CN211088297U - High-brightness light-emitting diode - Google Patents

Abstract

The utility model discloses a high-brightness light-emitting diode. The light-emitting diode comprises a semiconductor substrate and a light-emitting region, the semiconductor substrate is made of gallium arsenide material, and the light-emitting region is sequentially composed of a heavily doped GaAs contact layer and an AlGaInP upper cladding layer. , an AlGaInP active layer, an AlGaInP lower cladding layer, an AlAs etching stop layer and a GaAs buffer layer, and the GaAs buffer layer contacts the semiconductor substrate. The utility model realizes a light-emitting diode with a metal coating reflecting permanent substrate, which effectively and reliably ensures the brightness of the light-emitting diode.

Description

A high-brightness light-emitting diode

technical field

The utility model relates to a light emitting diode (LED) technology with a metal coating reflective permanent substrate.

Background technique

A cross-sectional view of a conventional light-emitting diode is shown in FIG. 1 . The light-emitting diode 100 includes a semiconductor substrate 102 , a first ohmic contact electrode 101 formed on the back side of the semiconductor substrate 102 , a light-emitting region 103 formed on the semiconductor substrate 102 , The second ohmic contact electrode 106 formed on the light emitting region 103 . The light-emitting region 103 is composed of a p-type region and an n-type region, and is grown on the gallium arsenide (GaAs) substrate 102. Due to the current crowding effect, the emission angle of light is limited, and the light absorption of the substrate is limited, which makes the illuminance of the light-emitting diode. Not strong. The lattice constants of most of the light-emitting regions 103 match the lattice constants of the gallium arsenide substrate, that is, the visible light emitting diodes are fabricated directly on the gallium arsenide substrate 102 . Since the energy gap of gallium arsenide is 1.43eV smaller than that of visible light, and the light emitted from the diode is isotropic, part of the light enters the substrate and is absorbed by the gallium arsenide substrate, making the illumination of the light-emitting diode not strong .

In order to enhance the brightness of the diode, there are two solutions currently used:

As shown in FIG. 2 , the structure of the light emitting diode 200 is composed of the transparent window layer 204 grown on the light emitting diode 100 shown in FIG. 1 . The transparent window layer reduces the current crowding effect of the traditional light emitting diode and increases the current Divergence. Suitable materials for the transparent window layer 204 include GaP, GaAsP, AlGaAs, etc., whose energy gap is larger than the material in the AlGaInP light-emitting region. In this case, the critical angle of the emitted light can be increased, the current crowding effect can be reduced, and the illumination of the light-emitting diode can be enhanced. . In terms of electrical characteristics, since the material on the uppermost layer of the transparent window layer 204 and the AlGaInP light generating region has a heterojunction, the difference in energy gap causes the forward bias voltage vf of the light emitting diode to increase, and as a result, the power consumption of the light emitting diode Increase.

As shown in FIG. 3 , the light emitting diode includes a semiconductor substrate 302 , a lower multilayer reflector 305 formed on the semiconductor substrate 302 , a light generating region 303 formed on the lower multilayer reflector 305 , and a light generating region 303 formed on the lower multilayer reflector 305 . The upper multilayer reflector 304 , the first ohmic contact electrode 306 formed on the upper multilayer reflector 304 , and the second ohmic contact electrode 301 formed on the back side of the semiconductor substrate 302 . Light transmitted to the substrate is back-reflected by a semiconductor multilayer reflector, a distributed Bragg reflector (DBR), so that it is emitted from the light-emitting diode, thereby increasing illumination. In the light-emitting diode of the prior art, the multilayer reflector 305 in the lower layer reflects 90% of the light emitted by the light-emitting area to the light-absorbing substrate, and the multilayer reflector in the upper layer guides the light to the light-emitting diode. the upper surface, thereby increasing the illuminance of the light. Therefore, the problem of light absorption by the substrate is alleviated, and the problems related to the limited critical angle are also improved, but since the multilayer reflector has many heterojunctions, the effect of the energy gap difference is increased, which increases the Forward bias voltage Vf. For oblique incident light (d2, d3, and d4 as shown in Figure 3), the reflectivity decreases, which limits the improvement of LED illumination in the visible light band, while the DBR structure increases the difficulty of thin film epitaxial growth and increases the manufacturing cost . Therefore, the light absorption problem of the substrate can be completely solved, since the transparent substrate disclosed in the prior art is composed of slits, a thick slit window layer is required to properly handle the thin epitaxial layer. Therefore, after removing the gallium arsenide substrate, because of its thicker window layer, the LED device is relatively thin, which makes the light emitting diode easier to break and more difficult to manufacture.

Utility model content

The technical problem to be solved by the utility model is to realize an LED structure with higher illuminance and color tone.

In order to achieve the above purpose, the technical scheme adopted by the present invention is as follows: a high-brightness light-emitting diode, the light-emitting diode comprises a semiconductor substrate and a light-emitting region, the semiconductor substrate is made of gallium arsenide, and the light-emitting region is sequentially composed of heavily doped gallium arsenide. A hetero-GaAs contact layer, an AlGaInP upper cladding layer, an AlGaInP active layer, an AlGaInP lower cladding layer, an AlAs etching stop layer and a GaAs buffer layer are formed, and the GaAs buffer layer contacts the semiconductor substrate.

The light emitting region has a p/i/n structure and/or an n/i/p structure, and the AlAs etch stop layer serves as an etch stop layer.

The thickness of the heavily doped GaAs contact layer is 0.1-0.3mm, the thickness of the AlGaInP upper cladding layer is 0.2-1mm, the thickness of the AlGaInP active layer is 0.2-1mm, and the thickness of the AlGaInP lower cladding layer is 0.2-1 mm, the thickness of the AlAs etch stop layer is 0.1 mm, and the thickness of the GaAs buffer layer is 0.1 mm.

The beneficial effects of the present utility model are as follows:

(1) Use permanent substrates with mirrors instead of traditional light-absorbing substrates (such as GaAs) or colored substrates (such as GaP), the optical properties of the substrate are irrelevant, because the light is reflected before reaching the substrate , thus improving the illuminance and tone of the LED;

(2) The utility model is heat-treated at a relatively low temperature (about 300-450° C.) for about 5-10 minutes to provide bonding energy, without affecting the original p-n junction of the LED, and impurity morphology does not occur at a lower temperature pollution and redistribution;

(3) The feature of the bonding tool of the present invention is that stainless steel screws are used instead of quartz sleeves. Because the thermal expansion coefficient of stainless steel is greater than that of graphite, the stainless steel exerts axial pressure on the wafer during high-temperature bonding.

Description of drawings

Below is a brief description of the content expressed in each drawing in the description of the present utility model and the marks in the drawing:

1 is a cross-sectional view of a background art light-emitting diode;

2 is a cross-sectional view of a conventional light emitting diode having a transparent window layer;

Figure 3 shows a light-emitting diode with a conventional multilayer reflective structure;

4A-4D are the manufacturing flow charts of the light-emitting diodes of the present invention, by bonding the LED elements on the metal-coated reflective permanent substrate;

5 is a cross-sectional view of an LED element of an embodiment of the present invention;

Fig. 6 is the flow chart that the LED element of the present invention is attached to the permanent substrate with reflector;

7 is a cross-sectional view of the wafer bonding tool of the present invention.

Detailed ways

Below with reference to the accompanying drawings, through the description of the embodiments, the specific implementation of the present utility model, such as the shape and structure of each component involved, the mutual position and connection relationship between each part, the function and working principle of each part, manufacturing The process, operation and use method, etc., are further described in detail to help those skilled in the art to have a more complete, accurate and in-depth understanding of the utility model concept and technical solution of the present invention.

In the present invention, LED elements are first grown on a temporary substrate, and the LED elements are also attached to a permanent substrate with a metal reflector. The temporary substrate is then removed so that the light emitted by the light emitting diode element is not absorbed by the substrate, so as to enhance the illuminance of the emitted light. The light emitting diode element using the technology of the present invention is shown in FIG. 5 .

The LED element includes a light emitting region 52 and a gallium arsenide substrate 53 . The light emitting area includes a heavily doped GaAs contact layer 521 with a thickness of 0.1-0.3 mm, an AlGaInP upper cladding layer 522 with a thickness of 0.2-1 mm, an AlGaInP active layer 523 with a thickness of 0.2-1 mm, and an AlGaInP lower cladding layer with a thickness of 0.2-1 mm Layer 524, AlAs etch stop 525 and GaAs buffer layer 526 with a thickness of 0.1 mm. The LED light emitting region 52 has a p/i/n structure and or an n/i/p structure. AlAs is used as an etch stop layer.

Figure 6 shows a process flow diagram for bonding an LED element to a metal-coated reflective permanent substrate. It is important to note that the temporary substrate is removed after the LED element is bonded to the metal-coated reflective permanent substrate. Thus, the need for thick epitaxial layers is avoided.

The utility model relates to a manufacturing process of an LED element with a metal coating reflecting permanent substrate, comprising the following steps:

(A) Selecting a temporary substrate 42, and growing a light-emitting region 41 on the temporary substrate 42 for forming an LED element as shown in FIG. 4A;

(B) Selecting a permanent substrate 44 coated with a metal mirror 43, and using a metal adhesive to adhere the LED elements to the permanent substrate 44, as shown in Figure 4B;

(C) removing the temporary substrate 42 by mechanical grinding or chemical etching, as shown in FIG. 4C;

(D) Fabrication of planar LED elements with permanent substrates;

(E) forming ohmic contact electrodes 411 and 412 on the planar LED element, as shown in FIG. 4D;

(F) Etch the light emitting region onto the metal bond, if the material of the metal bond is the same as that of the metal contact electrode 411, such as gold and beryllium alloy (AuBe), replace the ohmic contact electrode 411 with the metal bond.

The temporary substrate 42 is selected from GaAs or InP, and the permanent substrate 44 is selected from materials with high thermal conductivity, such as Si, GaAs and Al2O3. SiC, GaP, BN, AlN, glass, quartz or metals can also be used as permanent substrate 44 . The optical properties of the permanent substrate 44 are irrelevant because light is reflected before reaching the substrate. Metal binders are iodine, tin (Sn), aluminum (Al), gold (Pt), platinum (titanium), zinc (Ti), zinc (n), silver (Ag), palladium (Pd), gold beryllium ( AuBe), gold germanium nickel (AuGeNi), lead tin (Pb-Sn) alloy, etc.

The etchant is formed of hydrochloric acid and phosphoric acid, the LED element can have p/n junction or n/p junction, and an etch stop layer 525 as shown in FIG. 5 is formed between the light emitting region and the substrate to effectively remove the substrate. The material of the etch stop layer is mainly formed of a material that is resistant to the etching solution of the substrate, and is different from the material of the substrate.

The technical details of manufacturing the light-emitting diode are as follows: (1) Before bonding the LED elements (temporary substrate 42, light-emitting region 41) with the permanent substrate 44, the permanent substrate 44 is cleaned first, and the permanent substrate 44 is placed in acetone , the dust on the permanent substrate 44 was removed by cleaning with an ultrasonic cleaner for 5 minutes. If the permanent substrate is not made of any metal or alloy, it is cleaned with sulfuric acid at a temperature of 90-100°C. The organics or heavy metals on the permanent substrate 44 are removed in about 10 minutes. A metal mirror (metal binder) 43 is deposited by thermal or electron gun evaporation, the metal serving as both the bonding layer and the mirror surface. In an embodiment of the present invention, the detailed structure of the LED element is shown in FIG. 5 .

(2) Before bonding the LED element to the permanent substrate, it is first necessary to clean the contamination on the surface of the LED element, put the LED element in acetone, then clean it with an ultrasonic cleaner for 5 minutes to remove dust, and then use a buffered HF Remove the oxide layer on the surface of the LED element.

(3) The cleaned LED element is combined with the permanent substrate 44 coated with the metal bonding agent 43 in air or alcohol, and the structure is shown in FIG. 4A . The LED components and permanent substrate 44 are then placed into a wafer bonding tool as shown in FIG. 7 .

(4) The LED element temporary substrate 42, the light-emitting region 41 and the permanent substrate 44 coated with the metal bonding agent 43 are heat-treated at a temperature of 300-450° C. for about 5-10 minutes, and then naturally cooled, the structure is shown in FIG. 4B Show.

(5) Use an etchant (NH40H:OH2O2) to mechanically grind or chemically etch to remove the temporary GaAs substrate 42 from the processed sample (LED element and permanent substrate coated with metal bond 43), the structure shown in Figure 4C.

(6) The p/n region of the LED element adopts a selective etching process to make a plate, that is, HCl:H3PO4 etches p-type AlGaInP or n-type AlGaInP, and the structure is shown in Figure 4D.

(7) The planar electrodes 411 and 412, that is, ohmic contact electrodes of p-type AlGaInP or n-type AlGaInP are formed.

Figure 6 shows a flow chart for bonding the LED element to the permanent substrate. First, the permanent substrate is cleaned (step 61). Then, the LED wafer is cleaned (step 62). Next, the metal adhesive 43 is evaporated and coated on the permanent substrate using a thermal coater or electron gun (step 63). The LED elements are bonded to the permanent substrate in water, air or alcohol (step 64). The bonding structure (wafer pair) is placed in a wafer bonding tool and thermally processed (step 65), the GaAs temporary substrate is removed from the wafer pair, and then etched into planar LED elements (step 66).

The cross-sectional view of the wafer bonding tool of the present invention is shown in FIG. One wafer pair (ie, the permanent substrate and the LED wafer) 74 is clamped, and due to the different thermal expansion coefficients of the two materials in the wafer bonding tool, the two pieces of the wafer pair are compressed so that they are at a higher fused at the temperature. The feature of the bonding tool of the utility model is that the stainless steel screw is used instead of the quartz sleeve, because the thermal expansion coefficient of the stainless steel is greater than that of the graphite, in the high temperature bonding process, the stainless steel exerts an axial pressure on the wafer.

The present utility model has been exemplarily described above in conjunction with the accompanying drawings. Obviously, the specific implementation of the present utility model is not limited by the above-mentioned methods, as long as various non-substantial improvements made by the method concept and technical solutions of the present utility model are adopted, or If the concept and technical solutions of the present invention are directly applied to other occasions without improvement, they all fall within the protection scope of the present invention.

Claims (2)

1. A high-brightness light-emitting diode comprises a semiconductor substrate and a light-emitting region, wherein the semiconductor substrate is made of gallium arsenide material, and the high-brightness light-emitting diode is characterized in that: the light-emitting region is sequentially composed of a heavily doped GaAs contact layer, an AlGaInP upper cladding layer, an AlGaInP active layer, an AlGaInP lower cladding layer, an AlAs etching stop layer and a GaAs buffer layer, and the GaAs buffer layer is in contact with the semiconductor substrate;

the light emitting region has a p/i/n structure and/or an n/i/p structure, and the AlAs etch stop layer functions as an etch stop layer.

2. A high brightness led according to claim 1, wherein: the thickness of heavily doped GaAs contact layer is 0.1-0.3mm, the thickness of AlGaInP upper cladding layer is 0.2-1mm, the thickness of AlGaInP active layer is 0.2-1mm, the thickness of AlGaInP lower cladding layer is 0.2-1mm, the thickness of AlAs etching stop layer is 0.1mm, and the thickness of GaAs buffer layer is 0.1 mm.

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