CN104916747B - Light emitting element - Google Patents

Abstract

The invention discloses a light-emitting element, comprising: a substrate; a light-emitting stack located above the substrate and capable of emitting light of an infrared (IR) wavelength; and a semiconductor window layer composed of AlGaInP series materials and located between the substrate and the light-emitting stack.

Description

Light emitting element

technical field

The invention relates to a light-emitting element, in particular to an infrared light-emitting element.

Background technique

Light-emitting diodes (Light-Emitting Diodes; LEDs) have good photoelectric properties such as low power consumption, low heat generation, long operating life, shock resistance, small size, fast response speed, and stable output light wavelength, so they are suitable for various purposes.

Among them, infrared light-emitting diodes (Infrared LEDs; IR LEDs) are more and more widely used, from traditional applications in remote controls and monitors, to applications in smart phones and touch panels recently. Since each touch panel relatively uses a relatively large number of infrared light emitting diodes, the price requirement is lower compared to other applications, so it is necessary to reduce the cost of infrared light emitting diodes.

Fig. 1 is a cross-sectional view of an existing infrared light-emitting element. As shown in Fig. 1, the light-emitting element includes a permanent substrate 101, above which there is a light-emitting laminated layer 102 and a metal reflective layer 103 in sequence from top to bottom. A barrier layer 104 and a bonding structure 105 . In addition, a first electrode 106E1 and its extension electrode 106E1' are disposed on the light emitting stack 102, and a second electrode 106E2 is disposed on the permanent substrate 101. The first electrode 106E1, its extension electrode 106E1' and the second electrode 106E2 are used to transmit current. The light-emitting stack 102 can emit light in an infrared band. In terms of manufacturing process, the light-emitting laminated layer 102 of this conventional infrared light-emitting element is originally grown on the growth substrate (not shown in the figure), and then the originally separated light-emitting laminated layer 102 and the permanent substrate 101 are bonded by the bonding structure 105, so it can Before the two are bonded, the metal reflective layer 103 is formed on the light emitting stack 102 and then bonded. However, as mentioned above, when a specific application, such as a touch panel application, requires low cost, the bonding process and the metal reflective layer 103 are the main causes of high cost. In addition, in the application of the touch panel, better side light output is also required to achieve a larger light output angle. In practical applications, it has been found that the above-mentioned existing infrared light emitting elements cannot meet this requirement.

Contents of the invention

In order to solve the above problems, the present invention discloses a light emitting element. The light-emitting element disclosed in the present invention comprises: a substrate; a light-emitting laminate located above the substrate, capable of emitting light of an infrared (IR) wavelength; and a semiconductor window layer, composed of AlGaInP series materials, located between the substrate and the light-emitting laminate between layers.

Description of drawings

FIG. 1 shows a conventional light-emitting element.

FIG. 2 shows a light emitting element according to a first embodiment of the present invention.

FIG. 3 shows the second electrode pattern in the light emitting element of the first embodiment of the present invention.

FIG. 4 shows another pattern of the second electrode in the light emitting device according to the first embodiment of the present invention.

Symbol Description

101 permanent substrate

102 light stack

103 metal reflective layer

104 barrier layer

105 joint structure

106E1 first electrode

106E1' (first electrode's) extension electrode

106E2 Second Electrode

20 substrates

21 buffer layer

22 semiconductor window layer

23 Light Overlay

231 First electrical semiconductor layer

232 luminous layer

232b ₁ , 232b ₂ ,…232 _bn barrier layer

232w ₁ ,232w ₂ ,…232w _n-1 well layer

233 Second electrical semiconductor layer

24 side light extraction layer

25 contact layer

26 first electrode

26a (of the first electrode) extended electrode

27 Second electrode

S1 Substrate bottom surface

S2 Substrate side

S3 Light-emitting element upper surface

Detailed ways

FIG. 2 is a light emitting element of the first embodiment of the present invention. As shown in Figure 2, the light-emitting element includes: a substrate 20; a light-emitting stack 23 located on the substrate 20, which can emit light of an infrared (IR) wavelength; and a semiconductor window layer 22, made of AlGaInP series materials , located between the substrate 20 and the light emitting stack 23 . Wherein, the substrate 20 includes, for example, a gallium arsenide (GaAs) substrate. The infrared (IR) wavelength is between about 750nm and 1100nm. In one embodiment, the infrared (IR) wavelength is greater than 900nm, such as 940nm. The semiconductor window layer 22 is a single layer structure and is in direct contact with the light emitting stack 23 . In the manufacturing process, after the semiconductor window layer 22 is formed, the type or ratio of the gas to be fed can be adjusted on the same machine, so as to form the light-emitting laminated layer 23 subsequently. In one embodiment, the semiconductor window layer 22 includes (Al _x Ga _1-x ) _0.5 In _0.5 P, where x is 0.1˜1. It is worth noting that the light emitting stack 23 has a first refractive index n ₁ , the semiconductor window layer 22 has a second refractive index n ₂ , and the first refractive index n ₁ is greater than the second refractive index n ₂ by at least 0.2. Therefore, for the light of the infrared wavelength emitted by the above-mentioned light-emitting stack 23, it travels from a high refractive index to a low refractive index between the light-emitting stack 23 and the semiconductor window layer 22, plus the first refractive index n1 of the light-emitting stack ₂₃ The difference with the _second refractive index n of the semiconductor window layer 22 makes the light of the infrared wavelength emitted by the light-emitting stack 23 prone to total reflection on the semiconductor window layer 22, that is, the semiconductor window layer 22 provides a reflection of a single-layer structure Mirror function, and compared with the general distributed Bragg reflection structure (DBR), it provides better lateral reflection function. Generally, the distributed Bragg reflective structure (DBR) requires dozens of layers to achieve a certain degree of reflectivity, and its reflective function is limited to a certain range of positive angles, generally between 0° and 17° with the normal of the reflective structure. ; and the present embodiment can only reflect the light of 50-90 degrees with the normal line of the semiconductor window layer 22 through the semiconductor window layer 22 of a single layer structure, and provide better side light output to form a larger light output angle, and Because the light extraction is improved, the overall luminous power is thus increased. In actual testing, the light-emitting elements emitting at 850nm and 940nm were respectively tested. The light-emitting stack 23 of the embodiment of the present invention uses aluminum gallium arsenide (AlGaAs) in the first electrical semiconductor layer 231, and has a first refractive index _{n1approximately} 3.4, the semiconductor window layer 22 is made of (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P, has a second refractive index n ₂ of about 2.98, and the difference between the two refractive index values is about 0.42, which is the same as other conditions, but only the semiconductor window layer 22 is replaced by arsenic Compared with the light-emitting element of aluminum gallium (AlGaAs) (refractive index about 3.4), the luminous power of the 850nm light-emitting element of the embodiment of the present invention is compared from 4.21mW to 4.91mW, an increase of about 17%; the embodiment of the present invention emits light at 940nm The luminous power of the device is increased by about 4% from 5.06mW to 5.27mW. In addition, in terms of manufacturing process and cost, the semiconductor window layer 22 is in direct contact with the light-emitting stack 23 and is a single-layer structure. Compared with the general distributed Bragg reflection structure, the manufacturing process is more simplified and the cost is lower. In terms of thickness, in one embodiment, the thickness of the semiconductor window layer 22 is less than 1 μm to have a good reflection effect.

The light emitting stack 23 includes a first electrical semiconductor layer 231 located on the semiconductor window layer 22; an active layer 232 located on the first electrical semiconductor layer 231; and a second electrical semiconductor layer 233 located on the active layer 232 , wherein the first electrical semiconductor layer 231 is in direct contact with the semiconductor window layer 22 . The first electrical type semiconductor layer 231 , the active layer 232 , and the second electrical type semiconductor layer 233 are formed of III-V group materials. The first electrical type semiconductor layer 231 and the second electrical type semiconductor layer 233 are electrically different. For example, the first electrical type semiconductor layer 231 is an n-type semiconductor layer, while the second electrical type semiconductor layer 233 is a p-type semiconductor layer. When external power is applied, the first electrical type semiconductor layer 231 and the second electrical type semiconductor layer 233 respectively generate carriers (electrons/holes) and recombine in the active layer 232 to generate light. In one embodiment, the first electrical type semiconductor layer 231 is doped with tellurium (Te) or selenium (Se). In one embodiment, the active layer 232 includes a multiple quantum well structure (MQW), and the multiple quantum well structure includes multiple barrier layers, such as barrier layers 232b ₁ , _{232b 2} , . . . Well layers, such as well layers 232w ₁ , 232w ₂ , ... 232w _n-1 , there is a well layer between two adjacent barrier layers, for example, there is a well layer between two adjacent barrier layers 232b ₁ and 232b ₂ 232w ₁ . Among the plurality of barrier layers 232b ₁ , 232b ₂ , ... 232b _n , the barrier layer closest to the first electrical type semiconductor layer 231 (that is, the barrier layer 232b ₁ ) and the barrier layer closest to the second electrical type semiconductor layer 233 One layer (ie barrier layer 232b _n ) does not contain phosphorus (P), while the remaining barrier layers (barrier layers 232b ₂ , . . . 232b _n−1 ) contain phosphorus (P). In one embodiment, the well layers _{232w 1} , 232w ₂ , . Adjust to reach the aforementioned infrared band range. However, since the well layers 232w ₁ , 232w ₂ , ... 232w _n-1 contain indium (In), the lattice constant becomes large, and the above-mentioned barrier layers (barrier layers 232b ₂ , ... 232b _n-1 ) contain phosphorus ( P) can make the lattice constant smaller and adjust the overall lattice constant back to an appropriate range. In one embodiment, the barrier layers 232b ₂ , . . . 232b _n-1 include aluminum gallium arsenide phosphide (AlGaAsP), for example. As mentioned above, the barrier layer (barrier layer 232b ₁ ) closest to the first electrical type semiconductor layer 231 and the barrier layer (barrier layer 232b _n ) closest to the second electrical type semiconductor layer 233 do not contain phosphorus (P ), the lattice constant will not be too small when its thickness is thicker; and the thicker barrier layer 232b ₁ and barrier layer 232b _n can affect the adjacent first electrical type semiconductor layer 231 and the second electrical type semiconductor layer The dopant in 233 has a better diffusion barrier effect. In one embodiment, the barrier layer 232b ₁ and the barrier layer _232bn include aluminum gallium arsenide (AlGaAs), for example.

The light-emitting element of the first embodiment of the present invention also includes a buffer layer 21 located between the substrate 20 and the semiconductor window layer 22, the buffer layer 21 is doped with silicon (Si), for example gallium arsenide (GaAs) doped with silicon (Si). . As mentioned above, the first electrical semiconductor layer 231 is doped with tellurium (Te) or selenium (Se), and the buffer layer 21 is doped with silicon (Si). Such a configuration allows more adjustments in the manufacturing process of the light-emitting element. Elasticity, for example, is the adjustment of lattice constants. In addition, the light-emitting element of the first embodiment of the present invention also includes a lateral light extraction layer 24 located on the light-emitting stack 23, a contact layer 25 located on the lateral light extraction layer 24, and a first electrode 26 disposed on the on the contact layer 25 , and a second electrode 27 is disposed on the substrate 20 . The side light extraction layer 24 is helpful for light extraction, especially because the increase in thickness increases the side light output, so its thickness can be relatively thick, for example, about 5 μm to 30 μm. In one embodiment, the side light extraction layer 24 Contains gallium arsenide (GaAs) doped with zinc (Zn) and has a thickness of about 10 μm. The contact layer 25 is used to form an ohmic contact with the first electrode 26 thereon to reduce the resistance value. In one embodiment, the contact layer 25 includes gallium arsenide (GaAs) doped with zinc (Zn). The side light extraction layer 24 and the contact layer 25 are also gallium arsenide (GaAs) doped with zinc (Zn), which can simplify the configuration of the machine on the manufacturing process, but it should be noted that the side light extraction layer 24 and the contact layer The functions of the layer 25 are different. In order to form an ohmic contact, the zinc (Zn) content in the contact layer 25 is much larger than that of the side light extraction layer 24 to form an ohmic contact. The first electrode 26 may be provided with an extension electrode 26a to facilitate current spreading. It should be noted that, when the infrared wavelength light emitted by the light-emitting stack 23 travels toward the substrate 20 , part of it may still not be totally reflected by the semiconductor window layer 22 . As mentioned above, a larger light output angle may be required for specific applications. Therefore, as shown in the figure, in this embodiment, the second electrode 27 is a patterned electrode. Please refer to FIG. 3 for more detailed description. And FIG. 4, when viewed from the top (top view), the pattern of the second electrode 27 can be, for example, a grid (mesh) as shown in FIG. 3 . FIG. 3 shows a substrate 20 formed with grid-shaped germanium gold (GeAu) second electrode 27; or as shown in Figure 4, the pattern of the second electrode 27 can be a plurality of circles, and Figure 4 shows that a gallium arsenide (GaAs) substrate 20 is formed with A plurality of circular germanium-gold (GeAu) second electrodes 27; the second electrode 27 patterned in this way forms a scattering center for the light that is not totally reflected in the semiconductor window layer 22, which can increase the scattering and make the light output angle smaller big. In addition, roughening (not shown in the figure) can also be selectively formed on the lower surface S1 of the substrate 20 where the second electrode 27 is not provided, which can also increase the scattering of light and make it easy for light to exit from the side of the substrate 20. Even the substrate The side surface S2 of 20 and the upper surface S3 of the light emitting element may also be roughened (not shown in the figure) where the first electrode 26 is not provided.

The above-mentioned embodiments are only illustrative to illustrate the principles and effects of the present invention, and are not intended to limit the present invention. Anyone with ordinary knowledge in the technical field of the present invention can modify and change the above-mentioned embodiments without violating the technical principle and spirit of the present invention. Therefore, the protection scope of the present invention is as listed in the appended claims.

Claims (15)

1. A light-emitting element, comprising: Substrate; The light-emitting stack is located above the substrate and can emit light of an infrared (IR) wavelength. The light-emitting stack includes a first electrical semiconductor layer and a second electrical semiconductor layer, wherein the first electrical semiconductor layer is arsenic aluminum gallium (AlGaAs) material; and The semiconductor window layer is composed of AlGaInP series materials and is located between the substrate and the light-emitting laminated layer. The semiconductor window layer is a single-layer structure and is in direct contact with the first electrical semiconductor layer. 2. The light emitting device as claimed in claim 1, wherein the substrate comprises gallium arsenide (GaAs). 3. The light-emitting element according to claim 1, wherein the light-emitting stack has a first refractive index n ₁ , the semiconductor window layer has a second refractive index n ₂ , the first refractive index n ₁ is greater than the second refractive index n ₂ is at least 0.2 or more. 4. The light-emitting device according to claim 1, wherein the semiconductor window layer comprises (Al _x Ga _1-x ) _0.5 In _0.5 P, wherein x is 0.1˜1. 5. The light emitting device according to claim 1, wherein the light emitting stack comprises: The active layer is located between the first electrical semiconductor layer and the second electrical semiconductor layer. 6. The light-emitting device as claimed in claim 5, wherein the active layer comprises a multiple quantum well structure (MQW), and the multiple quantum well structure comprises a plurality of barrier layers and a well layer is located between two adjacent barrier layers Between layers, wherein among the plurality of barrier layers, the barrier layer closest to the first electrical type semiconductor layer and the barrier layer closest to the second electrical type semiconductor layer do not contain phosphorus (P), and the rest of the barrier layers The barrier layer contains phosphorus (P). 7. The light emitting device of claim 1, further comprising a silicon (Si)-doped gallium arsenide (GaAs) buffer layer between the substrate and the semiconductor window layer. 8. The light emitting device according to claim 1, further comprising a lateral light extraction layer located on the light emitting stack. 9. The light-emitting device as claimed in claim 1, wherein the thickness of the semiconductor window layer is less than 1 μm. 10. The light emitting device as claimed in claim 1, wherein the infrared (IR) wavelength is between about 750 nm to 1100 nm. 11. The light emitting device as claimed in claim 1, wherein the first electrical semiconductor layer is doped with tellurium (Te) or selenium (Se). 12. The light emitting device as claimed in claim 1, further comprising a patterned bottom electrode located under the substrate. 13. The light emitting device as claimed in claim 12, wherein the pattern of the bottom electrode is a mesh or a plurality of circles. 14. The light-emitting device as claimed in claim 1, wherein the infrared (IR) wavelength is greater than 900 nm, and the thickness of the semiconductor window layer is less than 1 μm. 15. The light emitting device as claimed in claim 1, wherein the light emitting device does not have any distributed Bragg reflective structure (DBR) between the substrate and the light emitting stack.