Schottky diode with silver layer contacting the ZnO and MgxZn1-xO films

• US 20050145970A1
• Filed: 01/25/2005
• Published: 07/07/2005
• Est. Priority Date: 01/04/2002
• Status: Active Grant

• Current Assignee: Rutgers University
• Original Assignee: Rutgers University
• Inventors: Muthukumar, Sriram, Sheng, Haifeng, Lu, Yicheng, Zhong, Jian, Liang, Shaohua, Emanetoglu, Nuri William
• Granted Patent: US 7,400,030 B2
• Time in Patent Office: Days
• US Class Current: 257/449
• CPC Class Codes: H01L 31/022408 for devices characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H01L 31/0392 including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate textured substrates H01L31/02366
• CPC Class Codes: H01L 31/108 the potential barrier being of the Schottky type
• CPC Class Codes: H01L 31/1123 the device being a photo MESFET
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

In the present invention, there is provided semiconductor devices such as a Schottky UV photodetector fabricated on n-type ZnO and Mg_xZn_1-xO epitaxial films. The ZnO and Mg_xZn_1-xO films are grown on R-plane sapphire substrates and the Schottky diodes are fabricated on the ZnO and Mg_xZn_1-xO films using silver and aluminum as Schottky and ohmic contact metals, respectively. The Schottky diodes have circular patterns, where the inner circle is the Schottky contact, and the outside ring is the ohmic contact. Ag Schottky contact patterns are fabricated using standard liftoff techniques, while the Al ohmic contact patterns are formed using wet chemical etching. These detectors show low frequency photoresponsivity, high speed photoresponse, lower leakage current and low noise performance as compared to their photoconductive counterparts. This invention is also applicable to optical modulators, Metal Semiconductor Field Effect Transistors (MESFETs) and more.

Claims

1. A semiconductor Schottky contact comprising:

a ZnO semiconductor epitaxial film having (11{overscore (2)}0) family of planes, grown on a single crystal substrate having an orientation wherein primary symmetric axis (0001) of said ZnO semiconductor epitaxial film lies on the surface of said substrate, thereby resulting in zero net charge on said ZnO film and zero net dipole moment perpendicular to surface of said ZnO film; and

a metal layer deposited on said film to form a Schottky contact.

2. The Schottky contact of claim 1 wherein lattice mismatch between said ZnO semiconductor film and the substrate is small.

3. The Schottky contact of claim 1 wherein said substrate is R-plane sapphire, i.e., (01{overscore (1)}2) Al₂O₃.

4. The Schottky contact of claim 1 wherein said metal layer is silver, Ag.

5. A semiconductor Schottky contact comprising:

a Mg_xZn_1-xO semiconductor epitaxial film having a (11{overscore (2)}0) family of planes, grown on a single crystal substrate having an orientation wherein primary symmetric axis (0001) of said Mg_xZn_1-xO semiconductor epitaxial film lies on the surface of said substrate, thereby resulting in zero net charge on said Mg_xZn_1-xO film and zero net dipole moment perpendicular to surface of said Mg_xZn_1-xO film; and

a metal layer deposited on said Mg_xZn_1-xO film to form a Schottky contact.

6. The Schottky contact of claim 5 wherein said substrate is R-plane sapphire, i.e., (11{overscore (2)}0) Al₂O₃.

7. The Schottky contact of claim 5 wherein said metal layer is silver, Ag.

8. The Schottky contact of claim 7 wherein energy bandgap of the Mg_xZn_1-xO film varies with Mg content.

9. A semiconductor Schottky diode, comprising:

a ZnO semiconductor epitaxial film having (11{overscore (2)}0) family of planes, grown on a single crystal substrate having an orientation wherein primary symmetric axis (0001) of said ZnO semiconductor epitaxial film lies on the surface of said substrate, thereby resulting in zero net charge on said ZnO film and zero net dipole moment perpendicular to surface of said ZnO film;

a metal deposited on said ZnO film to form a Schottky contact; and

an ohmic metal deposited on said ZnO film to form an ohmic contact.

10. The Schottky diode of claim 9 wherein the substrate is R-plane sapphire, i.e., (01{overscore (1)}2) Al₂O₃.

11. The Schottky diode of claim 9 wherein the lattice mismatch between the said substrate and said ZnO semiconductor film is small.

12. The Schottky diode of claim 9 wherein said metal is silver.

13. The Schottky diode of claim 9 wherein said ohmic metal is aluminum.

14. The Schottky diode of claim 9 having means to being applied as a low leakage and high speed ultraviolet photodetector.

15. The Schottky diode of claim 14 wherein said ultraviolet photodetector comprising:

a circular metal-semiconductor-metal structure having an inner circle pattern of the Schottky contact deposited on said ZnO film having (11{overscore (2)}0) family of planes and an outer ring pattern of the ohmic electrode deposited on said ZnO film.

16. The photodetector of claim 15 wherein said Schottky contact is formed with a silver layer.

17. The photodetector of claim 15 wherein said ohmic electrode is formed with an aluminum layer.

18. The Schottky diode of claim 14 wherein said ultraviolet photodetector comprising:

a metal-semiconductor-metal structure with an interdigital (IDT) pattern, wherein the semiconductor is said ZnO film having (11{overscore (2)}0) family of planes grown on said single crystal substrate, and the metal is the Schottky metal deposited on said ZnO film.

19. The photodetector of claim 15 wherein said substrate is R-plane sapphire, i.e. (01{overscore (1)}2) Al₂O₃.

20. The photodetector of claim 15 wherein said Schottky metal is silver.

21. A semiconductor Schottky diode, comprising:

a Mg_xZn_1-xO semiconductor film having (11{overscore (2)}0) family of planes, grown on a single crystal substrate having an orientation wherein primary symmetric axis (0001) of said Mg_xZn_1-xO semiconductor epitaxial film lies on the surface of said substrate, thereby resulting in zero net charge on said Mg_xZn_1-xO film and zero net dipole moment perpendicular to surface of said Mg_xZn_1-xO film;

a metal deposited on said Mg_xZn_1-xO film to form a Schottky contact; and

an ohmic metal deposited on said Mg_xZn_1-xO film to form an ohmic contact.

22. The Schottky diode of claim 21 wherein energy bandgap of the Mg_xZn_1-xO film varies with Mg content.

23. The Schottky diode of claim 21 wherein said substrate is R-plane sapphire, i.e. (01{overscore (1)}2) Al₂O₃.

24. The Schottky diode of claim 21 wherein said Schottky metal is silver.

25. The Schottky diode of claim 21 wherein said ohmic metal is aluminum.

26. The Schottky diode of claim 21 having means to being applied as a low leakage and high speed ultraviolet photodetector.

27. The Schottky diode of claim 26 wherein said ultraviolet photodetector comprising:

a circular metal-semiconductor metal structure having an inner circle pattern of the Schottky contact deposited on said Mg_xZn_1-xO film having (11{overscore (2)}0) family of planes and an outer ring pattern of the ohmic electrode deposited on said Mg_xZn_1-xO film.

28. The photodetector of claim 27 wherein wavelength of said photodetector varies with Mg content.

31. The Schottky diode of claim 26 wherein said ultraviolet photodetector comprising:

a metal-semiconductor-metal structure with an interdigital (IDT) pattern, wherein the semiconductor is said Mg_xZn_1-xO film having (11{overscore (2)}0) family of planes grown on the single crystal substrate, and the metal is the Schottky metal deposited on said Mg_xZn_1-xO film.

32. The photodetector of claim 31 wherein said substrate is R-plane sapphire, i.e., (01{overscore (1)}2) Al₂O₃.

33. The photodetector of claim 31 wherein said Schottky metal is silver.

34. The photodetector of claim 31 wherein wavelength of said photodetector varies with Mg content.

30. The photodetector of claim 30 wherein said ohmic electrode is formed with an aluminum layer deposited on said Mg_xZn_1-xO film.

29. The photodetector of claim 30 wherein said Schottky contact is formed with a silver layer deposited on said Mg_xZn_1-xO film.