Infrared LED element

Abstract

To provide an infrared LED element capable of lighting with a driving voltage lower than that in the conventional related art.SOLUTION: An infrared LED element capable of emitting infrared light having a peak wavelength of 1350 nm to 2000 nm comprises: a first stacked body having a first semiconductor layer having a first conductivity type and an intermediate layer having a thickness of 15 nm or more; an active layer disposed on an upper layer of the intermediate layer of the first stacked body; and a second stacked body disposed on the upper layer of the active layer. The second stacked body having at least a second semiconductor layer having a second conductivity type different from the first conductivity type. When a bandgap energy of the active layer is represented by Ea, and the bandgap energy of the intermediate layer is represented by Em, and when the bandgap energy of the first semiconductor layer is represented by Ep, the following relation is satisfied: Ea<Em<Ep.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an infrared LED element, and more particularly to an infrared LED element with an emission wavelength of 1350 nm or more. [Background technology]

[0002] In recent years, semiconductor light-emitting elements that emit light in the infrared region with wavelengths of 1000 nm or more have been widely used in applications such as security and surveillance cameras, gas detectors, medical sensors, and industrial equipment.

[0003] Semiconductor light-emitting devices with an emission wavelength of 1000 nm or more are generally manufactured using the following procedure: a first conductivity type semiconductor layer, an active layer (sometimes called an "emission layer"), and a second conductivity type semiconductor layer are epitaxially grown in this order on an InP substrate used as a growth substrate, and then electrodes for current injection are formed on the semiconductor wafer. The resulting wafer is then cut into chips.

[0004] For example, an infrared LED element having an active layer and a cladding layer made of InP is known, as disclosed in Patent Document 1. This structure is relatively simple for achieving light emission of 1000 nm or more. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6617218 Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors have been conducting extensive research into improving the luminous efficiency of LED elements with an emission wavelength of 1000 nm or more, and have come to realize the following problems.

[0007] The inventors investigated the drive voltage (hereinafter sometimes referred to as "forward voltage") required to light an LED element with an emission wavelength of 1000 nm or longer. They then discovered that the drive voltage required to light an LED element tends to be higher than the theoretical drive voltage as the emission wavelength becomes longer. Here, the theoretical forward voltage is the drive voltage derived based on the relationship between energy E and wavelength λ (E(eV)=hc / λ=1240 / λ). Details will be provided later in the "Mode for Carrying Out the Invention" section.

[0008] An increase in drive voltage can also cause heat generation in LED elements. LED elements also have the characteristic that their luminous efficiency decreases depending on the temperature when they are turned on. For this reason, it is extremely important to suppress the increase in drive voltage.

[0009] Therefore, having found the above problem, the inventors conducted extensive research into the factors that cause the drive voltage required to light an LED element to differ from the theoretical drive voltage, and further conducted extensive research into how to address these factors to realize an LED element that lights up at a drive voltage closer to the theoretical drive voltage than conventional LED elements, i.e., at a lower drive voltage.

[0010] In view of the above problems, an object of the present invention is to provide an infrared LED element that can be turned on with a lower driving voltage than conventional elements. [Means for solving the problem]

[0011] The infrared LED element of the present invention is An infrared LED element capable of emitting infrared light with a peak wavelength of 1350 nm to 2000 nm, a first stacked body having, in a stacking direction, a first semiconductor layer exhibiting a first conductivity type that is n-type or p-type, and an intermediate layer having a thickness of 15 nm or more; an active layer disposed on the intermediate layer of the first stack; a second stacked body disposed above the active layer, the second stacked body having a second semiconductor layer exhibiting a second conductivity type different from the first conductivity type; The band gap energy of the active layer is E a , the band gap energy of the intermediate layer is E m , the band gap energy of the first semiconductor layer is E p When E a <E m <E p It is characterized in that:

[0012] The inventors have inferred that the reason why the driving voltage required to turn on a conventional LED element becomes higher than expected as the emission wavelength becomes longer is due to the difference in band gap energy between the active layer and the cladding layer (corresponding to the "first semiconductor layer" and "second semiconductor layer" in the above-mentioned infrared LED element).

[0013] In general, it is considered preferable for the cladding layer of a conventional infrared LED element to have a large band gap in order to confine electrons within the active layer. In addition, InP is generally used as the cladding layer material in infrared LED elements that use an InP single crystal substrate, which enables emission of light with a peak wavelength of 1000 nm to 2000 nm.

[0014] Here, the bandgap energy of the active layer decreases as the peak wavelength increases. Therefore, the difference in bandgap energy between the active layer and the cladding layer increases as the peak wavelength increases. The inventors have estimated that, in the portion where the bandgap energy between the active layer and the cladding layer changes discontinuously, when the difference in bandgap energy exceeds a certain level, a significant voltage drop occurs in that portion, and have inferred that this voltage drop is the cause of the increase in drive voltage.

[0015] As will be described in detail with reference to the drawings in the section "Form for Carrying Out the Invention," the inventors have confirmed that the difference between the theoretical value and the actual value of the drive voltage required to light up an infrared LED element is large for infrared LEDs that emit light with a peak wavelength of 1350 nm or more (see Figure 3A).

[0016] Based on the above speculation, the inventors conducted extensive research and came up with the idea of ​​forming an intermediate layer between the active layer and the cladding layer that satisfies the above-mentioned relationship in order to suppress the voltage drop due to the difference in band gap energy between them. The inventors then confirmed that the drive voltage required for lighting an infrared LED element with the above configuration is lower than that of conventional LED elements, and more specifically, approaches the theoretical drive voltage (see Figure 3A).

[0017] Furthermore, through repeated trial manufacturing and investigation, the present inventors have also found that if the thickness of the intermediate layer is 15 nm or more, the driving voltage is significantly reduced (see FIG. 3B).

[0018] In other words, with the above configuration, an infrared LED element can be turned on by applying a voltage that is closer to the theoretical driving voltage than conventional ones, i.e., an infrared LED element that can be turned on by a lower driving voltage than conventional ones can be realized.

[0019] In the above infrared LED element, The active layer is formed by stacking well layers and barrier layers, and the band gap energy of the barrier layers is set to E b When E a <E b <E m It's okay if that's the case.

[0020] With the above configuration, electrons and holes are confined in the well layers sandwiched between the barrier layers, facilitating recombination of electrons and holes in the active layer, thereby improving light-emitting efficiency.

[0021] In the above infrared LED element, The intermediate layer has a dopant concentration of 2×1018 / cm 3 The following semiconductor layers may also be used.

[0022] A common method for reducing the voltage drop at the portion where the bandgap energy changes discontinuously is to increase the doping concentration near the interface where the bandgap energy changes discontinuously, thereby reducing the electrical resistance. However, because the interface is also near the active layer, increasing the doping concentration may cause high-concentration impurity atoms to diffuse into the active layer and become non-radiative recombination centers, resulting in a decrease in luminous efficiency.

[0023] The inventors of the present invention have conducted a series of trial manufacturing studies and have determined that the doping concentration is 2×10 18 / cm 3 Preferably, it is 5 x 10 or less. 17 / cm 3 It has been found that the following is more preferable.

[0024] In addition, in the infrared LED element, The active layer may have a thickness of 30 nm or more.

[0025] Our research and development has shown that in light-emitting diodes (LEDs), if the total thickness of the active layer is thinner than 30 nm, electrons introduced into the active layer cannot be sufficiently converted into light, resulting in a decrease in light-emitting efficiency, especially at high current densities. For this reason, in the infrared LED element of the present invention, the thickness of the active layer is preferably 30 nm or more, and more preferably 40 nm or more. When the active layer has a quantum well structure in which well layers and barrier layers are stacked, the sum of the thicknesses of the well layers corresponds to the "thickness of the active layer."

[0026] In addition, in the infrared LED element, The first semiconductor layer may be a layer made of InP.

[0027] In addition, in the infrared LED element, The active layer may be a layer made of GaInAsP.

[0028] In addition, in the infrared LED element, The first stack may include an electron blocking layer made of AlInAs disposed above the first semiconductor layer.

[0029] In addition, in the infrared LED element, The band gap energy of the active layer is E a and the band gap energy of the first semiconductor layer is E p When the difference between these is 100%, the band gap energy of the active layer is E a and the band gap energy E of the intermediate layer m The difference may be within a range of 30% to 60%. [Effects of the Invention]

[0030] According to the present invention, an infrared LED element that can be turned on with a lower driving voltage than conventional elements is realized. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a cross-sectional view schematically illustrating the structure of an infrared LED element according to one embodiment. [Figure 2A] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2B] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2C] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2D] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2E]2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2F] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2G] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2H] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2I] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2J] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2K] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2L] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2M] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 2N] 2 is a cross-sectional view illustrating a step in a method for manufacturing the infrared LED element shown in FIG. 1. FIG. [Figure 3A] 1 is a graph plotting the results of verification experiment 1. [Figure 3B] 10 is a graph plotting the results of verification experiment 2. [Figure 4] FIG. 10 is a cross-sectional view schematically showing the structure of an infrared LED element according to another embodiment. [Figure 5] FIG. 10 is a cross-sectional view schematically showing the structure of an infrared LED element according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0032] The infrared LED element of the present invention will be described below with reference to the drawings. Note that the drawings relating to the infrared LED element are all schematic illustrations, and the dimensional ratios and numbers in the drawings do not necessarily correspond to the actual dimensional ratios and numbers.

[0033] In this specification, the expression "Layer B is disposed on Layer A" is intended to include not only the case where Layer B is formed directly on the surface of Layer A, but also the case where Layer B is disposed on the surface of Layer A via a thin film. Note that the "thin film" referred to here refers to a layer with a thickness of 50 nm or less, and preferably a layer with a thickness of 10 nm or less.

[0034] Furthermore, in this specification, the expression "layer B is disposed above layer A" is used as a concept that also encompasses the case where, if the position of the infrared LED element is rotated, layer B is located above layer A. In other words, the above expression does not limit the above when the infrared LED element is disposed in a certain orientation, but rather suggests that layer A and layer B are disposed in this order in the first direction, which is the stacking direction.

[0035] 1 is a cross-sectional view schematically showing the structure of an infrared LED element of this embodiment. In the following description, the XYZ coordinate system shown in FIG. 1 will be referred to where appropriate.

[0036] In the following description, when a positive or negative direction is to be distinguished when expressing a direction, the direction is described with a positive or negative sign, such as "+X direction" or "-X direction." When a direction is to be expressed without distinguishing between positive and negative directions, the direction is simply described as "X direction." In other words, in this specification, when simply referring to "X direction," both the "+X direction" and the "-X direction" are included. The same applies to the Y direction and the Z direction. In this embodiment, when "layer B is disposed above layer A," it is intended to mean that layer B is disposed on the +Y side of layer A.

[0037] In the infrared LED element 1, infrared light L is generated in the active layer 25, which will be described later. More specifically, as shown in Fig. 1, the infrared light L (L1, L2) is extracted in the +Y direction with respect to the active layer 25. The infrared light L has a peak wavelength of 1350 nm to 2000 nm.

[0038] [Element structure] The structure of the infrared LED element 1 will be described in detail below.

[0039] (Support substrate 11) The support substrate 11 is made of a semiconductor such as Si or Ge, or a metal material such as Cu or CuW. When the support substrate 11 is made of a semiconductor, it may be doped with a high concentration of dopant to exhibit conductivity. For example, the support substrate 11 may be doped with 1×10 boron (B). 19 / cm 3 The support substrate 11 is a Si substrate doped with a dopant concentration of 10 mΩ cm or less and having a resistivity of 10 mΩ cm or less. In addition to boron (B), other dopants that can be used include phosphorus (P), arsenic (As), and antimony (Sb). From the viewpoint of achieving both high heat dissipation and low manufacturing costs, the support substrate 11 is preferably a Si substrate.

[0040] The thickness (length in the Y direction) of the support substrate 11 is not particularly limited, but is, for example, 50 μm to 500 μm, and preferably 100 μm to 300 μm.

[0041] (Metal bonding layer 13) The infrared LED element 1 includes a metal bonding layer 13 disposed on the +Y side of the support substrate 11. The metal bonding layer 13 is made of a low-melting-point solder material, such as Au, Au-Zn, Au-Sn, Au-In, Au-Cu-Sn, Cu-Sn, Pd-Sn, or Sn. As will be described later with reference to FIG. 2H, this metal bonding layer 13 is used in step S8 to bond the growth substrate 3, on the upper surface of which the first stack 20a is formed, to the support substrate 11. The thickness of the metal bonding layer 13 is not particularly limited, but is, for example, 0.5 μm to 5.0 μm, and preferably 1.0 μm to 3.0 μm.

[0042] A barrier layer may be formed on the +Y side of the metal bonding layer 13. The barrier layer may be provided for the purpose of suppressing diffusion of the solder material that constitutes the metal bonding layer 13. The material is not limited as long as it achieves this function, but the barrier layer may be realized by a material containing, for example, Ti, Pt, W, Mo, or Ni. A more specific example is a Ti / Pt laminate, and the barrier layer may be configured by laminating multiple layers of the laminate, such as Ti / Pt / Ti / Pt / Ti / Pt...

[0043] (Reflection layer 15) The infrared LED element 1 of this embodiment includes a reflective layer 15 disposed on the +Y side of the metal bonding layer 13.

[0044] The infrared light L generated in the active layer 25 includes infrared light L1 traveling toward the light emitting surface side (+Y side) and infrared light L2 traveling toward the opposite side (-Y side) from the light emitting surface. The reflective layer 15 has the function of reflecting the infrared light L2 traveling toward the support substrate 11 side (-Y side) of the infrared light L generated in the active layer 25 and guiding it to the +Y side. The reflective layer 15 is made of a conductive material that exhibits high reflectivity with respect to the infrared light L. The reflectivity of the reflective layer 15 with respect to the infrared light L is 50% or more, preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

[0045] When the peak wavelength of the infrared light L is 1350 nm to 2000 nm, Ag, Ag alloy, Au, Al, Cu, etc. can be used as the material of the reflective layer 15. This material can be selected appropriately depending on the wavelength of the infrared light L.

[0046] The thickness of the reflective layer 15 is not particularly limited, but is, for example, 0.1 μm to 2.0 μm or less, and preferably 0.3 μm to 1.0 μm or less.

[0047] In addition, when a barrier layer such as that described above is formed between the reflective layer 15 and the metal bonding layer 13, it is possible to prevent the material constituting the metal bonding layer 13 from diffusing toward the reflective layer 15, thereby preventing the reflectivity of the reflective layer 15 from decreasing.

[0048] (insulating layer 17) The infrared LED element 1 shown in Fig. 1 includes an insulating layer 17 disposed on the +Y side of the reflective layer 15. The insulating layer 17 is made of a material that exhibits electrical insulation and is highly transparent to infrared light L. The transmittance of the insulating layer 17 to infrared light L is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

[0049] When the peak wavelength of the infrared light L is 1350 nm to 2000 nm, SiO2, SiN, Al2O3, ZrO, HfO, MgO, or the like can be used as the material for the insulating layer 17. This material can be selected appropriately depending on the wavelength of the light generated in the active layer 25.

[0050] (First stack 20a, second stack 20b, active layer 25) The infrared LED element 1 shown in Fig. 1 has a first stacked body 20a arranged on the +Y side of the insulating layer 17, an active layer 25 arranged on top of the first stacked body 20a, and a second stacked body 20b arranged on top of the active layer 25. The first stacked body 20a is formed, for example, by stacking a first contact layer 21, a first cladding layer 23, and a first intermediate layer 23a in the Y direction. The second stacked body 20b is formed, for example, by stacking a second cladding layer 27 and a second intermediate layer 27a in the Y direction. Each layer (21, 23, 24, 25, 27, 28) is made of a material that is lattice-matched to a growth substrate 3 (described below) and can be epitaxially grown.

[0051] The total thickness of the multilayer structure including the first stacked body 20a, the active layer 25, and the second stacked body 20b is 30 μm (30,000 nm) or less, and preferably 5 μm to 20 μm.

[0052] <<First contact layer 21, first cladding layer 23>> In this embodiment, the first contact layer 21 is made of any semiconductor material, but is preferably made of a III-V group semiconductor containing As, such as p-type InGaAs, p-type GaInAsP, or p-type GaAs. The thickness of the first contact layer 21 is not limited, but is, for example, 10 nm to 1000 nm, and preferably 50 nm to 500 nm. The p-type dopant concentration of the first contact layer 21 is preferably 5×10 17 / cm 3 ~3×10 19 / cm 3 and more preferably 1×10 18 / cm 3 ~2×10 19 / cm 3 In order to obtain a good ohmic contact, the dopant concentration of the first contact layer 21 in at least the region in contact with the Au / Zn / Au layer described later is set to 5×10 18 / cm 3 It is preferable that this is equal to or greater than this.

[0053] In this embodiment, the first cladding layer 23 is disposed on the +Y side of the first contact layer 21 and is made of, for example, p-type InP. The thickness of the first cladding layer 23 is not limited, but is, for example, 1000 nm to 10000 nm, and preferably 2000 nm to 5000 nm. The p-type dopant concentration of the first cladding layer 23 at a position away from the active layer 25 is preferably 1×10 17 / cm 3 ~3×10 18 / cm 3 or less, more preferably 5×10 17 / cm 3 ~3×10 18 / cm 3 The following is the result.

[0054] The p-type dopant contained in the first contact layer 21 and the first cladding layer 23 can be Zn, Mg, Be, or the like, with Zn or Mg being preferred, and Zn being particularly preferred. In this embodiment, the first contact layer 21, the first intermediate layer 23a, and the first cladding layer 23 correspond to the "first semiconductor layer," and the p-type corresponds to the "first conductivity type."

[0055] 《First intermediate layer 23a》 In this embodiment, the first intermediate layer 23a is disposed on the +Y side of the first cladding layer 23 and is a p-type doped layer, but may be undoped. The first intermediate layer 23a adjusts the band gap energy of the active layer 25 to E a , the band gap energy of the first cladding layer 23 is E p , the band gap energy of the first intermediate layer 23a is E m1 When E a <E m1 <E p It is configured as a layer that satisfies the following.

[0056] The thickness of the first intermediate layer 23a is not limited, but is preferably 15 nm or more, and more preferably 30 nm or more. From the viewpoint of confining electrons within the active layer 25, a certain band gap difference and film thickness between the active layer 25 and the cladding layers (23, 27) are necessary. In the wavelength range of emitted light of 1350 nm to 2000 nm, the band gap energy between the active layer 25 and the cladding layers is large, so InP is generally used for the cladding layers (23, 27). Therefore, the band gap energy of the active layer 25 is set to E a and the band gap energy of the cladding layer (23, 27) is E p When these differences are taken as 100%, a layer having the band gap difference of 80% or more and a film thickness of 200 nm or more is recognized as a cladding layer.

[0057] The p-type dopant concentration of the first intermediate layer 23a is determined based on the above-mentioned band gap energy relationship (E a <E m1 <E p), preferably 2 × 10 18 / cm 3 or less, more preferably 5×10 17 / cm 3 The following is the result.

[0058] In addition, the band gap energy E a and the band gap energy E of the first cladding layer 23. p When the difference between the band gap energy E a and the band gap energy E of the first intermediate layer 23a. m1 The difference is preferably in the range of 40% to 60%, and more preferably in the range of 45% to 55%.

[0059] The material of the first intermediate layer 23a is appropriately selected from materials that do not absorb the infrared light L generated in the active layer 25 and that are capable of epitaxial growth by lattice matching with the growth substrate 3. When an InP substrate is used as the growth substrate 3, the material of the first intermediate layer 23a can be InP, GaInAsP, AlGaInAs, or the like, but InP is preferred.

[0060] 《Active layer 25》 In this embodiment, the active layer 25 is disposed on the +Y side of the first cladding layer 23. The material of the active layer 25 is appropriately selected from materials that can generate light having a peak wavelength within a target wavelength range and that can be lattice-matched with the growth substrate 3 and epitaxially grown.

[0061] When manufacturing an infrared LED element 1 that emits infrared light L with a peak wavelength of 1350 nm to 2000 nm, the active layer 25 may have a single layer structure of GaInAsP, AlGaInAs, or InGaAs, or preferably has an MQW (Multiple Quantum Well) structure including a well layer made of GaInAsP, AlGaInAs, or InGaAs and a barrier layer made of GaInAsP, AlGaInAs, InGaAs, or InP that has a larger bandgap energy than the well layer. When an MQW structure is adopted for the active layer 25, the bandgap energy of the active layer 25 is set to E a , the band gap energy of the first intermediate layer 23a is E m1 , the band gap energy of the barrier layer is E b When E a <E b <E m1 It is configured to satisfy the following.

[0062] The thickness of the active layer 25 is preferably 30 nm or more, and more preferably 40 nm or more. More specifically, when the active layer 25 has a single-layer structure, the thickness is preferably 30 nm to 2000 nm, and more preferably 50 nm to 1000 nm. When the active layer 25 has an MQW structure, well layers and barrier layers each having a thickness of 5 nm to 20 nm are stacked in a range of 2 to 50 periods, and the total thickness of all the well layers is preferably 30 nm or more, and more preferably 40 nm or more.

[0063] The active layer 25 may be doped to n-type or p-type, or may be undoped. When doped to n-type, for example, Si can be used as the dopant.

[0064] Second Cladding Layer 27 In this embodiment, the second cladding layer 27 is disposed on the +Y side of the active layer 25 and is made of, for example, n-type InP. The second cladding layer 27 is required to have a certain film thickness and impurity concentration in order to spread current. The thickness of the second cladding layer 27 is not limited, but is, for example, 2000 nm to 15000 nm, and preferably 5000 nm to 10000 nm. The n-type dopant concentration of the second cladding layer 27 is preferably 5×10 17 / cm 3 More preferably, 1×10 18 / cm 3 In addition, when current dispersion and the like are also taken into consideration, the range of the n-type dopant concentration of the second cladding layer 27 is preferably 5×10 17 / cm 3 ~1×10 19 / cm 3 and more preferably 1×10 18 / cm 3 ~5×10 18 / cm 3 is.

[0065] The material of the second cladding layer 27 is appropriately selected from materials that do not absorb the infrared light L generated in the active layer 25 and that are lattice-matched with the growth substrate 3 (see FIG. 2B) and can be epitaxially grown. When an InP substrate is used as the growth substrate 3, the material of the second cladding layer 27 can be InP, GaInAsP, AlGaInAs, or the like, but InP is preferred.

[0066] The n-type impurity material doped into the second cladding layer 27 may be Sn, Si, S, Ge, Se, or the like, with Si being particularly preferred. In this embodiment, the second intermediate layer 27a and the second cladding layer 27 correspond to the "second semiconductor layer," and the n-type corresponds to the "second conductivity type."

[0067] As shown in Fig. 1, in the infrared LED element 1 of this embodiment, an uneven portion 40 is formed on the +Y side surface (hereinafter referred to as the "first surface 27p") of the second cladding layer 27. Although this uneven portion 40 is shown in Fig. 1 as having a periodic shape, in reality it has a random uneven shape formed by a dipping process using an etching solution.

[0068] 《Second intermediate layer 27a》 In this embodiment, the second intermediate layer 27a is disposed on the −Y side of the second cladding layer 27 and is an n-type doped layer, but may be undoped. The second intermediate layer 27a adjusts the band gap energy of the active layer 25 to E a , the band gap energy of the second cladding layer 27 is E q , the band gap energy of the second intermediate layer 27a is E m2 When E q >E m2 >E a It is configured as a layer that satisfies the following.

[0069] The thickness of the second intermediate layer 27a is not limited, but similar to the first intermediate layer 23a, it is preferably 15 nm or more, more preferably 30 nm or more. The n-type dopant concentration of the second intermediate layer 27a is determined based on the above-mentioned band gap energy relationship (E a <E m <E p ), preferably 2 × 10 18 / cm 3 or less, more preferably 5×10 17 / cm 3 The following is the result.

[0070] The material of the second intermediate layer 27a is appropriately selected from materials that do not absorb the infrared light L generated in the active layer 25 and that can be epitaxially grown by lattice matching with the growth substrate 3. When an InP substrate is used as the growth substrate 3, the material of the second intermediate layer 27a can be InP, GaInAsP, AlGaInAs, or the like, but InP is preferred.

[0071] (Protective film 29) The protective film 29 is a film formed primarily for the purpose of protecting the exposed surface of the active layer 25. Examples of materials that can be used for the protective film 29 include Si3N4, SiO2, and an intermediate material between Si3N4 and SiO2. Si3N4 film is preferable as the protective film 29 because it has a better moisture barrier effect than SiO2 film. For manufacturing convenience, the protective film 29 may be configured to cover the first surface 27p of the second stack, as shown in FIG. 1 . When the refractive index of the protective film 29 at the wavelength λ of infrared light L generated in the active layer 25 is n, the thickness T of the protective film 29 preferably satisfies the relationship T = λ / (4n) from the viewpoint of anti-reflection effect, so that the light generated in the active layer 25 can be efficiently extracted to the outside.

[0072] (Internal electrode 31) The infrared LED element 1 shown in FIG. 1 has internal electrodes 31 formed in through holes that penetrate the insulating layer 17 in the Y direction at multiple locations, and electrically connects the first semiconductor layer (21, 23) and the support substrate 11 via the reflective layer 15 and the metal bonding layer 13.

[0073] The internal electrode 31 in this embodiment is made of a material that can form an ohmic contact with the first contact layer 21. Examples of the material for the internal electrode 31 include Au, Zn, Be, and alloys thereof.

[0074] (Top electrode 32) The infrared LED element 1 shown in Fig. 1 has a top electrode 32 disposed on the top surface of the second laminate 20b. Typically, multiple top electrodes 32 are formed to extend in a predetermined direction on the XZ plane. As an example, multiple top electrodes 32 extend in the X and Z directions along the sides of the second laminate 20b, forming a comb shape. However, the arrangement pattern of the top electrodes 32 is arbitrary, and may be, for example, a lattice shape or a spiral shape.

[0075] The top electrode 32 is formed over a wide range on the XZ plane while exposing the surface of the second cladding layer 27 located on the -Y side (except directly or a part of the dielectric layer formed on the same surface). This allows the current flowing in the active layer 25 to be spread in a direction parallel to the XZ plane, and light can be emitted over a wide range in the active layer 25.

[0076] The upper electrode 32 is made of, for example, a material such as AuGe / Ni / Au or AuGe, and may include a plurality of these materials.

[0077] (Pad electrode 34) As shown in Fig. 1, the infrared LED element 1 has a pad electrode 34 disposed on the upper surface of a portion of the upper electrode 32. Although Fig. 1 shows the pad electrode 34 formed on the entire surface of the upper electrode 32, this is for convenience of illustration. In reality, the pad electrode 34 may be formed on a portion of the surface of the upper electrode 32 extending in the planar direction.

[0078] The pad electrode 34 is made of, for example, Ti / Au or Ti / Pt / Au, etc. The pad electrode 34 is provided for the purpose of securing an area for contacting a bonding wire for power supply, but in the present invention, whether or not the pad electrode 34 is provided is optional.

[0079] (Back electrode 33) 1 includes a back electrode 33 disposed on the surface of the support substrate 11 opposite to the first laminate 20a (-Y side). The back electrode 33 is in ohmic contact with the support substrate 11. The back electrode 33 is made of, for example, a material such as Ti / Au or Ti / Pt / Au, and may include a plurality of these materials.

[0080] [Manufacturing method] An example of a method for manufacturing the above-mentioned infrared LED element 1 will be described with reference to Figures 2A to 2M. Each of Figures 2A to 2M is a cross-sectional view of one step in the manufacturing process. The order of the following steps can be changed as appropriate as long as it does not affect the manufacturing of the infrared LED element 1.

[0081] (Step S1) As shown in FIG. 2A, a growth substrate 3 is prepared. In this embodiment, an InP substrate having one of its main surfaces as a (001) plane is preferably used as the growth substrate 3. For example, the thickness is 370 μm, and the diameter of the main surface is 2 inches. However, the thickness and size of the growth substrate 3 are set as appropriate.

[0082] (Step S2) The growth substrate 3 is transferred into, for example, an MOCVD (Metal Organic Chemical Vapor Deposition) apparatus, and a buffer layer 22, an etching stop layer (ES layer) 24, a second cladding layer 27, a second intermediate layer 27a, an active layer 25, a first intermediate layer 23a, a first cladding layer 23, and a first contact layer 21 are epitaxially grown in this order on the growth substrate 3 to form a first stack 20a, an active layer 25, and a second stack 20b (see FIG. 2B ). In this step S2, the type and flow rate of the source gas, the processing time, the ambient temperature, and the like are appropriately adjusted depending on the material or film thickness of the layer to be grown.

[0083] An example of forming the first stack 20a, the active layer 25, and the second stack 20b is as follows. First, n-type InP doped with Si is stacked on the growth substrate 3 to a predetermined thickness (e.g., about 500 nm) to obtain the buffer layer 22. Next, a layer of a material different from the buffer layer 22 (here, an InGaAs layer) is stacked to a predetermined thickness (e.g., about 200 nm) to obtain the ES layer 24. Thereafter, the second cladding layer 27, the second intermediate layer 27a, the active layer 25, the first intermediate layer 23a, the first cladding layer 23, and the first contact layer 21 are sequentially formed under conditions set to achieve the above-mentioned thicknesses and compositions.

[0084] As a specific example, n-type InP doped with Si is deposited to a thickness of 7000 nm to obtain the second cladding layer 27. Next, n-type InP doped with Si is deposited to a thickness of 30 nm to obtain the second intermediate layer 27a.

[0085] Furthermore, InGaAsP is deposited to a thickness of 900 nm to obtain the active layer 25. Here, the conditions are set so that the peak wavelength of the infrared light L emitted from the infrared LED element 1 is 1450 nm. However, as mentioned above, by adjusting the composition ratio of the materials constituting the active layer 25 or by employing an MQW structure, the peak wavelength of the infrared light L can be adjusted within the range of 1350 nm to 2000 nm.

[0086] Then, p-type InP doped with Zn is deposited to a thickness of 30 nm to obtain the first intermediate layer 23a, p-type InP doped with Zn is deposited to a thickness of 3000 nm to obtain the first cladding layer 23, and then p-type GaInAsP doped with Zn is deposited to a thickness of 200 nm to obtain the first contact layer 21.

[0087] (Step S3) After the wafer on which the second stack 20b, the active layer 25, and the first stack 20a are formed on the growth substrate 3 is removed from the MOCVD apparatus, an insulating layer 17 made of, for example, SiO2 is formed by plasma CVD (see FIG. 2C). An example of the thickness is 200 nm. Next, a resist mask patterned by photolithography is formed on the surface of the insulating layer 17. A portion of the insulating layer 17 corresponding to the resist opening is removed by etching using a predetermined agent such as buffered hydrofluoric acid, thereby forming a through-hole 31c (see FIG. 2D).

[0088] (Step S4) Next, the internal electrode 31 is formed in the through hole 31c (see FIG. 2E). Specifically, after an Au / Zn / Au layer is formed in the through hole 31c as the internal electrode 31, the resist mask is removed and then annealing is performed by heating at 420°C for 10 minutes, for example, to form an ohmic contact between the first contact layer 21 and the Au / Zn / Au layer.

[0089] (Step S5) 2E, the reflective layer 15 and the metal bonding layer 13a are sequentially formed on the upper surface of the insulating layer 17. For example, the reflective layer 15 is formed by depositing an Al / Au film to a predetermined thickness using an EB evaporation device, and then the metal bonding layer 13a is formed by depositing a Ti / Au film to a predetermined thickness. The reflective layer 15 may be made of the same material as the internal electrode 31 described above.

[0090] An example of the material film for the reflective layer 15 is Al / Au=5 nm / 200 nm. An example of the film thickness for the metal bonding layer 13a is Ti / Au=150 nm / 1500 nm. As described above, a barrier layer may be formed between the reflective layer 15 and the metal bonding layer 13a. An example of the material film for the barrier layer is Ti / Pt=150 nm / 300 nm.

[0091] (Step S6) As shown in FIG. 2F, a support substrate 11 is prepared in addition to the growth substrate 3. In this embodiment, a conductive Si substrate having a (001) plane as one of its main surfaces and doped with a high concentration of boron (B) is used. The electrical resistivity of the support substrate 11 is preferably less than 10 mΩ·cm (=0.1 mΩ·m).

[0092] (Step S7) 2G, metal bonding layer 13b is formed on the main surface of support substrate 11. Metal bonding layer 13b can be formed by the same method as metal bonding layer 13a described above in step S4. As described above, a barrier layer may be formed between support substrate 11 and metal bonding layer 13b.

[0093] (Step S8) As shown in FIG. 2H, the growth substrate 3 and the support substrate 11 are bonded together with pressure applied via the metal bonding layers 13 (13a, 13b) using, for example, a wafer bonding device. Preferably, the surfaces of the metal bonding layers 13 (13a, 13b) are cleaned before being bonded together. This bonding process is performed, for example, at 300°C and 1 MPa. This process melts and integrates the metal bonding layer 13a on the growth substrate 3 and the metal bonding layer 13b on the support substrate 11 (metal bonding layer 13).

[0094] (Step S9) As shown in FIG. 2I, the growth substrate 3 is removed. For example, the growth substrate 3 is removed by immersing the bonded wafer in a hydrochloric acid-based etchant. At this time, the ES layer 24, which is made of a material different from the growth substrate 3 and the buffer layer 22, is insoluble in the hydrochloric acid-based etchant, so the etching process stops when the ES layer 24 is exposed.

[0095] (Step S10) 2J, the ES layer 24 is removed to expose the second cladding layer 27. For example, after washing with pure water as necessary, the ES layer 24 is removed by immersing it in a predetermined chemical solution that is soluble in the ES layer 24 but insoluble in the second cladding layer 27. As an example, a mixed solution of sulfuric acid and hydrogen peroxide (SPM) can be used.

[0096] (Step S11) 2K, an upper electrode 32 is formed on the exposed surface of the second cladding layer 27. Specifically, the process is carried out as follows.

[0097] A resist mask patterned by photolithography is formed on the surface of the second cladding layer 27. Next, a material for forming the upper electrode 32 (e.g., Au / Ge / Au) is deposited using an EB evaporation system, and then lifted off to form the upper electrode 32. An example of the film thickness of the upper electrode 32 is Au / Ge / Au=10 nm / 30 nm / 150 nm.

[0098] Next, a pad electrode 34 is formed on the upper surface of the upper electrode 32 at a predetermined position. This can also be achieved by a film formation process using an EB evaporation apparatus and a lift-off process, similar to the upper electrode 32. The pad electrode 34 is formed, for example, from Ti / Pt / Au, with thicknesses of Ti / Pt / Au=150 nm / 300 nm / 1500 nm, for example.

[0099] (Step S12) As shown in FIG. 2L, the first surface 27p of the second cladding layer 27 has an uneven portion 40 formed thereon.

[0100] As an example of a specific method, first, a patterned resist is formed on the first surface 27p of the second cladding layer 27 by photolithography. This resist has a pattern in which a plurality of holes, each 3 μm in diameter, are arranged in a triangular lattice pattern with a periodic length of 6 μm, except for the region where the top electrode 32 is formed. The region where the top electrode 32 is formed is covered with resist in which no holes are formed.

[0101] Using this patterned resist, the first surface 27p of the second cladding layer 27 is etched using an etchant such as a hydrochloric acid-phosphoric acid mixture. As a result, an etching pattern having a depth of, for example, 1 μm is formed on the first surface 27p through the holes formed in the resist. Thereafter, the resist is removed with a cleaning liquid such as acetone. Note that the order of steps S11 and S12 may be reversed.

[0102] (Step S13) As shown in FIG. 2M, mesa etching is performed to separate each element. Specifically, the non-etched areas of the surface of the second cladding layer 27 are masked with resist patterned by photolithography, and then wet etching is performed using a predetermined etchant. As a result, parts of the first stack 20a, active layer 25, and second stack 20b located in the unmasked areas are removed.

[0103] As an example of a specific method, first, the second cladding layer 27 is removed by etching using a hydrochloric acid-phosphoric acid mixture. This reaction is stopped when the active layer 25 is exposed. Next, the active layer 25 is removed by etching using a mixed solution of sulfuric acid and hydrogen peroxide (SPM). This reaction is stopped at the first cladding layer 23. Next, the first cladding layer 23 and the first contact layer 21 are removed by etching using a hydrochloric acid-phosphoric acid mixture, and the insulating layer 17 is exposed. Thereafter, the resist is removed by a cleaning liquid such as acetone.

[0104] (Step S14) 2N, a protective film 29, which also functions as an anti-reflection film, is formed by plasma CVD on the exposed surfaces of the first stack 20a, the active layer 25, and the second stack 20b. After the film formation, an opening pattern for the pad electrode portion is formed by photolithography, and the pad electrode 34 is exposed by etching using a predetermined chemical solution such as buffered hydrofluoric acid. The resist is then removed using an organic solvent such as acetone.

[0105] (Step S15) After the thickness of the back surface side of the support substrate 11 is adjusted, a back surface electrode 33 is formed on the back surface side of the support substrate 11 (see FIG. 1). Specifically, the back surface electrode 33 can be formed by depositing a film of the material for forming the back surface electrode 33 (e.g., Ti / Pt / Au) using a vacuum deposition apparatus, similar to the method for forming the top surface electrode 32. An example of the film thickness of the back surface electrode 33 is Ti / Pt / Au=150 nm / 300 nm / 1500 nm. After the back surface electrode is formed, a heat treatment is performed at 250°C for 10 minutes to improve the adhesion between the top surface electrode and the pad electrode and to stabilize the ohmic characteristics between the back surface electrode and the support substrate.

[0106] The thickness of the support substrate 11 can be adjusted by any method, but one example is to adhere the second laminate 20b side to back-grinding tape and then grind it with a back-grinder. The thickness after grinding is adjusted to within a range of 50 μm to 250 μm, for example, and is selected appropriately depending on the application of the infrared LED element 1 and subsequent processes. As a specific example, the thickness of the support substrate 11 after grinding is 150 μm. After the grinding process is completed, it is peeled off from the tape and washed.

[0107] The adjustment of the thickness of the back surface side of the support substrate 11 may be performed as needed, and is not necessarily an essential step.

[0108] (Step S16) Next, the wafer is diced together with the support substrate 11 to be made into chips. For example, with the back electrode 33 side attached with dicing tape, dicing is performed together with the support substrate 11 from the top electrode 32 side using a diamond blade or the like along the dicing line formed by mesa etching in step S13.

[0109] The chipped infrared LED element 1 is then mounted on a stem or the like using a conductive adhesive such as Ag paste, etc. The pad electrode 34 is connected to the post portion of the stem by wire bonding.

[0110] [Verification experiment 1] Here, a verification experiment was carried out to confirm the relationship between the peak wavelength of the emitted light and the driving voltage (forward voltage) of the infrared LED element 1, and the details of this experiment are described below.

[0111] (sample) Each example, comparative example, and reference example is as shown in the following Table 1. In Table 1, the elements of comparative examples 1 to 4 and reference examples 3 to 7 do not have an intermediate layer (23a, 27a).

[0112] [Table 1]

[0113] (Measurement method) The value of the drive voltage (forward voltage Vf) applied between the anode terminal and the cathode terminal of the sample was measured so that the current supplied to the sample (supply current If) was 100 mA.

[0114] (result) FIG. 3A is a graph plotting the results of Verification Experiment 1. In FIG. 3A, square plots indicate plots of samples (Examples 1 to 5, Reference Examples 1 and 2) that have intermediate layers (23a, 27a), and circular plots indicate plots of samples (Comparative Examples 1 to 4, Reference Examples 3 to 7) that do not have intermediate layers (23a, 27a). The graph in FIG. 3A also shows the band gap energy E a The theoretical forward voltage curve calculated based on is represented by the dashed line.

[0115] Here, the theoretical forward voltage is the forward voltage Vf of an infrared LED element with a peak wavelength of 1050 nm, as described above. 1050 It was derived based on the relationship between energy E and wavelength λ (E(eV)=hc / λ=1240 / λ), where h is Planck's constant and c is the speed of light. More specifically, when the peak wavelength is λ x The forward voltage Vf of an infrared LED element with a peak wavelength of 1050 nm is 1050 The magnitude of the voltage drop is ΔVf, so Vf=Vf 1050 -ΔVf(λ x )=Vf 1050 -(1240 / 1050-1240 / λ x ) was derived.

[0116] 3A, for samples with peak wavelengths less than 1350 nm, the forward voltage Vf was found to be sufficiently close to the theoretical curve, regardless of whether an intermediate layer was present. In contrast, for samples with peak wavelengths of 1350 nm or greater, differences in forward voltage Vf were apparent depending on whether an intermediate layer was present. For Comparative Examples 1 to 4 without an intermediate layer, the samples with longer peak wavelengths had forward voltages Vf that deviated significantly from the theoretical curve. For Examples 1 to 5 with an intermediate layer, the forward voltages Vf were found to be close to the theoretical curve, regardless of peak wavelength.

[0117] [Verification experiment 2] Next, a verification experiment was conducted on the infrared LED element 1 to confirm the relationship between the thickness of the first intermediate layer 23a and the driving voltage (forward voltage) of the infrared LED element, and the details thereof will be described below.

[0118] (sample) The experimental samples prepared had first intermediate layers 23a with thicknesses of 0 nm (four samples), 10 nm (one sample), 15 nm (one sample), 20 nm (one sample), and 50 nm (two samples). All samples were infrared LED elements emitting light with a peak wavelength of 1550 nm.

[0119] (Measurement method) The value of the drive voltage (forward voltage Vf) applied between the anode terminal and the cathode terminal of the sample was measured so that the current supplied to the sample (supply current If) was 100 mA.

[0120] (result) Fig. 3B is a graph plotting the results of verification experiment 2. As shown in Fig. 3B, it can be confirmed that the forward voltage Vf drops sharply when the thickness of the intermediate layer (23a, 27a) is 15 nm or more.

[0121] As described above, the infrared LED element 1 having the above configuration has a drive voltage (forward voltage) that is sufficiently close to the theoretically derived value by providing the first intermediate layer 23a, even when the active layer 25 is a layer that emits light with a peak wavelength of 1350 nm or more. In other words, the infrared LED element 1 having the above configuration has a reduced forward voltage compared to conventional infrared LED elements, and as a result, its light-emitting efficiency is improved.

[0122] [Another embodiment] Another embodiment will be described below.

[0123] <1> Figure 4 is a cross-sectional view schematically showing the structure of an infrared LED element 1 according to another embodiment. As shown in Figure 4, the infrared LED element 1 of this embodiment includes an InP substrate 50, a first laminate 20a, an active layer 25, a second laminate 20b, an insulating layer 17, reflective electrodes (51, 52) corresponding to reflective layers, a first electrode 53, a second electrode 54, an internal electrode 55, and a height-adjusting electrode 56.

[0124] The InP substrate 50 is a growth substrate, and its surface constitutes a light emitting surface 50a for extracting infrared light L. As shown in FIG. 4, the light emitting surface 50a has an uneven portion formed thereon, similar to the above-described embodiment.

[0125] Similar to the above-described embodiment, the first stacked body 20a, the active layer 25, and the second stacked body 20b have a structure in which the first cladding layer 23, the first intermediate layer 23a, the active layer 25, the second intermediate layer 27a, and the second cladding layer 27 are stacked. When viewed in the Y direction, the first stacked body 20a of this embodiment has the first cladding layer 23 formed over the entire InP substrate 50, but the first intermediate layer 23a, the active layer 25, the second intermediate layer 27a, and the second cladding layer 27 formed only on a portion of the InP substrate 50. Here, in another embodiment, the first cladding layer 23 corresponds to the "first semiconductor layer," the second cladding layer 27 corresponds to the "second semiconductor layer," and the first intermediate layer 23a corresponds to the "intermediate layer."

[0126] The reflective electrodes (51, 52) each correspond to a reflective layer that reflects the infrared light L emitted from the active layer 25 and traveling toward the insulating layer 17 side (-Y side) either directly or after repeated reflection within the element, so that the light travels toward the InP substrate 50 side (+Y side). As described above, the flip-chip type infrared LED element 1 of this embodiment is flip-mounted onto the submount 58.

[0127] The first electrode 53 is provided so as to be electrically connected to a region of the first cladding layer 23 where the first intermediate layer 23a is not disposed as an upper layer, and the second electrode 54 is provided so as to be in contact with the surface of the reflective electrode 52 on the opposite side (-Y side) from the side on which the insulating layer 17 is formed.

[0128] The insulating layer 17 is arranged to connect the side surfaces of the first stack 20a, the active layer 25, and the second stack 20b, the upper surface of the second clad layer 27, and the upper surface of the first clad layer 23 in the area where the first intermediate layer 23a is not arranged as an upper layer.

[0129] <2> Fig. 5 is a cross-sectional view schematically showing the structure of an infrared LED element 1 according to another embodiment different from that shown in Fig. 4. As shown in Fig. 5, the first laminate 20a may include an electron blocking layer 23b on the +Y side of the first cladding layer 23 and on the -Y side of the first intermediate layer 23a. The electron blocking layer 23b may be made of, for example, AlInAs.

[0130] <3> In the above-described embodiments, the first intermediate layer 23a and the second intermediate layer 27a are provided, but it is sufficient to provide at least one of them.

[0131] <4> In the above-described embodiment, the first stack 20a (first contact layer 21, first intermediate layer 23a, first cladding layer 23) is a p-type semiconductor, and the second stack 20b (second intermediate layer 27a, second cladding layer 27) is an n-type semiconductor, but the conductivity types of the two may be reversed. Furthermore, the intermediate layers (first intermediate layer 23a and second intermediate layer 27a) may be undoped.

[0132] <5> The configuration of the infrared LED element 1 described above is merely an example, and the present invention is not limited to the configurations shown in the drawings. [Explanation of symbols]

[0133] 1: Infrared LED element 3: Growth substrate 11: Support substrate 13,13a,13b: Metal bonding layer 15 : Reflective layer 17: Insulating layer 20a: First laminate 20b: Second laminate 21: First contact layer 22: Buffer layer 23: First cladding layer 23a : First intermediate layer 23b: Electron blocking layer 24: ES layer 25: Active layer 27: Second cladding layer 27a : Second intermediate layer 27p: Front page 29: Protective film 31 : Internal electrode 31c: Through hole 32: Top electrode 33: Back electrode 34: Pad electrode 40: Uneven part 50: InP substrate 50a: Light exit surface 51,52 : Reflective electrode 53: First electrode 54: Second electrode 55 : Internal electrode 55a: Conductive oxide layer 55b: Filled bed 56: Height adjustment electrode 57a, 57b: pattern electrodes 58: Submount L,L1,L2 : Infrared light

Claims

1. An infrared LED element capable of emitting infrared light having a peak wavelength of 1350 nm to 2000 nm, a first stacked body including, in a stacking direction, a first semiconductor layer exhibiting a first conductivity type that is n-type or p-type, and an intermediate layer having a thickness of 15 nm or more; an active layer disposed on the intermediate layer of the first stack; a second stacked body having a second semiconductor layer exhibiting a second conductivity type different from the first conductivity type and disposed above the active layer; The band gap energy of the active layer is E a , the band gap energy of the intermediate layer is E m , the band gap energy of the first semiconductor layer is E p When E a <E m <E p An infrared LED element characterized by:

2. The active layer is formed by stacking well layers and barrier layers, and the band gap energy of the barrier layers is set to E b When E a <E b <E m 2. The infrared LED element according to claim 1, wherein

3. The intermediate layer has a dopant concentration of 2×10 18 / cm 3 3. The infrared LED element according to claim 1, wherein the semiconductor layer is:

4. 3. The infrared LED element according to claim 1, wherein the active layer has a thickness of 30 nm or more.

5. 3. The infrared LED element according to claim 1, wherein the first semiconductor layer is made of InP.

6. 3. The infrared LED element according to claim 1, wherein the active layer is made of GaInAsP.

7. 3. The infrared LED element according to claim 1, wherein the first stacked body includes an electron blocking layer made of AlInAs disposed above the first semiconductor layer.

8. The band gap energy of the active layer is E a and the band gap energy of the first semiconductor layer is E p When the difference between these is 100%, the band gap energy of the active layer is E a and the band gap energy E of the intermediate layer m 3. The infrared LED element according to claim 1, wherein the difference between the values ​​of the luminance and the luminance is in the range of 30% to 60%.

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