High power gallium nitride electronics using miscut substrates
A method of fabricating an electronic device includes providing a III-V substrate having a hexagonal crystal structure and a normal to a growth surface characterized by a misorientation from the <0001> direction of between 0.15° and 0.65°. The method also includes growing a first III-V epitaxial layer coupled to the III-V substrate and growing a second III-V epitaxial layer coupled to the first III-V epitaxial layer. The method further includes forming a first contact in electrical contact with the III-V substrate and forming a second contact in electrical contact with the second III-V epitaxial layer.
1. A field effect transistor comprising:
a III-V substrate having a hexagonal crystal structure and a normal to a growth surface characterized by a misorientation from the <0001> direction towards the <1 1 00> direction by an angle ranging between −0.3° and −0.6° and towards the <11 2 0> direction by an angle ranging between −0.1° and −0.2°;
a first epitaxial layer coupled to the III-V substrate;
a second epitaxial layer coupled to the first epitaxial layer;
a drain contact in electrical contact with the III-V substrate;
a source contact in electrical contact with the first epitaxial layer; and
a gate contact in electrical contact with the second epitaxial layer.
2. The field effect transistor of claim 1 wherein the III-V substrate comprises an n-type GaN substrate.
3. The field effect transistor of claim 1 wherein the first epitaxial layer comprises an n-type GaN epitaxial layer and the second epitaxial layer comprises a p-type GaN epitaxial layer.
4. The field effect transistor of claim 1 further comprising an isolation region disposed laterally to the second epitaxial layer.
5. The field effect transistor of claim 1 further comprising a third epitaxial layer disposed between the second epitaxial layer and the gate contact, wherein a doping density of the third epitaxial layer is higher than a doping density of the second epitaxial layer.
6. The field effect transistor of claim 1 wherein the first epitaxial layer has a thickness greater than 5 μm.
7. The field effect transistor of claim 1 wherein a dopant concentration in the first epitaxial layer varies as a function of a thickness of the first epitaxial layer.
8. The field effect transistor of claim 1 wherein a dopant concentration in the second epitaxial layer varies as a function of a thickness of the second epitaxial layer.
9. A method of fabricating a field effect transistor, the method comprising:
providing a III-V substrate having a hexagonal crystal structure and a normal to a growth surface characterized by a misorientation from the <0001> direction towards the <1 1 00> direction by an angle ranging between −0.3° and −0.6° and towards the <11 2 0> direction by an angle ranging between −0.1° and −0.2°;
growing a first epitaxial layer coupled to the III-V substrate;
growing a second epitaxial layer coupled to the first epitaxial layer;
forming a drain contact in electrical contact with the III-V substrate;
forming a source contact in electrical contact with the first epitaxial layer; and
forming a gate contact in electrical contact with the second epitaxial layer.
10. The method of claim 9 wherein the III-V substrate comprises an n-type GaN substrate.
11. The method of claim 9 wherein the first epitaxial layer comprises an n-type GaN epitaxial layer having a thickness greater than 3 μm and the second epitaxial layer comprises a p-type GaN epitaxial layer.
12. The method of claim 11 wherein the n-type GaN epitaxial layer has a thickness greater than 5 μm.
13. The method of claim 9 further comprising forming an isolation region disposed laterally to the second epitaxial layer.
14. The method of claim 9 further comprising forming a third epitaxial layer disposed between the second epitaxial layer and the gate contact, wherein a doping density of the third epitaxial layer is higher than a doping density of the second epitaxial layer.
15. The method of claim 9 wherein a dopant concentration in the first epitaxial layer or the second epitaxial layer varies as a function of thickness.