III-V nitride semiconductor device, and protection element and power conversion apparatus using the same

• US 20030098462A1
• Filed: 11/14/2002
• Published: 05/29/2003
• Est. Priority Date: 11/27/2001
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Yoshida, Seikoh
• Granted Patent: US 6,768,146 B2
• Time in Patent Office: Days
• US Class Current: 257/183
• CPC Class Codes: H01L 21/28575 on semiconductor bodies comprising AIIIBV compounds
• CPC Class Codes: H01L 21/28581 Deposition of Schottky electrodes
• CPC Class Codes: H01L 27/0605 integrated circuits made of compound material, e.g. AIIIBV
• CPC Class Codes: H01L 27/0727 in combination with diodes, or capacitors or resistors
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/475 on AIII-BV compounds
• CPC Class Codes: H01L 29/66143 Schottky diodes
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

A GaN-based Schottky diode includes a sapphire substrate on which are formed a GaN buffer layer, an n⁺-type GaN layer, and an n-type GaN layer that has a surface portion thereof shaped to form a protrusion having an upper face with which a Ti electrode forms a Schottky junction and a side face with which a Pt electrode forms a Schottky junction through an Al_0.2Ga_0.8N layer. A cathode electrode constituted by a TaSi layer forms an ohmic junction with the n⁺-type GaN layer. The Ti and Pt electrodes constitute a combined anode electrode contributing to increasing a withstand voltage of and decreasing an on-voltage of the Schottky diode.

Claims

1. A GaN-based semiconductor device comprising:

a III-V nitride semiconductor layer having a predetermined width;

a first anode electrode forming a Schottky junction with said III-V nitride semiconductor layer, with a junction width narrower than the predetermined width of said III-V nitride semiconductor layer; and

a second anode electrode forming a Schottky junction with a portion of said III-V nitride semiconductor layer other than a portion at which said first anode electrode is in contact with said III-V nitride semiconductor layer, said second anode electrode being electrically connected with said first anode electrode, a Schottky barrier formed between said first anode electrode and said III-V nitride semiconductor layer being lower in height than that formed between said second anode electrode and said III-V nitride semiconductor layer.

2. The GaN-based semiconductor device according to claim 1, wherein said first anode electrode has a width varying from 0.3 μ

m to 2 μ

m.

3. The GaN-based semiconductor device according to claim 1, wherein the predetermined width of said III-V nitride semiconductor layer is equal to or less than 6 μ

m.

5. The GaN-based semiconductor device according to any one of claims 1-4, wherein said first anode electrode is constituted by any one of Ti, W, and Ag.

6. The GaN-based semiconductor device according to any one of claims 1-4, wherein said second anode electrode is constituted by any one of Pt, Ni, Pd, and Au.

7. The GaN-based semiconductor device according to any one of claims 1-4, wherein said III-V nitride semiconductor layer has a carrier concentration equal to or less than 2×

10¹⁷ cm^{31 3}.

8. The GaN-based semiconductor device according to claim 7, further comprising:

a semiconductor layer interposed between the upper face of the protrusion of said III-V nitride semiconductor layer and said first anode electrode and having a carrier concentration higher than that of said III-V nitride semiconductor layer.

9. The GaN-based semiconductor device according to any one of claims 1-4, wherein the Schottky barrier formed between said first anode electrode and said III-V nitride semiconductor layer is lower in height than 0.8 eV, and the Schottky barrier between said second anode electrode and said III-V nitride semiconductor layer is higher in height than 0.8 eV.

12. The GaN-based semiconductor device according to any one of claims 1-4, further comprising:

an insulating or semi-insulating substrate,

wherein a cathode electrode is formed on said III-V nitride semiconductor layer so as to form an ohmic junction therewith.

13. The GaN-based semiconductor device according to claim 12, further comprising:

a III-V nitride semiconductor layer formed between said III-V nitride semiconductor layer and said cathode electrode and having an electrical conductivity higher than that of said III-V nitride semiconductor layer.

14. The GaN-based semiconductor device according to any one of claims 1-4, further comprising:

an electrically conductive substrate,

wherein a cathode electrode is formed on a rear face of said electrically conductive substrate so as to form an ohmic junction therewith.

15. The GaN-based semiconductor device according to claim 12, 13 or 14, wherein said cathode electrode is constituted by TaSi.

16. The GaN-based semiconductor device according to any one of claims 1-4, wherein said III-V nitride semiconductor layer has surface portions thereof shaped to form protrusions,

said first anode electrode is formed on respective upper faces of the protrusions so as to form a Schottky junction therewith, and

said second anode electrode is formed on respective side faces of the protrusions so as to form a Schottky junction therewith.

4. A GaN-based semiconductor device comprising:

a III-V nitride semiconductor layer having a surface portion thereof shaped to form a protrusion;

a first anode electrode forming a Schottky junction with an upper face of the protrusion of said III-V nitride semiconductor layer; and

a second anode electrode forming a Schottky junction with a side face of the protrusion of said III-V nitride semiconductor layer and electrically connected with said first anode electrode, a Schottky barrier formed between said first anode electrode and said III-V nitride semiconductor layer being lower in height than that formed between said second anode electrode and said III-V nitride semiconductor layer.

10. The GaN-based semiconductor device according to claim 4, further comprising:

a III-V nitride semiconductor layer formed between the side face of the protrusion of said III-V nitride semiconductor layer and said second anode electrode and having bandgap energy higher than that of said III-V nitride semiconductor layer.

11. The GaN-based semiconductor device according to claim 4, further comprising:

an undoped III-V nitride semiconductor layer formed between the side face of the protrusion of said III-V nitride semiconductor layer and said second anode electrode.

17. The GaN-based semiconductor device according to claim 4, wherein the protrusion of said III-V nitride semiconductor layer has a width that is not smaller than 5 nm and not larger than 10 μ

m.

18. A III-V nitride semiconductor device comprising:

an electrically conductive substrate;

a III-V nitride semiconductor layer formed on said substrate and having a surface portion thereof shaped to form a protrusion;

a source electrode formed on an upper face of the protrusion of said III-V nitride semiconductor layer so as to form an ohmic junction therewith;

a gate electrode formed on a side face of the protrusion so as to form a Schottky junction therewith; and

a drain electrode formed on a rear face of said substrate so as to form an ohmic junction therewith.

19. The semiconductor device according to claim 18, wherein said III-V nitride semiconductor layer has a carrier concentration not higher than 2×

10¹⁷ cm^{31 3}.

20. The semiconductor device according to claim 18, further comprising:

a III-V nitride semiconductor layer formed between the side face of the protrusion of said III-V nitride semiconductor layer and said gate electrode and having bandgap energy higher than that of said III-V nitride semiconductor layer.

21. The semiconductor device according to claim 18, further comprising:

an undoped III-V nitride semiconductor layer formed between the side face of the protrusion of said III-V nitride semiconductor layer and said gate electrode.

22. The semiconductor device according to claim 18, further comprising:

a III-V nitride semiconductor layer formed between said III-V nitride semiconductor layer and said source electrode and having an electrical conductivity higher than that of said III-V nitride semiconductor layer.

23. The semiconductor device according to claim 18, wherein the protrusion of said III-V nitride semiconductor layer has a width that is not smaller than 5 nm and is not larger than 10 μ

m.

24. In a protection element for protecting a switching element constituting a power conversion circuit of a power conversion apparatus, the improvement comprising:

said protection element being a GaN-based Schottky diode that has an on-voltage equal to or lower than 1 volt and a withstand voltage equal to or higher than 300 volts.

25. The protection element according to claim 24, wherein said GaN-based Schottky diode includes:

a substrate;

a first semiconductor layer formed on said substrate and constituted by a III-V nitride semiconductor;

a second semiconductor layer formed on said first semiconductor layer and constituted by an undoped III-V nitride semiconductor having a bandgap higher than that of said undoped III-V nitride semiconductor;

a third semiconductor layer formed on said first semiconductor layer so as to be connected to a heterojunction between said first and second semiconductor layers and constituted by an n-type III-V nitride semiconductor;

an anode electrode formed on said second semiconductor layer so as to form a Schottky junction therewith; and

a cathode electrode formed on said third semiconductor layer so as to form an ohmic junction therewith.

26. The protection element according to claim 25, further comprising:

an insulating thin film formed between said second semiconductor layer and said anode electrode.

27. The protection element according to claim 24, wherein said GaN-based Schottky diode includes:

a substrate;

a III-V nitride semiconductor layer formed on said substrate and having a surface portion thereof shaped to form a protrusion;

a first anode electrode forming a Schottky junction with an upper face of the protrusion; and

a second anode electrode forming a Schottky junction with a side face of the protrusion of said III-V nitride semiconductor layer and being electrically connected with said first anode electrode,

wherein a Schottky barrier formed between said first anode electrode and said semiconductor layer is lower in height than a Schottky barrier formed between said second anode electrode and said semiconductor layer.

28. The protection element according to claim 24, wherein said GaN-based Schottky diode and a GaN-based field effect transistor constituting said switching element are integrated on said substrate.

29. The protection element according to claim 24, wherein said power conversion circuit is an inverter circuit or a converter circuit.

30. The protection element according to claim 28, wherein said GaN-based field effect transistor and said GaN-based Schottky diode include:

a substrate;

a first semiconductor layer formed on said substrate and constituted by an undoped III-V nitride semiconductor;

a second semiconductor layer formed on said first semiconductor layer and constituted by an undoped III-V nitride semiconductor having a bandgap higher than that of the III-V nitride semiconductor constituting said first semiconductor layer;

two third semiconductor layers formed on said first semiconductor layer so as to be adjacent to said second semiconductor layer and constituted by an n-type III-V nitride semiconductor;

a source/cathode electrode and a drain electrode respectively formed on said two third semiconductor layer so as to form an ohmic junction therewith;

a gate electrode formed on said second semiconductor layer so as to form a Schottky junction therewith, said second semiconductor layer being arranged between said two third semiconductor layers; and

an anode electrode formed on that portion of said second semiconductor layer which is on a side opposite said gate electrode, so as to form a Schottky junction therewith, said source and cathode electrode being arranged between said anode and gate electrodes.

31. The protection element according to claim 30, further comprising:

insulating thin films formed between said second semiconductor layer and said anode electrode and between said second semiconductor layer and said gate electrode, respectively.

32. In a protection element for protecting a switching element constituting a power conversion circuit of a power conversion apparatus, the improvement comprising:

said protection element being a GaN-based field effect transistor having an on-voltage equal to or lower than 1 volt and a withstand voltage equal to or higher than 300 volts.

33. The protection element according to claim 32, wherein said GaN-based field effect transistor includes:

an electrically conductive substrate;

a III-V nitride semiconductor layer formed on said substrate and having a surface portion thereof shaped to form a protrusion;

a source electrode formed on an upper face of the protrusion of said III-V nitride semiconductor layer so as to form an ohmic junction therewith;

a gate electrode formed on a side face of the protrusion so as to form a Schottky junction therewith; and

a drain electrode formed on a rear face of said substrate so as to form an ohmic junction therewith.

34. The protection element according to claim 32, wherein said power conversion circuit is an inverter circuit or a converter circuit.

35. A power conversion apparatus comprising:

a power conversion circuit including a switching element; and

a protection element, constituted by a GaN-based Schottky diode, for protecting the switching element.

37. The power conversion apparatus according to claim 35 or 36, wherein said switching element is a field effect transistor.

38. The power conversion apparatus according to claim 35 or 36, wherein said switching element is an insulating gate type bipolar transistor.

40. The power conversion apparatus according to claim 35 or 36, wherein said power conversion circuit is an inverter circuit or a converter circuit.

41. The power conversion apparatus according to claim 35, wherein said protection element is a GaN-based Schottky diode having an on-voltage equal to or lower than 1 volt and a withstand voltage equal to or higher than 300 volts.

36. A power conversion apparatus comprising:

a power conversion circuit including a switching element; and

a protection element, constituted by a GaN-based field effect transistor, for protecting the switching element.

42. The power conversion apparatus according to claim 36, wherein said protection element is a GaN-based field effect transistor having an on-voltage equal to or lower than 1 volt and a withstand voltage equal to or higher than 300 volts.

39. The power conversion apparatus according to clam 35, wherein said switching element is a GaN-based field effect transistor, and

the GaN-based Schottky diode serving as said protection element is accommodated in the GaN-based field effect transistor serving as the switching element.