Apparatus, methods, and systems having gas sensor with catalytic gate and variable bias

• US 20060270053A1
• Filed: 05/26/2005
• Published: 11/30/2006
• Est. Priority Date: 05/26/2005
• Status: Abandoned Application

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Sandvik, Peter Micah, Matocha, Kevin Sean, Tilak, Vinayak
• Application Number:
  US11/137,845
• Publication Number:
  US 20060270053A1
• Time in Patent Office: Days
• US Class Current: 436/143
• CPC Class Codes: G01N 27/4141 specially adapted for gases
• CPC Class Codes: Y10T 436/218 Total hydrocarbon, flammability, combustibility [e.g., air-fuel mixture, etc.]

Abstract

According to some embodiments, an electronics based physical gas sensor includes a semiconductor layer, and at least one contact is electrically coupled to the semiconductor layer. A catalytic gate, having a property that changes when the gate is exposed to an analyte, and a variable bias from a voltage source are also provided.

Claims

1. An electronics based physical gas sensor, comprising:

a semiconductor layer;

at least one contact electrically coupled to the semiconductor layer;

a catalytic gate, wherein a property of the catalytic gate is to change when the gate is exposed to an analyte; and

a voltage source to provide a variable bias.

2. The sensor of claim 1, wherein the variable bias is associated with a selectivity of the sensor to the analyte.

3. The sensor of claim 1, wherein adsorption of the analyte by the catalytic gate changes its Schottky barrier height and creates a layer of ions between the catalytic gate and a dielectric interface.

4. The sensor of claim 1, wherein adsorption of the analyte by the catalytic gate changes its capacitance.

5. The sensor of claim 1, wherein the voltage source is to provide the variable bias to at least one of:

(i) the catalytic gate, or (ii) a drain contact electrically coupled to the semiconductor layer.

6. The sensor of claim 1, wherein the voltage source is to provide a bias that varies dynamically over time.

7. The sensor of claim 6, wherein the contact is a source contact electrically coupled to ground, and further comprising:

a dielectric layer between a surface of the semiconductor layer and the catalytic gate; and

a drain contact electrically coupled to the semiconductor layer and a drain voltage source.

8. The sensor of claim 6, wherein the catalytic gate is to influence a channel between the drain contact and the source contact when exposed to the analyte.

9. The sensor of claim 6, wherein the voltage source is to provide a first bias associated with a first analyte and a second bias associated with a second analyte.

10. The sensor of claim 12, wherein the source contact, drain contact, and catalytic gate are associated with:

(i) a metal oxide semiconductor field effect transistor, (ii) a heterostructure field effect transistor, or (iii) a metal-insulator semiconductor heterostructure field effect transistor.

11. The sensor in claim 1 wherein the ohmic contact, a catalytic gate contact over a dielectric layer on top of a semiconductor, fabricated to form a capacitor.

12. The sensor of claim 6, wherein the dielectric layer comprises at least one of:

(i) silicon dioxide, (ii) silicon nitride, or (iii) hafnium oxide.

13. The sensor of claim 6, wherein the voltage source is to provide an alternating bias to the catalytic gate.

14. The sensor of claim 6, wherein the alternating bias is to have a variable frequency.

15. The sensor of claim 1, wherein the catalytic gate is a first catalytic gate, and further comprising:

a second catalytic gate, wherein the voltage source is to provide a first bias associated with the first catalytic gate that varies from a second bias associated with the second catalytic gate.

16. The sensor of claim 15, wherein the first bias is to be provided to the first catalytic gate and the second bias is to be provided to the second catalytic gate.

17. The sensor of claim 15, wherein the first bias is to be provided to a first drain associated with the first catalytic gate and the second bias is to be provided to a second drain associated with the second catalytic gate.

18. The sensor of claim 15, further comprising:

a voltage divider to provide the first bias and the second bias.

19. The sensor of claim 15, wherein the first catalytic gate is to sense a first analyte and the second catalytic gate is to sense a second analyte.

20. The sensor of claim 15, further comprising:

a passivating layer comprising of silicon nitride or hafnium oxide or silicon dioxide or any combination thereof to prevent the second catalytic gate from being exposed to the analyte.

21. The sensor of claim 15, wherein the first catalytic gate is associated with an enhancement mode field effect transistor and the second catalytic gate is associated with a depletion mode field effect transistor

22. The sensor of claim 1, wherein the contact and the catalytic gate are proximate to a top surface of the semiconductor layer, and further comprising:

a substrate on which the semiconductor is grown and forms the bottom surface.

23. The sensor of claim 1, wherein a substrate bias is applied to the substrate.

24. The sensor of claim 1, wherein the analyte comprises at least one of:

NO_X, CO_x, SO_x, NH₃, O₂, CH₄, C₂H₂, C₂H₄ or H₂.

25. The sensor of claim 1, wherein the semiconductor layer comprises at least one of:

(i) silicon carbide, (ii) group III nitride like Gallium Nitride, Aluminum Nitride or Indium Nitride or any alloy of these semiconductors, (iii) any semiconductor with a bandgap of greater than 2 eV, (iv) a metal oxide.

26. The sensor of claim 1, wherein the catalyst gate material includes a:

platinum, ruthenium, silver, palladium, iridium, indium, rhodium, titanium, gold, rhenium, tantalum, osmium, gallium oxide, silver oxide, indium oxide, vanadium oxide, Mn₂O₃, CuO, Cr₂O₃, Co₂O₃, ZnO, Ge₂O₃, FeO₂, or bismuth molybdate or any combination thereof It may also include a material of formula ABO₃ where A is lanthanum and B is any transition metal or alkaline earth metal.

27. The sensor of claim 1, further comprising a heater.

28. The sensor of claim 1, wherein the sensor is a physical gas sensor system device.

29. A method, comprising:

applying a variable bias to a sensor having a catalytic gate, wherein a property of the catalytic gate changes when the gate is exposed to an analyte; and

measuring an electrical characteristic associated with the sensor to detect the analyte.

30. The method of claim 29, wherein the variable bias is applied to at least one of:

(i) the catalytic gate, or (ii) a drain contact of the sensor.

31. The method of claim 29, wherein the electrical characteristic is associated with at least one of:

(i) a source drain current, (ii) a gate current, (iii) a body current, (iv) a threshold voltage, (v) a frequency of a response signal waveform, or (vi) a time constant of a response signal waveform.

32. The method of claim 29, wherein said applying comprises:

applying a specific bias to improve detection of a particular analyte.

33. The method of claim 29, wherein said applying comprises:

applying an alternating current having a first frequency to detect a first species of analyte; and

applying an alternating current having a second frequency to detect a second species of analyte.

34. The method of claim 29, further comprising:

applying a reset signal to expel the analyte from the catalytic gate.

35. A system, comprising:

a gas sensor, including;

a wide bandgap semiconductor layer,

a contact electrically coupled to the semiconductor layer,

an insulating layer formed on the semiconductor layer,

a catalytic gate formed on the insulating layer, and

a voltage source to provide a bias that is at least one of;

(i) variable over time, or (ii) variable between sensors or (iii) having a variable frequency;

a sensor dependent device.

36. The system of claim 35, wherein the sensor dependent device is associated with at least one of:

(i) an air quality device, (ii) an oil quality device, (iii) an industrial process control device, (iv) an emissions management device, or (v) a turbine sensor.