# US 5,710,441 A · Microcavity LED with photon recycling

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- Number: US 5,710,441 A
- Document ID: US5710441A
- Status: Granted
- Kind: A
- Application number: 08/550,147
- Filed: 1995-10-30
- Granted: 1998-01-20
- Earliest claimed: 1995-10-30
- Assignees: Motorola, Inc.
- Inventors: Donald E. Ackley; Chan-Long Shieh; Michael S. Lebby
- Web page: https://patentgrep.com/patent/US5710441A

## CPC

- H10H 20/8142: {forming resonant cavity structures}
- H10H 20/835: {Reflective materials}
- H10H 20/862: {Resonant cavity structures (formed by reflecting means in the bodies H10H20/8142)}
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS

## Abstract

A microcavity LED with photon recycling including a substrate having at least one layer of material positioned thereon, and a first cladding layer, a second cladding layer and an active region sandwiched therebetween forming a mesa on the layer of material. The mesa has generally vertical sides and an upper surface with an electrically conductive and light reflective system positioned on the vertical sides of the mesa and partially covering the upper surface to form a first electrical contact for the LED, the electrically conductive and light reflective system defining a centrally located light emitting opening on the surface of the mesa, the mesa having a diametric dimension of the surface greater than one time larger than a diametric dimension of the opening.

## Claims

### Claim 1

A microcavity LED with photon recycling comprising:
a substrate having at least one layer of material positioned thereon;
a first cladding layer of a first conductivity type positioned on the layer of material;
an active region positioned on the first cladding layer;
a second cladding layer of a second conductivity type positioned on the active region;
the first cladding layer, the active region and the second cladding layer forming a mesa on the layer of material, the mesa having generally vertical sides and an upper surface; and
an electrically conductive and light reflective system positioned on the vertical sides of the mesa and partially covering the upper surface to form a first electrical contact for the LED, the electrically conductive and light reflective system defining a centrally located light emitting opening on the upper surface of the mesa, the mesa having a diametric dimension of the surface greater than one time larger than a diametric dimension of the opening.

### Claim 2 (depends on 1)

A microcavity LED with photon recycling as claimed in claim 1 wherein diametric diameter of the surface of the mesa is in the range of 2 to 10 times larger than the diametric dimension of the light emitting opening.

### Claim 3 (depends on 1)

A microcavity LED with photon recycling as claimed in claim 1 wherein the electrically conductive and light reflective system includes a dielectric layer deposited on the vertical sidewalls of the mesa, and a first metal contact layer deposited on the dielectric layer and on the upper surface of the mesa to form the first electrical contact.

### Claim 4 (depends on 3)

A microcavity LED with photon recycling as claimed in claim 3 wherein the cladding layers are thin and lightly doped to reduce internal free carrier loss.

### Claim 5 (depends on 4)

A microcavity LED with photon recycling as claimed in claim 4 wherein the active region includes a plurality of quantum well layers separated by barrier layers.

### Claim 6 (depends on 1)

A microcavity LED with photon recycling as claimed in claim 1 wherein the at least one layer of material includes a mirror stack.

### Claim 7 (depends on 6)

A microcavity LED with photon recycling as claimed in claim 6 wherein the mirror stack includes approximately thirty pairs of layers.

### Claim 8 (depends on 7)

A microcavity LED with photon recycling as claimed in claim 7 wherein the thirty pairs of layers each include layers of AlGaAs.

### Claim 9 (depends on 8)

A microcavity LED with photon recycling as claimed in claim 8 wherein the thirty pairs of layers each include layers of different amounts of aluminum to provide different indexes of refraction.

### Claim 10

A microcavity LED with photon recycling comprising:
a substrate having at least one layer of material positioned thereon;
a first cladding layer of a first conductivity type positioned on the layer of material;
an active region positioned on the first cladding layer;
a second cladding layer of a second conductivity type positioned on the active region;
the first cladding layer, the active region and the second cladding layer forming a mesa on the at least one layer of material, the mesa having generally vertical sides and an upper surface;
a layer of dielectric material positioned on the vertical sides of the mesa; and
an electrically conductive and light reflective layer positioned on the layer of dielectric material and partially covering the upper surface to form a first electrical contact for the LED, the electrically conductive layer defining a centrally located light emitting opening on the upper surface of the mesa, the mesa having a diametric dimension of the surface greater than one time larger than a diametric dimension of the opening.

### Claim 11 (depends on 10)

A microcavity LED with photon recycling as claimed in claim 10 wherein the diametric dimension of the surface of the mesa is in the range of 2 to 10 times larger than the diametric dimension of the light emitting opening.

### Claim 12 (depends on 10)

A microcavity LED with photon recycling as claimed in claim 10 wherein the at least one layer of material includes a mirror stack.

### Claim 13 (depends on 12)

A microcavity LED with photon recycling as claimed in claim 12 wherein the mirror stack includes approximately thirty pairs of layers.

### Claim 14 (depends on 13)

A microcavity LED with photon recycling as claimed in claim 13 wherein the thirty pairs of layers each include layers of AlGaAs.

### Claim 15 (depends on 14)

A microcavity LED with photon recycling as claimed in claim 14 wherein the thirty pairs of layers each include layers of different amounts of aluminum to provide different indexes of refraction.

### Claim 16

A microcavity LED with photon recycling comprising:
a substrate;
a mirror stack positioned on the substrate;
a first cladding layer of a first conductivity type positioned on a mirror stack;
an active region positioned on the first cladding region;
a second cladding layer of a second conductivity type positioned on the active layer;
the first cladding layer, the active region and the second cladding layer forming a mesa on the mirror stack, the mesa having generally vertical sides and an upper surface;
a layer of dielectric material positioned on the vertical sides of the mesa; and
an electrically conductive and light reflective layer positioned on the layer of dielectric material and partially covering the upper surface to form a first electrical contact for the LED, the electrically conductive layer defining a centrally located light emitting opening on the upper surface of the mesa, the surface of the mesa having a diametric dimension in the range of 2 to 10 times larger than a diametric dimension of the opening.

### Claim 17 (depends on 16)

A microcavity LED with photon recycling as claimed in claim 16 wherein the mirror stack includes approximately thirty pairs of layers.

### Claim 18 (depends on 17)

A microcavity LED with photon recycling as claimed in claim 17 wherein the thirty pairs of layers each include layers of AlGaAs.

### Claim 19 (depends on 18)

A microcavity LED with photon recycling as claimed in claim 18 wherein the thirty pairs of layers each include layers of different amounts of aluminum to provide different indexes of refraction.