Over-voltage protection of gallium nitride semiconductor devices

1. A monolithically integrated semiconductor assembly, comprising:

a substrate comprising silicon carbide (SiC);

a gallium nitride (GaN) semiconductor device fabricated on the substrate, wherein the GaN semiconductor device comprises a high electron mobility transistor (HEMT), a junction gate field effect transistor (JFET), or a metal-oxide-semiconductor field-effect transistor (MOSFET); and

in addition to the GaN semiconductor device, at least one transient voltage suppressor (TVS) structure fabricated in or on the substrate, comprising:

a first semiconductor region having a first conductivity type;

a second semiconductor region having a second conductivity type, and in electrical contact with the first semiconductor region; and

a third semiconductor region having a first conductivity type, and in electrical contact with the second semiconductor region, such that the TVS structure is configured to operate in a punch-through mode when an applied voltage across the GaN semiconductor device is greater than a threshold voltage.

2. The monolithically integrated semiconductor assembly of claim 1 , wherein the TVS structure comprises at least one of silicon carbide, gallium nitride, diamond, aluminum nitride, boron nitride, or combinations thereof.

3. The monolithically integrated semiconductor assembly of claim 1 , wherein the TVS structure is configured laterally.

4. The monolithically integrated semiconductor assembly of claim 1 , wherein the TVS structure is configured vertically.

5. The monolithically integrated semiconductor assembly of claim 1 , wherein the first conductivity type is n+-type and the second conductivity type is p-type.

6. The monolithically integrated semiconductor assembly of claim 1 , wherein the first semiconductor region, the second semiconductor region, and the third semiconductor region are formed in the SiC substrate.

7. The monolithically integrated semiconductor assembly of claim 1 , wherein the first semiconductor region, the second semiconductor region, and the third semiconductor region are epitaxially grown on the SiC substrate.

8. The monolithically integrated semiconductor assembly of claim 1 , wherein the TVS structure further comprises a GaN layer disposed on at least a portion of the SiC substrate, and wherein the first semiconductor region, the second semiconductor region, and the third semiconductor region are formed in the GaN layer.

9. The monolithically integrated semiconductor assembly of claim 1 , wherein the TVS structure is in electrical contact with the GaN semiconductor device via a gate-source terminal, a drain-source terminal, a gate-drain terminal, or combinations thereof.

10. A monolithically integrated semiconductor assembly, comprising:

a substrate comprising silicon carbide (SiC);

a gallium nitride (GaN) semiconductor device fabricated on the substrate, wherein the GaN semiconductor device comprises a high electron mobility transistor (HEMT); and

in addition to the GaN semiconductor device, at least one transient voltage suppressor (TVS) structure comprising silicon carbide (SiC) fabricated in or on the substrate, comprising:

a first semiconductor region having a first conductivity type;

a second semiconductor region having a second conductivity type, and in electrical contact with the first semiconductor region; and

a third semiconductor region having a first conductivity type, and in electrical contact with the second semiconductor region;

wherein the TVS structure is in electrical contact with the GaN semiconductor device, such that the TVS structure is configured to operate in a punch-through mode when an applied voltage across the GaN semiconductor device is greater than a threshold voltage.

11. The monolithically integrated semiconductor assembly of claim 10 , wherein the assembly is configured to operate at temperatures greater than 150 degree Celsius.

12. The monolithically integrated semiconductor assembly of claim 10 , wherein the assembly is configured to have a leakage current of less than about 1 μA/cm 2 at 90% of a breakdown voltage.

13. The monolithically integrated semiconductor assembly of claim 10 , wherein the assembly is configured to have an operation current density greater than about 150 A/cm 2 .

14. A method of making a monolithically integrated semiconductor assembly comprising:

(a) providing a substrate comprising silicon carbide (SiC);

(b) fabricating a gallium nitride (GaN) semiconductor device on the substrate, wherein the GaN semiconductor device comprises a high electron mobility transistor (HEMT), a junction gate field effect transistor (JFET), or a metal-oxide-semiconductor field-effect transistor (MOSFET);

(c) in addition to the GaN semiconductor device, fabricating at least one transient voltage suppressor (TVS) in or on the substrate, the at least one TVS comprising:

a first semiconductor region having a first conductivity type;

a second semiconductor region having a second conductivity type, and in electrical contact with the first semiconductor region; and

a third semiconductor region having a first conductivity type, and in electrical contact with the second semiconductor region; and

(d) electrically coupling the TVS structure with the GaN semiconductor device,

wherein the TVS structure is configured to operate in a punch-through mode when an applied voltage across the GaN semiconductor device is greater than a threshold voltage.

15. The method of claim 14 , wherein the first conductivity type is n+-type and the second conductivity type is p-type.

16. The method of claim 14 , wherein the step (c) comprises forming the first semiconductor region, the second semiconductor region, and the third semiconductor region in the SiC substrate by ion implantation.

17. The method of claim 14 , wherein the step (c) comprises epitaxially growing the first semiconductor region, the second semiconductor region, and the third semiconductor region on the SiC substrate.

18. The method of claim 14 , further comprising disposing a GaN layer on at least a portion of the SiC substrate, and forming the first semiconductor region, the second semiconductor region, and the third semiconductor region in the GaN layer.

19. The method of claim 14 , wherein the step (d) comprises electrically coupling the TVS structure with the GaN semiconductor device via a gate-source terminal, a drain-source terminal, a gate-drain terminal, or combinations thereof.

20. The monolithically integrated semiconductor assembly of claim 1 , wherein the first semiconductor region and the third semiconductor region in the TVS structure are in electrical contact with the GaN semiconductor device.

21. The monolithically integrated semiconductor assembly of claim 20 , wherein the first semiconductor region and the third semiconductor region in the TVS structure are in electrical contact with the GaN semiconductor device via a gate-source terminal, a drain-source terminal, or combinations thereof.

22. The monolithically integrated semiconductor assembly of claim 20 , wherein the first semiconductor region is in electrical contact with a source terminal of the GaN semiconductor device, and the third semiconductor region is in electrical contact with a gate terminal or a drain terminal of the GaN semiconductor device.

23. The monolithically integrated semiconductor assembly of claim 1 , further comprising a second TVS structure.