the substrate.
6. The method of claim 1 wherein making at least a portion of the first III-nitride layer porous comprises making an entire thickness of the first III-nitride layer porous.
7. The method of claim 6 further comprising making at least a portion of the substrate porous.
8. The method of claim 1 wherein making at least a portion of the first III-nitride layer porous comprises making an entire thickness of the first III-nitride layer porous, such that porous material is in direct contact with the substrate.
9. The method of claim 1 wherein the second III-nitride layer has a composition of indium equal to or less than a composition of indium in the III-nitride light emitting layer.
10. The method of claim 1 wherein the second III-nitride layer is In x Ga 1-x N, where 0.05≤x≤0.15.
11. The method of claim 2 wherein making at least a portion of the first III-nitride layer porous occurs before forming a mask over the first III-nitride layer.
12. The method of claim 2 wherein making at least a portion of the first III-nitride layer porous occurs after forming a mask over the first III-nitride layer and forming a plurality of openings in the mask.
13. The method of claim 2 wherein growing a second III-nitride layer comprises growing a first portion of the second III-nitride layer under conditions that favor the formation of pyramids of material, then growing a second portion of the second III-nitride layer under conditions that favor lateral growth.
14. The method of claim 1 , wherein the n-type region comprises the second III-nitride layer.