阅读说明：本技术 发光元件 (Light emitting element ) 是由 林义杰 于 2014-03-14 设计创作，主要内容包括：本发明公开一种发光元件,包含：一基板；一发光叠层位于基板的上方,可发出一红外线(IR)波长的光；以及一半导体窗户层,由AlGaInP系列的材料组成,位于基板与发光叠层之间。(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.)

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.

Technical Field

The present invention relates to a light emitting device, and more particularly, to an infrared light emitting device.

Background

Light-Emitting diodes (LEDs) have good optoelectronic properties such as low power consumption, low heat generation, long operating life, shock resistance, small volume, fast response speed, and stable output Light wavelength, and are therefore suitable for various applications.

Among them, Infrared light emitting diodes (IR LEDs) are used more and more widely, and are conventionally used in remote controllers and monitors, and are recently developed to be used in smart phones and touch panels. Because each touch panel uses a relatively large number of infrared light emitting diodes, the price of the touch panel is also lower than that of other applications, and it is necessary to reduce the cost of the 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, on which a light emitting stack 102, a metal reflective layer 103, a barrier layer 104, and a bonding structure 105 are sequentially formed from top to bottom. In addition, a first electrode 106E1 and its extension electrode 106E 1' 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 106E 1' and the second electrode 106E2 are used to transmit current. The light emitting layer 102 can emit light in an infrared 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 originally separated light emitting stack 102 and the permanent substrate 101 are bonded by the bonding structure 105, so that the metal reflective layer 103 is formed on the light emitting stack 102 before the two are bonded. However, as mentioned above, when the specific application, such as the application of touch panel, requires low cost, the bonding process and the metal reflective layer 103 are all the main reasons for high cost. In addition, in the application of touch panel, it is also required to emit light from a better side to achieve a larger light-emitting angle, and it has been found in practical applications that the above-mentioned conventional infrared light-emitting device is difficult to meet the requirements in this respect.

Disclosure of Invention

To solve the above problems, the present invention discloses a light emitting device. The disclosed light-emitting element includes: 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.

Drawings

Fig. 1 shows a conventional light emitting device.

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 device according to 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.

Description of the symbols

101 permanent substrate

102 light emitting stack

103 metal reflective layer

104 barrier layer

105 joint structure

106E1 first electrode

106E 1' (of the first electrode) extended electrode

106E2 second electrode

20 base plate

21 buffer layer

22 semiconductor window layer

23 light emitting laminate

231 first conductivity type semiconductor layer

232 light emitting layer

232b₁,232b₂,…232_bnBarrier layer

232w₁,232w₂,…232w_n-1Well layer

233 second conductivity 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 lower surface of substrate

S2 side surface of substrate

S3 Upper surface of light emitting element

Detailed Description

Fig. 2 is a light-emitting device according to a first embodiment of the present invention. As shown in fig. 2, the light emitting device includes: a substrate 20; a light-emitting laminate 23 disposed over the substrate 20 and emitting light having an Infrared (IR) wavelength; and a semiconductor window layer 22 made of AlGaInP series material and located between the substrate 20 and the light emitting stack 23. The substrate 20 includes, for example, a gallium arsenide (GaAs) substrate. The Infrared (IR) wavelength is between about 750nm and 1100nm, and in one embodiment, the Infrared (IR) wavelength is greater than 900nm, 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 fabrication process, after the semiconductor window layer 22 is formed, the type or ratio of the introduced gas is adjusted on the same machine table to form the light emitting stack 23. In one embodiment, the semiconductor window layer 22 comprises (Al)_xGa_1-x)_0.5In_0.5P, wherein x is 0.1-1. It is noted that the light-emitting stack 23 has a first refractive index n₁The semiconductor window layer 22 has a second refractive index n₂First refractive index n₁Greater than the second refractive index n₂At least 0.2 or more. Therefore, the light of the infrared wavelength emitted from the light-emitting laminate 23 travels from the high refractive index to the low refractive index between the light-emitting laminate 23 and the semiconductor window layer 22, and the first refractive index n of the light-emitting laminate 23 is added₁A second refractive index n with respect to the semiconductor window layer 22₂The difference between the two layers makes the light of the infrared wavelength emitted by the light-emitting laminated layer 23 easily generate total reflection at the semiconductor window layer 22, i.e. the semiconductor window layer 22 provides a single-layer structure of reflector function, and provides better lateral reflection function compared to the general Distributed Bragg Reflector (DBR) structure. A general Distributed Bragg Reflector (DBR) structure requires tens of layers to achieve a certain degree of reflectivity, and its reflection function is limited to a certain range of forward angles, generally, 0-17 degrees from the normal of the reflector structure; in the present embodiment, only the semiconductor window layer 22 with a single layer structure can reflect light at an angle of 50 to 90 degrees from the normal of the semiconductor window layer 22, thereby providing better side light emission to form a larger light emission angle, and the overall light emission power is improved due to the improved light extraction. In practical tests, testing light emitting devices emitting 850nm and 940nm light respectively, the light emitting stack 23 of the embodiment of the invention employs aluminum gallium arsenide (AlGaAs) in the first electrical semiconductor layer 231 and has a first refractive index n₁About 3.4, the semiconductor window layer 22 is made of (Al)_0.6Ga_0.4)_0.5In_0.5P having a second refractive index n₂About 2.98, with a difference of about 0.42 between the two refractive index values, which is the same as the other conditions but only with the semiconductor window layer 22 modified with aluminum gallium arsenide (AlGaAs) (refractive index of about 3.4)Compared with the light emitting device, the light emitting power of the 850nm light emitting device of the embodiment of the invention is increased to 4.91mW from 4.21mW, which is increased by about 17%; compared with the light emitting device with 940nm of the invention, the light emitting power of the light emitting device is increased to 5.27mW from 5.06mW, which is increased by about 4%. In addition, the semiconductor window layer 22 is directly contacted with the light emitting stack layer 23 in terms of manufacturing process or cost, and is a single layer structure, so that the manufacturing process is simplified and the cost is lower compared with the general distributed bragg reflection structure. In terms of thickness, in one embodiment, the semiconductor window layer 22 has a thickness less than 1 μm to achieve good reflection.

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 conductivity type semiconductor layer 233 on the active layer 232, wherein the first conductivity type semiconductor layer 231 is in direct contact with the semiconductor window layer 22. The first conductivity type semiconductor layer 231, the active layer 232, and the second conductivity type semiconductor layer 233 are formed of III-V 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, and when an external power is applied, the first electrical type semiconductor layer 231 and the second electrical type semiconductor layer 233 generate carriers (electrons/holes) and recombine in the active layer 232 to generate light, respectively. 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 comprises a multiple quantum well structure (MQW) comprising a plurality of barrier layers, such as barrier layer 232b₁,232b₂,…232b_nAnd one or more well layers, e.g. well layer 232w₁,232w₂,…232w_n-1With a well layer between two adjacent barrier layers, e.g. two adjacent barrier layers 232b₁And 232b₂With a well layer 232w therebetween₁. Wherein the plurality of barrier layers 232b₁,232b₂,…232b_nThe barrier layer (i.e., the barrier layer 232 b) nearest to the first electrical type semiconductor layer 231₁) And a barrier layer (i.e., barrier layer 232 b) nearest to the second electrical type semiconductor layer 233_n) Is not limited toPhosphorus (P), and the rest of the barrier layer (barrier layer 232 b)₂,…232b_n-1) Phosphorus (P) is contained. In one embodiment, the well layer 232w₁,232w₂,…232w_n-1Comprises indium gallium arsenide (InGaAs), wherein the indium content is about 2% -30% and is adjusted according to the wavelength of the light to be emitted by the light emitting stack 23, so as to reach the wavelength range of the infrared ray. Due to the well layer 232w₁,232w₂,…232w_n-1The barrier layer (barrier layer 232 b) containing indium (In) increases the lattice constant₂,…232b_n-1) Phosphorus (P) in the medium allows the lattice constant to be small and the overall lattice constant to be adjusted back to an appropriate range. In one embodiment, the barrier layer 232b₂,…232b_n-1Including, for example, aluminum gallium arsenide phosphide (AlGaAsP). As described above, the barrier layer (barrier layer 232 b) closest to the first electrical semiconductor layer 231₁) And a barrier layer (barrier layer 232 b) nearest to the second electrical type semiconductor layer 233_n) The thickness of the material is thicker, the lattice constant of the material is not too small because the material does not contain phosphorus (P); while the thicker barrier layer 232b₁And barrier layer 232b_nThe diffusion barrier effect for the dopants in the adjacent first electrical type semiconductor layers 231 and second electrical type semiconductor layers 233 can be improved. In one embodiment, the barrier layer 232b₁And barrier layer 232b_nIncluding, for example, aluminum gallium arsenide (AlGaAs).

The light emitting device of the first embodiment of the present invention further comprises a buffer layer 21 between the substrate 20 and the semiconductor window layer 22, the buffer layer 21 being doped with silicon (Si), such as silicon (Si) -doped gallium arsenide (GaAs). 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), which makes the light emitting device more flexible in terms of adjustment, such as adjustment of lattice constant, in the manufacturing process. In addition, the light emitting device of the first embodiment of the invention further includes a lateral light extraction layer 24 on the light emitting stack 23, a contact layer 25 on the lateral light extraction layer 24, and a first electrode 26 on the contact layer 25, and a second electrode 27 on the substrate 20. The lateral light extraction layer 24 facilitates light extraction, particularly since side light extraction is increased due to the increased thickness, and may be relatively thick, such as about 5 μm to 30 μm, in one embodiment, the lateral light extraction layer 24 comprises zinc (Zn) -doped gallium arsenide (GaAs) having 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, and in one embodiment, the contact layer 25 comprises gallium arsenide (GaAs) doped with zinc (Zn). The lateral light extraction layer 24 and the contact layer 25 are made of gallium arsenide (GaAs) doped with zinc (Zn) to simplify the configuration of the machine in the fabrication process, but it should be noted that the lateral light extraction layer 24 and the contact layer 25 have different functions, and in order to form the ohmic contact, the zinc (Zn) content in the contact layer 25 is much higher than that of the lateral light extraction layer 24, so that the ohmic contact can be formed. The first electrode 26 may be provided with an extended electrode 26a to facilitate current spreading. It should be noted 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 portion of the semiconductor window layer 22 that is not totally reflected. As mentioned above, in a specific application, a larger light-emitting angle may be required, and therefore, as shown in the figure, in the present embodiment, the second electrode 27 is a patterned electrode, and please refer to fig. 3 and fig. 4 for a more detailed description, when viewing from the top view (top view), the pattern of the second electrode 27 may be, for example, a grid (mesh) as shown in fig. 3, fig. 3 shows that a grid-shaped gold germanium (GeAu) second electrode 27 is formed on a gallium arsenide (GaAs) substrate 20; or as shown in fig. 4, the pattern of the second electrode 27 may be a plurality of circles, and fig. 4 shows that a gallium arsenide (GaAs) substrate 20 is formed with a plurality of round-shaped gold germanium (GeAu) second electrodes 27; the second electrode 27 thus patterned forms scattering centers for light that is not totally reflected in the semiconductor window layer 22, which increases scattering and increases the angle of light output. In addition, roughening (not shown) may be selectively formed on the lower surface S1 of the substrate 20 where the second electrode 27 is not disposed, so as to increase light scattering, so that light is easily emitted from the side surface of the substrate 20, and even the side surface S2 of the substrate 20 and the upper surface S3 of the light emitting device where the first electrode 26 is not disposed may be roughened (not shown).

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify and change the above-described embodiments without departing from the technical principles and spirit of the present invention. The scope of the invention is therefore indicated by the appended claims.