Thin-film transistors based on tunneling structures and applications

• US 20060012000A1
• Filed: 04/25/2005
• Published: 01/19/2006
• Est. Priority Date: 05/21/2001
• Status: Active Grant

• Current Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Original Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Inventors: Estes, Michael J., Eliasson, Blake J.
• Granted Patent: US 7,173,275 B2
• Time in Patent Office: Days
• US Class Current: 257/425
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 27/1446 in a repetitive configuration
• CPC Class Codes: H01L 29/7311 Tunnel transistors
• CPC Class Codes: H01L 29/7606 Transistor-like structures, e.g. hot electron transistor [HET]; metal base transistor [MBT]
• CPC Class Codes: H01L 29/82 controllable by variation of the magnetic field applied to the device
• CPC Class Codes: H01L 31/08 in which radiation controls flow of current through the device, e.g. photoresistors
• CPC Class Codes: H01L 31/101 Devices sensitive to infrared, visible or ultraviolet radiation
• CPC Class Codes: H01L 33/0004 Devices characterised by their operation
• CPC Class Codes: H01L 33/0037 having a MIS barrier layer
• CPC Class Codes: H10N 60/10 Junction-based devices
• CPC Class Codes: H10N 70/00 Solid-state devices having no potential barriers, and specially adapted for rectifying, amplifying, oscillating or switching integrated devices or assemblies of multiple devices H10N79/00

Abstract

A hot electron transistor includes an emitter electrode, a base electrode, a collector electrode, and a first tunneling structure disposed and serving as a transport of electrons between the emitter and base electrodes. The first tunneling structure includes at least a first amorphous insulating layer and a different, second insulating layer such that the transport of electrons includes transport by means of tunneling. The transistor further includes a second tunneling structure disposed between the base and collector electrodes. The second tunneling structure serves as a transport of at least a portion of the previously mentioned electrons between the base and collector electrodes by means of ballistic transport such that the portion of the electrons is collected at the collector electrode. An associated method for reducing electron reflection at interfaces in a thin-film transistor is also disclosed.

Claims

1. A hot electron transistor adapted for receiving at least one input signal, said transistor comprising:

an emitter electrode;

a base electrode spaced apart from said emitter electrode such that at least a portion of said input signal may be applied across the emitter and base electrodes and, consequently, electrons are emitted from the emitter electrode toward the base electrode;

a first tunneling structure disposed between said emitter and base electrodes and configured to serve as a transport of electrons between and to said emitter and base electrodes, said first tunneling structure including at least a first amorphous insulating layer and a different, second insulating layer disposed directly adjacent to and configured to cooperate with said first amorphous insulating layer such that the transport of electrons includes, at least in part, transport by means of tunneling;

a collector electrode spaced apart from said base electrode; and

a second tunneling structure disposed between said base and collector electrodes and configured to serve as a transport, between said base and collector electrodes, of at least a portion of said electrons emitted from said emitter electrode by means of ballistic transport such that the portion of the electrons is collectable at said collector electrode.

2. The transistor of Claim 1, wherein at least a selected one of said base electrode and said collector electrode is formed, at least in part, of a semi-metal.

3. The transistor of Claim 1 wherein at least a selected one of said base electrode and said collector electrode is formed, at least in part, of a metal-silicide.

4. The transistor of claim 1 wherein at least a selected one of said base electrode and said collector electrode is formed, at least in part, of a metal-nitride.

5. The transistor of claim 1 wherein said second tunneling structure is configured to exhibit a first value of hot electron reflection, and wherein said second tunneling structure includes a shaped barrier energy band characteristic such that said first value of hot electron reflection is lower than a second value of hot electron reflection that would be exhibited by the second tunneling structure without the shaped barrier energy band characteristic.

6. The transistor of claim 5 wherein said shaped barrier energy band characteristic includes a parabolic grading of said second tunneling structure.

7. The transistor of claim 5 wherein said shaped barrier energy band characteristic includes a rounded grading of said second tunneling structure.

8. The transistor of claim 5 wherein said shaped barrier energy band characteristic includes a linear grading of said second tunneling structure.

9. The transistor of claim 1 wherein said emitter electrode is configured to exhibit a given Fermi level, and wherein said first tunneling structure is configured to exhibit a given conduction band such that said given conduction band differs from said given Fermi level by less than 2 eV.

10. A hot electron transistor adapted for receiving at least one input signal, said transistor comprising:

an emitter electrode;

a base electrode spaced apart from said emitter electrode such that at least a portion of said input signal may be applied across the emitter and base electrodes and, consequently, electrons are emitted from the emitter electrode toward the base electrode;

a first tunneling structure disposed between said emitter and base electrodes and configured to serve as a transport of electrons between and to said emitter and base electrodes, said first tunneling structure including at least a first insulating layer such that the transport of electrons includes, at least in part, transport by means of tunneling;

a collector electrode spaced apart from said base electrode; and

a second tunneling structure disposed between said base and collector electrodes and configured to serve as a transport, between said base and collector electrodes, of at least a portion of said electrons emitted from said emitter electrode by means of ballistic transport such that said portion of the electrons is collectable at said collector electrode,

wherein at least a selected one of said base electrode and said collector electrode is formed, at least in part, of a semi-metal.

11. The transistor of claim 10 wherein said selected one of said base electrode and said collector electrode further includes a metal-silicide.

12. The transistor of claim 10 wherein said selected one of said base electrode and said collector electrode further includes a metal-nitride.

13. The transistor of claim 10 wherein said second tunneling structure is configured to exhibit a first value of hot electron reflection, and wherein said second tunneling structure includes a shaped barrier energy band characteristic such that said first value of hot electron reflection is lower than a second value of hot electron reflection that would be exhibited by the second tunneling structure without the shaped barrier energy band characteristic.

14. The transistor of claim 13 wherein said shaped barrier energy band characteristic includes a parabolic grading of said second tunneling structure.

15. The transistor of claim 10 wherein said emitter electrode is configured to exhibit a given Fermi level, and wherein said first tunneling structure is configured to exhibit a given conduction band such that said given conduction band differs from said given Fermi level by less than 2 eV.

16. A transistor adapted for receiving at least one input signal, said transistor comprising:

an emitter electrode;

a base electrode spaced apart from said emitter electrode such that at least a portion of said input signal may be applied across the emitter and base electrodes and, consequently, electrons are emitted from the emitter electrode toward the base electrode;

a first tunneling structure disposed between said emitter and base electrodes and configured to serve as a transport of electrons between and to said emitter and base electrodes, said first tunneling structure including at least a first amorphous layer such that the transport of electrons includes, at least in part, transport by means of tunneling;

a collector electrode spaced apart from said base electrode; and

a second tunneling structure disposed between said base and collector electrodes and configured to serve as a transport, between said base and collector electrodes, of at least a portion of said electrons emitted by said emitter electrode by means of ballistic transport such that said portion of the electrons is collectable at said collector electrode,

wherein said second tunneling structure is configured to exhibit a first value of hot electron reflection, and wherein said second tunneling structure includes a shaped barrier energy band characteristic such that said first value of hot electron reflection is lower than a second value of hot electron reflection that would be exhibited by the second tunneling structure without the shaped barrier energy band characteristic.

17. The transistor of claim 16 wherein said shaped barrier energy band characteristic includes a parabolic grading of said second tunneling structure.

18. The transistor of claim 16 wherein said shaped barrier energy band characteristic includes a rounded grading of said second tunneling structure.

19. The transistor of claim 16 wherein said shaped barrier energy band characteristic includes a linear grading of said second tunneling structure.

20. The transistor of claim 16 wherein said emitter electrode is configured to exhibit a given Fermi level, and wherein said first tunneling structure is configured to exhibit a given conduction band such that said given conduction band differs from said given Fermi level by less than 2 eV.

21. A transistor adapted for receiving at least one input signal, said transistor comprising:

an emitter electrode;

a base electrode spaced apart from said emitter electrode such that at least a portion of said input signal may be applied across the emitter and base electrodes and, consequently, electrons are emitted from the emitter electrode toward the base electrode;

a first tunneling structure disposed between said emitter and base electrodes and configured to serve as a transport of electrons between and to said emitter and base electrodes, said first tunneling structure including at least a first amorphous insulating layer such that the transport of electrons includes, at least in part, transport by means of tunneling;

a collector electrode spaced apart from said base electrode; and

a second tunneling structure disposed between said base and collector electrodes and configured to serve as a transport, between said base and collector electrodes, of at least a portion of said electrons emitted by said emitter electrode by means of ballistic transport such that said portion of the electrons is collectable at said collector electrode,

wherein said transistor is configured to exhibit a first value of electron emission energy width, and wherein said first tunneling structure includes a shaped barrier energy band characteristic such that said first value of electron emission energy width is lower than a second value of electron emission energy width that would be exhibited by the transistor without the shaped barrier energy band characteristic.

22. The transistor of claim 21 wherein said shaped barrier energy band characteristic includes a parabolic grading of said first tunneling structure.

23. The transistor of claim 21 wherein said shaped barrier energy band characteristic includes a rounded grading of said first tunneling structure.

24. A hot electron transistor adapted for receiving at least one input signal, said transistor comprising:

an emitter electrode configured to exhibit a given Fermi level;

a base electrode spaced apart from said emitter electrode such that at least a portion of said input signal may be applied across the emitter and base electrodes and, consequently, electrons are emitted from the emitter electrode toward the base electrode;

a first tunneling structure disposed between said emitter and base electrodes and configured to serve as a transport of electrons between and to said emitter and base electrodes, said first tunneling structure including at least a first insulating layer such that the transport of electrons includes, at least in part, transport by means of tunneling;

a collector electrode spaced apart from said base electrode; and

a second tunneling structure disposed between said base and collector electrodes and configured to serve as a transport, between said base and collector electrodes, of at least a portion of said electrons emitted from said emitter electrode by means of ballistic transport such that said portion of the electrons is collectable at said collector electrode,

wherein said first tunneling structure is configured to exhibit a given conduction band such that said given conduction band differs from said given Fermi level of said emitter electrode by less than 2 eV.

25. A hot hole transistor adapted for receiving at least one input signal, said transistor comprising:

an emitter electrode;

a base electrode spaced apart from said emitter electrode such that at least a portion of said input signal may be applied across the emitter and base electrodes and, consequently, holes are emitted from the emitter electrode toward the base electrode;

a first tunneling structure disposed between said emitter and base electrodes and configured to serve as a transport of holes between and to said emitter and base electrodes, said first tunneling structure including at least a first amorphous insulating layer and a different, second insulating layer disposed directly adjacent to and configured to cooperate with said first amorphous insulating layer such that the transport of holes includes, at least in part, transport by means of tunneling;

a collector electrode spaced apart from said base electrode; and

a second tunneling structure disposed between said base and collector electrodes and configured to serve as a transport, between said base and collector electrodes, of at least a portion of said hot holes emitted by said emitter electrode by means of ballistic transport such that said portion of the holes is collectable at said collector electrode.

26. The transistor of claim 25, wherein at least a selected one of said base electrode and said collector electrode is formed, at least in part, of a semi-metal.

27. The transistor of claim 25 wherein at least a selected one of said base electrode and said collector electrode is formed, at least in part, of a metal-silicide.

28. The transistor of claim 25 wherein at least a selected one of said base electrode and said collector electrode is formed, at least in part, of a metal-nitride.

29. The transistor of claim 25 wherein said second tunneling structure is configured to exhibit a first value of hot hole reflection, and wherein said second tunneling structure includes a shaped barrier energy band characteristic such that said first value of hot hole reflection is lower than a second value of hot hole reflection that would be exhibited by the second tunneling structure without the shaped barrier energy band characteristic.

30. The transistor of claim 29 wherein said shaped barrier energy band characteristic includes a parabolic grading of said second tunneling structure.

31. The transistor of claim 25 wherein said emitter electrode is configured to exhibit a given Fermi level, and wherein said first tunneling structure is configured to exhibit a given conduction band such that said given conduction band differs from said given Fermi level by less than 2 eV.

32. In a hot electron transistor including a plurality of layers with a plurality of interfaces defined therebetween and ballistic electrons being transported therebetween, said plurality of layers including at least a first layer and a second layer adjacent and juxtaposed to each other and defining a first interface therebetween such that at least a portion of said ballistic electrons may be reflected at said first interface, a method for reducing electron reflection at at least said first interface comprising:

configuring said first layer to exhibit a first, selected wave function; and

configuring said second layer to exhibit a second, selected wave function such that a first fraction of said ballistic electrons is reflected at said first interface,

wherein said first fraction is smaller than a second fraction of said ballistic electrons that would be reflected at said first interface without said second layer being configured to exhibit said second, selected wave function.

33. The method of claim 32 wherein said second layer exhibits a given energy band structure, and wherein configuring said second layer includes grading said energy band structure in a particular way.

34. The method of claim 33 wherein grading said energy band structure includes forming said second layer such that said energy band structure exhibits a parabolic shape.

35. The method of claim 32 wherein said second layer includes at least one planar surface, and wherein configuring said second layer includes adding a surface texture to said one planar surface.

36. A transistor adapted for receiving at least one input signal, said transistor comprising:

an emitter electrode;

a base electrode spaced apart from said emitter electrode such that at least a portion of said input signal may be applied across the emitter and base electrodes and, consequently, electrons are emitted from the emitter electrode toward the base electrode;

a first tunneling structure disposed between said emitter and base electrodes and configured to serve as a transport of electrons between and to said emitter and base electrodes;

a collector electrode spaced apart from said base electrode; and

a second tunneling structure disposed between said base and collector electrodes and configured to serve as a transport, between said base and collector electrodes, of at least a portion of said electrons emitted by said emitter electrode by means of ballistic transport such that said portion of the electrons is collectable at said collector electrode,

wherein said second tunneling structure is configured to exhibit a first value of hot electron reflection, and wherein said second tunneling structure is further configured to exhibit a selected wave function such that said first value of hot electron reflection is lower than a second value of hot electron reflection that would be exhibited by the second tunneling structure without said selected wave function.

37. The transistor of claim 36 wherein said second tunneling structure includes a shaped barrier energy band characteristic.

38. The transistor of claim 36 wherein said second tunneling structure is formed of a selected material exhibiting a first value of dielectric constant such that said second tunneling structure exhibits said given wave function.

39. A linear amplifier adapted for receiving at least one input signal, said linear amplifier comprising:

a hot electron transistor including

a first emitter electrode,

a first base electrode spaced apart from said first emitter electrode such that at least a first portion of said input signal may be applied across the first emitter and first base electrodes and, consequently, electrons are emitted from the first emitter electrode toward the first base electrode,

a first tunneling structure disposed between said first emitter and first base electrodes and configured to serve as a transport of electrons between and to said first emitter and first base electrodes, said first tunneling structure including at least a first amorphous insulating layer and a different, second insulating layer disposed directly adjacent to and configured to cooperate with said first amorphous insulating layer such that the transport of electrons includes, at least in part, transport by means of tunneling,

a first collector electrode spaced apart from said first base electrode, and

a second tunneling structure disposed between said first base and first collector electrodes and configured to serve as a transport, between said first base and first collector electrodes, of at least a portion of said electrons emitted from said first emitter electrode by means of ballistic transport such that said portion of the electrons is collectable at said first collector electrode; and

a hot hole transistor including

a second emitter electrode,

a second base electrode spaced apart from said second emitter electrode such that at least a second portion of said input signal may be applied across the second emitter and second base electrodes and, consequently, holes are emitted from the second emitter electrode toward the second base electrode,

a third tunneling structure disposed between said second emitter and second base electrodes and configured to serve as a transport of holes between and to said second emitter and second base electrodes, said third tunneling structure including at least a third amorphous insulating layer and a different, fourth insulating layer disposed directly adjacent to and configured to cooperate with said third amorphous insulating layer such that the transport of holes includes, at least in part, transport by means of tunneling,

a second collector electrode spaced apart from said second base electrode, and

a fourth tunneling structure disposed between said second base and second collector electrodes and configured to serve as a transport, between said second base and second collector electrodes, of at least a portion of said hot holes emitted by said second emitter electrode by means of ballistic transport such that said portion of the holes is collectable at said second collector electrode;

wherein said hot electron transistor and said hot hole transistor are configured in a push-pull amplifier configuration.