CN110854249A - Light emitting element - Google Patents

Abstract

The invention discloses a light-emitting element, comprising: a substrate; a light-emitting laminate disposed above the substrate and capable of emitting light of Infrared (IR) wavelength; and a semiconductor window layer composed of AlGaInP series material and located between the substrate and the light emitting laminated layer.

Description

light-emitting element

This application is a divisional application of a Chinese invention patent application (application number: 201410094885.6, application date: March 14, 2014, invention name: light-emitting element).

technical field

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

Background technique

Light-Emitting Diode (LED) has good optoelectronic properties such as low energy consumption, low heat generation, long operating life, shock resistance, small size, fast response speed and stable output light wavelength, so it is suitable for various purposes.

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

FIG. 1 is a cross-sectional view of a conventional infrared light-emitting device. As shown in FIG. 1, the light-emitting device includes a permanent substrate 101 with a light-emitting stack 102, a metal reflective layer 103, 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 and 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 wavelength band. In the manufacturing process, the light-emitting stack 102 of the conventional infrared light-emitting device is originally grown on a growth substrate (not shown), and the bonding structure 105 is used to bond the light-emitting stack 102 and the permanent substrate 101 that were originally separated. Before joining the two, the metal reflective layer 103 is formed on the light emitting stack 102 before joining. However, as mentioned above, when a specific application, such as the application of a touch panel, requires low cost, the above-mentioned bonding fabrication process and the metal reflective layer 103 are the main reasons for the high cost. In addition, in the application of the touch panel, better side emitting light is also required to achieve a larger light emitting angle. In practical applications, it has been found that the above-mentioned existing infrared light emitting elements are difficult to meet this requirement.

SUMMARY 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 stack is located above the substrate and can emit light of an infrared (IR) wavelength; and a semiconductor window layer, which is composed of AlGaInP series materials, is located on the substrate and the light-emitting stack 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 a second electrode pattern in the light-emitting element according to the first embodiment of the present invention.

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

Symbol Description

101 Permanent substrate

102 Light Emitting Stack

103 Metal reflective layer

104 Barrier layer

105 Joint structure

106E1 first electrode

106E1’ (first electrode) extension electrode

106E2 second electrode

20 substrate

21 buffer layer

22 Semiconductor window layer

23 Light Emitting Stacks

231 first electrical type semiconductor layer

232 light-emitting layer

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

232w ₁ , 232w ₂ ,…232w _n-1 well layer

233 second electrical type semiconductor layer

24 Lateral light extraction layer

25 Contact layer

26 First electrode

26a (of the first electrode) extension electrode

27 Second electrode

S1 substrate lower surface

S2 substrate side

S3 light-emitting element upper surface

Detailed ways

FIG. 2 is a light-emitting element according to the first embodiment of the present invention. As shown in FIG. 2, the light-emitting element includes: a substrate 20; a light-emitting stack 23 located above the substrate 20, which can emit light of an infrared (IR) wavelength; and a semiconductor window layer 22, which is composed of AlGaInP series materials , located between the substrate 20 and the light emitting stack 23 . The substrate 20 includes, for example, a gallium arsenide (GaAs) substrate. The wavelength of the infrared (IR) is between about 750 nm and 1100 nm. In one embodiment, the wavelength of the infrared (IR) is greater than 900 nm, such as 940 nm. 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 proportion of the gas introduced can be adjusted on the same machine, so as to form the light emitting stack 23 . 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 should be noted 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 or more. Therefore, for the light of the infrared wavelengths emitted by the light-emitting stack 23, the light-emitting stack 23 and the semiconductor window layer 22 progress from a high refractive index to a low refractive index, and the first refractive index n ₁ of the light-emitting stack 23 is added. The difference between the second refractive index n ₂ of the semiconductor window layer 22 and the second refractive index n 2 of the semiconductor window layer 22 makes the light of the infrared wavelength emitted by the light emitting stack 23 prone to total reflection in the semiconductor window layer 22 , that is, the semiconductor window layer 22 provides a single-layer structure of reflection Mirror function, and compared to the general distributed Bragg reflector (DBR), it provides better lateral reflection function. Generally, the distributed Bragg reflection structure (DBR) needs dozens of layers to achieve a certain degree of reflectivity, and its reflection function is limited to a certain range of angles in the forward direction, generally between 0 degrees and 17 degrees with the normal of the reflection structure. In this embodiment, only the semiconductor window layer 22 with a single-layer structure can reflect the light of 50 degrees to 90 degrees with the normal line of the semiconductor window layer 22, so as to provide better side light out to form a larger light out angle, and Because of the improved light extraction, the overall luminous power increases accordingly. In the actual test, the light-emitting elements of 850 nm and 940 nm are tested respectively. The light-emitting stack 23 of the embodiment of the present invention uses aluminum gallium arsenide (AlGaAs) in the first electrical type semiconductor layer 231, and has a first refractive index n ₁ about 3.4, the semiconductor window layer 22 adopts (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 uses arsenic instead Compared with the light-emitting element of aluminum gallium (AlGaAs) (refractive index of about 3.4), the light-emitting power of the 850nm light-emitting element of the embodiment of the present invention is increased from 4.21mW to 4.91mW, an increase of about 17%; the light-emitting power of the embodiment of the present invention is 940nm. The luminous power of the device is thus increased from 5.06mW to 5.27mW, an increase of about 4%. In addition, in terms of manufacturing process or cost, the semiconductor window layer 22 is in direct contact with the light emitting stack 23 and is a single-layer structure, so the manufacturing process is simpler and the cost is lower compared to the general distributed Bragg reflector structure. 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 type semiconductor layer 231 on the semiconductor window layer 22 ; an active layer 232 on the first electrical type semiconductor layer 231 ; and a second electrical type semiconductor layer 233 on the active layer 232 above, wherein the first electrical type 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, and the second electrical type semiconductor layer 233 is a p-type semiconductor layer. When an external power supply is used, 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) including a plurality of barrier layers, such as barrier layers 232b ₁ , 232b ₂ , . . . _232bn , and one or more 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 , . . . _232bn , the barrier layer closest to the first electrical type semiconductor layer 231 (ie, 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), and the remaining barrier layers (barrier layers 232b ₂ , . . . 232b _n-1 ) contain phosphorus (P). In one embodiment, the well layers 232w ₁ , 232w ₂ , . . . 232w _n-1 include indium gallium arsenide (InGaAs), wherein the content of indium is about 2%˜30% and depends on the wavelength of light emitted by the light emitting stack 23 . Adjust to reach the wavelength range of the aforementioned infrared. Since the well layers 232w ₁ , 232w ₂ , . . . 232w _n-1 contain indium (In), the lattice constant will increase, and the above-mentioned barrier layers (the 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, for example, aluminum gallium arsenide phosphide (AlGaAsP). 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 the thickness is thicker; and the thicker barrier layer 232b ₁ and the barrier layer _232bn can prevent the adjacent first electrical type semiconductor layer 231 and the second electrical type semiconductor layer The dopant in 233 has better diffusion barrier effect. In one embodiment, the barrier layer 232b ₁ and the barrier layer _232bn include, for example, aluminum gallium arsenide (AlGaAs).

The light-emitting element according to the first embodiment of the present invention further 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), such as gallium arsenide (GaAs) doped with silicon (Si). . As mentioned above, the first electrical type semiconductor layer 231 is doped with tellurium (Te) or selenium (Se), and the buffer layer 21 is doped with silicon (Si). Such a configuration enables more adjustments in the fabrication 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 further 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 On the contact layer 25 , a second electrode 27 is disposed on the substrate 20 . The lateral light extraction layer 24 is helpful for light extraction, especially because the thickness of the lateral light extraction increases, so its thickness can be relatively thick, for example, about 5 μm to 30 μm. In one embodiment, the lateral light extraction layer 24 Contains gallium arsenide (GaAs) doped with zinc (Zn), about 10 μm thick. 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 lateral light extraction layer 24 and the contact layer 25 are also made of gallium arsenide (GaAs) doped with zinc (Zn), which can simplify the configuration of the machine in the manufacturing process, but it should be noted that the lateral light extraction layer 24 and the contact The functions of the layers 25 are different. In order to form an ohmic contact, the zinc (Zn) content in the contact layer 25 is much higher than that in the lateral 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 is worth noting that when the light of the infrared wavelength emitted by the light emitting stack 23 travels toward the substrate 20 , there may still be a part of the light that is not totally reflected by the semiconductor window layer 22 . As mentioned above, a larger light-emitting angle may be required in certain applications. Therefore, as shown in the figure, in this embodiment, the second electrode 27 is a patterned electrode. Please refer to FIG. 3 for a detailed description. 4 , when viewed from the top view, the pattern of the second electrode 27 may be, for example, a mesh as shown in FIG. 3 . FIG. 3 shows that a gallium arsenide (GaAs) substrate 20 is formed with A grid-shaped second electrode 27 of germanium gold (GeAu); or as shown in FIG. 4 , the pattern of the second electrode 27 may be a plurality of circles. FIG. 4 shows a gallium arsenide (GaAs) substrate 20 formed with A plurality of circular-shaped second electrodes 27 of germanium gold (GeAu); the second electrodes 27 patterned in this way form scattering centers for the light that is not totally reflected in the semiconductor window layer 22, which can increase the scattering and make the light exit angle relatively high. big. In addition, roughening can also be selectively formed on the lower surface S1 of the substrate 20 where the second electrode 27 is not provided (not shown in the figure), which can also increase the scattering of light, so that light can be easily emitted from the side of the substrate 20, even the substrate The side surface S2 of the 20 and the upper surface S3 of the light-emitting element where the first electrode 26 is not disposed can also be roughened (not shown).

The above-mentioned embodiments are only illustrative of 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 to which the present invention pertains can make modifications and changes to the above embodiments without departing from the technical principles and spirit of the present invention. Therefore, the scope of protection of the present invention is as set out in the appended claims.

Claims (2)

1. A light-emitting element, comprising:

a substrate comprising a first surface and a second surface;

the light-emitting laminated layer is positioned on the first surface and can emit light with an infrared wavelength;

a first electrode on the light emitting stack and having an extended electrode; and

and the second electrode is positioned on the second surface and has a grid-shaped or a plurality of circular patterns.

2. A light-emitting element, comprising:

a substrate comprising a first surface and a second surface;

the light-emitting laminated layer is positioned on the first surface and can emit light with an infrared wavelength;

a semiconductor window layer located between the substrate and the light emitting stack;

a first electrode on the light emitting stack and having an extended electrode; and

and the second electrode is positioned on the second surface and has a grid-shaped or a plurality of circular patterns.

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