LAYER STRUCTURES FOR CONTROLLING STRESS OF HETEROEPITAXIALLY GROWN III-NITRIDE LAYERS
A III-N layer structure is described that includes a III-N buffer layer on a foreign substrate, an additional III-N layer, a first III-N structure, and a second III-N layer structure. The first III-N structure atop the III-N buffer layer includes at least two III-N layers, each having an aluminum composition, and the III-N layer of the two III-N layers that is closer to the III-N buffer layer having the larger aluminum composition. The second III-N structure includes a III-N superlattice, the III-N superlattice including at least two III-N well layers interleaved with at least two III-N barrier layer. The first III-N structure and the second III-N structure are between the additional III-N layer and the foreign substrate.
1 . A III-N layer structure, comprising:
a III-N buffer layer on a foreign substrate;
an additional III-N layer;
a first III-N structure atop the III-N buffer layer comprising at least two III-N layers, each having an aluminum composition, and the III-N layer of the two III-N layers that is closer to the III-N buffer layer having a larger aluminum composition; and
a second III-N structure comprising a III-N superlattice, the III-N superlattice comprising at least two III-N well layers interleaved with at least two III-N barrier layers, the well layers and the barrier layers each having an aluminum composition, wherein the first III-N structure and the second III-N structure are between the additional III-N layer and the foreign substrate.
2 . The III-N layer structure of claim 1 , wherein a difference between the aluminum compositions of the at least two III-N well layers and the aluminum compositions of the at least two III-N barrier layers is less than about 0.5.
3 . The III-N layer structure of claim 1 , wherein a difference between the aluminum compositions of the at least two III-N well layers and the aluminum compositions of the at least two III-N barrier layers is less than about 0.2.
4 . The III-N layer structure of claim 1 , wherein the thickness of each of the III-N well layers is between about 20 and 150 nm.
5 . The III-N layer structure of claim 1 , wherein the thickness of each of the III-N barrier layers is less than about 100 Å.
6 . The III-N layer structure of claim 1 , wherein the thickness of each of the III-N barrier layers is less than about 20 Å.
7 . The III-N layer structure of claim 1 , wherein the III-N barrier layers have different thicknesses.
8 . The III-N layer structure of claim 1 , wherein the III-N barrier layers have aluminum compositions between about 1 and 50 percent.
9 . The III-N layer structure of claim 1 , wherein the III-N barrier layers have aluminum compositions between about 1 and 20 percent.
10 . The III-N layer structure of claim 1 , wherein the barrier layers are AlGaN and the well layers are GaN.
11 . The III-N layer structure of claim 1 , wherein the III-N well or barrier layers are doped with a dopant selected from the class consisting of Fe, Mg, and B.
12 . The III-N layer structure of claim 1 , wherein the foreign substrate is silicon.
13 . The III-N layer structure of claim 1 , wherein the foreign substrate is selected from the group consisting of SiC, sapphire and zinc oxide.
14 . The III-N layer structure of claim 1 , wherein the foreign substrate and the III-N layers each have thermal expansion coefficients, and wherein the thermal expansion coefficient of the foreign substrate is smaller than the thermal expansion coefficient of one of the III-N layers.
15 . The III-N layer structure of claim 1 , wherein the second III-N structure is atop the first III-N structure.
16 . The III-N layer structure of claim 1 , wherein the III-N buffer layer is AlN.
17 . The III-N layer structure of claim 1 , wherein the additional III-N layer is GaN.
18 . The III-N layer structure of claim 1 , wherein the additional III-N layer is AlGaN.
19 . The III-N layer structure of claim 1 , wherein the additional III-N layer is at least 2 microns thick.
20 . The III-N layer structure of claim 1 , wherein the additional III-N layer is at least 5 microns thick.
21 . The III-N layer structure of claim 1 , wherein the additional III-N layer is an epitaxial layer.
22 . The III-N layer structure of claim 1 , having further layers atop the additional III-N layer.
23 . A III-N layer structure, comprising:
a III-N buffer layer on a foreign substrate;
an additional III-N layer;
a first III-N structure comprising at least two Al x Ga y N layers where x+y is less than or equal to 1, and a layer of the two layers that is closer to the III-N buffer layer having a larger aluminum composition; and
a second III-N structure comprising a III-N superlattice, the III-N superlattice comprising at least two III-N well layers interleaved with at least two III-N barrier layers, the well layers and the barrier layers each having an aluminum composition, wherein the first III-N structure and the second III-N structure are between the additional III-N layer and the foreign substrate.
24 . The III-N layer structure of claim 23 , wherein each of the Al x Ga y N layers further includes an element selected from the group consisting of Indium, Boron, Phosphorus, Arsenic, and Antimony.
25 . The III-N layer structure of claim 23 , wherein a difference between the aluminum compositions of the at least two III-N well layers and the aluminum compositions of the at least two III-N barrier layers is less than about 0.5.
26 . The III-N layer structure of claim 23 , wherein a difference between the aluminum compositions of the at least two III-N well layers and the aluminum compositions of the at least two III-N barrier layers is less than about 0.2.
27 . The III-N layer structure of claim 23 , wherein the thickness of each of the III-N well layers is between about 20 and 150 nm.
28 . The III-N layer structure of claim 23 , wherein the thickness of each of the III-N barrier layers is less than about 100 Å.
29 . The III-N layer structure of claim 23 , wherein the thickness of each of the III-N barrier layers is less than about 20 Å.
30 . The III-N layer structure of claim 23 , wherein the III-N barrier layers have different thicknesses.
31 . The III-N layer structure of claim 23 , wherein the III-N barrier layers have aluminum compositions between about 1 and 50 percent.
32 . The III-N layer structure of claim 23 , wherein the III-N barrier layers have aluminum compositions between about 1 and 20 percent.
33 . The III-N layer structure of claim 23 , wherein the III-N well or barrier layers are doped with a dopant selected from the class consisting of Fe, Mg, and B.
34 . The III-N layer structure of claim 23 , wherein the barrier layers are AlGaN and the well layers are GaN.
35 . The III-N layer structure of claim 23 , wherein the foreign substrate is silicon.
36 . The III-N layer structure of claim 23 , wherein the foreign substrate is selected from the group consisting of SiC, sapphire and zinc oxide.
37 . The III-N layer structure of claim 23 , wherein the foreign substrate and the III-N layers each have thermal expansion coefficients, and wherein the thermal expansion coefficient of the foreign substrate is smaller than the thermal expansion coefficient of one of the III-N layers.
38 . The III-N layer structure of claim 23 , wherein the second III-N structure is atop the first III-N structure.
39 . The III-N layer structure of claim 23 , wherein the III-N buffer layer is AlN.
40 . The III-N layer structure of claim 23 , wherein the additional III-N layer is GaN.
41 . The III-N layer structure of claim 23 , wherein the additional III-N layer is AlGaN.
42 . The III-N layer structure of claim 23 , wherein the additional III-N layer is at least 2 microns thick.
43 . The III-N layer structure of claim 23 , wherein the additional III-N layer is at least 5 microns thick.
44 . The III-N layer structure of claim 23 , wherein the additional III-N layer is an epitaxial layer.
45 . The III-N layer structure of claim 23 , having further layers atop the additional III-N layer.