Method of making a vertical light emitting diode

• US 20060154392A1
• Filed: 01/11/2005
• Published: 07/13/2006
• Est. Priority Date: 01/11/2005
• Status: Active Grant

• Current Assignee: SemiLEDs Corporation (SemiLEDs Inc)
• Original Assignee: SemiLEDs Corporation (SemiLEDs Inc)
• Inventors: Tran, Chuong Anh, Doan, Trung Tri
• Granted Patent: US 7,413,918 B2
• Time in Patent Office: Days
• US Class Current: 438/22
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

Methods are disclosed for forming a vertical semiconductor light emitting diode (VLED) device having an active layer between an n-doped layer and a p-doped layer; and securing a plurality of balls on a surface of the n-doped layer of the VLED device.

Claims

1. A method of fabricating a semiconductor vertical light emitting diode (VLED) device, comprising:

forming multi-layer epitaxial structure of the VLED device that includes an n-gallium nitride (n-GaN) layer, an active layer, and an p-gallium nitride (p-GaN) layer; and

providing a plurality of balls on a surface of the n-GaN layer of the VLED device.

2. The method as defined in claim 1, further comprising using one of spin coating and spraying the balls on the n-GaN layer of the VLED device.

3. The method as defined in claim 1, further comprising controlling the density of the balls by adjusting a viscosity of an applied ball-containing solution.

4. The method as defined in claim 3, wherein the viscosity is adjusted by varying the amount and the density of balls in the applied ball-containing solution.

5. The method as defined in claim 3, wherein the applied ball-containing solution contains one or more of:

an alcohol component, a surfactant and an adhesion material.

6. The method as defined in claim 1, further comprising securing the balls on the surface of the n-GaN layer of the VLED device.

7. The method as defined in claim 2, further comprising applying a semi-transparent coating over the balls.

8. The method as defined in claim 1, further comprising forming an electrically conductive semi-transparent coating above the balls.

9. The method as defined in claim 1, wherein the balls are planar with the n-GaN layer of the VLED device.

10. The method as defined in claim 4, wherein the coating is greater than 80 percent transparent to the wavelength that the VLED transmits.

11. The method as defined in claim 6, wherein the securing the balls comprises applying a transparent coat to hold the balls.

12. The method as defined in claim 6, wherein the securing the balls comprises applying a conductive coat to hold the balls.

13. The method as defined in claim 6, wherein the securing the balls comprises applying sol-gel to hold the balls.

14. The method as defined in claim 6, wherein the securing the balls comprises spray coating or spin coating the balls.

15. The method as defined in claim 1, wherein the balls are dispersed in an organic solution.

16. The method as defined in claim 6, wherein the securing the balls comprises applying dry powder coating.

17. The method as defined in claim 16, further comprising applying an electrostatic coating to hold the balls.

18. The method as defined in claim 8, wherein the coating comprises one of:

ITO, Nickel, Gold.

19. The method as defined in claim 1, further comprising roughening the surface of the n-GaN layer of the VLED device to scatter and extract light from interior for emission out of the n-GaN layer.

20. The method as defined in claim 1, wherein the ball comprises a sub-micron sphere.

21. The method as defined in claim 1, wherein the ball has a radius between approximately 10 nm and about 2 micron.

22. The method as defined in claim 1, wherein the ball dimension is selected to optimally scatter light at approximately ½

λ

.

23. The method as defined in claim 1, wherein a refractive index of the ball is between approximately 2.0 and 3.0.

24. The method as defined in claim 1, wherein a refractive index of the ball is greater than approximately 2.3.

25. The method as defined in claim 1, wherein a refractive index of the ball is approximately equal to a refractive index of the n-GaN layer.

26. The method as defined in claim 1, wherein the ball comprises one of:

TiO2, Ta2O5, ZrO, ZnO, HfO2, GaN, AlN, ZnSe, and SiOxNy.

27. The method as defined in claim 1, wherein the balls are spread on a surface of the n-GaN layer of the VLED device surface using a coating method.

28. The method as defined in claim 1, wherein said forming of the multi-layer epitaxial structure of the VLED device is such that the emission of light by the VLED is through the n-GaN layer.

29. The method as defined in claim 6, wherein the secured balls form a mask for dry etching the n-GaN layer.

30. The method as defined in claim 29, wherein the etched n-GaN layer of the VLED device increases VLED surface roughness to extract more light from an interior thereof.

31. The method as defined in claim 1, wherein the active layer is a MQW active layer.

32. The method as defined in claim 1, further comprising depositing, over the balls, an ITO layer using one of PVD, CVD and e-beam evaporation.

33. The method as defined in claim 1, further comprising depositing, over the balls, a transparent coating using one of:

PVD, CVD and e-beam evaporation.

34. A method comprising:

forming a vertical light emitting diode (VLED) device having an active layer between an n-doped layer and a p-doped layer; and

securing a plurality of balls on a surface of the n-doped layer of the VLED device.

35. The method as defined in claim 34, wherein the securing a plurality of balls on a surface of the n-doped layer of the VLED device comprises a step selected from the group consisting of:

spinning a coating over the balls;

spraying a coating over the balls;

applying a transparent coating over the balls;

applying a semi-transparent coating over the balls;

forming an electrically conductive semi-transparent coating above the balls;

applying a coating over the balls that is greater than 80 percent transparent to the wavelength that the VLED transmits;

applying a conductive coat over the balls;

applying sol-gel over the balls;

applying a dry powder coating over the balls;

applying an electrostatic coating over the balls;

applying a coating over the balls comprising one of ITO, Nickel, and Gold; and

applying a transparent coating using one of PVD, CVD and e-beam evaporation.

36. The method as defined in claim 34, further comprising, prior to said securing, roughening a surface on the n-doped layer of the VLED device.

37. The method as defined in claim 36, wherein the roughing comprises drying etching the n-doped layer using the secured balls as a mask.

38. The method as defined in claim 34, wherein each said ball comprises a sub-micron sphere having a refractive index approximately equal to that of the n-doped layer.

39. The method as defined in claim 34, wherein the ball comprises one of:

TiO2, Ta2O5, ZrO, ZnO, HfO2, GaN, AlN, ZnSe, and SiOxNy.

40. The method as defined in claim 34, wherein:

the active layer comprises a MQW active layer;

the n-doped layer comprises an n-GaN layer for emitting light from the VLED; and

the p-doped layer comprises a p-GaN layer.

41. The method as defined in claim 34, further comprising:

forming an electrode in electrical communication with the n-doped layer; and

forming an electrode in electrical communication with the p-doped layer.

43. The method as defined in claim 41, wherein the n-GaN layer has a roughened surface to which the plurality of balls are secured.

44. The method as defined in claim 41, wherein light is emitted from the VLED through the n-GaN layer having a surface thereon to which the balls are secured.

42. A method comprising:

forming, for a vertical light emitting diode (VLED) device, a MQW active layer between an n-GaN layer and a p-GaN layer;

securing a plurality of balls to the n-GaN layer; and

forming opposing electrodes in electrical communication, respectively, with the n-GaN layer and the p-GaN layer.