DUAL SURFACE-ROUGHENED N-FACE HIGH-BRIGHTNESS LED

• US 20080277682A1
• Filed: 03/31/2008
• Published: 11/13/2008
• Est. Priority Date: 03/29/2007
• Status: Abandoned Application

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: DenBaars, Steven P., Nakamura, Shuji, Mishra, Umesh K., Grundmann, Michael
• Application Number:
  US12/059,918
• Publication Number:
  US 20080277682A1
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/04 with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

A light emitting diode, comprising a substrate, a buffer layer on the substrate, an active layer on the buffer layer and between an n-type layer and a p-type layer, a tunnel junction adjacent the p-type layer, and n-type contacts to the tunnel junction and the n-type layer, wherein the buffer layer, n-type layer, p-type layer, active region and tunnel junction comprise III-nitride material grown in a nitrogen-face (N-face) orientation. The substrate surface upon which the III-nitride material is deposited is patterned to provide embedded backside roughening. A top surface of the tunnel junction, which also the top surface of the III-nitride material, is roughened.

Claims

1. An optoelectronic device, comprising:

(a) a p-type layer on an n-type layer;

(b) a first n-type contact for the p-type layer;

(c) one or more intermediate layers between the first n-type contact and the p-type layer for transferring the device'"'"'s drive current between the p-type layer and the first n-type contact; and

(d) a second n-type contact for the n-type layer.

2. The optoelectronic device of claim 1, having only n-type contacts and no p-type contacts.

3. The optoelectronic device of claim 1, wherein:

(1) the optoelectronic device is a light emitting diode (LED);

(2) a roughened n-type surface terminates the LED to enhance light extraction;

(3) the LED'"'"'s power is supplied via the first n-type contact and the second n-type contact.

4. The optoelectronic device of claim 3, wherein the LED has a roughened backside.

5. The optoelectronic device of claim 3, wherein the LED is fabricated on a patterned substrate to provide embedded backside roughening.

6. The optoelectronic device of claim 3, wherein the LED is III-nitride based and the roughened n-type surface is a roughened nitrogen-face (N-face).

7. The optoelectronic device of claim 6, wherein the LED is comprised of an epitaxial growth having an N-face orientation.

8. The optoelectronic device of claim 1, wherein the intermediate layers comprise:

(1) a polarization-induced tunnel junction between the p-type layer and the n-type contact, which enables efficient tunneling transport between the p-type layer and the n-type contact;

(2) one or more n-type conductive layers between the polarization-induced tunnel junction and the n-type contact.

9. The optoelectronic device of claim 8, wherein the one or more n-type conductive layers is an n-type current spreading layer to compensate for minimal electrical contact created by the roughening.

10. The optoelectronic device of claim 8, wherein the polarization-induced tunnel junction is aluminum nitride, and the n-type conductive layer and p-type layer are gallium nitride.

11. An optoelectronic device, comprising:

one or more intermediate layers for electrically connecting an n-type contact to a p-type region, wherein the intermediate layers transfer sufficient charge to power light emission from the optoelectronic device.

12. The optoelectronic device of claim 11, wherein the intermediate layers create a depletion region at a junction between the n-type contact and the p-type region, and the depletion region is sufficiently small to enable tunneling transport between the n-type contact and the p-type region.

13. The optoelectronic device of claim 11, wherein the intermediate layers comprise an n-type layer on a polarization induced tunnel junction.

14. A method for fabricating an optoelectronic device, comprising:

(a) fabricating only n-type contacts to the device; and

(b) roughening a top surface of the device, which is an n-type surface, and a bottom surface of the device.

15. The method of claim 14, wherein the optoelectronic device is a III-nitride nitrogen-face (N-face) light emitting diode (LED).

16. An AlInGaN-based optoelectronic device, comprising:

(a) a roughened nitrogen face (N-face) surface; and

(b) an surface opposite the roughened N-face surface that is also roughened;

(c) wherein the surfaces are roughened to enhance light extraction from the device.