US5226053A — Light emitting diode

Claim 1

Independent Claim 257 words

A light emitting diode (LED) with a resonant Fabry-Perot cavity comprising: a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order: a substrate of a first conductivity type, a bottom confining layer of the first conductivity type, an active layer capable of emitting light spontaneously under forward bias conditions, the thickness of the active layer being within a range of from 1 to 30 nanometers, a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and a semiconductor contact layer of the second conductivity type, said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises: a bottom mirror and a top mirror placed on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom mirror is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R B ≧99%), and said top electrode is a thin metal layer deposited in a thickness permitting passage of light emission through the metal and acting as the top mirror of the resonant cavity, the reflectivity, R T , of said top mirror being 25% ≦R T <99%, preferably 40% ≦R T ≦97%.

Claim 2

Dependent Claim 257 words

A light emitting diode (LED) with a resonant Fabry-Perot cavity comprising: a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order: a substrate of a first conductivity type, a bottom confining layer of the first conductivity type, an active layer capable of emitting light spontaneously under forward bias conditions, the thickness of the active layer being within a range of from 1 to 30 nanometers, a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and a semiconductor contact layer of the second conductivity type, said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises: a bottom mirror and a top mirror placed on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom mirror is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R B ≧99%), and said top electrode is a thin metal layer deposited in a thickness permitting passage of light emission through the metal and acting as the top mirror of the resonant cavity, the reflectivity, R T , of said top mirror being 25% ≦R T <99%, preferably 40% ≦R T ≦97%.

Claim 3

Dependent Claim 81 words

The LED of claim 1, in which said bottom mirror is a multilayer distributed Bragg reflector (DBR) mirror comprising a plurality of pairs of semiconductor layers, one layer in each pair having an index of refraction which is higher than the index of refraction of the other layer in the pair, each layer being λ/4 n thick, wherein λ is a spontaneous emission wavelength of the active layer and n is the refractive index of the material of the respective layers.

Claim 4

Dependent Claim 24 words

The LED of claim 1, in which said structure is an Al x Ga 1-x As/GaAs system with x ranging from 0 to 1.

Claim 5

Dependent Claim 42 words

The LED of claim 2, in which said active layer is GaAs, said low refractive index material comprises AlAs and said high refractive material is selected from GaAs,Al 0 .05 Ga 0 .95 As and Al 0 .14 Ga 0 .86 As.

Claim 6

Dependent Claim 25 words

The LED of claim 1, in which said metal layer consists essentially of a metal selected from the group consisting of silver, aluminum and gold.

Claim 7

Dependent Claim 19 words

The LED of claim 5, in which said metal layer is silver from 15 nm to 50 nm thick.

Claim 8

Dependent Claim 240 words

A light emitting diode (LED) with a resonant Fabry-Perot cavity comprising: a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order: a substrate of a first conductivity type, a bottom confining layer of a first conductivity type, an active layer capable of emitting light spontaneously under forward bias conditions, a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and a semiconductor contact layer of the second conductivity type, said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises a bottom mirror and a top mirror placed on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom layer is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R B ≧99%), and said top electrode is provided with a centrally located aperture in which is exposed an upper surface of the contact layer, the interface between said upper surface and air overlaying said upper surface forming said top mirror having reflectivity 25% ≦R T ≦99%, preferably 25% ≦R T ≦35%.

Claim 9

Dependent Claim 240 words

A light emitting diode (LED) with a resonant Fabry-Perot cavity comprising: a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order: a substrate of a first conductivity type, a bottom confining layer of a first conductivity type, an active layer capable of emitting light spontaneously under forward bias conditions, a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and a semiconductor contact layer of the second conductivity type, said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises a bottom mirror and a top mirror placed on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom layer is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R B ≧99%), and said top electrode is provided with a centrally located aperture in which is exposed an upper surface of the contact layer, the interface between said upper surface and air overlaying said upper surface forming said top mirror having reflectivity 25% ≦R T ≦99%, preferably 25% ≦R T ≦35%.

Claim 10

Dependent Claim 35 words

The LED of claim 7, in which said top electrode is a metal alloy selected from Au-Zn and Au-Be and deposited on the contact layer in a thickness ranging from 50 nm to 300 nm.

Claim 11

Dependent Claim 81 words

The LED of claim 7, in which said bottom mirror is a multilayer distributed Bragg reflector (DBR) mirror comprising a plurality of pairs of simiconductor layers, one layer in each pair having an index of refraction which is higher than the index of refraction of the other layer in the pair, each layer being λ/4 n thick, wherein λ is a spontaneous emission wavelength of the active layer and n is the refractive index of the material of the respective layers.

Claim 12

Dependent Claim 24 words

the LED of claim 7, in which said structure is an Al x Ga 1-x As/GaAs system with x ranging from 0 to 1.

Claim 13

Dependent Claim 43 words

The LED of claim 9, in which said active layer is GaAs, said low refractive index material comprises AlAs and said high refractive material is selected from GaAs, Al 0 .05 Ga 0 .95 As and Al 0 .14 Ga 0 .86 As.

Claim 14

Dependent Claim 268 words

A light emitting diode (LED) with a resonant Fabry-Perot cavity comprising: a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order: a substrate of a first conductivity type, a bottom confining layer of a first conductivity type, an active layer capable of emitting light spontaneously under forward bias conditions, a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and a semiconductor contact layer of the second conductivity type, said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises a bottom mirror and a top mirror placed on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom layer is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R B ≧99%), and said top electrode comprises a thin metal layer overlying the contact layer and an optically transparent conductive semiconductor material overlying said metal layer, the conductive semiconductor material is selected from the group consisting of cadmium tin oxide and indium tin oxide, and said metal layer and said conductive semiconductor layer acting simultaneously as the top electrode and the top mirror of said LED, the reflectivity, R T , of the top mirror being 25%≦R T ≦99%.

Claim 15

Dependent Claim 268 words

A light emitting diode (LED) with a resonant Fabry-Perot cavity comprising: a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order: a substrate of a first conductivity type, a bottom confining layer of a first conductivity type, an active layer capable of emitting light spontaneously under forward bias conditions, a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and a semiconductor contact layer of the second conductivity type, said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises a bottom mirror and a top mirror placed on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom layer is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R B ≧99%), and said top electrode comprises a thin metal layer overlying the contact layer and an optically transparent conductive semiconductor material overlying said metal layer, the conductive semiconductor material is selected from the group consisting of cadmium tin oxide and indium tin oxide, and said metal layer and said conductive semiconductor layer acting simultaneously as the top electrode and the top mirror of said LED, the reflectivity, R T , of the top mirror being 25%≦R T ≦99%.

Claim 16

Dependent Claim 41 words

The LED of claim 12, in which said metal layer is of silver deposited in a thickness of from 15 nm to 50 nm, and said transparent conductive semiconductor material is deposited in a thickness of from 50 to 500 nm.

Claim 17

Dependent Claim 80 words

The LED of claim 12, in which said bottom mirror is a multilayer distributed Bragg reflector (DBR) mirror comprising a plurality of pairs of semiconductor layers, one layer in each pair having an index of refraction which is higher than the index of refraction of the other layer in the pair, each layer being λ/4n thick, wherein λ is a spontaneous emission wavelength of the active layer and n is the refractive index of the material of the respective layers.

Claim 18

Dependent Claim 24 words

The LED of claim 12, in which said structure is an Al x Ga 1-x As/GaAs system with x ranging from 0 to 1.

Claim 19

Dependent Claim 42 words

The LED of claim 14, in which said active layer is GaAs, said low refractive index material comprises AlAs and said high refractive material is selected from GaAs,Al 0 .05 Ga 0 .95 As and Al 0 .14 Ga 0 .86 As.

Claim 20

Dependent Claim 273 words

A light emitting diode (LED) comprising: a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order: a substrate of a first conductivity type, a bottom confining layer of the first conductivity type, an active layer capable of emitting light spontaneously under forward bias conditions, a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and a semiconductor contact layer of the second conductivity type, said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises: a bottom mirror and a top mirror on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom mirror is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R B ≧99%), and said top electrode comprises an annular thin metal layer overlying the contact layer, and said top mirror comprises a stack of a plurality of pairs of high index of refraction and low index of refraction layers, said stack overlying that surface of the contact layer which is exposed in the central aperture of the annular metal layer and partially overlapping an edge of the annular metal layer adjacent said aperture, the reflectivity, R T , of the top mirror being 25%≦R T ≦99%, preferably 80%≦R T ≦99%.

Claim 21

Dependent Claim 273 words

A light emitting diode (LED) comprising: a semiconductor structure comprising a plurality of layers of semiconductor material and a bottom and a top electrode on opposite surfaces of said structure, wherein said semiconductor material is selected from Group III-V and Group II-VI compound semiconductor materials, said structure comprises in an ascending order: a substrate of a first conductivity type, a bottom confining layer of the first conductivity type, an active layer capable of emitting light spontaneously under forward bias conditions, a top confining layer of a second conductivity type, said top and bottom confining layers and the active layer forming an optical cavity of the LED, and a semiconductor contact layer of the second conductivity type, said top electrode is in contact with an upper surface of said contact layer forming an ohmic contact with the contact layer, wherein said LED further comprises: a bottom mirror and a top mirror on opposite sides of said optical cavity and forming a Fabry-Perot resonant cavity, said bottom mirror is located between the bottom confining layer and the substrate and is a high reflectivity mirror (R B ≧99%), and said top electrode comprises an annular thin metal layer overlying the contact layer, and said top mirror comprises a stack of a plurality of pairs of high index of refraction and low index of refraction layers, said stack overlying that surface of the contact layer which is exposed in the central aperture of the annular metal layer and partially overlapping an edge of the annular metal layer adjacent said aperture, the reflectivity, R T , of the top mirror being 25%≦R T ≦99%, preferably 80%≦R T ≦99%.

Claim 22

Dependent Claim 43 words

The LED of claim 17, in which said annular metal layer is Ag ranging from 50 to 300 nm in thickness, with an outer diameter ranging from 10 μm. to 100 μm and an inner diameter ranging from 5 μm to 50 μm.

Claim 23

Dependent Claim 48 words

The LED of claim 18, in which said stack included from 2 to 20 pairs of high/low index material selected from GaP/borosilicate and ZnS/CaF 2 , each layer in the stack being λ/4n thick, said stack overlapping a 5 to 50 μm wide strip of said top electrode.

Claim 24

Dependent Claim 80 words

The LED of claim 17, in which said bottom mirror is a multilayer distributed Bragg reflector (DBR) mirror comprising a plurality of pairs of semiconductor layers, one layer in each pair having an index of refraction which is higher than the index of refraction of the other layer in the pair, each layer being λ/4n thick, wherein λ is a spontaneous emission wavelength of the active layer and n is the refractive index of the material of the respective layers.

Claim 25

Dependent Claim 24 words

The LED of claim 17, in which said structure is an Al x Ga 1-x As/GaAs system with x ranging from 0 to 1.

Claim 26

Dependent Claim 42 words

The LED of claim 20, in which said active layer is GaAs, said low refractive index material comprises AlAs and said high refractive material is selected from GaAs,Al 0 .05 Ga 0 .95 As and Al 0 .14 Ga 0 .86 As.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1996-07-05	1997-01-04	1997-07-06	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2000-07-05	2001-01-04	2001-07-06	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2004-07-05	2005-01-04	2005-07-06	$7700.00	Window Closed / Lapsed

Light emitting diode

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