Ultraviolet semiconductor laser element and method for manufacturing ultraviolet semiconductor laser element

Abstract

To provide an ultraviolet semiconductor laser element of good quality and a method for manufacturing an ultraviolet semiconductor laser element of good quality.SOLUTION: A nitride semiconductor light emitting element 1 has a double-quantum-well active layer 13B, a second guide layer 13C stacked on the surface of the double-quantum-well active layer 13B, an electron blocking layer 14 stacked on the surface of the second guide layer 13C that blocks the flow of electrons from the double-quantum-well active layer 13B side, and a cladding layer 15 stacked on the surface of the electron blocking layer 14.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultraviolet semiconductor laser device and a method for manufacturing an ultraviolet semiconductor laser device. [Background technology]

[0002] Patent Document 1 discloses a nitride semiconductor device capable of lasing ultraviolet light. This device has a composition gradient layer and a p-type semiconductor layer stacked in this order on the surface of an upper guide layer through crystal growth, and the portion of the p-type semiconductor layer close to the upper guide layer is given the function of blocking electrons moving from the active layer toward the surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-184456 Summary of the Invention [Problem to be solved by the invention]

[0004] The electron blocking function of the p-type semiconductor layer can be improved by increasing the molar fraction of AlN in the portion of the p-type semiconductor layer closer to the upper guide layer. Specifically, it is believed to be effective to increase the molar fraction of AlN in the portion of the p-type semiconductor layer closer to the upper guide layer to differentiate it from the p-type semiconductor layer located above this portion. However, in the device of Patent Document 1, the molar fraction of AlN is smoothly continuous between the portion of the p-type semiconductor layer closer to the upper guide layer and the portion of the p-type semiconductor layer located above this portion. In other words, it is believed that the device of Patent Document 1 has room for further improving the electron blocking function of the p-type semiconductor layer.

[0005] The present invention has been made in view of the above-described conventional circumstances, and an object to be achieved is to provide a high-quality ultraviolet semiconductor laser element and a method for manufacturing a high-quality ultraviolet semiconductor laser element. [Means for solving the problem]

[0006] The ultraviolet semiconductor laser device of the first invention is an active layer; a guide layer laminated on the surface of the active layer; an electron blocking layer laminated on a surface of the guide layer to block the flow of electrons from the active layer; a clad layer laminated on the surface of the electron blocking layer; It is equipped with:

[0007] According to this configuration, the electron blocking layer can effectively prevent electrons from flowing from the active layer to the surface.

[0008] The method for manufacturing an ultraviolet semiconductor laser device according to the second invention comprises the steps of: a guide layer lamination step of laminating a guide layer on the surface of the active layer; an electron blocking layer lamination step of laminating an electron blocking layer on a surface of the guide layer to block electrons from flowing from the active layer side; a clad layer laminating step of laminating a clad layer on the surface of the electron blocking layer; Equipped with a first interruption step of interrupting the supply of raw materials into the reactor, the first interruption step being performed between the guide layer laminating step and the electron block layer laminating step; and a second interruption step of interrupting the supply of the raw material into the reactor, the second interruption step being performed between the electron blocking layer deposition step and the cladding layer deposition step.

[0009] According to this configuration, the first interruption process can clearly form the boundary between the electron blocking layer and the guide layer, and the second interruption process can clearly form the boundary between the electron blocking layer stacking process and the cladding layer, allowing the electron blocking layer to perform its function well. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a schematic diagram showing the structure of a nitride semiconductor light-emitting device according to Example 1. FIG. [Figure 2] 1A is a time chart showing the steps from the guide layer lamination step to the cladding layer lamination step in the nitride semiconductor light-emitting device of Example 1, and FIG. 1B is a time chart showing the steps from the guide layer lamination step to the cladding layer lamination step in the sample of Comparative Example 1. [Figure 3] 1 is a graph showing the emission spectra of the nitride semiconductor light-emitting device of Example 1 and the sample of Comparative Example 1. [Figure 4] (A) is a transmission electron microscope image showing a cross section from the second guide layer to the cladding layer of the nitride semiconductor light-emitting element of Example 1, and (B) is a transmission electron microscope image showing a cross section from the second guide layer to the cladding layer of the sample of Comparative Example 1. [Figure 5] Graph (A) shows the results of analyzing the molar fractions of AlN and GaN from the second guide layer to the cladding layer of the nitride semiconductor light-emitting element of Example 1 using energy dispersive X-ray analysis, and graph (B) shows the results of analyzing the molar fractions of AlN and GaN from the second guide layer to the cladding layer of the sample of Comparative Example 1 using energy dispersive X-ray analysis. [Figure 6] 1 is a band diagram showing the results of analyzing, using a device simulator, the energy at the bottom of the conductor in the stacking direction of the nitride semiconductor light-emitting device of Example 1 and the sample of Comparative Example 1. [Figure 7] 1 is a graph showing the results of an analysis performed using a device simulator on the relationship between the injection efficiency and the current density of the nitride semiconductor light-emitting device of Example 1 and the sample of Comparative Example 1. [Figure 8] 1 is a graph plotting the relationship between the injection efficiency and the thickness of the electron blocking layer for the nitride semiconductor light-emitting device of Example 1 and the sample of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] A preferred embodiment of the present invention will now be described.

[0012] In the first aspect of the present invention, the AlN mole fraction in the cladding layer may be graded so that it decreases in the direction away from the active layer in the stacking direction. This configuration allows the cladding layer to be polarized well in the stacking direction, thereby enabling the ultraviolet semiconductor laser device to function well.

[0013] In the first aspect of the present invention, the maximum molar fraction of AlN in the electron blocking layer may be greater than the maximum molar fraction of AlN in the cladding layer by 0.05 or more. This configuration makes it possible to clearly distinguish the difference in the molar fraction of AlN between the electron blocking layer and the cladding layer, thereby enabling the electron blocking layer to function more effectively.

[0014] In the first aspect of the present invention, the maximum molar fraction of AlN in the electron blocking layer may be greater than the maximum molar fraction of AlN in the guide layer by 0.05 or more. This configuration makes it possible to clearly distinguish the difference in the molar fraction of AlN between the electron blocking layer and the guide layer, thereby enabling the electron blocking layer to function more effectively.

[0015] In the first aspect of the present invention, the thickness of the electron blocking layer in the stacking direction may be 5 nm or more, which allows the layer to function as an electron blocking layer even better.

[0016] In the second aspect of the present invention, the first interruption step may be performed for a period of 2 to 5 minutes. This configuration allows the boundary between the electron blocking layer and the guide layer to be more clearly defined.

[0017] In the second aspect of the present invention, the second interruption step may be performed for 2 to 5 minutes. This configuration allows the boundary between the electron blocking layer and the cladding layer to be more clearly defined.

[0018] Next, a first embodiment of the ultraviolet semiconductor laser device according to the first invention and the method for manufacturing the ultraviolet semiconductor laser device according to the second invention will be described with reference to the drawings.

[0019] Example 1 1, the nitride semiconductor light-emitting device 1 of Example 1 includes a sapphire substrate 10A, a first AlN layer 10B, a second AlN layer 11, a u-AlGaN layer 12A, an n-AlGaN layer 12B, a first guide layer 13A, a double quantum well active layer 13B, a second guide layer 13C which is a guide layer, an electron blocking layer 14, a cladding layer 15, a p-AlGaN layer 16, and a p-GaN layer 17. The nitride semiconductor light-emitting device 1 of Example 1 is grown by stacking layers using MOVPE (metal-organic vapor phase epitaxy). The nitride semiconductor light-emitting device 1 is an ultraviolet semiconductor laser device that emits ultraviolet light in the UV-B wavelength range.

[0020] The C-plane ((0001) plane) of the sapphire substrate 10A is the surface (the front is the upper side in FIG. 1, the same applies below). The first AlN layer 10B is deposited on the surface of the sapphire substrate 10A using a sputtering method. The first AlN layer 10B has a thickness of 450 nm. After the first AlN layer 10B is deposited, annealing is performed in an N2 (nitrogen) atmosphere at 1700°C for 3 hours. In this way, an AlN template substrate 10 having the sapphire substrate 10A and the first AlN layer 10B is fabricated using a sputtering method. Thereafter, a layer structure is formed using an MOVPE method.

[0021] The AlN template substrate 10 is placed in a reactor capable of carrying out the MOVPE method (hereinafter simply referred to as the reactor), and while NH3 (ammonia), which is an N (nitrogen) raw material, is flowed onto the surface of the AlN template substrate 10 (the surface of the first AlN layer 10B) (hereinafter, the supply is not stopped), the temperature of the AlN template substrate 10 is raised to 1200°C in an H2 (hydrogen) atmosphere, and then held for 10 minutes.

[0022] Next, a second AlN layer 11 is stacked on the surface of the first AlN layer 10B and crystal growth is performed. The thickness of the second AlN layer 11 is 1550 nm. The second AlN layer 11 is formed by supplying TMAl (trimethylaluminum), an Al (aluminum) raw material, into a reactor while the temperature of the AlN template substrate 10 is set to 1200°C. The total thickness of the first AlN layer 10B and the second AlN layer 11 is 2000 nm.

[0023] [Convex part formation process] Next, a convex portion forming process is performed to form multiple convex portions 11A extending in a columnar shape in the stacking direction on the surface of the second AlN layer 11. Specifically, a 420 nm SiO2 layer is deposited on the surface of the second AlN layer 11 using a sputtering device. Then, a resist is applied to the surface of the SiO2 layer to form a resist film, and a fine pattern with a pitch of 1000 nm and an outer diameter of 500 nm is formed on the resist film using a nanoimprinting device. The surface of the SiO2 layer is exposed outside this fine pattern. Then, using an ICP device, the exposed SiO2 layer is inductively coupled plasma etched with CF4 gas, followed by removal of SiO2 layer residue using buffered hydrofluoric acid. Then, using Cl2 gas, the surface side of the second AlN layer 11 is inductively coupled plasma etched to a depth of 300 nm. The SiO2 layer and resist film used as a mask are then removed using hydrofluoric acid. In this way, the convex portion forming step is carried out.

[0024] Next, a u-AlGaN layer 12A is deposited on the surface of the second AlN layer 11 with the protrusions 11A formed thereon for crystal growth. Specifically, the AlN template substrate 10 with the protrusions 11A formed thereon is placed back into the reactor. The temperature of the AlN template substrate 10 is then raised to 1200°C. Once the temperature reaches a predetermined level, H2, TMGa (trimethylgallium), TMAl, and NH3 (Ga (gallium) precursors) are supplied into the reactor so that the AlN mole fraction becomes 68%. The pressure inside the reactor is 7 kPa. The thickness of the u-AlGaN layer 12A is 3 μm. By making the thickness of the u-AlGaN layer 12A 3 μm, the surface of the second AlN layer 11 with the protrusions 11A formed thereon can be buried and planarized. The u-AlGaN layer 12A is not doped with impurities such as Si or Mg. However, the u-AlGaN layer 12A may be replaced with an n-AlGaN layer doped with Si or the like. Here, the thickness of the u-AlGaN layer 12A is the dimension from the base end of the protrusion 11A to the surface of the u-AlGaN layer 12A.

[0025] Next, the n-AlGaN layer 12B is deposited on the surface of the u-AlGaN layer 12A for crystal growth. Specifically, while H2, TMGa, TMAl, and NH3 are continuously supplied to the reactor, SiH4 is supplied to the reactor. The Si concentration in the n-AlGaN layer 12B is 6×10 18 cm -3 The supply flow rates of the raw materials are adjusted so that the thickness of the n-AlGaN layer 12B is 2 μm. The mole fraction of AlN in the n-AlGaN layer 12B is 62%.

[0026] Next, a first guide layer 13A and a double quantum well active layer 13B are stacked in this order on the surface of the n-AlGaN layer 12B for crystal growth. Specifically, the temperature of the AlN template substrate 10 is lowered to 1050°C, and the pressure in the reactor is set to 30 kPa. TMGa is then switched to TEGa (triethylgallium). Once the temperature of the AlN template substrate 10 reaches a predetermined temperature, a double quantum well active layer 13B is stacked, which includes two stacked layers: a 50 nm-thick first guide layer 13A (AlN molar fraction: 45%), a 4 nm-thick well layer (AlN molar fraction: 35%), and an 8 nm-thick barrier layer (AlN molar fraction: 45%).

[0027] After the double quantum well active layer 13B is deposited, as shown in FIG. 2(A), a guide layer deposition step, a first interruption step, an electron block layer deposition step, a second interruption step, and a cladding layer deposition step are performed.

[0028] [Guide layer lamination process] While maintaining the temperature of the AlN template substrate 10 and the pressure inside the reactor at the conditions for depositing the double quantum well active layer 13B, a guide layer deposition process is carried out in which a second guide layer 13C is deposited on the surface of the double quantum well active layer 13B, which is the active layer, and crystal growth is carried out. In the guide layer deposition process, the flow rate of the raw material supplied into the reactor is adjusted so that the molar fraction of AlN in the second guide layer 13C is 45%. By carrying out the guide layer deposition process for 10 minutes, a second guide layer 13C (AlN molar fraction is 45%) with a thickness of 55 nm is deposited.

[0029] [1st interruption process] Next, a first interruption step is performed to interrupt the supply of raw materials into the reactor. Specifically, after the guide layer lamination step is performed to complete the crystal growth of the second guide layer 13C, the supply of the group III raw materials (TEGa, TMAl) into the reactor is stopped, and the supply of the group V raw material NH3 is continued for two minutes to interrupt the crystal growth.

[0030] [Electron block layer stacking process] Next, an electron block layer deposition process is performed in which an electron block layer 14 that blocks the flow of electrons from the double quantum well active layer 13B side is deposited on the surface of the second guide layer 13C by crystal growth. Specifically, after the first interruption process, the supply of group III raw materials into the reactor is resumed and maintained for 1.4 minutes. In other words, the first interruption process is performed between the guide layer deposition process and the electron block layer deposition process. In the electron block layer deposition process, the flow rate of raw materials supplied into the reactor is adjusted so that the molar fraction of AlN in the electron block layer 14 is 95%. The group III raw materials whose supply is resumed at this time are TMGa and TMAl. In this way, a 5-nm-thick electron block layer 14 (with an AlN molar fraction of 95%) is deposited on the surface of the second guide layer 13C.

[0031] [Second interruption process] Next, a second interruption step is performed to interrupt the supply of raw materials into the reactor. Specifically, after the electron block layer deposition step is performed to complete the crystal growth of the electron block layer 14, the supply of the group III raw materials (TMGa, TMAl) into the reactor is stopped, and the supply of the group V raw material NH3 is continued for two minutes to interrupt the crystal growth. In the first and second interruption steps, if the time period during which the supply of the group III raw materials (TEGa, TMGa, TMAl) into the reactor is stopped and the supply of the group V raw material NH3 is continued is too short, the effect of the interruption is weakened, and if it is too long, there is a concern that the crystal may deteriorate. Therefore, in the first and second interruption steps, the time period during which the supply of the group III raw materials into the reactor is stopped and the supply of the group V raw material NH3 is continued is preferably two to five minutes. In other words, the time period during which each of the first and second interruption steps is performed is preferably two to five minutes.

[0032] [Clad layer lamination process] Next, a cladding layer deposition process is performed in which a cladding layer 15 is deposited on the surface of the electron blocking layer 14 and crystal growth is performed. Specifically, after the second interruption process, the supply of group III raw materials into the reactor is resumed. That is, the second interruption process is performed between the block layer deposition process and the cladding layer deposition process. In the cladding layer deposition process, the flow rate of the raw materials supplied into the reactor is adjusted so that the AlN molar fraction in the cladding layer 15 becomes 90%. Then, the flow rate of the raw materials supplied into the reactor is adjusted so that the AlN molar fraction gradually changes from 90% to 60% over 22.2 minutes. In this way, a cladding layer 15 having a thickness of 320 nm is deposited on the surface of the electron blocking layer 14. The AlN molar fraction of the cladding layer 15 thus deposited has a composition gradient that decreases in the direction away from the double quantum well active layer 13B in the deposition direction (see FIG. 5(A)).

[0033] Next, a p-AlGaN layer 16 is deposited on the surface of the cladding layer 15 for crystal growth. Specifically, after the crystal growth of the cladding layer 15 is completed, the flow rate of the raw materials supplied to the reactor is adjusted so that the AlN molar fraction gradually changes from 60% to 0% over 7.1 minutes. In this way, a p-AlGaN layer 16 with a thickness of 75 nm is deposited on the surface of the cladding layer 15. The cladding layer 15 and the p-AlGaN layer 16 have different rates of change in the AlN molar fraction per unit thickness in the deposition direction. If the cladding layer 15 and the p-AlGaN layer 16 are considered as one crystal layer C (see Figure 1), the rate of change in the AlN molar fraction per unit thickness in the deposition direction of the crystal layer C changes in two stages in the deposition direction.

[0034] Next, a p-GaN layer 17, which serves as a contact layer with a P-type electrode (not shown), is deposited on the surface of the p-AlGaN layer 16 for crystal growth. The supply of TMGa and TMAl to the reactor is then stopped to terminate the crystal growth, and the temperature of the AlN template substrate 10 is lowered to room temperature while H2 and NH3 are flowed into the reactor. After the temperature of the AlN template substrate 10 has reached room temperature, the reactor is thoroughly purged, and the AlN template substrate 10 is removed from the reactor. In this way, a nitride semiconductor light-emitting element 1 having a UV-B semiconductor laser structure capable of lasing ultraviolet light in the UV-B wavelength range is fabricated using the MOVPE method.

[0035] Here, a sample of Comparative Example 1 was fabricated by crystal growth without performing the first interruption step and the second interruption step among the above steps. Specifically, as shown in Fig. 2(B), after the guide layer stacking step was performed for 10 minutes to stack the second guide layer 13C, TEGa was switched to TMGa, and the flow rate of the raw material supplied into the reactor was immediately adjusted so that the molar fraction of AlN became 95%, and the electron block layer stacking step was performed for 1.4 minutes.

[0036] Then, after performing the electron blocking layer deposition step to deposit electron blocking layer 14, the flow rate of the raw materials supplied into the reactor is adjusted so that the AlN molar fraction becomes 90%, and the cladding layer deposition step is performed for 22.2 minutes. Then, p-AlGaN layer 16 and p-GaN layer 17 are deposited in this order on the surface of cladding layer 15, similar to the nitride semiconductor light-emitting device 1 of Example 1, and crystal growth is performed. In this way, the sample of Comparative Example 1 was fabricated using the MOVPE method.

[0037] As shown in FIG. 3, it was found that the nitride semiconductor light-emitting device 1 of Example 1 exhibited a stronger emission intensity than the sample of Comparative Example 1.

[0038] As shown in FIGS. 4 and 5, in the sample of Comparative Example 1, a pulling layer P is formed between the second guide layer 13C and the cladding layer 15, where Al in the electron blocking layer 14 is diffused toward the second guide layer 13C, making the boundary between the electron blocking layer 14 and the cladding layer 15 unclear (see FIGS. 4(B) and 5(B)). The pulling layer P is a part of the second guide layer 13C. Furthermore, as shown in FIG. 5(B), the molar fraction of AlN gradually decreases in the stacking direction between the electron blocking layer 14 and the cladding layer 15, and there is no sudden change in the molar fraction of AlN in the boundary region between the electron blocking layer 14 and the cladding layer 15.

[0039] In contrast to this, in the nitride semiconductor light emitting device 1 of Example 1, although the pulling layer P is formed, the boundary between the electron blocking layer 14 and the cladding layer 15 is clear.

[0040] The maximum molar fraction of AlN on the cladding layer 15 side is approximately 87%. The maximum molar fraction of AlN in the electron blocking layer 14 is approximately 95%. Therefore, the maximum molar fraction of AlN in the electron blocking layer 14 is 8% (i.e., 5% or more) larger than the maximum molar fraction of AlN in the cladding layer 15.

[0041] The maximum molar fraction of AlN in the second guiding layer 13C (including the pulling layer P) is approximately 85%. Therefore, the maximum molar fraction of AlN in the electron blocking layer 14 is 10% (i.e., 5% or more) larger than the maximum molar fraction of AlN in the second guiding layer 13C.

[0042] In the sample of Comparative Example 1, the reason why the pulling layer P is formed and the boundary between the electron blocking layer 14 and the cladding layer 15 is unclear is thought to be because the molar fraction of AlN is high in the early stage of crystal growth of the cladding layer 15. However, a high molar fraction of AlN in the early stage of crystal growth of the cladding layer 15 is necessary to create a polarization doping structure.

[0043] In contrast to this, by performing the first interruption step and the second interruption step as in the nitride semiconductor light-emitting element 1 of Example 1, even if the molar fraction of AlN is high in the initial stage of crystal growth of the cladding layer 15, it is possible to rapidly change the molar fraction of AlN in the boundary region between the second guide layer 13C and the electron blocking layer 14 and in the boundary region between the electron blocking layer 14 and the cladding layer 15, and it has been found that this makes it possible to form an electron blocking layer 14 with a clear boundary between the second guide layer 13C and the cladding layer 15.

[0044] Based on the above experimental results, the analysis results obtained using the device simulator SiLENSe are described below. The horizontal axis in FIG. 6 indicates the crystal stacking direction, and the vertical axis indicates the energy of the conduction band minimum corresponding to the stacking direction. The position around 3150 nm in FIG. 6 corresponds to the electron blocking layer 14. As shown in FIG. 6, the nitride semiconductor light-emitting device 1 of Example 1 exhibits a steeper rise in energy in the electron blocking layer 14 than the sample of Comparative Example 1, and it was found that a high energy barrier is formed in the conductor. This shows that electrons supplied from the n-layer side (the left side in FIG. 6, the sapphire substrate 10A side) can be effectively prevented from flowing out to the p-layer side (the right side in FIG. 6, the p-GaN layer 17 side).

[0045] 7 is a graph showing the analysis results of the relationship between injection efficiency and current density, obtained by using the device simulator SiLENSe. As shown in FIG. 7, it was found that the nitride semiconductor light-emitting device 1 of Example 1 had an injection efficiency with respect to current density that was approximately 1.5 times higher than that of the sample of Comparative Example 1. This analysis result shows that the effect of improving the injection efficiency with respect to current density can be obtained by performing the first interruption step and the second interruption step.

[0046] FIG. 8 is a graph plotting the relationship between the injection efficiency and the thickness of the electron blocking layer 14. As shown in FIG. 8, when the thickness of the electron blocking layer 14 is 5 nm or more, the injection efficiency is found to be greater than 0.07. In other words, when the thickness of the electron blocking layer 14 is 5 nm or more, the injection efficiency is found to be good. Note that FIG. 8 plots the injection efficiency up to the case where the thickness of the electron blocking layer 14 is 50 nm, but it is considered that the injection efficiency is good even when the thickness of the electron blocking layer 14 is 50 nm or more. It is considered that the maximum value of the AlN molar fraction of the electron blocking layer 14 needs to be 5% or more higher than the maximum value of the AlN molar fraction of the second guiding layer 13C (including the pulling layer P), and that the maximum value of the AlN molar fraction of the electron blocking layer 14 needs to be 5% or more higher than the maximum value of the AlN molar fraction of the cladding layer 15.

[0047] Next, the operation of the above embodiment will be described.

[0048] The ultraviolet semiconductor laser device includes a double quantum well active layer 13B, a second guide layer 13C stacked on the surface of the double quantum well active layer 13B, an electron blocking layer 14 stacked on the surface of the second guide layer 13C and blocking the flow of electrons from the double quantum well active layer 13B side, and a cladding layer 15 stacked on the surface of the electron blocking layer 14. With this configuration, the electron blocking layer 14 blocks the flow of electrons from the double quantum well active layer 13B toward the surface, allowing the double quantum well active layer 13B to emit light satisfactorily.

[0049] In the ultraviolet semiconductor laser device, the molar fraction of AlN in the cladding layer 15 is graded so that it decreases in the direction away from the double quantum well active layer 13B in the stacking direction. With this configuration, the cladding layer 15 can be polarized well in the stacking direction, and the device can function well as an ultraviolet semiconductor laser device.

[0050] In the ultraviolet semiconductor laser device, the maximum value of the molar fraction of AlN in electron blocking layer 14 is 5% or more larger than the maximum value of the molar fraction of AlN in cladding layer 15. With this configuration, the difference in the molar fraction of AlN between electron blocking layer 14 and cladding layer 15 can be made clear, allowing electron blocking layer 14 to perform its function better.

[0051] In the ultraviolet semiconductor laser device, the maximum value of the molar fraction of AlN in the electron blocking layer 14 is 5% or more larger than the maximum value of the molar fraction of AlN in the second guide layer 13C. With this configuration, the difference in the molar fraction of AlN between the electron blocking layer 14 and the second guide layer 13C can be made clear, allowing the electron blocking layer 14 to function better.

[0052] In the ultraviolet semiconductor laser device, the thickness of the electron blocking layer 14 in the stacking direction is 5 nm or more. With this configuration, the function of the electron blocking layer 14 can be further improved.

[0053] The method for manufacturing an ultraviolet semiconductor laser device includes a guide layer lamination step of laminating a second guide layer 13C on the surface of a double quantum well active layer 13B, an electron blocking layer lamination step of laminating an electron blocking layer 14 that blocks the flow of electrons from the double quantum well active layer 13B side on the surface of the second guide layer 13C, and a cladding layer lamination step of laminating a cladding layer 15 on the surface of the electron blocking layer 14, and further includes a first interruption step that is performed between the guide layer lamination step and the electron blocking layer lamination step and interrupts the supply of raw materials into the reactor, and a second interruption step that is performed between the electron blocking layer lamination step and the cladding layer lamination step and interrupts the supply of raw materials into the reactor. According to this configuration, the first interruption process can clearly form the boundary between the electron blocking layer 14 and the second guide layer 13C, and the second interruption process can clearly form the boundary between the electron blocking layer 14 and the cladding layer 15, so that the function of the electron blocking layer 14 can be well exhibited.

[0054] In the method for manufacturing an ultraviolet semiconductor laser device, the first interruption step is performed for 2 to 5 minutes. This configuration allows the boundary between the electron blocking layer 14 and the second guide layer 13C to be formed more clearly.

[0055] In the method for manufacturing an ultraviolet semiconductor laser device, the second interruption step is performed for 2 to 5 minutes. This configuration allows the boundary between the electron blocking layer 14 and the cladding layer 15 to be formed more clearly.

[0056] The present invention is not limited to the first embodiment described above with reference to the drawings, and the following embodiments are also included within the technical scope of the present invention. (1) In Example 1, Si is added as an n-type impurity to form an n-AlGaN layer, but this is not limiting and n-type impurities such as Ge and Te may also be used. Furthermore, Mg, Zn, Be, Ca, Sr, Ba, etc. may also be added as p-type impurities to form a p-AlGaN layer. Alternatively, a u-AlGaN layer may be initially grown, followed by the growth of an n-AlGaN layer. (2) In the first embodiment, a sapphire substrate is used, but an AlN layer may be laminated on another substrate such as an AlN substrate for crystal growth. (3) In Example 1, an AlN layer formed by sputtering is included, but instead of sputtering, only an AlN layer grown by MOVPE may be used. (4) In the first embodiment, convex portions are formed on the underlayer, but a flat underlayer structure without convex portions may also be used. [Explanation of symbols]

[0057] 1...Nitride semiconductor light-emitting element (ultraviolet semiconductor laser element) 13B...Double quantum well active layer (active layer) 13C...Second guide layer (guide layer) 14...Electron blocking layer 15...cladding layer

Claims

1. an active layer; a guide layer laminated on the surface of the active layer; an electron blocking layer laminated on a surface of the guide layer to block the flow of electrons from the active layer; a clad layer laminated on the surface of the electron blocking layer; It is equipped with the guide layer, the electron blocking layer, and the cladding layer contain Al; an electron blocking layer having a maximum AlN mole fraction that is 5% or more greater than the maximum AlN mole fraction of the cladding layer and that is 5% or more greater than the maximum AlN mole fraction of the guide layer;

2. 2. The ultraviolet semiconductor laser device according to claim 1, wherein the mole fraction of AlN in said cladding layer is graded so as to decrease in a direction away from said active layer in the stacking direction.

3. An ultraviolet semiconductor laser element as described in claim 1 or claim 2, wherein the thickness of the electron blocking layer in the stacking direction is 5 nm or more.

4. A guide layer lamination step of laminating a guide layer on the surface of the active layer; an electron blocking layer lamination step of laminating an electron blocking layer on a surface of the guide layer to block electrons from flowing from the active layer side; a clad layer lamination step of laminating a clad layer on the surface of the electron blocking layer; Equipped with a first interruption step of interrupting the supply of raw materials into the reactor, the first interruption step being performed between the guide layer laminating step and the electron block layer laminating step; a second interruption step of interrupting the supply of the raw material into the reactor, the second interruption step being performed between the electron blocking layer deposition step and the cladding layer deposition step; A method for manufacturing an ultraviolet semiconductor laser device comprising the steps of:

5. A method for manufacturing an ultraviolet semiconductor laser element as described in Claim 4, wherein the time for performing the first interruption step is 2 to 5 minutes.

6. A method for manufacturing an ultraviolet semiconductor laser element as described in claim 4 or claim 5, wherein the time for performing the second interruption step is 2 to 5 minutes.

Images