Low resistance current spreading to n-contacts of micro-LED array

Patent metadata

Field	Value
Publication number	US-12243906-B2
Application number	US-202117525442-A
Country	US
Kind code	B2
Filing date	Nov 12, 2021
Priority date	Nov 30, 2020
Publication date	Mar 4, 2025
Grant date	Mar 4, 2025

Abstract

A light source includes an epitaxial layer stack that includes an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer. The epitaxial layer stack includes a two-dimensional (2-D) array of mesa structures formed therein. The light source further includes an array of p-contacts electrically coupled to the p-type semiconductor layer of the 2-D array of mesa structures, a metal layer in regions surrounding individual mesa structures of the 2-D array of mesa structures, and a plurality of n-contacts coupling the metal layer to the n-type semiconductor layer at a plurality of locations between the individual mesa structures of the 2-D array of mesa structures.

First claim

What is claimed is:

1. A light source comprising:
an epitaxial layer stack including an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer, the epitaxial layer stack including a two-dimensional (2-D) array of mesa structures formed therein;
an array of p-contacts electrically coupled to the p-type semiconductor layer of the 2-D array of mesa structures;
a metal layer surrounding each individual mesa structure of the 2-D array of mesa structures; and
a plurality of n-contacts coupling the metal layer to the n-type semiconductor layer at a plurality of locations between the individual mesa structures of the 2-D array of mesa structures.

2. The light source of claim 1 , wherein the plurality of n-contacts and the array of p-contacts are on a same side of the n-type semiconductor layer or are on opposite sides of the n-type semiconductor layer.

3. The light source of claim 1 , further comprising an elongated n-contact at an area outside of the 2-D array of mesa structures, the elongated n-contact coupling the metal layer to the n-type semiconductor layer at the area outside of the 2-D array of mesa structures.

4. The light source of claim 1 , further comprising an array of micro-lenses on a surface of the n-type semiconductor layer.

5. The light source of claim 4 , wherein the array of micro-lenses is formed in the n-type semiconductor layer or a dielectric layer formed on the n-type semiconductor layer.

6. The light source of claim 4 , wherein the metal layer is between individual micro-lenses of the array of micro-lenses.

7. The light source of claim 1 , wherein the metal layer is on sidewalls of the 2-D array of mesa structures and regions between the 2-D array of mesa structures.

8. The light source of claim 7 , further comprising a dielectric layer between the sidewalls of the 2-D array of mesa structures and the metal layer, wherein the dielectric layer and the metal layer form a sidewall reflector.

9. The light source of claim 1 , further comprising a transparent conductive material layer between the array of p-contacts and the p-type semiconductor layer.

10. The light source of claim 1 , wherein each n-contact of the plurality of n-contacts is located at a center of a square region including four mesa structures.

11. The light source of claim 1 , wherein:
a pitch of the 2-D array of mesa structures is equal to or less than 5 μm; and
each mesa structure of the 2-D array of mesa structures is characterized by a lateral linear dimension equal to or less than 3 μm.

12. The light source of claim 1 , further comprising a second metal layer on a surface of the n-type semiconductor layer, wherein the metal layer and the second metal layer are on opposite sides of the n-type semiconductor layer.

13. The light source of claim 12 , wherein the second metal layer is configured to absorb visible light.

14. The light source of claim 1 , wherein the metal layer is characterized by at least one of:
a thickness greater than 50 nm; or
a drive current density equal to or greater than 1 A/cm 2 at a drive voltage equal to or less than 4.5 V.

15. The light source of claim 1 , wherein the metal layer includes Al, Au, Ni, Ti, Pd, Ge, Ag, Cu, or any combination thereof.

16. The light source of claim 1 , wherein at least one of the metal layer or the plurality of n-contacts is configured to absorb visible light.

17. The light source of claim 1 , wherein the n-type semiconductor layer includes a heavily doped sublayer.

18. The light source of claim 1 , further comprising a semiconductor substrate including electrical circuits fabricated thereon, the electrical circuits electrically coupled to the array of p-contacts and the plurality of n-contacts.

19. A method comprising:
fabricating a micro-light emitting diode (micro-LED) array that comprises:
an epitaxial layer stack including an n-type semiconductor layer, a light-emitting layer, and a p-type semiconductor layer, the epitaxial layer stack including a two-dimensional (2-D) array of mesa structures formed therein;
an array of p-contacts electrically coupled to the p-type semiconductor layer of the 2-D array of mesa structures;
a metal layer surrounding each individual mesa structure of the 2-D array of mesa structures; and
a plurality of n-contacts coupling the metal layer to the n-type semiconductor layer at a plurality of locations between the individual mesa structures of the 2-D array of mesa structures;

fabricating electrical circuits on a semiconductor substrate; and
bonding the micro-LED array to the semiconductor substrate such that the electrical circuits are coupled to the array of p-contacts and the plurality of n-contacts.

20. The method of claim 19 , further comprising forming a second metal layer on the n-type semiconductor layer, the metal layer and the second metal layer on opposite sides of the n-type semiconductor layer.

21. The method of claim 19 , wherein fabricating the micro-LED array comprises:
growing the epitaxial layer stack on a second substrate;
etching the epitaxial layer stack to form the 2-D array of mesa structures in the epitaxial layer stack;
depositing a first dielectric layer on surfaces of the 2-D array of mesa structures;
forming the plurality of n-contacts at regions between mesa structures of the 2-D array of mesa structures;
depositing the metal layer on the first dielectric layer and the plurality of n-contacts;
patterning the metal layer;
forming a patterned second dielectric layer on the metal layer;
forming the array of p-contacts in the patterned second dielectric layer;
forming a patterned third dielectric layer; and
forming p-electrodes and n-electrodes in the patterned third dielectric layer, the p-electrodes electrically connected to the array of p-contacts, and the n-electrodes electrically connected to the plurality of n-contacts.

Assignees

• Meta Platforms Tech Llc

Inventors

• Lutgen Stephan
• Broell Markus
• Lauermann Thomas
• Hahn Berthold
• Hurni Christophe Antoine
• Lheureux Guillaume

Classifications

• H10W90/00

  Package configurations · CPC title

• H10H20/0364

  of interconnections · CPC title

• H10H20/857

  Interconnections, e.g. lead-frames, bond wires or solder balls · CPC title

• H10H20/819

  characterised by their shape, e.g. curved or truncated substrates · CPC title

• H10H20/01

  Manufacture or treatment · CPC title