JP2007053291A - Optical semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical semiconductor element in which current density is enhanced by constituting a current layer having band gap energy lower than that of a light emitting layer abutting against the light emitting layer, and a current layer having band gap energy higher than that of the light emitting layer of any one of quantum well, quantum lattice, or quantum dot structure, and dopant is prevented from advancing into the light emitting layer. <P>SOLUTION: Out of two laminated layers 106 and 107, one layer 107 has lower band gap energy and higher current density than those of the other layer 106. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an optical semiconductor device. In particular, the present invention relates to a high-output optical semiconductor device having a structure in which impurities are not easily collected in a light emitting layer by eliminating the deviation of current distribution in the entire device. Here, the optical semiconductor element refers to a semiconductor element that emits light, such as a light emitting diode (hereinafter referred to as LED), a semiconductor laser (hereinafter referred to as LD) having a double hetero structure.

In recent years, LEDs, LDs, and the like using gallium nitride compound semiconductors such as GaN, InGaN, and AlGaN have been mass-produced. A light-emitting element using a gallium nitride-based compound semiconductor can adjust the emission color from the ultraviolet region to the infrared region by changing the mixed crystal ratio. A technique for growing a gallium nitride compound semiconductor is disclosed in, for example, Patent Document 1.

Since GaN has a high melting point (1,700 ° C.) and a high decomposition vapor pressure of nitrogen, it is difficult to produce a bulk substrate, and since there is no substrate with a similar lattice constant or thermal expansion coefficient, the lattice mismatch is 14%. A large sapphire (Al2O3) substrate is used.
JP-A-11-214744

However, even when a buffer layer of GaN or the like was formed as a countermeasure for threading dislocation due to lattice mismatch, the threading dislocation density was 10 ^ 9 to 10 ^ 10 cm-2. Impurities are likely to collect at this dislocation part. As a result, there is a drawback that the light output is lowered due to the entry of impurities into the light emitting layer.

  Further, a dopant is added to make the upper and lower portions of the light emitting layer P-type and N-type, but there is a second disadvantage that the dopant is collected in the light emitting layer and the light output is lowered.

In consideration of such drawbacks, an object of the present invention is to provide an optical semiconductor element in which impurities are unlikely to collect in a light emitting portion.

In order to solve the above-mentioned problems, in the present invention of claim 1, one of the two laminated layers is a layer having a lower band gap energy and a higher current density than the other layers.

In the present invention of claim 2, one of the two laminated layers is a layer having a lower band gap energy and a higher current density than the other layers, and one of the two layers is a current layer and the other layer emits light. Is a layer.

In the present invention of claim 3, one of the two laminated layers is a layer having a lower band gap energy and a higher current density than the other layers, and the layer having a higher current density is a quantum dot, a quantum lattice, or It consists of a quantum well structure.

In the present invention of claim 4, one of the two laminated layers is a layer having a lower band gap energy and a higher current density than the other layers, and the layer having a higher current density is a quantum dot, a quantum lattice, or A layer having a quantum well structure and having a low inner bandgap energy is a current layer, and the other layer is a light emitting layer.

In the present invention according to claim 5, one of the two laminated layers is a layer having higher band gap energy and higher current density than the other layers.

In the present invention of claim 6, one of the two laminated layers is a layer having a higher band gap energy and a higher current density than the other layers, and the two layers having a higher inner band gap energy are current layers. The other layer is a light emitting layer.

In the present invention of claim 7, one of the two laminated layers is a layer having a higher band gap energy and a higher current density than the other layers, and the layer having a higher current density is a quantum dot, a quantum lattice, or a quantum It consists of a well structure.

In the present invention of claim 8, one of the two laminated layers has a band gap energy higher than that of the other layers, and a layer having a high current density is formed of a quantum dot, a quantum lattice, or a quantum well structure. A layer having a high inner band gap energy is a current layer, and the other layer is a light emitting layer.

In the present invention of claim 9, among the three layers stacked, the layer between the layers is lower in bandgap energy than the other layers, and the layers on both sides are layers with high current density.

In the present invention of claim 10, among the three layers stacked, the layer between the layers is lower in bandgap energy than the other layers, the layers on both sides are layers with high current density, and the layers on both sides are between the current layers. This layer is a light emitting layer.

In the present invention of claim 11, among the three stacked layers, the layer between the layers has a lower band gap energy than the other layers, and the layers with high current density on both sides are formed of quantum dots, quantum lattices, or quantum well structures. .

In the present invention of claim 12, among the three laminated layers, the layer between the layers is higher in bandgap energy than the other layers, and the layers on both sides are layers with high current density.

In the present invention of claim 13, among the three stacked layers, the layer between the layers has higher bandgap energy than the other layers, the layers on both sides are layers with high current density, and the layers on both sides are between the current layers. This layer is a light emitting layer.

   In the present invention of claim 14, the layer between the three layers stacked has higher bandgap energy than the other layers, and the layer with high current density on both sides is formed of a quantum dot, quantum lattice, or quantum well structure. .

   In the present invention according to claim 15, among the three stacked layers, the layers on both sides are composed of a layer having a lower band gap energy and a layer having a higher band gap energy than the other layers therebetween, and the layers on both sides are composed of a layer having a high current density.

In the present invention according to claim 16, among the three laminated layers, the layers on both sides are composed of a layer having a lower band gap energy and a layer having a higher band gap energy than the layers in between, the layers on both sides are composed of layers having a high current density, These layers are current layers and the layers between them are light emitting layers.

In the present invention according to claim 17, among the three stacked layers, the layers on both sides are composed of a layer having a lower band gap energy and a layer having a higher band gap energy than the layers in between, and the layers having a higher current density on both sides are quantum dots and quantum lattices. Or a quantum well structure.

According to the optical semiconductor element of the present invention, the light emitting layer and the current layer are formed in layers, and the light emitting layer and the current layer are in direct contact with each other without providing a barrier layer between the light emitting layer and the current layer. Therefore, a current layer having a band gap energy smaller than that of the light emitting layer can be used as the current concentration layer.

In addition, according to the optical semiconductor device of the present invention, the light emitting layer and the current layer are formed in layers, and the light emitting layer and the current layer are in direct contact with each other without providing a barrier layer between the light emitting layer and the current layer. Therefore, a current layer having a band gap energy larger than that of the light emitting layer can be used as the current diffusion layer.

In addition, according to the optical semiconductor device of the present invention, the light emitting layer and the current layer are formed in layers, and the light emitting layer and the current layer are in direct contact with each other without providing a barrier layer between the light emitting layer and the current layer. Thus, by providing a current layer having a band gap energy larger than that of the light emitting layer on the light emitting layer, impurities are captured instead of the light emitting layer to prevent a decrease in output of the light emitting layer. By forming a current layer with a lower band gap energy than the light emitting layer below the light emitting layer, the driving voltage is lowered, ensuring lattice matching with the lower layer and preventing impurities from entering the light emitting layer. The output is prevented from being reduced by impurities.

A blue LED element 100 according to the best mode 1 for carrying out the present invention will be described below with reference to the cross-sectional view of FIG. In FIG. 1, reference numeral 101 denotes a cathode made of Au or the like. Reference numeral 102 denotes an n-type GaN substrate. The n-type GaN contact layer 103, n-Ga0.82Al0.18N, an n-type cladding layer 104 having a band gap energy of 3.9 eV, and In0.49Ga0. A current layer 1 (105) composed of 51N and having a band gap energy of 2.65 eV, and a light emitting layer that emits blue light with a band gap energy of 2.7 eV and composed of In0.46Ga0.54N on the current layer 1 (105). The current layer 2 (107) made of, for example, In0.49Ga0.51N and having a band gap energy of 2.65 eV is formed on the light emitting layer 106. Here, no barrier layer is provided between the light emitting layer 106 and the current layer 1 (105) and the current layer 2 (107). In addition, the current layer 1 (105) and the current layer 2 (107) are formed of any one of a quantum well structure, a quantum lattice structure, and a quantum dot structure. A p-type cladding layer 108 made of Ga0.82Al0.18N and having a band gap energy of 3.9 eV, a p-type GaN contact layer 109, and an anode 110 made of Au or the like on the surface of the element 100 are formed on the current layer 2 (107). The

In FIG. 1, an n-type contact layer 103, an n-type cladding layer 104, a current layer 1 (105), a light emitting layer 106, a current layer 2 (107), a p-type cladding layer 108, and a p-type contact layer 109 are composed of an organometallic compound. These are sequentially formed on the n-type substrate 102 by a vapor deposition method (hereinafter referred to as MOCVD method) or the like. The anode 110 and the cathode 101 are each formed by sputtering a metal film made of Au on the p-type contact layer 109 for the anode 110 and on the back surface of the n-type substrate 102 for the cathode 101. It is.

In the above configuration, the n-type cladding layer 104 and the p-type cladding layer 108 have a refractive index of 2.23, the current layer 1 (105) and the current layer 2 (107) have a refractive index of 2.86, and the light emitting layer 106. Has a refractive index of 2.86.

Here, the LED of this embodiment is characterized in that the current layer 1 (105) and the current layer 2 (107) function as a current concentration layer.
That is, in the configuration of the LED shown in FIG. 1, when the applied voltage is gradually increased up to the band gap energy of 2.65 eV between the current layer 1 (105) and the current layer 2 (107) between the anode 110 and the cathode 101. The current layer 1 (105) and the current layer 2 (107) have the smallest band gap energy (2.65 eV). Therefore, electrons flowing from the n-side contact layer 103 to the p side first have the smallest band gap energy (2 .65 eV) flows into the conduction band of the current layer 1 (105), and the holes flowing from the p-side contact layer 109 to the n-side flow into the valence band of the current layer 2 (107).

   Here, as described above, in this embodiment, a voltage corresponding to 2.65 eV which is the band gap energy of the current layer 2 (107) is applied, and the band gap energy of the light emitting layer 106 is 2.7 eV. However, since the current layer 2 (107) has the smallest band gap energy, the current injected from the anode 110 flows to the current layer 2 (107). The current density of the light emitting layer 106 formed in contact with the current layer 2 (107) increases. Therefore, the threshold current is reduced, and the drive voltage can be reduced below 2.7 eV, which is the band gap energy of the light emitting layer 106. The band gap energy of the light emitting layer 106 is 2.7 eV, which is only 0.05 eV greater than the band gap energy of 2.65 eV of the current layer 2 (107), so the light emitting layer 106 is a carrier (hole in this case) confinement layer. As a result, the holes flow into the valence band of the light-emitting layer 106 and the holes are not confined in the current layer 2 (107). The holes flowing into the valence band of the light emitting layer 106 flow into the current layer 1 (105) having a band gap energy of 2.65 eV and smaller than the light emitting layer 106. Furthermore, although holes are pulled toward the cathode 101, as is clear from FIG. 1, the band gap energy of the n-type cladding layer 104 formed under the current layer 1 (105) is 3.9 eV, Since the band gap energy of the light emitting layer 106 and the current layer 1 (105) is larger, the n-type cladding layer 104 acts as a carrier (here, hole) confinement layer, and as a result, holes are emitted from the light emitting layer 106 and the current. It will be confined within the valence band of layer 1 (105).

On the other hand, electrons flowing from the cathode 101 into the conduction band of the current layer 1 (105) are pulled toward the anode 110, but the band gap energy of the light emitting layer 106 formed on the surface of the current layer 1 (105) is Since it is 2.7 eV and only 0.05 eV larger than the band gap energy 2.65 eV of the current layer 1 (105), the light emitting layer 106 acts as a carrier (electron here) confinement layer of the current layer 1 (105). As a result, electrons flow into the conduction band of the light-emitting layer 106, so that electrons flowing into the conduction band of the current layer 1 (105) are not confined in the current layer 1 (105). Since the band gap energy of the current layer 2 (107) formed on the surface of the light emitting layer 106 is 2.65 eV, which is smaller than the band gap energy of the light emitting layer 106, electrons flowing into the conduction band of the light emitting layer 106 are current layer 2. It flows into the conduction band of (107). The electrons flowing into the conduction band of the current layer 2 (107) are pulled toward the anode 110, but the band gap energy of the p-type cladding layer 108 formed on the surface of the current layer 2 (107) is Since it is 3.9 eV, which is larger than the band gap energy of the light emitting layer 106 and the current layer 2 (107), the p-type cladding layer 108 acts as a carrier (electron here) confinement layer. Is confined in the conduction band of the light emitting layer 106 and the current layer 2 (107).

Since electrons are not confined in the conduction band of the current layer 1 (105), effective recombination of electrons and holes does not occur in the current layer 1 (105), and light emission occurs in the current layer 1 (105). Although it does not occur, electrons are confined in the conduction band of the light-emitting layer 106 and holes are confined in the valence band, so that effective recombination of electrons and holes occurs in the light-emitting layer 106, and blue light emission occurs. Since holes are not confined in the valence band of the current layer 2 (107), effective recombination of electrons and holes does not occur in the current layer 2 (107), and in the current layer 2 (107), No light emission

As described above, according to the present embodiment, since the current layer 1 (105) and the current layer 2 (107) have the smallest band gap energy (2.65 eV), the current injected from the anode 110 is The current layer 2 (107) in contact with the light emitting layer 106 and the current layer 1 (105) tend to flow in a concentrated manner (current concentration effect). Accordingly, since the current injected from the anode 110 flows through the current layer 2 (107) and the current layer 1 (105), it is formed in contact with the current layer 2 (107) and the current layer 1 (105). As a result, the threshold current can be reduced and the driving voltage can be lowered.

Further, according to the present embodiment, in the nitride compound optical semiconductor such as GaN, impurities are likely to collect at threading dislocations due to lattice mismatch from the cathode 101 side, but the current layer 1 (105) in contact with the light emitting layer 106 Is a layer whose band gap energy is lower than that of the light-emitting layer 106, and collects N-type impurities from the cathode 101 side in place of the light-emitting layer 106, but does not emit light, so any one of the quantum well structure, quantum lattice structure, and quantum dot structure Thus, the current density can be increased, and the light output of the light emitting layer 106 can be prevented from being lowered, and the life can be extended.

The current layer 1 (105) in contact with the light emitting layer 106 has a lower band gap energy than that of the light emitting layer 106, and ensures lattice matching with the lower n-type clad layer 104 to increase dislocation from the n-type substrate 102 side. To prevent.

Further, according to the present embodiment, in the nitride compound optical semiconductor such as GaN, impurities such as P-type dopants are likely to collect in the light emitting layer portion, but the current layer 2 (107) in contact with the light emitting layer 106 has the band gap energy. Is a layer lower than the light-emitting layer 106 and collects P-type impurities from the anode 110 side instead of the light-emitting layer 106, but does not emit light, and thus has a quantum well structure, a quantum lattice structure, or a quantum dot structure. The density can be increased, and the light output of the light emitting layer 106 can be prevented from being lowered, and the life can be extended.

FIG. 2 shows a blue LED element 200 according to the best mode 2 for carrying out the present invention. In FIG. 2, 101 is a cathode made of Au or the like, 102 is an n-GaN substrate, and an n-GaN contact layer 103 and n-Ga0.82Al0.18N are formed on the n-type substrate 102, and the band gap energy is 3 .9eV clad layer 104 and In0.39Ga0.61N and band gap energy 2.8eV on current layer 3 (205) and current layer 3 (205) on In0.46Ga0.54N band gap energy. A light emitting layer 106 that emits blue light at 2.7 eV is formed. On the light emitting layer 106, a current layer 4 (207) made of, for example, In0.39Ga0.61N and having a band gap energy of 2.8 eV is formed. Has been. Here, no barrier layer is provided between the light emitting layer 106 and the current layer 3 (205) and the current layer 4 (207). Further, the current layer 3 (205) and the current layer 4 (207) are constituted by any one of a quantum well structure, a quantum lattice structure, and a quantum dot structure. A p-type cladding layer 108 made of p-Ga0.82Al0.18N and having a band gap energy of 3.9 eV on the current layer 4 (207), a p-type GaN contact layer 109, and an anode 110 made of Au or the like on the surface of the element 200. Composed.

In FIG. 2, an n-type contact layer 103, an n-type cladding layer 104, a current layer 3 (205), a light emitting layer 106, a current layer 4 (207), a p-type cladding layer 108, and a p-type contact layer 109 are formed of an organometallic compound. These are sequentially formed on the n-type substrate 102 by a vapor deposition method (hereinafter referred to as MOCVD method) or the like. The anode 110 and the cathode 101 are each formed by sputtering a metal film made of Au.

In the above configuration, the n-type cladding layer 104 and the p-type cladding layer 108 have a refractive index of 2.23, the current layer 3 (205) and the current layer 4 (207) have a refractive index of 2.82, and the light emitting layer 106. Has a refractive index of 2.86.

Here, the LED of this embodiment is characterized in that the current layer 3 (205) and the current layer 4 (207) function as a current diffusion layer.

That is, in the configuration of the LED shown in FIG. 2, when the applied voltage is gradually increased between the anode 110 and the cathode 101 to the band gap energy 2.7 eV of the light emitting layer 106, the light emitting layer 106 has the band gap energy. Since it is the smallest (2.7 eV), electrons flowing from the n-side cladding layer 104 to the p-side first flow into the conduction band of the light-emitting layer 106 having the smallest bandgap energy (2.7 eV), and the p-side contact layer The holes flowing from 109 to the n side flow into the valence band of the light emitting layer 106.

Here, as described above, in this embodiment, a voltage corresponding to 2.7 eV which is the band gap energy of the light emitting layer 106 is applied, and the bands of the current layer 3 (205) and the current layer 4 (207) are applied. Although a voltage corresponding to 2.8 eV, which is the gap energy, is not applied, the light-emitting layer 106 has the smallest bandgap energy, so that the current injected from the anode 110 is the current layer 4 (207), the light-emitting layer. Therefore, the current density of the current layer 4 (207) formed in contact with the light emitting layer 106 increases. The holes flowing into the valence band of the light emitting layer 106 are pulled toward the cathode 101, but as is clear from FIG. 2, the band gap of the current layer 3 (205) formed below the light emitting layer 106. Since the energy is 2.8 eV and is only 0.1 eV larger than the band gap energy of 2.7 eV of the light emitting layer 106, the current layer 3 (205) acts as a carrier (here, hole) confining layer of the light emitting layer 106. As a result, the holes that have flown into the conduction band of the light emitting layer 106 flow into the valence band of the current layer 3 (205). The band gap energy of the n-type cladding layer 104 formed under the current layer 3 (205) is 3.9 eV, which is larger than the band gap energy of the light emitting layer 106 and the current layer 3 (205). Layer 104 acts as a carrier (here, hole) confinement layer, so that holes are confined within the valence band of light emitting layer 106 and current layer 3 (205), and current layer 4 (207). It will not be trapped in the valence band.

On the other hand, the electrons flowing into the conduction band of the current layer 3 (205) are pulled toward the anode 110 but flow into the light emitting layer 106, and the band gap of the current layer 4 (207) formed on the light emitting layer 106. Since the energy is 2.8 eV and is only 0.1 eV larger than the band gap energy 2.7 eV of the light emitting layer 106, the current layer 4 (207) can act as a carrier (here, electron) confining layer of the light emitting layer 106. As a result, the electrons that have flown into the conduction band of the light-emitting layer 106 flow into the conduction band of the current layer 4 (207). The electrons flowing into the conduction band of the current layer 4 (207) are pulled toward the anode 110. As is apparent from FIG. 2, the p-type cladding layer 108 formed on the current layer 4 (207). The band gap energy of 3.9 eV is larger than the band gap energy of the light emitting layer 106 and the current layer 4 (207), so that the p-type cladding layer 108 acts as a carrier (electron) confinement layer, and as a result. The electrons are confined in the conduction band of the light emitting layer 106 and the current layer 4 (207), and are not confined in the conduction band of the current layer 3 (205).

That is, since electrons are not confined in the conduction band of the current layer 3 (205), effective recombination of electrons and holes does not occur in the current layer 3 (205), and in the current layer 3 (205), Although light emission does not occur, electrons are confined in the conduction band of the light-emitting layer 106 and holes are confined in the valence band. Therefore, effective recombination of electrons and holes is performed in the light-emitting layer 106, and blue light is emitted. Occur. Since holes are not confined in the valence band of the current layer 4 (207), effective recombination of electrons and holes does not occur in the current layer 4 (207), and in the current layer 4 (207), There is no light emission.

According to the present embodiment, in the nitride compound optical semiconductor such as GaN, impurities are likely to collect in threading dislocations due to lattice mismatch from the cathode 101 side, but the current layer 3 (205) in contact with the light emitting layer 106 is in a band. The gap energy is higher than that of the light-emitting layer 106, and N-type impurities from the cathode 101 side are collected instead of the light-emitting layer 106. Thus, the current density can be increased, and the light output of the light emitting layer 106 can be prevented from being lowered and the life can be extended.

Further, according to the present embodiment, in the nitride compound optical semiconductor such as GaN, impurities such as P-type dopants tend to collect in the light emitting layer portion, but the current layer 4 (207) in contact with the light emitting layer 106 has the band gap energy. Is a layer higher than the light-emitting layer 106, and collects P-type impurities from the anode 110 side instead of the light-emitting layer 106, but does not emit light. Therefore, the current is composed of one of a quantum well structure, a quantum lattice structure, and a quantum dot structure. The density can be increased, and the light output of the light emitting layer 106 can be prevented from being lowered to extend the life.

FIG. 3 shows a blue LED element 300 according to the best mode 3 for carrying out the present invention. In FIG. 3, 101 is a cathode 102 made of Au or the like, and an n-GaN substrate. An n-GaN contact layer 103 and n-Ga0.82Al0.18N are formed on the n-type substrate 102, and the band gap energy is 3.9 eV. N-type cladding layer 104 and In0.49Ga0.51N, and band gap energy of 2.65 eV and current layer 1 (105) and current layer 1 (105) on In0.46Ga0.54N bandgap energy. A light emitting layer 106 that emits blue light at 2.7 eV is formed. On the light emitting layer 106, a current layer 4 (207) made of, for example, In0.39Ga0.61N and having a band gap energy of 2.8 eV is formed. Has been. Here, no barrier layer is provided between the light emitting layer 106, the current layer 1 (105), and the current layer 4 (207). In addition, the current layer 1 (105) and the current layer 4 (207) are formed of any one of a quantum well structure, a quantum lattice structure, and a quantum dot structure. A p-type cladding layer 108 made of Ga0.82Al0.18N and having a band gap energy of 3.9 eV, a p-type GaN contact layer 109, and an anode 110 made of Au or the like on the surface of the element 300 are formed on the current layer 4 (207). The

In FIG. 3, the n-type contact layer 103, the n-type cladding layer 104, the current layer 1 (105), the light emitting layer 106, the current layer 4 (207), the p-type cladding layer 108, and the p-type contact layer 109 are composed of organometallic compounds. These are sequentially formed on the n-type substrate 102 by a vapor deposition method (hereinafter referred to as MOCVD method) or the like. The anode 110 and the cathode 101 are each formed by sputtering a metal film made of Au.

In the above configuration, the n-type cladding layer 104 and the p-type cladding layer 108 have a refractive index of 2.23, and the current layer 1 (105) and the current layer 4 (207) have a refractive index of 2.86 and 2.82. The refractive index of the light emitting layer 106 is 2.86.

Here, the LED of this embodiment is characterized in that the current layer 1 (105) functions as a current concentration layer and the current layer 4 (207) functions as a current diffusion layer.

That is, in the configuration of the LED shown in FIG. 3, when the applied voltage is gradually increased up to the band gap energy of 2.65 eV between the anode 110 and the cathode 101, the current layer 1 (105). Since the band gap energy is the smallest (2.65 eV), the electrons flowing from the n-side contact layer 103 to the p side first conduct in the current layer 1 (105) having the smallest band gap energy (2.65 eV). The holes flowing into the band and flowing from the p-side contact layer 109 to the n-side flow into the valence band of the current layer 1 (105).

Here, as described above, in this embodiment, a voltage corresponding to 2.65 eV which is the band gap energy of the current layer 1 (105) is applied, and 2.7 eV which is the band gap energy of the light emitting layer 106. However, since the current layer 1 (105) is the layer with the smallest band gap energy, the current injected from the anode 110 flows to the current layer 1 (105). The current density of the light emitting layer 106 formed in contact with the current layer 1 (105) increases. Therefore, the threshold current is reduced, and the drive voltage can be reduced below 2.7 eV, which is the band gap energy of the light emitting layer 106.

The electrons flowing into the conduction band of the current layer 1 (105) are pulled toward the anode 110, but the band gap energy of the light emitting layer 106 formed on the surface of the current layer 1 (105) is 2.7 eV. Since the current layer 1 (105) has a band gap energy of 2.65 eV which is only 0.05 eV, the light emitting layer 106 can act as a carrier (electron) confinement layer of the current layer 1 (105). As a result, the electrons flowing into the conduction band of the current layer 1 (105) flow into the conduction band of the light emitting layer 106 without being confined in the current layer 1 (105). The electrons flowing into the conduction band of the light emitting layer 106 are pulled toward the anode 110, but as is clear from FIG. 3, the band gap of the current layer 4 (207) formed on the upper surface of the light emitting layer 106. Since the energy is 2.8 eV and is only 0.1 eV larger than the band gap energy of 2.7 eV of the light emitting layer 106, the current layer 4 (207) acts as a carrier (electron here) confinement layer of the light emitting layer 106. As a result, the electrons flowing into the conduction band of the light emitting layer 106 flow into the conduction band of the current layer 4 (207). The band gap energy of the p-type cladding layer 108 formed on the current layer 4 (207) is 3.9 eV, which is larger than the band gap energy of the light emitting layer 106 and the current layer 4 (207). Layer 108 acts as a carrier (here, electron) confinement layer, so that the electrons are confined within the conduction band of light emitting layer 106 and current layer 4 (207).

On the other hand, holes flowing into the valence band of the current layer 4 (207), the light emitting layer 106, and the current layer 1 (105) due to the band gap energy difference are pulled toward the cathode 101, which is apparent from FIG. Thus, the band gap energy of the n-type cladding layer 104 formed under the current layer 1 (105) is 3.9 eV, which is larger than the band gap energy of the light emitting layer 106 and the current layer 1 (105). The n-type cladding layer 104 acts as a carrier (here, hole) confinement layer, and as a result, holes are confined within the valence band of the light emitting layer 106 and the current layer 1 (105). 4 (207) is not confined within the valence band.

That is, since electrons are not confined in the conduction band of the current layer 1 (105), effective recombination of electrons and holes does not occur in the current layer 1 (105), and in the current layer 1 (105), Although light emission does not occur, electrons are confined in the conduction band of the light-emitting layer 106 and holes are confined in the valence band. Therefore, effective recombination of electrons and holes is performed in the light-emitting layer 106, and blue light is emitted. Occur. Since holes are not confined in the valence band of the current layer 4 (207), effective recombination of electrons and holes does not occur in the current layer 4 (207), and the current layer 4 (207) Does not emit light.

According to the present embodiment, in the nitride compound optical semiconductor such as GaN, impurities are likely to collect in threading dislocations due to lattice mismatch from the cathode 101 side, but the current layer 1 (105) in contact with the light emitting layer 106 is in a band. The gap energy is lower than that of the light-emitting layer 106, and N-type impurities from the cathode 101 side are collected instead of the light-emitting layer 106. However, since it does not emit light, it is configured by one of a quantum well structure, a quantum lattice structure, and a quantum dot structure. Thus, the current density can be increased, and the light output of the light emitting layer 106 can be prevented from being lowered and the life can be extended.

The current layer 1 (105) in contact with the light-emitting layer 106 has a lower band gap energy than the light-emitting layer 106 and ensures lattice matching with the lower n-cladding layer 104 to increase dislocation from the n-type substrate 102 side. To prevent.

Further, according to the present embodiment, in the nitride compound optical semiconductor such as GaN, impurities such as P-type dopants tend to collect in the light emitting layer portion, but the current layer 4 (207) in contact with the light emitting layer 106 has the band gap energy. Is a layer higher than the light-emitting layer 106, and collects P-type impurities from the anode 110 side instead of the light-emitting layer 106, but does not emit light. Therefore, the current is composed of any one of a quantum well structure, a quantum lattice structure, and a quantum dot structure. The density can be increased, and the light output of the light emitting layer 106 can be prevented from being lowered, and the life can be extended.

The present invention is not limited to the best modes 1, 2, and 3 described above, and various modifications can be made based on the gist of the present invention, and they are excluded from the scope of the present invention. It is not a thing.

In FIGS. 1, 2, and 3, since the element shape is not a step structure as compared with FIG. 4, two wires are required when assembling the optical semiconductor element of FIG. 4, whereas FIGS.

1, 2 and 3, since the chip shape is not a step structure as shown in FIG. 4, the chip size can be reduced.

In the embodiment of the present invention, the light emitting layer is described as a single layer. However, the light emitting layer has a single quantum well structure (SQW), a multiple quantum well structure (MQW), a quantum lattice structure, or a quantum dot structure. You may comprise.

Further, in the embodiment of the present invention, in order to explain the structure of the light emitting element, for convenience, the substrate is positioned in the lower layer, and the crystal layer is stacked on the lower layer, the lower layer side is n-type, and the upper layer side is p-type. Although described as a mold, the n-side may be an upper layer side and the p-type may be a lower layer side.

In the embodiment of the present invention, an LED has been described as an optical semiconductor element. However, for example, a laser structure in which a current confinement layer is provided in a p-cladding layer or a p-contact layer may be used.

Further, a surface emitting laser configuration in which the light emitting layer described as the embodiment of the present invention is used as an active layer and the output of the active layer is output on the anode may be employed.

In the embodiment of the present invention, the substrate is an n-type GaN substrate. However, for example, Si, GaAs, sapphire substrate, SiC substrate, AlN substrate, ZnO substrate, InP substrate, etc. In consideration of the substrate, a substrate can be appropriately selected.

In the embodiment of the present invention, the cathode is formed of Au, but may be formed of Al.

In the embodiment of the present invention, the case where a current layer having a small band gap energy is used below a light emitting layer and a large current layer is used has been described, but a reverse configuration may be used.

In the embodiment of the present invention, the current layer sandwiching the light emitting layer is described. However, the same effect can be obtained in the two-layer structure of the light emitting layer and the current layer.

It is sectional drawing of LED100 which concerns on the best form 1 for implementing this invention. It is sectional drawing of LED200 which concerns on the best form 2 for implementing this invention. It is sectional drawing of LED300 which concerns on the best form 3 for implementing this invention. It is the schematic which shows the basic composition of the conventional optical semiconductor element.

Explanation of symbols

100, 200, 300: device 101: cathode 102: n-type substrate 103: n-type contact layer 104: n-type cladding layer 105: current layer 1, 205: current layer 3
106: Light emitting layer 107: Current layer 2, 207: Current layer 4
108: p-type cladding layer 109: p-type contact layer 110: anode

Claims (17)

An optical semiconductor element, wherein one of the two laminated layers is a layer having lower band gap energy and higher current density than the other layers. One of the two laminated layers has a lower band gap energy and a higher current density than the other layers, and the two lower inner band gap energy layers are current layers and the other layers are light emitting layers. An optical semiconductor element characterized by the above. One of the two layers laminated is characterized by having a band gap energy lower than the other layers and a layer having a high current density, and the layer having a high current density comprising a quantum dot, quantum lattice, or quantum well structure. An optical semiconductor device. Of the two layers stacked, one layer has a lower band gap energy than the other layers and has a higher current density, and the higher current density has a quantum dot, quantum lattice, or quantum well structure. An optical semiconductor element characterized in that a layer having a low inner band gap energy is a current layer and the other layer is a light emitting layer. An optical semiconductor element, wherein one of the two laminated layers is a layer having higher band gap energy and higher current density than the other layers. One of the two layers stacked has a higher band gap energy and higher current density than the other layers, and the two layers having a higher inner band gap energy are current layers and the other layers are light emitting layers. A featured optical semiconductor element. One of the two layers laminated is characterized in that it has a higher band gap energy and higher current density than the other layers, and the higher current density layer comprises a quantum dot, quantum lattice, or quantum well structure. An optical semiconductor device. One of the two layers stacked has a higher band gap energy than the other layers, and the layer with a higher current density is formed of a quantum dot, quantum lattice, or quantum well structure, and the two layers have a higher inner band gap energy. Is a current layer and the other layer is a light emitting layer. An optical semiconductor element characterized in that, among the three stacked layers, an intermediate layer has a lower band gap energy than other layers, and both layers are layers having a high current density. Among the three layers stacked, the layer between the layers has a lower band gap energy than the other layers, the layers on both sides are layers with high current density, the layers on both sides are current layers, and the layers between them are light emitting layers An optical semiconductor element characterized by the above. An optical semiconductor device characterized in that, among the three stacked layers, the layer between the layers has a lower band gap energy than the other layers, and the layers with high current density on both sides are formed of quantum dots, quantum lattices, or quantum well structures . An optical semiconductor element characterized in that, among the three stacked layers, an intermediate layer has a higher band gap energy than other layers, and both layers are layers having a high current density. Among the three layers stacked, the layer between the layers has higher bandgap energy than the other layers, the layers on both sides are layers with high current density, the layers on both sides are current layers, and the layers between them are light emitting layers An optical semiconductor element characterized by the above. An optical semiconductor device characterized in that, among the three stacked layers, the layer between the layers has higher band gap energy than the other layers, and the layers with high current density on both sides are formed of quantum dots, quantum lattices, or quantum well structures . An optical semiconductor element characterized in that, among the three stacked layers, layers on both sides are composed of a layer having a lower band gap energy and a layer having a higher band gap energy than other layers therebetween, and layers on both sides are composed of layers having a high current density. Of the three layers stacked, the layers on both sides have lower and higher bandgap energy than the other layers in between, the layers on both sides have higher current density, and the layers on both sides are between the current layers. An optical semiconductor element, wherein the layer is a light emitting layer. Of the three stacked layers, the layers on both sides are composed of layers with lower band gap energy and higher layers than the other layers in between, and the layers with high current density on both sides are composed of quantum dots, quantum lattices, or quantum well structures. An optical semiconductor element characterized by the above.

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