# US 12,604,591 B2 · Spacer LED architecture for high efficiency micro LED displays

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- Number: US 12,604,591 B2
- Document ID: US12604591B2
- Status: Granted
- Kind: B2
- Application number: 17/921,021
- Filed: 2021-05-26
- Published: 2023-04-27
- Granted: 2026-04-14
- Earliest claimed: 2020-06-03
- Assignees: Plessey Semiconductors Limited
- Applicants: Plessey Semiconductors Ltd
- Inventors: Andrea Pinos; WeiSin Tan; Samir Mezouari; John Lyle Whiteman
- Web page: https://patentgrep.com/patent/US12604591B2

## CPC

- H10H 20/831: characterised by their shape
- H10H 29/142: {Two-dimensional arrangements, e.g. asymmetric LED layout}
- H10H 20/82: Roughened surfaces, e.g. at the interface between epitaxial layers
- H10H 20/84: Coatings, e.g. passivation layers or antireflective coatings
- H10H 20/841: Reflective coatings, e.g. dielectric Bragg reflectors
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS

## Abstract

A method of forming an optical device, the method comprising the steps of forming a mesa, the mesa comprising an active layer configured to emit light from a first light emitting surface of the mesa when subjected to an electrical current, the mesa further comprising a second surface opposite the light emitting surface and substantially vertical sidewalls, forming spacers on the mesa sidewalls, the spacers being formed from a first electrically insulating, optically transparent material, and having an internal face facing the mesa sidewalls, and an opposing external face, depositing a first layer of transparent conducting oxide on the light emitting surface of the mesa, the transparent conducting oxide having an internal face facing the second surface of the mesa, and an opposing external face, and depositing a layer of reflective, electrically conducting material over the transparent conducting oxide and external faces of the spacers.

## Claims

### Claim 1

A method of forming an optical device, the method comprising the steps of:
forming a mesa, the mesa comprising an active layer configured to emit light from a first light emitting surface of the mesa when subjected to an electrical current, the mesa further comprising a second surface opposite the first light emitting surface and substantially vertical sidewalls, wherein the sidewalls of the mesa are roughened;
forming spacers on the mesa sidewalls, the spacers being formed from a first electrically insulating optically transparent material, and having an internal face facing the mesa sidewalls, and an opposing external face, wherein the external faces of the spacers are straight sided and angled outward away from the mesa sidewalls;
depositing a first layer of transparent electrically conducting material on the second light emitting surface of the mesa, the transparent electrically conducting material having an internal face facing the second surface of the mesa, and an opposing external face, wherein the external face of the first layer of transparent, electrically conducting material is substantially convex, and the external face of the first layer of transparent, electrically conducting material has a radius of curvature of between 1 and 1.5 microns;
forming a second layer of transparent, electrically conducting material on the first light emitting surface of the mesa; and
depositing a layer of reflective electrically conducting material over the transparent electrically conducting material and external faces of the spacers.

### Claim 2 (depends on 1)

The method of claim 1 wherein the transparent, electrically conducting material is a transparent conducting oxide.

### Claim 3 (depends on 2)

The method of claim 2 wherein the transparent conducting oxide is indium tin oxide.

### Claim 4 (depends on 1)

The method of claim 1 wherein the external faces of the spacers have a profile that approximates a Bézier curve having two control points with a Bézier coefficient of 0.5.

### Claim 5 (depends on 1)

The method of claim 1 wherein the spacers are formed of at least one of silicon nitride, silicon oxide or tin oxide.

### Claim 6 (depends on 1)

The method of claim 1 further comprising the step of depositing a second electrically insulating, optically transparent material on the external face of each of the spacers, the second electrically insulating, optically transparent material having a different refractive index to that of the first electrically insulating, optically transparent material.

### Claim 7 (depends on 1)

The method of claim 1 wherein the refractive index of the first electrically insulating, optically transparent material is greater than that of the second electrically insulating, optically transparent material.

### Claim 8 (depends on 1)

The method of claim 1 wherein the active layer of the mesa is between an n-doped n-cladding layer and a p-doped p-cladding layer.

### Claim 9 (depends on 8)

The method of claim 8 wherein a first electrical contact is made to the p-cladding layer via the first layer of transparent conducting oxide and the reflective, electrically conducting material and a second electrical contact is made to the n-cladding layer via the second layer of transparent conducting oxide.

### Claim 10 (depends on 1)

An array of optical devices manufactured according to the method of claim 1.