Gallium nitride based ultra-violet sensor with intrinsic amplification and method of operating same

Patent metadata

Field	Value
Publication number	US-11081613-B2
Application number	US-201916535548-A
Country	US
Kind code	B2
Filing date	Aug 8, 2019
Priority date	Aug 8, 2019
Publication date	Aug 3, 2021
Grant date	Aug 3, 2021

Abstract

A UV sensor includes a GaN stack including a low-resistance GaN layer formed over a nucleation layer, and a high-resistance GaN layer formed over the low-resistance GaN layer, wherein a 2DEG conductive channel exists at the upper surface of the high-resistance GaN layer. An AlGaN layer is formed over the upper surface of the high-resistance GaN layer. A source contact and a drain contact extend through the AlGaN layer and contact the upper surface of the high-resistance GaN layer (and are thereby electrically coupled to the 2DEG channel). A drain depletion region extends entirely from the upper surface of the high-resistance GaN layer to the low-resistance GaN layer under the drain contact. An electrical current between the source and drain contacts is a function of UV light received by the GaN stack. An electrode is connected to the low-resistance GaN layer to allow for electrical refresh of the UV sensor.

First claim

We claim:

1. An ultraviolet (UV) light sensor comprising:
a gallium nitride (GaN) stack including a lower GaN layer formed over a nucleation layer, and an upper GaN layer formed over the lower GaN layer, wherein the lower GaN layer has a lower resistivity than the upper GaN layer, and wherein a two-dimensional electron gas (2DEG) conductive channel exists at an upper surface of the upper GaN layer;
an aluminum gallium nitride (AlGaN) layer formed over the upper surface of the upper GaN layer;
a source contact that extends through the AlGaN layer and contacts the upper surface of the upper GaN layer, whereby the source contact is electrically coupled to the 2DEG conductive channel;
a drain contact that extends through the AlGaN layer and contacts the upper surface of the upper GaN layer, whereby the drain contact is electrically coupled to the 2DEG conductive channel; and
a drain depletion region that extends from the upper surface of the upper GaN layer to the lower GaN layer under the drain contact, wherein an electrical current between the source contact and the drain contact is a function of UV light received by the GaN stack.

2. The UV light sensor of claim 1 , wherein the nucleation layer is formed over a silicon substrate.

3. The UV light sensor of claim 1 , further comprising a third GaN layer having a thickness of 1 nm to 3 nm formed over the AlGaN layer.

4. The UV light sensor of claim 1 , further comprising a dielectric layer having a thickness of 5 nm to 200 nm formed over the AlGaN layer.

5. The UV light sensor of claim 4 , wherein the dielectric layer comprises silicon nitride.

6. The UV light sensor of claim 1 , further comprising an AlN layer having a thickness of 1 nm to 2 nm formed between the AlGaN layer and the upper GaN layer.

7. The UV light sensor of claim 1 , wherein the GaN stack has a thickness in the range 0.5 um to 6 um.

8. The UV light sensor of claim 1 , wherein the lower GaN layer is an unintentionally doped n-type layer.

9. The UV light sensor of claim 8 , wherein the lower GaN layer is doped with silicon.

10. The UV light sensor of claim 1 , wherein the source contact and the drain contact are separated by 1 um to 3000 um.

11. The UV light sensor of claim 1 , wherein the AlGaN layer has a doughnut shape between the source contact and the drain contact.

12. The UV light sensor of claim 1 , wherein the source contact and the drain contact comprise interdigitated structures.

13. The UV light sensor of claim 1 , wherein the nucleation layer is formed over a substrate, the UV light sensor further comprising a cavity formed through the substrate to the lower GaN layer.

14. The UV light sensor of claim 13 , further comprising a heater formed over the cavity.

15. The UV light sensor of claim 14 , wherein the heater comprises a 2DEG resistor formed in the upper GaN layer.

16. The UV light sensor of claim 15 , wherein the lower GaN layer is coupled to the 2DEG resistor.

17. The UV light sensor of claim 14 , wherein the heater comprises a polysilicon or metal structure formed over the cavity.

18. The UV light sensor of claim 13 , further comprising a backside electrode located in the cavity and electrically coupled to the lower GaN layer.

19. The UV light sensor of claim 1 , further comprising a front side electrode that extends through the upper GaN layer to contact the lower GaN layer.

20. A method of operating an ultraviolet (UV) light sensor comprising:
applying a first voltage across a source contact and a drain contact located on an upper gallium nitride (GaN) layer, wherein the upper GaN layer is located on a lower GaN layer, wherein the lower GaN layer has a lower resistivity than the upper GaN layer, and wherein a two-dimensional electron gas (2DEG) conductive channel exists at an upper surface of the upper GaN layer, wherein the first voltage results in the formation of a drain depletion region that extends from the upper surface of the upper GaN layer to the lower GaN layer under the drain contact; then
measuring an electrical current between the source contact and the drain contact while the first voltage is applied across the source contact and the drain contact, wherein the electrical current is a function of UV light received by the upper and lower GaN layers; and then
refreshing the UV light sensor by applying a second voltage to the lower GaN layer when no electrical current is flowing between the source contact and the drain contact.

21. The method of claim 20 wherein the first voltage is in the range of 3 Volts to 50 Volts.

22. The method of claim 20 , wherein refreshing the UV light sensor further comprises forcing current through a heater to increase the temperature of the upper and lower GaN layers.

23. The method of claim 22 , where the current forced through the heater is in the range from 1 mA to 100 mA.

24. The method of claim 22 , wherein refreshing the UV light sensor further comprises a sequence of forcing current through the heater and then applying the second voltage to the lower GaN layer.

25. The method of claim 22 , wherein the heater comprises a 2DEG resistor in the upper GaN layer, wherein forcing current through the heater comprises applying the same voltage to both the 2DEG resistor and to the lower GaN layer.

26. The method of claim 20 , wherein refreshing the UV light sensor further comprises applying 0 Volts to the drain contact while applying the second voltage to the lower GaN layer.

27. The method of claim 20 , wherein the second voltage is in the range of 3 Volts to 50 Volts.

28. The method of claim 20 , further comprising allowing the lower GaN layer to float while applying the first voltage across the source contact and the drain contact.

29. The method of claim 28 , wherein applying the first voltage across the source contact and the drain contact comprises applying 0 Volts to the source contact and applying a first positive voltage to the drain contact.

30. The method of claim 29 , further comprising applying the second voltage to the lower GaN layer in pulses having a first phase, and applying the first positive voltage to the drain contact in pulses having a second phase, opposite the first phase.

31. The method of claim 30 , wherein the second voltage is a positive voltage.

32. The method of claim 30 , where the pulses having the first phase have an amplitude in the range of 10 Volts to 50 Volts, and the pulses having the second phase have an amplitude in the range of 10 Volts to 50 Volts.

33. The method of claim 30 , where the pulses having the first phase are rectangular pulses having a duration from 1 second to 1 microsecond, and the pulses having the second phase are rectangular pulses having a duration from 1 second to 1 microsecond.

34. An ultraviolet (UV) light sensor comprising:
a first gallium nitride (GaN) layer formed over a nucleation layer;
a first aluminum gallium nitride (AlGaN) layer formed over the first GaN layer, wherein a first two-dimensional electron gas (2DEG) conductive channel exists at an upper surface of the first GaN layer, adjacent to the first AlGaN layer;
a second GaN layer formed over the first AlGaN layer; a second AlGaN layer formed over the second GaN layer, wherein a second two-dimensional electron gas (2DEG) conductive channe

Assignees

• Tower Semiconductor Ltd

Inventors

• Roizin Yakov
• Sahar Carmel
• Kairys Victor
• Shima-Edelstein Ruth

Classifications

• H10F77/12485

  comprising nitride compounds, e.g. InGaN · CPC title

• H10F77/60

  Arrangements for cooling, heating, ventilating or compensating for temperature fluctuations · CPC title

• H10F30/28

  the devices being characterised by field-effect operation, e.g. junction field-effect phototransistors · CPC title

• H10F77/143

  comprising quantum structures · CPC title

• H10F77/953

  for devices having potential barriers · CPC title