Semiconductor device

1. A semiconductor device comprising:

a substrate;

a first GaN field effect transistor disposed on or above the substrate, wherein the first GaN field effect transistor is a depletion mode field effect transistor;

a second GaN field effect transistor disposed on or above the substrate, wherein the second GaN field effect transistor is an enhancement mode field effect transistor;

a GaN diode disposed on or above the substrate, wherein the first GaN field effect transistor, the second GaN field effect transistor, and the GaN diode are all disposed on or above a same side of the substrate and electrically connected to each other; and

a power factor correction diode, wherein an anode of the power factor correction diode is electrically connected to a drain electrode of the first GaN field effect transistor.

2. The semiconductor device of claim 1 , wherein the first GaN field effect transistor is electrically connected in a cascoded configuration with the second GaN field effect transistor, and the GaN diode is connected in parallel with the second GaN field effect transistor.

3. The semiconductor device of claim 1 , wherein a drain electrode of the second GaN field effect transistor is electrically connected to a source electrode of the first GaN field effect transistor and a cathode of the GaN diode.

4. The semiconductor device of claim 1 , wherein the first GaN field effect transistor, the second GaN field effect transistor, and the GaN diode cooperate to function as a normally-off field effect transistor device.

5. The semiconductor device of claim 1 , further comprising a nitride layer disposed on or above the substrate, wherein the first GaN field effect transistor, the second GaN field effect transistor, and the GaN diode are all disposed on or above the nitride layer.

6. The semiconductor device of claim 1 , wherein the first GaN field effect transistor, the second GaN field effect transistor, and the GaN diode comprise at least one common heterojunction structure, and the heterojunction structure comprises at least Al x Ga 1-x N (0<x <0.3).

7. The semiconductor device of claim 1 , wherein the first GaN field effect transistor comprises:

a heterojunction structure disposed on or above the substrate, the heterojunction structure comprising a plurality of III-N semiconductor layers and at least one two-dimensional electronic gas (2DEG) channel therein;

a source electrode and a drain electrode separated from each other and electrically coupled with the 2DEG channel; and

a gate electrode disposed on or above the heterojunction structure and between the source electrode and the drain electrode.

8. The semiconductor device of claim 1 , wherein the second GaN field effect transistor comprises:

a heterojunction structure disposed on or above the substrate, the heterojunction structure comprising a plurality of III-N semiconductor layers and a two-dimensional electronic gas (2DEG) channel therein;

a source electrode and a drain electrode separated from each other and electrically coupled with the 2DEG channel;

a gate electrode disposed above the heterojunction structure and between the source electrode and the drain electrode; and

a p-type doped layer disposed between the heterojunction structure and the gate electrode.

9. The semiconductor device of claim 8 , wherein the p-type doped layer is made of p-GaN or p-AlGaN.

10. The semiconductor device of claim 1 , wherein the second GaN field effect transistor comprises:

a heterojunction structure disposed on or above the substrate, the heterojunction structure comprising a plurality of III-N semiconductor layers and a two-dimensional electronic gas (2DEG) channel therein, and the heterojunction structure having an inclined portion;

a source electrode and a drain electrode separated from each other and electrically coupled with the 2DEG channel; and

a gate electrode disposed between the source electrode and the drain electrode, wherein at least one portion of the gate electrode is disposed on or above the inclined portion of the heterojunction structure.

11. The semiconductor device of claim 1 , wherein the second GaN field effect transistor comprises:

a heterojunction structure disposed on or above the substrate, the heterojunction structure comprising a plurality of III-N semiconductor layers and a two-dimensional electronic gas (2DEG) channel therein, and the heterojunction structure having a recess;

a source electrode and a drain electrode separated from each other and electrically coupled with the 2DEG channel; and

a gate electrode disposed between the source electrode and the drain electrode, wherein at least one portion of the gate electrode is disposed on or above the recess of the heterojunction structure.

12. The semiconductor device of claim 1 , wherein the GaN diode comprises:

a heterojunction structure disposed on or above the substrate;

an anode and a cathode separated from each other and electrically coupled with the heterojunction structure; and

a p-type doped layer disposed on or above the heterojunction structure and between the anode and the heterojunction structure.

13. A semiconductor device comprising:

a substrate;

a heterojunction structure disposed on or above the substrate, wherein the heterojunction structure comprises a first region, a second region, and an interconnection region disposed between the first region and the second region, and the heterojunction structure creates a 2DEG channel within the heterojunction structure;

a first GaN field effect transistor disposed to include the first region of the heterojunction structure therein;

a second GaN field effect transistor disposed to include the second region of the heterojunction structure therein;

an interconnection structure disposed above the interconnection region of the heterojunction structure and electrically connecting the first GaN field effect transistor and the second GaN field effect transistor, wherein a top surface of the interconnection structure, a top surface of a drain electrode of the second GaN field effect transistor, and a top surface of a source electrode of the first GaN field effect transistor are substantially coplanar; and

a cap layer disposed between the interconnection structure and the heterojunction structure, wherein the 2DEG channel is substantially interrupted in the interconnection region of the heterojunction structure under the cap layer, and the heterojunction structure, the first GaN field effect transistor, the second GaN field effect transistor, the interconnection structure, and the cap layer are all disposed on a same side of the substrate.

14. The semiconductor device of claim 13 , wherein the cap layer is a p-type doped layer.

15. The semiconductor device of claim 13 , wherein the first GaN field effect transistor is a depletion mode field effect transistor, and the second GaN field effect transistor is an enhancement mode field effect transistor.

16. The semiconductor device of claim 15 , wherein the interconnection structure electrically connects the drain electrode of the enhancement mode field effect transistor and the source electrode of the depletion mode field effect transistor.

17. The semiconductor device of claim 13 , wherein the heterojunction structure comprises a first semiconductor layer and a second semiconductor layer disposed on the first semiconductor layer.

18. The semiconductor device of claim 17 , wherein the 2DEG channel exists adjacent to an interface between the first semiconductor layer and the second semiconductor layer.