One-chip micro-integrated optoelectronic sensor

• US 20020074553A1
• Filed: 12/15/2000
• Published: 06/20/2002
• Est. Priority Date: 12/15/2000
• Status: Active Grant

• Current Assignee: University of Houston (University of Houston System)
• Original Assignee: University of Houston (University of Houston System)
• Inventors: Berishev, Igor, Starikov, David, Bensaoula, Abdelhak
• Granted Patent: US 6,608,360 B2
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 31/108 the potential barrier being of the Schottky type
• CPC Class Codes: H01L 31/173 formed in, or on, a common substrate
• CPC Class Codes: H01L 31/1852 comprising a growth substrate not being an AIIIBV compound
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

This disclosure describes one-chip micro-integrated optoelectronic sensors and methods for fabricating and using the same. The sensors may include an optical emission source, optical filter and a photodetector fabricated on the same transparent substrate using the same technological processes. Optical emission may occur when a bias voltage is applied across a metal-insulator-semiconductor Schottky contact or a p-n junction. The photodetector may be a Schottky contact or a p-n junction in a semiconductor. Some sensors can be fabricated on optically transparent substrate and employ back-side illumination. In the other sensors provided, the substrate is not transparent and emission occurs from the edge of a p-n junction or through a transparent electrode. The sensors may be used to measure optical absorption, optical reflection, scattering or fluorescence. The sensors may be fabricated and operated to provide a selected spectrum of light emitted and a multi-quantum well heterostructure may be fabricated to filter light reaching the photodetector.

Claims

1. An optoelectronic device for providing light emission or detection, comprising:

an optically transparent substrate;

an optically transparent semiconductor layer on the substrate, the semiconductor layer having a top surface;

an insulating layer on a first area of the top surface of the semiconductor layer, the insulating layer having a selected thickness to provide tunneling from a Schottky barrier;

a layer of metal on the insulating layer, the metal forming a Schottky barrier and being selected to provide low diffusion rate of the metal through the insulating layer under conditions of deposition of the layer, and an ohmic contact to the layer of metal; and

an ohmic contact on a second area of the top surface of the semiconductor layer.

2. The device of claim 1 wherein the material of the optically transparent substrate is selected from the group of substances consisting of sapphire, quartz and glass.

3. The device of claim 1 wherein the semiconductor is selected from the group of substances consisting of III-V nitride compounds, zinc oxide, silicon carbide, tin oxide, indium oxide and diamond.

4. The device of claim 1 wherein the insulating layer is comprised of amorphous silicon.

5. The device of claim 1 wherein the thickness of the insulating layer is less than about 200 Angstroms.

6. The device of claim 1 wherein the thickness of the insulating layer is in the range from about 30 Angstroms to about 50 Angstroms.

7. The device of claim 1 wherein the layer of metal on the insulating layer is titanium.

8. The device of claim 1 wherein the ohmic contact on the second area of the top surface of the semiconductor is comprised of layers of platinum, nickel and gold.

9. An optoelectronic device, comprising:

an optically transparent substrate;

two or more optically transparent spaced apart semiconductor layers on the substrate, each of the semiconductor layers having a top surface;

an insulating layer on a first area of the top surface of each of the spaced apart semiconductor layers, each of the insulating layers having a selected thickness to provide tunneling from a Schottky barrier;

a layer of metal on each of the insulating layers, the metal forming a Schottky barrier and being selected to provide low diffusion rate of the metal through the insulating layer under conditions of deposition of the layer, and an ohmic contact to the layer of metal; and

an ohmic contact on a second area of the top surface of the semiconductor layers.

10. The device of claim 9 wherein the material of the optically transparent substrate is selected from the group of substances consisting of sapphire, quartz and glass.

11. The device of claim 9 wherein the material of the semiconductor layers is selected from the group of substances consisting of III-V nitride compounds, zinc oxide, silicon carbide, tin oxide, indium oxide and diamond.

12. The device of claim 9 wherein the insulating layers are comprised of amorphous silicon.

13. The device of claim 9 wherein the thickness of the insulating layers is less than about 200 Angstroms.

14. The device of claim 9 wherein the thickness of the insulating layers is in the range from about 30 Angstroms to about 50 Angstroms.

15. The device of claim 9 wherein the metal in the layer of metal on the insulating layers is titanium.

16. The device of claim 9 wherein the ohmic contact on the second area of the top surface of the semiconductor layers is comprised of layers of platinum, nickel and gold.

17. The device of claim 9 wherein Schottky contacts form a pattern on the substrate.

19. The device of claim 18 wherein the material of the semiconductor layer is selected from the group of substances consisting of III-V nitride compounds, zinc oxide, silicon carbide, tin oxide, indium oxide and diamond.

20. The device of claim 18 wherein the insulating layer is comprised of amorphous silicon.

21. The device of claim 18 wherein the thickness of the insulating layers is less than about 200 Angstroms.

22. The device of claim 18 wherein the thickness of the insulating layers is in the range from about 30 Angstroms to about 50 Angstroms.

23. The device of claim 18 wherein the metal in the layer of metal on the insulating layers is titanium.

24. The device of claim 18 wherein the photodetector is comprised of layers of n-InGaN and p-GaN.

25. The device of claim 18 further comprising a multi-quantum well heterostructure between the transparent substrate and the photodetector.

26. The device of claim 25 wherein the multi-quantum well heterostructure is comprised of alternating layers of p-GaN and n-InGaN.

28. The device of claim 27 wherein the thickness of the first and the second gallium nitride layers and the indium gallium nitride layer is in the range from about 0.5 to about 1 micrometers.

29. The device of claim 27 further comprising a multi-quantum well heterostructure between the first layer of gallium nitride and the silicon wafer.

18. An optoelectronic device, comprising:

an optically transparent substrate;

an optically transparent semiconductor layer on a first area of the substrate, the semiconductor layer having a top surface;

an insulating layer on a first area of the top surface of the semiconductor layer, the insulating layer having a selected thickness to provide tunneling from a Schottky barrier;

a layer of metal on the insulating layer, the metal being selected to form a Schottky barrier and provide a low diffusion rate of the metal through the insulating layer under conditions of deposition of the layer, and an ohmic contact to the layer of metal;

an ohmic contact on a second spaced apart area of the top surface of the semiconductor layer;

.

a photodetector on a second area of the substrate, the photodetector being spaced apart from the first area of the substrate.

27. An optoelectronic device, comprising:

a first ohmic contact on a first surface of a silicon wafer and a second ohmic contact on a first area of a second surface of the silicon wafer;

an aluminum nitride layer deposited on a second area of the second surface of the silicon wafer, a portion of the aluminum nitride having diffused into the silicon layer to form a p-n junction in the silicon wafer;

a first layer of gallium nitride deposited on the aluminum nitride layer;

a layer of indium gallium nitride deposited on the first layer of gallium nitride, the layer of indium gallium nitride having a top surface;

a second layer of gallium nitride deposited on a first area of the top surface of the indium gallium nitride layer and an ohmic contact on the second layer of gallium nitride; and

a second ohmic contact on a second area of the top surface of the layer of indium gallium nitride.

30. An optoelectronic device, comprising:

a silicon substrate;

a layer of semiconductor deposited on the silicon substrate;

an ohmic contact with a first area of the layer of semiconductor;

a metal-insulator layer on a second area of the layer of semiconductor to form an M-I-S Schottky contact;

a layer of a transparent electrode on the metal-insulator layer to form a metal-insulator-semiconductor Schottky contact on the second area of the layer of semiconductor, the layer of transparent electrode having an ohmic contact thereon;

a multi-quantum well heterostructure on a third area of the layer of semiconductor;

a gallium nitride layer deposited on the multi-quantum well heterostructure and having an ohmic contact; and

a layer of a transparent electrode deposited on a part of the layer of gallium nitride, the layer of transparent electrode having an ohmic contact.

31. The device of claim 30 wherein the transparent electrode is comprised of fluorine-doped tin oxide.

32. A method for using an optoelectronic device for measuring interaction of light with a sample, the device having a metal-insulator-semiconductor Schottky contact on an optically transparent substrate and ohmic contacts for applying bias voltage across the contact,, comprising:

providing a device to be used as a light source;

providing a photodetector, the photodetector having a selected interval of sensitivity;

providing a selected bias voltage across the ohmic contacts of the device such that a selected spectrum of light is emitted from the light source;

placing a sample to be measured such that light emitted from the device interacts with the sample; and

placing the photodetector such that light after interaction with the sample impinges on the photodetector.

33. The method of claim 32 wherein the selected spectrum of the light emitted from the device is selected to cause fluorescence in the sample and the selected interval of sensitivity of the photodetector is selected to detect fluorescence of the sample.

34. The method of claim 32 wherein the sample is placed in contact with the optically transparent substrate.

35. The method of claim 32 wherein the selected bias across the ohmic contacts is a reverse bias selected to produce electroluminescence.

37. The method of claim 36 wherein the selected bias voltage across the ohmic contacts of the device is a reverse bias selected to produce electroluminescence.

38. The method of claim 36 wherein the duration of the pulse is in the range from about 0.1 nanosecond to about 10 nanoseconds.

39. The method of claim 36 wherein the sample is placed in contact with the optically transparent substrate.

40. The method of claim 36 further comprising provided a multi-quantum well heterostructure between the sample and the device to be used as a light source and photodetector.

36. A method for using an optoelectronic device having a metal-insulator-semiconductor Schottky contact on an optically transparent substrate, the device having ohmic contacts for applying bias voltage across the contact, for measuring interaction of light with a sample capable of producing fluorescent light having a known range of wavelengths, comprising:

providing a single device to be used as a light source and a photodetector, the device being sensitive to the known range of wavelengths;

providing a pulse of a selected bias voltage and selected duration across the ohmic contacts of the device to produce a pulse of a selected spectrum of light from the device;

placing a sample to be measured such that the pulse of light emitted from the device interacts with the sample to produce fluorescent light having the known range of wavelength; and

detecting the fluorescent light from the sample after the duration of the pulse.

41. A method for using an optoelectronic device having a metal-insulator-semiconductor Schottky contact on an optically transparent substrate, the device having ohmic contacts for applying bias voltage across the contact and a photodetector on a surface of a single chip for measuring surface roughness, comprising:

providing a plurality of the optoelectronic devices on the surface of the chip;

placing a surface having a roughness to be measured at a selected location and applying an electrical voltage to produce light emission from the optical emission source; and

detecting light scattered from the surface with the photodetector.

42. The method of claim 41 wherein the optical emission source is operated in a pulsed mode.

43. The method of claim 42 wherein the device is operated with lock-in amplification.

44. A method for using an optoelectronic device having a metal-insulator-semiconductor Schottky contact on an optically transparent substrate, the device having ohmic contacts for applying bias voltage across the contact, and a photodetector on a surface of a single chip for measuring optical absorption, comprising:

providing a plurality of the optoelectronic devices on the surface of the chip;

placing a surface of a mirror at a selected location and applying an electrical voltage to produce light emission from the optical emission source;

placing a sample between the surface of the mirror and the chip; and

detecting light scattered from the surface of the mirror by the photodetector.

45. The method of claim 44 wherein the optical emission source is operated in a pulsed mode.

46. The method of claim 45 wherein the device is operated with lock-in amplification.

47. The method of claim 45 wherein the mirror includes a surface sensitive to the presence of a material to be measured.

49. The method of claim 48 wherein the transparent substrate is made of a material selected from the group of materials consisting of sapphire, quartz and optically transparent glasses.

50. The method of claim 48 wherein the Schottky barrier contact is formed by layers of a gallium nitride, silicon and titanium.

48. A method for making an optoelectronic device providing an optical emission source and a photodetector on a single substrate, comprising:

providing an optically transparent substrate;

growing by radio frequency-assisted molecular beam epitaxy an undoped gallium nitride buffer layer on the transparent substrate;

growing by radio frequency-assisted molecular beam epitaxy a doped p-gallium nitride layer;

on a first segment of the p-gallium nitride layer, growing a Schottky barrier contact by electron-beam evaporation of a material having high electrical resistivity, a metal layer suitable for forming the Schottky barrier contact and having low diffusion rate through the high resistivity layer, and a layer of metal to use as ohmic contact; and

on a second segment of the p-gallium nitride layer, growing a separate ohmic contact on the p-gallium nitride by electron beam evaporation of layers of metal.

51. A method for making an optoelectronic device, comprising:

providing a transparent substrate;

growing by radio frequency-assisted molecular beam epitaxy an undoped gallium nitride layer on the substrate and a first doped p-gallium nitride layer;

growing by radio frequency-assisted molecular beam epitaxy alternating layers of undoped indium gallium nitride and gallium nitride to form a multi-quantum well heterostructure having selected optical filter properties;

growing by radio frequency-assisted molecular beam epitaxy a barrier n-indium gallium nitride layer doped with silicon;

growing by radio frequency-assisted molecular beam epitaxy a second doped p-gallium nitride layer;

etching through the first gallium nitride layer to the substrate to form a photodetector on a first part of the substrate, the photodetector having a multi-quantum-well heterostructure, the heterostructure having selected optical filter properties;

etching through to the first gallium nitride layer on a second part of the substrate and to the n-indium gallium nitride layer on the second part of the substrate;

depositing a metal-insulator-semiconductor Schottky barrier contact and ohmic contact on the first gallium nitride layer on the second part of the substrate by electron beam evaporation of silicon and metals; and

depositing ohmic contacts on the p-gallium nitride layer on the second part of the substrate and the n-indium gallium nitride layer of the photodetector by electron beam evaporation of metals.

52. A method for using an optoelectronic device having a Schottky contact and a photodetector, the photodetector having a multi-quantum well heterostructure, on an optically transparent substrate, comprising:

providing a device;

applying a bias voltage across the Schottky contact to produce an optical emission having a selected spectral range;

disposing the device such that the optical emission interacts with a sample; and

disposing the device such that light emitted from the sample passes through the multi-quantum well heterostructure and onto the photodetector.

53. A method for making an optoelectronic device, comprising:

providing a silicon substrate having a top surface and a bottom surface;

growing by radio frequency-assisted molecular beam epitaxy a layer of undoped aluminum nitride on the top surface of the silicon substrate;

growing on the layer of aluminum nitride by radio frequency-assisted molecular beam epitaxy alternating layers of indium gallium nitride and aluminum nitride, the thickness of the layers and composition of the layers being selected to produce a multi-quantum well heterostructure having selected optical filter properties;

growing on the heterostructure by radio frequency-assisted molecular beam epitaxy a n-gallium nitride layer doped with silicon at a selected concentration;

growing on the n-gallium nitride layer by radio frequency-assisted molecular beam epitaxy a layer of n-indium gallium nitride doped with silicon at a selected concentration;

growing by radio frequency-assisted molecular beam epitaxy a p-gallium nitride layer;

depositing an ohmic contact to a first part of the p-gallium nitride layer by electron beam evaporation;

etching to the top of the multi-quantum well region on a first part of the silicon substrate, to the top of the n-indium gallium nitride layer in a first part of the n-indium gallium nitride layer and to the top surface of the silicon substrate in a second part of the silicon substrate; and

depositing an ohmic contact to the bottom surface of the n-silicon substrate and to the second part of the top surface of the silicon substrate.

54. An optical encoder, comprising:

a rotatable encoding disk having a surface, the surface having light reflective and light absorptive areas thereon;

an integrated light source and photodetector on an optically transparent substrate, the light source having a metal-insulator-semiconductor Schottky contact.

55. The encoder of claim 54 further comprising optical shields between the rotating disk and the substrate.

56. A method for providing a light emitting diode and a photodetector based on the same semiconductor junction, comprising:

providing a semiconductor junction that can produce pre-breakdown avalanche electroluminescence at a shorter wavelength than corresponding to the semiconductor'"'"'s bandgap energy and that has a selected spectrum of photosensitivity;

applying a voltage pulse to produce a selected value of reverse bias voltage across the junction to produce light emission having a selected spectrum of wavelength from the contact; and

subsequently using the semiconductor contact having the selected spectrum of photosensitivity as a photodetector.

57. A method for providing a source of optical emission and a photodetector based on the same semiconductor junction, comprising:

providing a first and a second semiconductor junction that can produce pre-breakdown avalanche electroluminescence at a shorter wavelength than corresponding to the semiconductor'"'"'s bandgap energy, each junction having a selected spectrum of photosensitivity;

applying a voltage to the first junction to produce a selected value of reverse bias voltage across the junction to produce optical emission from the junction, the optical emission having a selected spectrum of wavelength; and

at the same time using the second junction having the selected spectrum of photosensitivity as a photodetector.