TWI495151B - Light-emitting device - Google Patents

Description

Light-emitting element

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of fabricating a light-emitting element, and more particularly to a method of forming a highly reflective Bragg reflection structure using a wet oxygen process to increase the brightness of a light-emitting element.

At present, the growth substrate used for the aluminum gallium indium phosphide LED is a gallium arsenide substrate, and the disadvantage is that when the light generated by the active layer is incident on the gallium arsenide substrate, the arsenic is incident due to the small energy gap. The light of the gallium substrate is absorbed to affect the light extraction efficiency.

In order to solve the above disadvantages, a Bragg Reflector (DBR) is usually added to the gallium arsenide substrate to reflect the light incident on the gallium arsenide substrate and reduce the absorption of the gallium arsenide substrate. However, such DBR reflection The structure is effective only for light energy that is closer to the vertical incidence of the gallium arsenide substrate, and the reflectance is only 80%, and the wavelength range of the reflected light is small, so the effect is not large.

The present invention provides a method of fabricating a light-emitting device, comprising: providing a substrate; forming a first Bragg reflection structure on the substrate; forming a second Bragg reflection structure on the first Bragg reflection structure; forming a light-emitting structure a second Bragg reflection structure; forming a window layer on the light-emitting structure; forming a current spreading layer on the window layer; providing a wet oxygen process system; respectively forming an oxidation region in the first Bragg reflection structure and the second Prague a reflective structure in which an oxidized region is reacted in a wet oxygen process system; and an electrode is formed over the current spreading layer.

The present invention provides a method of fabricating a light-emitting element, wherein a first Bragg reflection structure is formed by stacking a plurality of first semiconductor layers and a plurality of second semiconductor layers; the second Bragg reflection structure is composed of a plurality of third semiconductor layers and A plurality of fourth semiconductor layers are formed by alternately stacking.

The invention provides a method for manufacturing a light-emitting element, wherein the first Prague inverse The radiation structure and the second Bragg reflection structure are highly reflective and have a current limiting effect.

The invention discloses a light emitting element structure and a manufacturing method thereof. In order to make the description of the present invention more detailed and complete, reference is made to the following description in conjunction with the drawings of Figures 1 through 4.

First, as shown in FIG. 1, the light-emitting device of the present invention has a structure in which a first Bragg reflection structure 2 and a second Bragg reflection structure 2 are sequentially grown by an MOCVD method on an n-type gallium arsenide (GaAs) substrate 1. ', a first conductive semiconductor layer 3, a light-emitting structure 4, a second conductive semiconductor layer 5, and a window layer 6. The first Bragg reflection structure 2 is formed by stacking a plurality of first semiconductor layers 2a and a plurality of second semiconductor layers 2b; the second Bragg reflection structure 2' is composed of a plurality of third semiconductor layers 2a' and a plurality of The four semiconductor layers 2b' are formed by alternate stacking. The first semiconductor layer 2a and the third semiconductor layer 2a' are easily oxidized in the wet oxygen process system because of the high aluminum content; relatively, the second semiconductor layer 2b and the fourth semiconductor layer 2b' are low in aluminum content. Therefore, it is not easy to generate an oxidation reaction in the wet oxygen process system. The first Bragg reflection structure 2 and the second Bragg reflection structure 2' may be composed of a high aluminum content aluminum gallium arsenide (AlGaAs)/low aluminum content aluminum gallium indium arsenide (AlGaInP), and a high aluminum content aluminum gallium arsenide ( AlGaAs) / low aluminum content aluminum gallium arsenide (AlGaAs), high aluminum content aluminum indium phosphide (AlInP) / low aluminum content aluminum gallium indium arsenide (AlGaInP), high aluminum content aluminum arsenide (AlAs) / low aluminum content Aluminum gallium indium phosphide (AlGaInP), or high aluminum content aluminum arsenide (AlAs) / low aluminum content Aluminium gallium arsenide (AlGaAs) alternating stacking; high aluminum content compounds (such as high aluminum content aluminum gallium arsenide (AlGaAs), high aluminum content aluminum gallium arsenide (AlGaAs), high aluminum content aluminum indium phosphide ( The aluminum content in AlInP)) is greater than 0.6, and the constituent materials of the first Bragg reflection structure 2 and the second Bragg reflection structure 2' are different. For example, the first Bragg reflection structure 2 is composed of a high aluminum content aluminum gallium arsenide (AlGaAs)/low aluminum content aluminum gallium indium arsenide (AlGaInP), and the second Bragg reflection structure 2' is composed of a high aluminum content aluminum arsenide. Gallium (AlGaAs) / low aluminum content aluminum gallium arsenide (AlGaAs). Each of the first Bragg reflection structure 2 and the second Bragg reflection structure 2' has a thickness of λ/4n, where λ is the emission wavelength of the light-emitting element, and n is the refractive index. The composition of the first Bragg reflection structure 2 and the second Bragg reflection structure 2' are different, and the refractive index thereof is also different, whereby the reflectance of the formed Bragg reflection structure is not only improved compared to the reflectance of the conventional Bragg reflection structure, and The wavelength of the reflection covers a wider range than the conventional Bragg reflection structure.

The first conductive semiconductor layer 3, the light emitting structure 4, and the second conductive semiconductor layer 5 may be formed of an aluminum gallium indium phosphide compound, and the first conductive semiconductor layer 3 and the second conductive semiconductor layer 5 are opposite in conductivity, for example The first conductive semiconductor layer 3 is formed of an n-type aluminum gallium indium compound, and the second conductive semiconductor layer 5 is formed of a p-type aluminum gallium indium compound. Forming a p-type gallium phosphide window layer 6 having a thickness of at least 30 μm on the second conductive semiconductor layer 5, the function of which can increase the efficiency of light extraction from the side of the light-emitting element and improve the current distribution; Forming a current spreading layer 7 on the layer 6 by evaporation, the function of which is to increase the current distribution effect, and the constituent material is one or more materials selected from the group consisting of indium tin oxide, cadmium tin oxide, A group consisting of antimony tin oxide, indium zinc oxide, zinc aluminum oxide, and zinc tin oxide.

The structure formed by the above steps is from the upper side to the first Bragg reflection structure 2 from the current spreading layer 7, and the surface of the gallium arsenide (GaAs) substrate 1 is exposed to form a scribe line 10. The component structure after the formation of the dicing street 10 is placed in the process tube 14 of the wet oxygen process system shown in Fig. 4 to carry out a wet oxygen process. The wet oxygen process procedure is as follows: the flow rate of nitrogen gas A into the system is controlled by the flow meter 11, and the nitrogen gas A enters a reactor 16 containing water B via the first gas line 13a to generate a nitrogen gas bubble C, and this There is a heater 12 below the reactor 16. The nitrogen and water vapor D formed by the reactor 16 enters the process tube 14 of the built-in element structure via the second stage gas line 13b, wherein the process tube 14 is heated to 300-800 °C. At this time, the plurality of first semiconductor layers 2a (containing a high aluminum content compound) of the first Bragg reflection structure 2 of the light-emitting element 100 and the plurality of third semiconductor layers 2a' of the second Bragg reflection structure 2' (containing a high aluminum content compound) ) an oxidation reaction with heated gas + water vapor D, respectively. The oxidation reaction starts from the side walls of the first semiconductor layer 2a and the third semiconductor layer 2a' (containing the high aluminum content compound) and the two side regions close to the scribe line 10, thereby forming the aluminum oxide (Al _x O _y ) layers 2c and 2c. And an unoxidized high aluminum content compound; wherein the alumina (Al _x O _y ) layers 2c and 2c' have a refractive index (n = 1.6) lower than that of the first semiconductor layer 2a and the third semiconductor layer 2a' Insulator. The gas remaining after the last oxidation reaction is discharged into the exhaust system 15 by the third-stage gas line 13c. The faster the oxidation reaction rate is as the temperature of the process tube 14 is higher, and the faster the aluminum content of the first semiconductor layer 2a and the third semiconductor layer 2a' is higher. Finally, a second electrode 8 and a first electrode 9 are formed on the current spreading layer 7 and under the gallium arsenide (GaAs) substrate 1, respectively, to form a structure of a light-emitting element 100, as shown in FIG. 3 is a top view of the light-emitting element 100 showing that the outer edge region of the light-emitting element 100 forms aluminum oxide (Al _x O _y ) layers 2c and 2c', and the inner side is the first semiconductor layer 2a and the third semiconductor which do not generate an oxidation reaction. Layer 2a'.

Since the first and second semiconductor layers 2a and 2a of the first Bragg reflection structure 2 and the second Bragg reflection structure 2' are reacted by a wet oxygen process to form aluminum oxide (Al _x O _y ) layers 2c and 2c' and After the oxidized high aluminum content compound, the value of the refractive index of the alumina (Al _x O _y ) layer is smaller than that of the first semiconductor layer 2a and the third semiconductor layer 2a'(n>3), and the Bragg reflection structure formed is The reflectance (close to 100%) is higher than the conventional Bragg structure reflectance (80%), and the wavelength coverage is wider than the conventional Bragg reflection structure. Since the aluminum oxide (Al _x O _y ) layers 2c and 2c' are an insulating region, current flows through the regions of the unoxidized high aluminum content compounds 2a and 2a', that is, the current is in the first Bragg reflection structure 2 and the second The Bragg reflection structure 2' is confined to a specific area.

The examples of the invention are intended to be illustrative only and not to limit the scope of the invention. Any changes or modifications of the present invention to those skilled in the art will be made without departing from the spirit and scope of the invention.

1‧‧‧Substrate

2‧‧‧First Bragg reflection structure

2a‧‧‧First semiconductor layer

2b‧‧‧second semiconductor layer

2c‧‧‧ Alumina layer

2'‧‧‧second Bragg reflection structure

2a’‧‧‧ Third semiconductor layer

2b’‧‧‧ fourth semiconductor layer

2c’‧‧‧ Alumina layer

3‧‧‧First conductive semiconductor layer

4‧‧‧Lighting structure

5‧‧‧Second conductive semiconductor layer

6‧‧‧Window layer

7‧‧‧current distribution layer

8‧‧‧second electrode

9‧‧‧First electrode

10‧‧‧ cutting road

11‧‧‧ Flowmeter

12‧‧‧heater

13, 13a, 13b, 13c‧‧‧ gas pipeline

14‧‧‧Processing furnace tube

15‧‧‧Exhaust system

16‧‧‧Reactor

100‧‧‧Lighting elements

A‧‧‧nitrogen

B‧‧‧Water

C‧‧‧ nitrogen bubbles

D‧‧‧Nitrogen and water vapor

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing the structure of a light-emitting element before wet oxygen processing according to the present invention.

Figure 2 is a cross-sectional view showing the structure of the light-emitting element after the wet oxygen process disclosed in the present invention. Schematic diagram.

Fig. 3 is a top view showing the structure of the light-emitting element after the wet oxygen process disclosed in the present invention.

Figure 4 is a schematic view of the wet oxygen process system disclosed in the present invention.

1‧‧‧Substrate

2‧‧‧First Bragg reflection structure

2a‧‧‧First semiconductor layer

2b‧‧‧second semiconductor layer

2c‧‧‧ Alumina layer

2'‧‧‧second Bragg reflection structure

2a’‧‧‧ Third semiconductor layer

2b’‧‧‧ fourth semiconductor layer

2c’‧‧‧ Alumina layer

3‧‧‧First conductive semiconductor layer

4‧‧‧Lighting structure

5‧‧‧Second conductive semiconductor layer

6‧‧‧Window layer

7‧‧‧current distribution layer

8‧‧‧second electrode

9‧‧‧First electrode

10‧‧‧ cutting road

100‧‧‧Lighting elements

Claims (9)

A method of fabricating a light emitting device, comprising: providing a substrate; forming a first Bragg reflection structure on the substrate, wherein the first Bragg reflection structure is stacked by a plurality of first semiconductor layers and a plurality of second semiconductor layers Forming a second Bragg reflection structure on the first Bragg reflection structure, wherein the second Bragg reflection structure is formed by alternately stacking a plurality of third semiconductor layers and a plurality of fourth semiconductor layers; forming a light emission a structure is disposed on the second Bragg reflection structure; a window layer is formed on the light emitting structure; a current spreading layer is formed on the window layer; and a wet oxygen process is performed to the first Bragg reflection structure and the The second Bragg reflection structure forms an oxidized region; and an electrode is formed over the current spreading layer; wherein a constituent material of the second Bragg reflector structure is different from a constituent material of the first Bragg reflector structure. The method of manufacturing a light-emitting device according to claim 1, wherein the oxidized region is formed by oxidizing the plurality of first semiconductor layers of the first Bragg reflection structure. The method of manufacturing a light-emitting device according to claim 1, wherein the oxidized region is formed by oxidizing the plurality of third semiconductor layers of the second Bragg reflection structure. The method for manufacturing a light-emitting device according to claim 1, wherein the first semiconductor layer/second semiconductor layer forming the first Bragg reflection structure is sequentially composed of a high aluminum content aluminum gallium arsenide (AlGaAs)/low aluminum Aluminium gallium indium arsenide (AlGaInP), high aluminum content aluminum gallium arsenide (AlGaAs) / low aluminum content aluminum gallium arsenide (AlGaAs), high aluminum content aluminum indium phosphide (AlInP) / low aluminum content aluminum phosphide Indium (AlGaInP), high aluminum content aluminum arsenide (AlAs) / low aluminum content aluminum gallium indium (AlGaInP), or high aluminum content aluminum arsenide (AlAs) / low aluminum content aluminum gallium arsenide (AlGaAs) alternately stacked And/or the third semiconductor layer/fourth semiconductor layer of the second Bragg reflection structure is sequentially composed of high aluminum content aluminum gallium arsenide (AlGaAs)/low aluminum content aluminum gallium indium arsenide (AlGaInP), high aluminum Aluminum gallium arsenide (AlGaAs) / low aluminum content aluminum gallium arsenide (AlGaAs), high aluminum content aluminum indium phosphide (AlInP) / low aluminum content aluminum gallium indium arsenide (AlGaInP), high aluminum content aluminum arsenide ( AlAs) / low aluminum content aluminum gallium indium arsenide (AlGaInP), or high aluminum content aluminum arsenide (AlAs) / low aluminum content aluminum gallium arsenide (AlGaAs) alternate stack. The method for producing a light-emitting device according to claim 4, wherein the aluminum content in the high aluminum content compound is more than 0.6. The method for producing a light-emitting device according to claim 1, wherein the wet oxygen process temperature is 300 to 800 °C. The method for producing a light-emitting device according to claim 6, wherein the wet oxygen process is carried out in an environment having water vapor. The method of manufacturing a light-emitting device according to claim 1, wherein the oxidized region is an insulating layer. The method for producing a light-emitting device according to claim 1, wherein the oxidized region is alumina (Al _x O _y ).