High electron mobility transistor (HEMT) device
A high electron mobility transistor (HEMT) device with epitaxial layers that provide an electron Hall mobility of 1080±5% centimeters squared per volt-second (cm 2 /V·s) at room temperature for a charge density of 3.18×10 13 /cm 2 and method of making the HEMT device is disclosed. The epitaxial layers include a channel layer made of gallium nitride (GaN), a first spacer layer made of aluminum nitride (AlN) that resides over the channel layer, a first spacer layer made of Al X Ga (1-X) N that resides over the first spacer layer, and a first barrier layer made of Sc y Al z Ga (1-y-z) N that resides over the second spacer layer. In at least one embodiment, a second barrier layer made of Al X Ga (1-X) N is disposed over the first barrier layer.
1. A high electron mobility transistor (HEMT) device comprising:
a substrate;
epitaxial layers over the substrate and comprising;
a channel layer made of gallium nitride (GaN);
a first spacer layer made of aluminum nitride (AlN) that resides over the channel layer;
a second spacer layer made of Al X Ga (1-X) N that resides over the first spacer layer; and
a first barrier layer made of Sc y Al z Ga (1-y-z) N that resides over the second spacer layer, wherein y is at least 0.005; and
a gate contact disposed on a surface of the epitaxial layers;
a source contact disposed on the surface of the epitaxial layers; and
a drain contact disposed on the surface of the epitaxial layers, wherein the source contact and the drain contact are spaced apart from the gate contact and each other.
2. The HEMT device of claim 1 having an electron Hall mobility of 1080±5% centimeters squared per volt-second (cm 2 /V·s) at room temperature for a charge density of 3.18×10 13 /cm 2 .
3. The HEMT device of claim 2 wherein a sheet resistance within the channel layer is no more than 195 Ohms/square.
4. The HEMT device of claim 1 wherein the first spacer layer has a thickness between 5 Angstoms (Å) and 15 Å.
5. The HEMT device of claim 1 wherein the second spacer layer has a thickness between 10 Å and 50 Å.
6. The HEMT device of claim 1 wherein the first spacer layer has a thickness between 5 Å and 15 Å, and the second spacer layer has a thickness between 10 Å and 50 Å.
7. The HEMT device of claim 5 wherein a combined thickness of the first spacer layer and the second spacer layer prevents carrier scattering from the first barrier layer made of Sc y Al z Ga (1-y-z) N.
8. The HEMT device of claim 1 wherein the a first barrier layer made of Sc y Al z Ga (1-y-z) N is between 30 Å and 300 Å thick and wherein y is between 0.005 and 0.3.
9. The HEMT device of claim 1 further including a second barrier layer, wherein the second barrier layer is made of Al X Ga (1-X) N resides over the first barrier layer and is between 10 Å and 100 Å thick.
10. The HEMT device of claim 1 further including a buffer layer made of GaN that resides between the substrate and the channel layer.
11. A method of making a HEMT device comprising:
providing a substrate;
disposing over the substrate, epitaxial layers comprising;
a channel layer made of gallium nitride (GaN);
a first spacer layer made of aluminum nitride (AlN) that resides over the channel layer;
a second spacer layer made of Al X Ga (1-X) N that resides over the first spacer layer; and
a first barrier layer made of Sc y Al z Ga (1-y-z) N that resides over the second spacer layer, wherein y is at least 0.005; and
disposing a gate contact on a surface of the epitaxial layers;
disposing a source contact on the surface of the epitaxial layers; and
disposing a drain contact on the surface of the epitaxial layers, wherein the source contact and the drain contact are spaced apart from the gate contact and each other.
12. The method of making a HEMT device of claim 11 wherein the HEMT device has an electron Hall mobility of 1080±5% centimeters squared per volt-second (cm 2 /V·s) at room temperature for a charge density of 3.18×10 13 /cm 2 .
13. The method of making the HEMT device of claim 12 wherein a sheet resistance within the channel layer is no more than 195 Ohms/square.
14. The method of making the HEMT device of claim 11 wherein the first spacer layer has a thickness between 5 Å and 15 Å.
15. The method of making the HEMT device of claim 11 wherein the second spacer layer has a thickness between 10 Å and 50 Å.
16. The method of making the HEMT device of claim 11 wherein the first spacer layer has a thickness between 5 Å and 15 Å, and the second spacer layer has a thickness between 10 Å and 50 Å.
17. The method of making the HEMT device of claim 15 wherein a combined thickness of the first spacer layer and the second spacer layer prevents carrier scattering from the first barrier layer made of Sc y Al z Ga (1-y-z) N.
18. The method of making the HEMT device of claim 11 wherein the a first barrier layer made of Sc y Al z Ga (1-y-z) N is between 30 Å and 300 Å thick and wherein y is between 0.005 and 0.3.
19. The method of making the HEMT device of claim 11 further including disposing a second barrier layer over the first barrier layer, wherein the second barrier layer is made of Al X Ga (1-X) N that is between 10 Å and 100 Å thick.
20. The method of making the HEMT device of claim 11 further including disposing a buffer layer made of GaN over the substrate before disposing the channel layer.