Infrared light emitting device

Abstract

To provide an infrared light-emitting device with a high emission intensity.SOLUTION: An infrared light-emitting device comprises a substrate and a plurality of mesa type semiconductor lamination parts. In each of the plurality of mesa type semiconductor lamination parts, a first semiconductor layer (21), a light-emitting layer, and a second semiconductor layer (23) are sequentially laminated on the substrate. A connection electrode (E) electrically connects the second semiconductor layers of first and second mesa type semiconductor lamination parts (101 and 102) and the first semiconductor layers of third and fourth mesa type semiconductor lamination parts (103 and 104) to each other. The first and second mesa type semiconductor lamination parts are electrically in parallel with each other. The third and fourth mesa type semiconductor lamination parts are electrically in parallel with each other. The connection electrode is formed so as to transverse at least one of the plurality of mesa type semiconductor lamination parts in a plan view.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to infrared light emitting devices. [Background technology]

[0002] In general, infrared rays in the long wavelength band, with wavelengths of 2 μm or more, are used in motion sensors that detect the human body, non-contact temperature sensors, gas sensors, etc., due to their thermal effect and the effect of infrared absorption by gases. For example, gas sensors can be used for monitoring and protecting the atmospheric environment, as well as for early detection of fires, and have been attracting attention in recent years. In particular, in the range of approximately 2.5 to approximately 10.0 μm, there are many absorption bands specific to various gases, making this wavelength band suitable for use in gas sensors.

[0003] The principle of the infrared gas sensor is as follows. For example, when a gas is injected into the space between the infrared light source and the light-receiving element, a specific gas absorbs infrared light of a specific wavelength. Therefore, the type and concentration of the gas can be measured by analyzing the wavelength spectrum before and after the gas is injected. Here, an incandescent bulb, for example, is used as the infrared light source, and the infrared light emitted from an incandescent bulb is white light. Therefore, in order to separate specific wavelengths, a filter must be installed on the light-receiving element side. Such filters are expensive and weaken the intensity of the infrared light, reducing the sensitivity of the gas sensor. Furthermore, the lifespan of incandescent bulbs is short, so the light source must be replaced frequently.

[0004] To solve the above problems, it is effective to use a semiconductor light-emitting element that emits infrared light of a specific wavelength as a light source. An example of a semiconductor light-emitting element that emits infrared light is an infrared LED (Light Emitting Diode). Analytical instruments that use infrared LEDs can be made smaller, lighter, and consume less power than analytical instruments that use other light sources (e.g., light bulbs). Infrared LEDs are effective light sources for portable, space-saving, and low-power analytical instruments. Infrared LEDs can also be driven using an integrated circuit (IC).

[0005] Such infrared LEDs have a structure known as a pn junction diode, in which an emitting layer with a band gap capable of emitting infrared light with wavelengths of approximately 2 μm or more is sandwiched between an n-layer and a p-layer. When a forward current flows in an infrared light-emitting device, electrons and holes recombine in the emitting layer, causing the device to emit infrared light corresponding to the band gap.

[0006] However, analytical instruments using LEDs as light sources, especially in the infrared region, have not yet become widespread. One of the reasons for this is that known infrared LEDs do not provide sufficient emission intensity, making it difficult to obtain sufficient signal strength (S / N ratio) for the analytical instrument as a whole. Since the S / N ratio improves with increasing emission intensity, sufficient infrared LED emission intensity must be obtained for widespread application.

[0007] Furthermore, because infrared light-emitting devices emit infrared light with wavelengths of approximately 2 μm or longer, the light-emitting layer is often made of a so-called narrow-gap material. Because the voltage applied to each diode stage is low, such infrared light-emitting devices often have a structure in which multiple diodes are connected in series. For example, Patent Document 1 discloses an infrared light-emitting device having a structure in which mesa-type LEDs are connected in multiple stages in series. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2019-009438 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to realize an infrared light emitting device with even higher emission intensity, further improvement in emission intensity is desired for semiconductor light emitting diodes (LEDs) that emit infrared rays.

[0010] In view of the above circumstances, an object of the present disclosure is to provide an infrared light emitting device with high emission intensity. [Means for solving the problem]

[0011] An infrared light emitting device according to an embodiment of the present disclosure includes: A substrate; a plurality of mesa-shaped semiconductor laminated portions including at least a first mesa-shaped semiconductor laminated portion, a second mesa-shaped semiconductor laminated portion, a third mesa-shaped semiconductor laminated portion, and a fourth mesa-shaped semiconductor laminated portion; Each of the plurality of mesa-shaped semiconductor laminated portions has a first semiconductor layer, a light-emitting layer, and a second semiconductor layer laminated in this order on the substrate, By connecting electrodes, the second semiconductor layer of the first mesa-shaped semiconductor laminate; the second semiconductor layer of the second mesa-shaped semiconductor laminate; the first semiconductor layer of the third mesa-shaped semiconductor laminate; the first semiconductor layer of the fourth mesa-shaped semiconductor laminate portion is electrically connected to the first semiconductor layer of the fourth mesa-shaped semiconductor laminate portion; the first mesa-shaped semiconductor laminate portion and the second mesa-shaped semiconductor laminate portion are electrically parallel to each other; the third mesa-shaped semiconductor laminate portion and the fourth mesa-shaped semiconductor laminate portion are electrically connected in parallel, The connection electrode is formed so as to cross at least one of the plurality of mesa-shaped semiconductor laminated portions in plan view. [Effects of the Invention]

[0012] According to the present disclosure, an infrared light emitting device with high emission intensity can be provided. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating the structure of an infrared light emitting device according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view illustrating the structure of a mesa-shaped semiconductor laminate portion. [Figure 3]FIG. 3 is a diagram for explaining the shape of the mesa-shaped semiconductor laminate portion in a plan view. [Figure 4] FIG. 4 is an enlarged view illustrating the structure of an infrared light emitting device according to an embodiment. [Figure 5] FIG. 5 is an enlarged view illustrating another structure of the infrared light emitting device according to an embodiment. [Figure 6] FIG. 6 is an enlarged view illustrating still another structure of the infrared light emitting device according to an embodiment. [Figure 7] FIG. 7 is a diagram illustrating the results of comparing luminous efficiencies. [Figure 8] FIG. 8 is a diagram illustrating the structure of an infrared light emitting device of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0014] An infrared light emitting device according to an embodiment of the present disclosure will be described below with reference to the drawings. In each drawing, identical or corresponding parts are designated by the same reference numerals. In the description of this embodiment, the description of identical or corresponding parts will be omitted or simplified as appropriate.

[0015] <Infrared light emitting device> Before describing the structure of the infrared light-emitting device according to this embodiment, a comparative example of an infrared light-emitting device will be described. FIG. 8 shows a comparative example of an infrared light-emitting device having a typical structure in which mesa-type infrared LEDs are connected in series in multiple stages. The comparative example of an infrared light-emitting device includes multiple mesa-type infrared LEDs that are rectangular in plan view. In the comparative example of an infrared light-emitting device, the p-layer of one mesa-type infrared LED and the n-layer of an adjacent mesa-type infrared LED are electrically connected by a connection electrode to form a series multistage connection. For example, the four mesa-type infrared LEDs included in area A1 of FIG. 8 are connected in series as shown in the circuit diagram at the bottom. Here, the connection electrodes are metal layers electrically connected to the p-layer and n-layer of the infrared LEDs.

[0016] For example, one method for improving the emission intensity of a mesa-type infrared LED is to increase the emission area of ​​one mesa by increasing the mesa width when the input current density per unit area is constant. However, simply increasing the mesa width results in a biased distribution of current density within the mesa. As a result, in a structure like the infrared light-emitting device of the comparative example, the effective emission area that contributes to improving emission intensity cannot be effectively increased, and the emission intensity does not improve even if the mesa width of the infrared LED is increased beyond a certain length. The inventors conducted extensive research to find a way to solve this problem and arrived at the structure of the infrared light-emitting device according to the present embodiment, which will be described below.

[0017] FIG. 1 is a schematic plan view showing the general structure of an infrared light-emitting device according to this embodiment. While the infrared light-emitting device of the comparative example has a structure in which mesa-type infrared LEDs are connected in multiple stages in series, the infrared light-emitting device according to this embodiment has pairs of mesa-type infrared LEDs electrically connected in parallel, and the pairs of infrared LEDs are connected in series. For example, the four mesa-type infrared LEDs included in area A1 of FIG. 1 have a structure in which two pairs of parallel-connected infrared LEDs are connected in series, as shown in the circuit diagram at the bottom. While the details of the structure will be described later, the electrically parallel mesa-type infrared LEDs can increase the effective light-emitting area to prevent uneven distribution of current density. Below, we will explain the outline of the cross-sectional structure of the infrared light-emitting device according to this embodiment, the elements of the substrate and mesa-type semiconductor stack (mesa-type infrared LEDs), and then the electrical connection of multiple infrared LEDs.

[0018] FIG. 2 is a cross-sectional view illustrating the structure of a mesa-shaped semiconductor laminate. In this embodiment, the mesa-shaped semiconductor laminate is a mesa-shaped infrared LED. Each of the multiple mesa-shaped semiconductor laminates includes a first semiconductor layer 21, a light-emitting layer 22, and a second semiconductor layer 23, and is formed on a substrate 10. As shown in FIG. 2, the first semiconductor layer 21, the light-emitting layer 22, and the second semiconductor layer 23 are stacked in this order on the substrate 10 to form the mesa-shaped semiconductor laminate. A SiO2 layer is formed on the side of the mesa-shaped semiconductor laminate, and a SiN layer serving as an insulating film is formed thereon. The insulating film is formed to cover the multiple mesa-shaped semiconductor laminates. A connection electrode E is formed on the insulating film and electrically connects the second semiconductor layer 23 (p layer) and the first semiconductor layer 21 (n layer) of the infrared LED. As will be described in detail later, the connection of the connection electrode E includes a parallel p-layer-p layer connection and an n-layer-n layer connection, as well as a serial n-layer-p layer connection. The connection electrodes E do not have a structure in which they face each other in the stacking direction via an insulating film, which means that in the manufacture of the infrared light emitting device according to this embodiment, the electrode formation step can be performed in one step.

[0019] FIG. 3 is a diagram illustrating the shape of the mesa-shaped semiconductor laminate portion in a planar view. In this embodiment, each of the multiple mesa-shaped semiconductor laminate portions is rectangular in a planar view. In the example of FIG. 3, the shape of the mesa-shaped semiconductor laminate portion in a planar view is shown as a rectangle R1. The rectangle R1 has a long side L11 and a short side L12. In the example of FIG. 3, a rectangle R2 corresponding to the second semiconductor layer 23 in a planar view is also shown. The rectangle R2 has a long side L21 and a short side L22. The connection portion between the first semiconductor layer 21 and the connection electrode E may be formed along the long side L11 of the rectangle R1. Furthermore, the connection portion between the second semiconductor layer 23 and the connection electrode E may be formed along the long side L21 of the rectangle R2. By forming the shape of the connection portion between the first semiconductor layer 21 or the second semiconductor layer 23 and the connection electrode E to be along the long side L11 or the long side L21, uneven distribution of current density within the mesa is less likely to occur.

[0020] <Substrate> The substrate 10 is a support substrate for supporting multiple semiconductor stacks formed by, for example, a known film formation technique. The substrate 10 may be made of a single-element semiconductor material or a compound semiconductor material. The substrate 10 is made of a material that transmits infrared radiation. For example, the substrate 10 may be made of a semiconductor material such as, but not limited to, gallium arsenide (GaAs), silicon (Si), indium phosphide (InP), or indium antimonide (InSb). The substrate 10 may typically be a single-crystal substrate, but is not limited thereto. In this embodiment, the substrate 10 is a single-crystal GaAs substrate selected from the perspective of single-crystal growth of compound semiconductors. The surface orientation of the substrate 10 is not particularly limited, but is preferably (001), (111), or (101). Alternatively, a surface orientation tilted by approximately 1° to 5° relative to these surface orientations may be used.

[0021] There is no restriction on doping with donor impurities or acceptor impurities in the substrate 10. However, from the viewpoint of enabling the connection of multiple infrared LEDs formed on the substrate 10 in series or parallel, it is desirable that the substrate 10 be electrically isolated (i.e., semi-insulating or insulating) from the semiconductor laminate portion.

[0022] Here, in the semiconductor manufacturing process, the surface of the substrate 10 may be heated in a vacuum to remove the oxide film, or after removing contaminants such as organic substances and metals, the surface may be subjected to a cleaning treatment using an acid or alkaline cleaning agent.

[0023] <First semiconductor layer> The first semiconductor layer 21 is a semiconductor layer of a first conductivity type formed on the substrate 10. The first semiconductor layer 21 is made of, for example, any one of aluminum arsenide (AlAs), gallium arsenide (GaAs), indium arsenide (InAs), aluminum antimonide (AlSb), gallium antimonide (GaSb), indium antimonide (InSb), and indium phosphide (InP), or a compound semiconductor material of a mixed crystal of any of these.

[0024] Furthermore, a semiconductor material having a band gap larger than that of the light emitting layer 22 can be selected for the first semiconductor layer 21. This is expected to improve the effect of confining carriers in the light emitting layer 22.

[0025] When the first semiconductor layer 21 has a laminated structure, it is preferable that at least the layer in the first semiconductor layer 21 that is in direct contact with the light emitting layer 22 has a band gap larger than that of the light emitting layer 22 .

[0026] The first semiconductor layer 21 has a first conductivity type, which is opposite to the second conductivity type of the second semiconductor layer 23 .

[0027] In the present disclosure, the conductivity type refers to either so-called n-type or p-type according to the type of carrier. Typically, an n-type semiconductor is an impurity semiconductor doped with a donor impurity such as phosphorus (P). A p-type semiconductor is an impurity semiconductor doped with an acceptor impurity such as boron (B). However, the first semiconductor layer 21 does not necessarily have to be doped with such impurities as long as it functions as a conductivity semiconductor. In the present disclosure, the first conductivity type is n-type and the second conductivity type is p-type from the viewpoint of improving infrared transmittance due to the Burstein-Moss effect. However, the combination is not limited to this, and the first conductivity type may be p-type and the second conductivity type may be n-type. Here, the dopant concentration (impurity density) of the first semiconductor layer 21 when doped with an impurity is 1×10 from the viewpoint of reducing contact resistance with metal. 18 cm -3 It is preferable that the crystallinity is 1×10 or more. 19 cm -3 It is preferable that:

[0028] <Light-emitting layer> The light emitting layer 22 is a semiconductor layer formed on the first semiconductor layer 21 and emits infrared light having a predetermined wavelength. In this embodiment, the light emitting layer 22 is made of a compound semiconductor having a band gap corresponding to the emission of infrared light having a wavelength of approximately 2 μm or more. As an example, the light emitting layer 22 is made of a semiconductor material that is a mixed crystal of any one of AlAs, GaAs, InAs, AlSb, GaSb, InSb, and InP.

[0029] The light emitting layer 22 may have a single layer structure or a multilayer structure. In this embodiment, the light emitting layer 22 has a multiple quantum well structure made of semiconductor layers with different bandgaps, but is not limited to this.

[0030] Furthermore, the light emitting layer 22 may be a conductive type (n-type or p-type) semiconductor, or may be an intrinsic (i-type) semiconductor that contains no or almost no impurities.

[0031] <Second semiconductor layer> The second semiconductor layer 23 is a semiconductor layer of a second conductivity type formed on the light emitting layer 22. In this embodiment, the second conductivity type is p-type. The second semiconductor layer 23 is made of a compound semiconductor material selected in consideration of a double heterojunction with the first semiconductor layer 21 and the light emitting layer 22, for example.

[0032] The second semiconductor layer 23 may have a single layer structure or a laminated structure. When the second semiconductor layer 23 has a laminated structure, it is preferable that at least the layer of the second semiconductor layer 23 that is in direct contact with the light emitting layer 22 has a band gap larger than that of the light emitting layer 22.

[0033] When doped with impurities, the dopant concentration (impurity density) of the second semiconductor layer 23 is set to 1×10 18 cm -3It is preferable that the crystallinity is 1×10 or more. 19 cm -3 It is preferable that:

[0034] <Electrode> Materials with high reflectivity in the mid-infrared range are preferred for the electrode (upper electrode layer) provided on the second semiconductor layer 23 and the electrode (lower electrode layer) provided on the first semiconductor layer 21, and Au or Al can be used, for example. The upper electrode layer and the lower electrode layer can also be made of different electrode materials to reduce contact resistance, improve adhesion, and prevent interdiffusion between the electrode material and the semiconductor material. For example, Ti, Pt, Ni, Cr, etc. can also be used. The film thickness of each layer is designed so as not to inhibit the reflectivity of the upper electrode layer. The electrode materials are not limited to these. The upper electrode layer and the lower electrode layer may be made of different materials or the same material. The upper electrode layer and the lower electrode layer may be formed simultaneously in a single process.

[0035] (Structure details) FIG. 4 is an enlarged view illustrating the structure of the infrared light-emitting device according to this embodiment. In the example of FIG. 4, a first mesa-type semiconductor laminate 101, a second mesa-type semiconductor laminate 102, a third mesa-type semiconductor laminate 103, and a fourth mesa-type semiconductor laminate 104 are shown as multiple mesa-type semiconductor laminates of the infrared light-emitting device. FIG. 4 corresponds to an enlarged view of a portion of region A1 in FIG. 1. Therefore, the multiple mesa-type semiconductor laminates of the infrared light-emitting device include at least these four mesa-type semiconductor laminates. The structures of the four mesa-type semiconductor laminates described below are also the same for the other mesa-type semiconductor laminates of the infrared light-emitting device.

[0036] The connection electrode E electrically connects the second semiconductor layer 23 of the first mesa-shaped semiconductor laminate 101, the second semiconductor layer 23 of the second mesa-shaped semiconductor laminate 102, the first semiconductor layer 21 of the third mesa-shaped semiconductor laminate 103, and the first semiconductor layer 21 of the fourth mesa-shaped semiconductor laminate 104. The first mesa-shaped semiconductor laminate 101 and the second mesa-shaped semiconductor laminate 102 are electrically parallel to each other and form a first set. The third mesa-shaped semiconductor laminate 103 and the fourth mesa-shaped semiconductor laminate 104 are electrically parallel to each other and form a second set. The connection electrode E connects the first set and the second set in series.

[0037] As shown in FIG. 4 , the connection electrode E includes a first group of extensions B, which are a plurality of extensions B electrically connected to the second semiconductor layer 23 of the first mesa-shaped semiconductor laminate 101, and a second group of extensions B, which are a plurality of extensions B electrically connected to the first semiconductor layer 21 of the fourth mesa-shaped semiconductor laminate 104. In FIG. 4 , the extensions B belonging to the first group of extensions are indicated as “B1.” The extensions B belonging to the second group of extensions are indicated as “B2.” This configuration of the connection electrode E determines the spacing D of the connection portions in a plan view. The connection portions are portions where the first semiconductor layer 21 or the second semiconductor layer 23 connects to the connection electrode E, and are indicated by dashed rectangles in FIG. 4 . It is desirable that the spacing D of the connection portions be equal to or shorter than a predetermined length to prevent uneven distribution of current density within the mesa. The predetermined length is, for example, 50 μm, but is not limited thereto. It is also desirable that the short side L22 of the rectangle R2 shown in FIG. 3 is equal to or shorter than a predetermined length.

[0038] Furthermore, the connection electrode E is formed so as to cross at least one of the plurality of mesa-shaped semiconductor laminated portions in plan view. In the example of Fig. 4, the connection electrode E crosses the third mesa-shaped semiconductor laminated portion 103 by the second extension portion (see region A2). The connection electrode E also crosses the second mesa-shaped semiconductor laminated portion 102 by the second extension portion, the first extension portion, and their connecting region. That is, the connection electrode E in the example of Fig. 4 is formed so as to cross at least two of the plurality of mesa-shaped semiconductor laminated portions in plan view.

[0039] Here, the connection electrode E is formed so as to be included inside the smallest rectangle that contains the first mesa-shaped semiconductor laminate 101, the second mesa-shaped semiconductor laminate 102, the third mesa-shaped semiconductor laminate 103, and the fourth mesa-shaped semiconductor laminate 104 in a plan view. The smallest rectangle corresponds to, for example, area A1 in FIG. 1 . The connection electrode E does not use an area outside the multiple mesa-shaped semiconductor laminates for wiring. In other words, the connection electrode E does not extend beyond the range of the multiple mesa-shaped semiconductor laminates in a plan view. Therefore, the infrared light emitting device according to this embodiment can be made smaller.

[0040] Here, the shape of the connection electrode E is not limited to the example shown in FIG. 4. FIG. 5 is an enlarged view illustrating another structure of the infrared light emitting device according to this embodiment. Unlike the case shown in FIG. 4, the connection electrode E has a shape in which the connection region between the first extension and the second extension is widened to cover the second semiconductor layer 23 of the second mesa-shaped semiconductor laminate 102 and the first semiconductor layer 21 of the third mesa-shaped semiconductor laminate 103. In the example shown in FIG. 5, the connection portion (C in FIG. 5) between the first semiconductor layer 21 and the connection electrode E is formed along the long side L11 of the rectangle R1 (see FIG. 3). Furthermore, the connection portion between the second semiconductor layer 23 and the connection electrode E is formed along the long side L21 of the rectangle R2 (see FIG. 3). This shape of the connection portion makes it difficult for uneven distribution of current density to occur within the mesa. Here, in the example of FIG. 5 as well, the connection electrode E crosses the third mesa-shaped semiconductor laminate portion 103 by the second extension portion (see region A2).

[0041] FIG. 6 is an enlarged view illustrating another structure of the infrared light-emitting device according to this embodiment. Unlike the cases of FIGS. 4 and 5, the connection electrode E in the example of FIG. 6 is configured such that the first extension, the second extension, and the portions corresponding to the connecting region are separated from one another. The connection electrode E corresponding to the first extension is indicated as "E1" in FIG. 6 and connects the p-layer to the p-layer. The connection electrode E corresponding to the second extension is indicated as "E2" in FIG. 6 and connects the n-layer to the n-layer. The connection electrode E corresponding to the connecting region is indicated as "E3" in FIG. 6 and connects the n-layer to the p-layer. In other words, the connection electrode E may be configured to include three metal layers, "E1," "E2," and "E3."

[0042] (Example) The effects of the infrared light emitting device according to the above embodiment were verified using examples. The infrared light emitting device of the example was manufactured by a known manufacturing method so as to have the structure of the infrared light emitting device according to the above embodiment. On the other hand, the comparative example had a general structure in which mesa-type infrared LEDs were connected in multiple stages in series, as shown in Figure 8, and was manufactured by a known manufacturing method.

[0043] FIG. 7 shows the results of comparing the luminous efficiency of the infrared light-emitting devices of the Example and Comparative Example when operated at a constant current (100 mA). When the luminous efficiency was measured for wavelengths from 2.5 μm to 5 μm, it was found that the luminous efficiency of the Example was higher than that of the Comparative Example, particularly for infrared light emission with wavelengths from 3 μm to 4 μm. Here, the solid curve in FIG. 7 represents the Comparative Example (conventional structure), and the dashed curve represents the Example (present embodiment). Furthermore, when the current density dependence of the luminous efficiency was measured for the same Example and Comparative Example, a decrease in luminous efficiency was observed in the Comparative Example as the current density increased. In other words, it was found that the improvement in luminous efficiency of the Example was due to the suppression of biased current density distribution.

[0044] For example, referring to FIG. 4, in the infrared light-emitting device of the embodiment, the diode formed by the first mesa-shaped semiconductor laminate 101 and the diode formed by the second mesa-shaped semiconductor laminate 102, which are connected in parallel, operate in the same manner depending on the voltage applied to the infrared light-emitting device. Therefore, these two diodes behave as a single diode connected in series as a whole. In this case, the effective mesa width per stage is the sum of the mesa widths of the first mesa-shaped semiconductor laminate 101 and the second mesa-shaped semiconductor laminate 102. This is equivalent to twice the mesa width per stage of the infrared light-emitting device of the comparative example. However, the mesa width of each diode in the infrared light-emitting device of the embodiment remains unchanged. Therefore, in the infrared light-emitting device of the embodiment, the effective mesa width per series stage can be increased while the mesa width of each diode can be designed to be equal to or less than a predetermined length at which no current density distribution occurs, thereby improving the light emission intensity.

[0045] As is clear from the comparison between the examples and the comparative examples, the infrared light emitting device according to this embodiment can increase the emission intensity.

[0046] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art would easily be able to make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications and alterations are included within the scope of the present disclosure. For example, the functions included in each component may be rearranged so as not to be logically inconsistent, and multiple components may be combined or divided into one.

[0047] In the above embodiment, the number of parallel mesa-type semiconductor laminated portions is two, but it may be three or more.

[0048] In the above embodiment, the number of parallel connections before and after the series connection is the same (2), but the number of parallel connections before and after the series connection may be different. In other words, the number of parallel connections before and after the series connection may be asymmetric.

[0049] 4, the connection electrode E has a group of first extensions, but may have only one first extension. Similarly, the connection electrode E has a group of second extensions, but may have only one second extension.

[0050] In the example of FIG. 4 and the like, the number of groups of first extension portions and the number of groups of second extension portions provided in the connection electrode E are the same, but these numbers may be different, that is, asymmetric.

[0051] 4 and the like, the first extension portion and the second extension portion extend with a uniform width, but the width may be different between the connection portion with the first semiconductor layer 21 or the second semiconductor layer 23 and other portions. For example, in order to reduce contact resistance, the width of the connection portion with the first semiconductor layer 21 or the second semiconductor layer 23 may be wide, and the width of other wiring portions may be narrow. [Explanation of symbols]

[0052] 10 Substrate 21 First semiconductor layer 22 Light-emitting layer 23 Second semiconductor layer 101 First mesa-shaped semiconductor laminate 102 Second mesa-shaped semiconductor laminate 103 Third mesa-shaped semiconductor laminate 104 Fourth mesa-shaped semiconductor laminate B Extension part E Connection electrode

Claims

1. A substrate; a plurality of mesa-shaped semiconductor laminated portions including at least a first mesa-shaped semiconductor laminated portion, a second mesa-shaped semiconductor laminated portion, a third mesa-shaped semiconductor laminated portion, and a fourth mesa-shaped semiconductor laminated portion; Each of the plurality of mesa-shaped semiconductor laminated portions includes a first semiconductor layer, a light-emitting layer, and a second semiconductor layer laminated in this order on the substrate, By connecting electrodes, the second semiconductor layer of the first mesa-shaped semiconductor laminate; the second semiconductor layer of the second mesa-shaped semiconductor laminate; the first semiconductor layer of the third mesa-shaped semiconductor laminate; the first semiconductor layer of the fourth mesa-shaped semiconductor laminate portion is electrically connected to the first semiconductor layer of the fourth mesa-shaped semiconductor laminate portion; the first mesa-shaped semiconductor laminate portion and the second mesa-shaped semiconductor laminate portion are electrically parallel to each other, the third mesa-shaped semiconductor laminate portion and the fourth mesa-shaped semiconductor laminate portion are electrically connected in parallel, the connection electrode is formed so as to cross at least one of the plurality of mesa-shaped semiconductor laminated portions in a plan view, The connection electrode is a group of first extension portions that are a plurality of extension portions electrically connected to the second semiconductor layer of the first mesa-shaped semiconductor laminate portion; a group of second extension portions that are a plurality of extension portions electrically connected to the first semiconductor layer of the fourth mesa-shaped semiconductor laminate portion.

2. The infrared light emitting device according to claim 1 , wherein the connection electrode is formed so as to cross at least two of the plurality of mesa-shaped semiconductor laminated portions in a plan view.

3. Each of the plurality of mesa-shaped semiconductor laminated portions has a rectangular shape in a plan view, 3. The infrared light emitting device according to claim 1, wherein a connection portion between the first semiconductor layer and the connection electrode is formed along a long side of the rectangle.

4. The infrared light emitting device according to claim 1 , wherein the connection electrodes do not have a structure in which they face each other with an insulating film interposed therebetween.

5. The infrared light emitting device according to claim 1 , wherein the connection electrodes are formed on an insulating film formed so as to cover the plurality of mesa-shaped semiconductor laminated portions.

6. 6. The infrared light emitting device according to claim 1, wherein the connection electrode is formed so as to be included inside the smallest rectangle that contains the first mesa-shaped semiconductor laminate portion, the second mesa-shaped semiconductor laminate portion, the third mesa-shaped semiconductor laminate portion, and the fourth mesa-shaped semiconductor laminate portion in a planar view.

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