JP4169821B2 - Light emitting diode - Google Patents

Light emitting diode Download PDF

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JP4169821B2
JP4169821B2 JP3563898A JP3563898A JP4169821B2 JP 4169821 B2 JP4169821 B2 JP 4169821B2 JP 3563898 A JP3563898 A JP 3563898A JP 3563898 A JP3563898 A JP 3563898A JP 4169821 B2 JP4169821 B2 JP 4169821B2
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light emitting
layer
formed
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JPH11233893A (en
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元隆 種谷
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シャープ株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor light emitting device, and more particularly, to a highly reliable semiconductor light emitting device formed on a substrate with a semiconductor material having a lattice constant or a thermal expansion coefficient different from that of the substrate.
[0002]
[Prior art]
When a crystal material constituting a semiconductor light emitting element is formed on a substrate having a lattice constant different by 3% or more, or when a semiconductor crystal is grown on a substrate having a thermal expansion coefficient different by 10% or more, the crystal material is first formed on the substrate. A semiconductor light-emitting element is formed after a continuous film semiconductor layer is formed by growing a crystal material thickly so that the lattice constant and the thermal expansion coefficient are substantially equal to the material constituting the semiconductor light-emitting element (both lattice constant and thermal expansion coefficient are within 1%). Attempts have been made. It has been reported that a semiconductor layer stacked on a continuous film semiconductor layer has reduced crystal defects. As a typical example of such a light-emitting element, FIG. 8 shows a conventional technique in which a continuous film semiconductor layer is formed by growing a thick GaN layer on a sapphire substrate 800 and a blue light-emitting diode (LED) is formed thereon. Here is an example.
[0003]
A method of manufacturing this conventional LED will be described. On the sapphire substrate 800, a GaN layer 801 is first grown to a thickness of 5 μm by a halide vapor phase growth method (HVPE method). Next, a selective growth mask 802 made of SiO 2 is formed on the surface of the GaN layer 801 in a lattice shape (20 μm wide SiO 2 stripes having a pitch of 200 μm are perpendicular to each other). FIG. 8A shows a process cross-sectional view manufactured up to the above.
[0004]
Next, an n-type GaN continuous film semiconductor layer 803 is grown on the sapphire substrate 800 to a thickness of 300 μm by HVPE. In this, n-type GaN continuous semiconductor layer 803 grown by the HVPE process is grown from a portion the sapphire substrate 800 is exposed begins, along with its thickness increases, the selective growth mask 802 above of SiO 2 The film was grown to the left and right so as to overhang, and finally covered the selective growth mask 802 made of SiO 2 having a width of 20 μm. In this way, an n-type GaN continuous film semiconductor layer 803 having a flat surface was formed.
[0005]
Next, an n-GaN cladding layer 804, an InGaN active layer 805, and p-GaN are formed on a wafer having an n-type GaN continuous film semiconductor layer 803 formed on the sapphire substrate 800 by metal organic chemical vapor deposition (MOCVD). A contact layer 806 was formed. FIG. 8B shows a process cross-sectional view manufactured up to the above.
[0006]
Next, as shown in FIG. 9 (a) a top view of a conventional LED and (b) a cross-sectional view taken along the line AA ′ of the conventional LED, a 300 μm square light emitting region 810 is left and surrounded. Then, the p-GaN contact layer 806, the InGaN active layer 805, and the n-GaN cladding layer 804 are removed by using a normal photolithography technique and a dry etching technique to expose the n-type GaN continuous film semiconductor layer 803. It was. Finally, an n-type electrode 807 was formed on the surface of the n-type GaN continuous film semiconductor layer 803, and a light-transmitting p-type electrode 808 was formed on the surface of the 300 μm square p-GaN contact layer 806. Thus, it scribed around the light emission area | region 810 from the produced wafer, and each LED was cut out as the element. A conventional LED manufactured in this manner has been reported.
[0007]
[Problems to be solved by the invention]
However, as a result of the inventors testing the characteristics of the LED thus manufactured, the luminous efficiency (conversion efficiency of electrons into photons) when a current of 20 mA is injected varies from 0.3% to 10% depending on individual elements. %, The yield that achieves the desired 5% or higher luminous efficiency is very low at 2%, and the luminous efficiency of all devices in the initial reliability test for about 100 hours at 80 ° C. Has been found to be drastically reduced to about 30% or less at the start of the test.
[0008]
As a result of detailed studies by the inventor on the defects of these conventional elements, the following facts have been found.
(1) Light emission at the InGaN active layer 805 portion located in the region 811 immediately above the selective growth mask where the selective growth mask 802 exists is very small. It has also been found that this reduction in luminous efficiency is particularly noticeable when the region 811 directly above the selective growth mask is located in the central region of the light emitting region 810 rather than the peripheral region of the light emitting region 810 of the chip. As a result, the light emission efficiency varies greatly depending on which part of the light emitting region 810 the region 811 immediately above the selective growth mask is located.
(2) Even in the above-described device with poor reliability, after running the reliability test for 100 hours, the InGaN active layer 805 in the region 811 (width 20 μm) immediately above the selective growth mask includes about 30 μm on both sides and a total of 80 μm. No light emission is observed in the region of.
[0009]
Further, as a result of crystal analysis of the conventional element, crystal transition concentrates in the InGaN active layer 805 located in the region 811 immediately above the selective growth mask through the n-type GaN continuous film semiconductor layer 803 having a thickness of 300 μm. It became clear that it was introduced. FIG. 10 shows the results of measuring the density of crystal transition in the InGaN active layer 805 using the distance from the edge of the selective growth mask 802 as a parameter. The InGaN active layer 805 of width 20μm selective growth mask regions above 811 are concentrated the crystal transition of density 10 12 cm -2, further selective growth from the edge of the mask 802 10 [mu] m apart even of 10 11 cm -2 at the position A metastasis was observed. The crystal transition decreased as the distance from the edge of the selective growth mask 802 decreased, and the crystal transition decreased to 10 7 to 10 8 cm −3 in the InGaN active layer 805 located at a distance of 30 μm or more. Such a tendency was observed in any part of the wafer produced as described above.
[0010]
Further, the semiconductor laser is formed on the n-type GaN continuous film semiconductor layer 803 as described above by the same method, the light emitting region includes the region 811 directly above the selective growth mask, the oscillation threshold current is as large as 700 mA, and the device lifetime is also room temperature. It was very short, about 1 second.
[0011]
As described above, the following problems have been clarified in the prior art. (1) In a light emitting device on a continuous film semiconductor layer manufactured using the selective growth method, since the light emission efficiency is reduced in the region 811 immediately above the selective growth mask, in a chip in which the region directly above the selective growth mask is included in the light emission region The luminous efficiency decreases dramatically.
(2) The semiconductor laser device formed on the GaN continuous film has a short life, and no semiconductor laser device was obtained.
[0012]
For this reason, a continuous film semiconductor layer having a lattice constant or a thermal expansion coefficient different from that of the substrate is grown on the substrate, and the light emitting efficiency caused by the difference of the lattice constant or the thermal expansion coefficient is formed on the semiconductor light emitting element formed thereon. It was impossible to prevent deterioration and poor reliability.
[0013]
Therefore, when a continuous film semiconductor layer having a lattice constant or a thermal expansion coefficient different from that of the substrate is formed by using the partial growth suppression structure, the light emission efficiency is lowered and the reliability is deteriorated when a semiconductor light emitting device is further formed. The purpose is to prevent.
[0014]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a semiconductor light emitting device having a continuous film semiconductor layer including a region immediately above a growth suppressing structure obtained by crystal growth on the growth suppressing structure, and an active layer for generating light. Among the layers, a light emitting region that generates light by current injection is formed in a region other than the region directly above the growth suppressing structure.
[0015]
According to a second aspect of the present invention, the light emitting region is formed by being formed at a position separated by 30 μm or more from the region immediately above the growth suppressing structure. Further, the third aspect is characterized in that the light emitting region and the region immediately above the growth suppressing structure are formed. In the region between them, the active layer is removed.
[0016]
On the other hand, according to a fourth aspect of the present invention, the first step of forming the growth suppressing structure on the substrate and the continuous film having a lattice constant or a thermal expansion coefficient different from that of the substrate so as to continuously cover both the substrate and the growth suppressing structure. A second step of forming a semiconductor layer, a third step of forming a multilayer structure including an active layer for generating light on the continuous film semiconductor layer, and the active except for a region directly above the growth suppression structure. And a fourth step of forming a structure for defining a light emitting region in the layer, and further comprising a step of dividing the semiconductor light emitting device into a plurality of semiconductor light emitting devices from the wafer. And a fifth step of dividing the semiconductor light emitting device from the wafer so that the active layer immediately above the growth suppressing structure is not included in the semiconductor light emitting device after the fourth step. According to a sixth aspect of the present invention, in the fifth step, in the fifth step, the semiconductor light emitting device is arranged such that the active layer remaining in a region within 30 μm from the end immediately above the growth suppressing structure is not included in the semiconductor light emitting device. It is configured by dividing.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described using an example in which the present invention is implemented.
(Embodiment 1)
FIG. 1 shows an example of a semiconductor laser device embodying the present invention. This semiconductor laser device, n-GaN continuous film semiconductor layer 102, n-GaN buffer layer 103, n-Al 0.1 Ga 0.9 N cladding layer 104, MQW active layer 105, p-Al 0.1 Ga 0.9 N cladding layer 106 , A p-GaN contact layer 107, a mesa stripe 110 for defining a laser emission region as a ridge waveguide, and a p-type electrode 111 and an n-type electrode 112 for current injection. Yes.
[0018]
Next, a manufacturing process of the element of this example will be described with reference to FIGS. First, a GaN buffer layer 101 is grown to a thickness of 1 μm on the sapphire substrate 100 by MOCVD. Next, after a 0.4 μm thick SiO 2 film is formed on the surface of the GaN buffer layer 101 by a normal sputtering method, it is made of periodic SiO 2 having a width of 10 μm and a pitch of 150 μm by a normal photolithography technique and an etching technique. A selective growth mask 150 and a selective growth mask 151 made of periodic SiO 2 having a width of 10 μm and a pitch of 500 μm were formed in a shape orthogonal to each other. FIG. 2A shows a process cross-sectional view of the semiconductor laser device manufactured up to the above.
[0019]
Subsequently, the n-GaN continuous film semiconductor layer 102 was grown to a thickness of 150 μm on the wafer by HVPE. The substrate temperature was 1020 ° C., and growth of 150 μm thickness was completed by growth for 35 minutes. During this growth, the selective growth masks 150 and 151 function as a growth suppressing structure. Therefore, as described in the conventional example, the growth occurs only in the region where the GaN buffer film 101 is exposed at the initial stage of growth, and gradually the selective growth mask. At the stage where the growth progressed laterally on 150 and 151 and finally the growth of 150 μm thickness was completed, the n-GaN continuous film semiconductor layer 102 exhibited a continuous film, and the surface thereof became smooth.
[0020]
Next, by the MOCVD method, the n-GaN buffer layer 103 is 0.5 μm thick and the n-Al 0.1 Ga 0.9 N cladding layer 104 is 0.2 μm thick and 4 nm on the n-GaN continuous film semiconductor layer 102. A multi-quantum well active layer 105 composed of two In 0.25 Ga 0.75 N well layers having a thickness of three and three In 0.05 Ga 0.95 N barrier layers having a thickness of 3 nm, and a p-Al 0.1 Ga 0.9 N cladding layer 106 having a thickness of 0.2 μm, p The GaN contact layer 107 was grown to a thickness of 0.7 μm. FIG. 2B shows a process cross-sectional view of the semiconductor laser device manufactured up to the above.
[0021]
Subsequently, a mesa stripe 110 having a width of 2 μm and a height of 0.7 μm was formed almost in parallel with the selective growth mask 150 in a region other than the region 152 immediately above the selective growth mask 150. At this time, the mesa stripe 110 was observed from above the element so as to be positioned at substantially the center of the adjacent selective growth mask 150. A normal photolithography technique and a dry etching technique are applied to the formation of the mesa stripe 110. Thereafter, a p-type electrode 111 having a stripe shape is formed on the top surface of the mesa stripe 110, and then the wafer back surface is polished to make the wafer thickness about 120 μm (that is, the sapphire substrate 100, the GaN buffer layer 101, the selective growth mask). 150 and 151 are completely removed so that the n-GaN continuous film semiconductor layer 102 is exposed on the back surface of the wafer), and an n-type electrode 112 is formed on the entire exposed back surface of the n-GaN continuous film semiconductor layer 102. FIG. 2C shows a process cross-sectional view of the semiconductor laser device manufactured up to the above.
[0022]
Next, a mirror surface constituting a laser resonator was formed by cleavage. This cleavage step was performed as follows. First, scratch marks are made at two locations near the corner of the wafer back surface (that is, the n-GaN continuous film layer 103 side), and cleaved in the direction parallel to the direction in which the selective growth mask 151 is formed at the position of the scratch marks. Thus, a laser resonator mirror was formed. At this time, two scratches were formed at positions 50 μm away from the edge portions of the selective growth mask 151 adjacent to each other so that the region 153 immediately above the selective growth mask 151 was not included in the laser element. Therefore, the laser cavity length was 400 μm. Finally, the portion of the region 152 immediately above the selective growth mask 150 was scribed and divided into individual laser chips. The laser element shown in FIG. 1 is completed through the above steps.
[0023]
The laser element manufactured as described above could realize laser oscillation with a threshold current of 25 mA. In addition, as a result of the reliability test of this laser device under the conditions of 50 ° C atmosphere and 3 mW output, most of the devices have been confirmed to have a lifetime of 1000 hours or more, except for the laser device that fails within the initial 50 hours. The median lifetime (time for half of the tested devices to fail) was 1500 hours. This reliability is a sufficient characteristic even when the element is used as a light source for an optical disk. In the present laser device, this improvement in reliability is achieved by directly overlying the regions 152, 153 where crystal defects are concentrated on the selective growth masks 150, 151, which are growth suppression structures formed to grow the n-GaN continuous film semiconductor layer 102. Are not included in the light emitting region of the laser element (in this case, the portion where the mesa stripe 110 in which current is selectively injected into the active layer 105 is formed) It can be understood that the relative position of the mesa stripe 110 with respect to the growth mask 150 and the relative position for cleavage of the laser resonator mirror with respect to the selective growth mask 151 are set.
[0024]
In the laser device in which the above-described invention is implemented, the mesa stripe 110 is formed so as to be in the center between the regions 152 immediately above the adjacent selective growth mask 150 (that is, at a portion 70 μm away from the edge of the selective growth mask 150). Yes. With the same structure as the above-described embodiment element, the distance from the edge of the region 152 directly above the mesa stripe 110 (that is, the selective growth mask 150) is 0 μm (that is, when the mesa stripe 110 is formed in the region 152 immediately above), 10 μm, 20 μm. , 30 μm, 50 μm, and 70 μm were fabricated, and the same reliability test as described above was performed. At this time, the scribe position for element isolation was set near the center of the adjacent mesa stripe 110 in any element, and the relative distance from the mesa stripe 110 at the scribe position was constant. The result is shown in FIG. The horizontal axis indicates the distance from the center of the region 152 immediately above to the mesa stripe 110, and the vertical axis indicates the median life. From this result, it was found that the mesa stripe 110 needs to be formed at a position 30 μm or more away from the immediately above region 152 in order to ensure a median life of 1000 hours or more that is practically required.
[0025]
(Embodiment 2)
Next, the case where the present invention is applied to a light emitting diode will be described. FIG. 4 shows a structural diagram of the element of the second embodiment. n-GaN continuous film semiconductor layer 401, n-GaN buffer layer 402, In 0.1 Ga 0.9 N strain relaxation layer 403, In 0.5 Ga 0.5 N single quantum well active layer 404, p-Al 0.2 Ga 0.8 N evaporation prevention layer 405 , A p-GaN contact layer 406, an n-type electrode 407, and a p-type electrode 408. In the element of this embodiment, the light emitting region is defined by the mesa 410.
[0026]
Next, a method for manufacturing the light-emitting element will be described. First, a groove structure 450 having a width of 40 μm and a depth of 50 μm is formed in a lattice pattern at a pitch of 400 μm on the surface of the sapphire substrate 400 by dicing. FIG. 5A is a process cross-sectional view of the semiconductor element manufactured so far.
[0027]
Next, an n-GaN continuous film semiconductor layer 401 having a thickness of 300 μm is grown by HVPE. At this time, since there is a groove structure 450 formed in the sapphire substrate 400, the n-GaN continuous film semiconductor layer 401 cannot grow as a flat surface in the early stage of growth, but gradually increases from the left and right walls as the growth layer thickness increases. Growing filled the groove structure 450, and the groove on the surface was filled flat. That is, the same effect as that of the slow growth in the trench 450 can be realized, and the n-GaN continuous film layer 401 can be formed into a single layer with a flat continuous surface at the end of the growth of 300 μm. It was.
[0028]
Next, by molecular beam epitaxy (MBE), the n-GaN buffer layer 402 is 0.4 μm thick and the In 0.2 Ga 0.8 N strain relaxation layer 403 is 0.05 μm thick on the n-GaN continuous film semiconductor layer 401. In 0.45 Ga 0.55 N single quantum well active layer 404 was grown to a thickness of 4 nm, p-Al 0.1 Ga 0.9 N evaporation preventing layer 405 was grown to a thickness of 0.1 μm, and p-GaN contact layer 406 was grown to a thickness of 0.4 μm. FIG. 5B is a process cross-sectional view of the light-emitting element manufactured so far.
[0029]
Further, a 300 μm square mesa 410 including the In 0.45 Ga 0.55 N single quantum well active layer 404 is periodically left by using a normal photolithography technique and a dry etching technique, and a region therebetween is etched with a width of 100 μm, and n − The GaN continuous film semiconductor layer 401 was exposed on the bottom surface of the etching. That is, the etched region has a lattice shape with a pitch of 400 μm, and accordingly, the region 451 immediately above the groove structure 450 containing many defects grown on the groove structure 450 and the In 0.45 Ga contained in the periphery thereof. The 0.55 N single quantum well active layer 404 was completely removed. In the present embodiment, the groove structure 450 is a growth suppressing structure. FIG. 5C is a process cross-sectional view of the light-emitting element manufactured so far.
[0030]
Next, the back surface of the wafer is polished, the sapphire substrate 400 is completely removed, and the n-GaN continuous film semiconductor layer 401 is exposed on the back surface of the wafer, and then an n-type electrode 407 is formed on the n-GaN continuous film semiconductor layer 401. A light-transmitting p-type electrode 408 was formed on the surface of the mesa 410. Finally, individual light emitting diode chips were obtained by scribing in the region 451 immediately above the groove structure 450. FIG. 4 is a process cross-sectional view of the light-emitting element manufactured so far.
[0031]
As a result of measuring the conversion efficiency of the light-emitting diodes thus produced into electrons to photons, the yield of devices with a conversion efficiency of 5% or more that can be regarded as having no practical problem was as high as 85%. Furthermore, when a reliability test was performed on the element of this example under the same conditions as those of the conventional element, a light emission intensity of 95 to 103% at the start of the test could be obtained even after 1000 hours. Reliability without problems was ensured.
[0032]
The light emitting region in the light emitting device of this embodiment corresponds to the mesa 410 part in which the In 0.45 Ga 0.55 N single quantum well active layer 404 remains. Since the mesa 410 is formed in a region excluding the region 451 immediately above the groove structure 450 used as a growth suppressing structure during the growth of the n-GaN continuous film semiconductor layer 401, the groove in the light emitting region is formed in all the light emitting devices manufactured. The region 451 immediately above the structure 450 is not included. The width of the In 0.45 Ga 0.55 N single quantum well active layer 404 removed by etching is 100 μm, and the light emitting region of the mesa 410 part is formed 30 μm away from the end of the groove structure 450 having a width of 40 μm. Will be. As described above, an element with high light emission efficiency can be obtained with high yield, and reliability without problems can be realized by concentrating on the region 451 immediately above the groove structure 450 by the crystal growth process by the HVPE method and the MOCVD method. The influence of the introduced crystal defects does not adversely affect the light emission in the In 0.45 Ga 0.55 N single quantum well active layer 404, and it is possible to place the light emitting region with good controllability in a portion with relatively few crystal defects. It is thought that it became.
[0033]
In addition, in the light emitting element of the above embodiment, the light emitting element manufacturing process and the structure are substantially the same, and a light emitting element in which only the pitch of the groove structure 450 is changed from 400 μm to 500 μm and 300 μm in the above example was manufactured. Even in this case, the size and the production pitch of the mesa 410 were 300 μm and 400 μm, respectively, and the elements of the above-described embodiment were kept as they were. When the light emission characteristics of these light emitting elements were measured, the yield at which the light emission efficiency of 5% or more was obtained was drastically reduced to 16% in the elements in which the pitch of the grooves 450 was as small as 300 μm. On the other hand, it was 38% in the light emitting element widened to 500 μm. This indicates that it is important that the pitch of the groove structure 450 is the same as the production pitch of the mesas 410 forming the individual light emitting diodes. Therefore, in order to manufacture more light-emitting elements from a wafer having the same area, the light-emitting area should not contain the region 451 immediately above the groove structure in all the light-emitting elements. In this sense, it goes without saying that the pitch of the groove structure 450 may be an integral multiple of the mesa 410 manufacturing pitch.
[0034]
(Embodiment 3)
Next, an embodiment in which the growth suppression structure itself is left in the laser element will be described. FIG. 6 shows an element structure diagram of this embodiment. The element structure of the present embodiment includes an n-SiC substrate 600, a GaN buffer layer 601, an n-GaN continuous film semiconductor layer 602, an n-GaN buffer layer 603, an n-Al 0.1 Ga 0.9 N cladding layer 604, a 3 nm thick In layer. Multiple quantum well active layer 605 composed of three 0.1 Ga 0.85 Al 0.05 N barrier layers and two 3 nm thick In 0.2 Ga 0.8 N quantum well layers, p-Al 0.1 Ga 0.9 N clad layer 606, p-GaN contact layer 607 , A p-type electrode 611, an n-type electrode 612, a mesa stripe 610 defining a waveguide and a current path, and an etched mirror 613 serving as a resonator mirror.
[0035]
Hereinafter, a method for manufacturing the laser element of this embodiment will be described. (The process diagram is similar to that of FIG. 2 and is omitted here.) First, a selective growth mask 650 made of SiN x and having a width of 10 μm and a period of 100 μm and a width of 10 μm and a period are formed on the n-SiC substrate 600. The selective growth mask 651 having a thickness of 400 μm is formed so as to be orthogonal to each other. On this wafer, the GaN buffer layer 601 is 30 nm thick, the n-GaN continuous film semiconductor layer 602 is 100 μm thick, the n-GaN buffer layer 603 is 0.1 μm, and the n-AlGaN cladding layer 604 is 0.3 μm thick by MOCVD. The multiple quantum well active layer 605 and the p-AlGaN cladding layer 606 are continuously grown by 0.3 μm thickness and the p-GaN contact layer 607 is continuously grown by 1.0 μm thickness. At this time, in the growth of the n-GaN continuous film semiconductor layer 602, when the thickness is 30 μm or less, an ungrown portion remains on the selective growth masks 650 and 651, and the crystal does not exhibit a continuous film. However, at the stage where the growth further reaches 100 μm, the surface of the n-GaN continuous film semiconductor layer 602 exhibits a flat and continuous single film as in the first embodiment, and is continuously formed thereon. The layers 603 to 607 included in the laminated structure formed in the above were also grown as flat layers.
[0036]
Next, a mesa stripe 610 having a height of 0.8 μm and a width of 2 μm was formed in parallel with the selective growth mask 651 by using a normal photolithography technique and an etching technique. The mesa stripe 610 not only forms a laser waveguide in the active layer 605, but also defines the path of current injected into the active layer 605 in the vicinity immediately below the mesa stripe 610 to efficiently convert electrons into laser light. do. In this step, the mesa stripe 610 is formed so that the center of the region 653 immediately above the selective growth mask 651 on both sides, that is, the distance between the edge of the selective growth mask 651 and the edge of the mesa stripe 610 is 39 μm.
[0037]
Next, an etched mirror 613 to be a laser resonator mirror was formed by using a photolithography technique for forming an ordinary etched mirror and a dry etching technique. At this time, the etched mirror 613 is parallel to the selective growth mask 650 and the entire width around the region 652 immediately above the selective growth mask 650 is centered so that the active layer 605 in the region 652 directly above the selective growth mask 650 is removed by etching. Etching was performed on the 100 μm region, and etching was performed until the n-GaN continuous film semiconductor layer 602 was exposed on the bottom surface of the etching. By this process, a set of resonator mirrors to be a laser resonator is formed, and the resonator length in the laser element of this embodiment is 300 μm. That is, the etching for forming the etched mirror is performed at the same period of 400 μm as the period of the selective growth mask 650.
[0038]
Finally, a p-type electrode 611 is formed on the upper surface of the mesa stripe 610 and an n-type electrode 612 is formed on the entire back surface of the n-SiC substrate 600, and then scribed in the regions 652 and 653 immediately above the selective growth masks 650 and 651. Divided into individual laser elements.
[0039]
When the reliability test was performed on the laser element of the present embodiment under the condition of 5 mW light output under the atmosphere of 60 ° C. of the second embodiment, all the elements were 1000 hours or more except for the element that showed the initial 24 hours of abnormal deterioration. It was confirmed to have a lifetime of The median life in this case was about 1600 hours. In this way, a highly reliable laser can be realized only in a region where the region 652 immediately above the selective growth mask 650 is not included in the mesa stripe 610 as the light emitting region and there are few crystal defects that cause deterioration of the laser element. It is presumed that the active layer 605 contributes to light emission.
[0040]
By the way, in the first embodiment, the cleavage position of the laser element is limited to a portion outside the region 152 immediately above the selective growth mask 150. This includes the region 152 immediately above the selective growth mask that contains many crystal defects in the vicinity of the cleaved surface easily broken in the mesa stripe 110 that becomes the laser emission region when cleaved in the region 152 immediately above the selective growth mask 150. This is to avoid instantaneous deterioration when the element is operated. However, when the cleavage is performed in the vicinity of the region 152 directly above the selective growth mask 150 in parallel with the region 152 directly above the selective growth mask 150 as in the first embodiment, a step is partially generated on the cleavage surface, resulting in a partial In some cases, the region 152 immediately above the selective growth mask 150 is included in the mesa stripe 110 in the above element. This is presumably because the region 152 immediately above the selective growth mask 150 contains many crystal defects, is weak as a crystal, and is more likely to break. That is, in the first embodiment, the vicinity of the selective growth mask 150 is cleaved regardless of whether the crystal has the property of being easily cleaved. This phenomenon is observed not only when the element is divided by cleavage but also when the element is divided by scribing, and the selection mask 151 is compared to the case where the scribing is performed in the region 153 immediately above the selection mask 151. The yield was low when scribing with good controllability in parallel with the region 153 directly above the selection mask 151 in the vicinity of the region 153 immediately above.
[0041]
On the other hand, in the element of the present embodiment, the element dividing position by scribing on all four sides when dividing the element can be limited to the regions 652 and 653 immediately above the selective growth masks 650 and 651. Thus, the mesa stripe 610 did not include the region 652 immediately above the selection mask, and the shape of the element did not deviate from a predetermined shape (rectangular shape as shown in FIG. 6 as viewed from above). As a result, errors in element shape recognition when mounting elements can be reduced, and the element mount yield can be improved. This point is also a great merit in the element of this embodiment.
[0042]
(Embodiment 4)
Next, an embodiment of the present invention in the case where the active layer in the region immediately above the growth suppression structure remains in the device will be described using an example of a light emitting diode. FIG. 7 shows a structural view observed from the upper surface of the light emitting device of this embodiment. The formation method of the GaN continuous film layer and the semiconductor laminated structure are the same as those in the second embodiment (in the description of this embodiment, the common layers are marked with the same symbols as in the second embodiment). The difference from the second embodiment is that the shape of the mesa 710 including the In 0.45 Ga 0.55 N single quantum well active layer 404 has a shape as shown in FIG. 7 and the size is increased to 390 μm square. is there. For this reason, in the light emitting device of this embodiment, the In 0.45 Ga 0.55 N single quantum well active layer 404 located in the region 751 immediately above the groove structure 450 which is a growth suppressing structure during the growth of the n-GaN continuous film layer 401 is the mesa 710. It is included in the form.
[0043]
However, in the light emitting device of this embodiment, the p-type electrode 711 is arranged in the central region of the mesa 710 with a 300 μm square. That is, the p-type electrode is not formed in the region 75 μm from the end of the region 751 immediately above and the region 751 directly above the groove structure 450. On the other hand, the n-type electrode 712 was formed at one corner of the light emitting device from which the In 0.45 Ga 0.55 N single quantum well active layer 404 was removed as shown in FIG.
[0044]
With such a configuration, the current injected from the p-type contact layer 406 and the p-type electrode 711 is such that the p-GaN contact layer 406 is made of p-GaN having a relatively high resistivity, and 0. Since the film thickness is as small as 4 μm, the current hardly diffuses in the lateral direction in the p-type contact layer 406, and the current is applied only to the In 0.45 Ga 0.55 N single quantum well active layer 404 immediately below the p-type electrode 711. Can be injected.
[0045]
As a result of evaluating the characteristics of the light emitting device of the present embodiment, the chip having an electron-photon conversion efficiency of 5% or more reaches 79% of the inspected, and a marked improvement is recognized over the light emitting device configured by the prior art. It was. Further, when a reliability test of these light-emitting elements (conditions are the same as those in Embodiment 2), the emission luminance after 1000 hours is in the range of 85 to 99% with respect to the initial emission luminance. It was confirmed that the light emitting device had no problem in practical use.
[0046]
As described above, in the light emitting device of the embodiment, the example in which the gallium nitride-based light emitting device is manufactured using the GaN continuous film semiconductor layer has been described, but it is needless to say that the present invention can be applied to the following cases. .
(1) When the substrate material, the material of the continuous film semiconductor layer, and the material constituting the light emitting element are different (for example, when the substrate is Si and the continuous film semiconductor layer is GaAs, or when the substrate is Si and GaAs and the continuous film layer is If it is GaN, etc.).
(2) When the material of the selective growth mask that is a growth suppressing structure is different (SiN x , SiO x , AlO x , etc.), or when the structure itself is other than the selective growth mask or groove structure (for example, formed on a sapphire substrate) Ridge stripes and other uneven structures, etc.).
(3) When the order of the steps is changed so that the substrate is completely removed after the continuous film semiconductor layer is formed and before the light emitting layer is formed.
[0047]
【The invention's effect】
As described above, by applying the present invention, when a semiconductor light-emitting element is formed on a continuous film semiconductor layer having a lattice constant or a thermal expansion coefficient different from that of the substrate, the light emission efficiency is prevented from being lowered and the light emission efficiency is improved. High light emitting diodes and semiconductor lasers were realized. Further, according to the present invention, it is possible to ensure practically sufficient reliability in these light emitting elements.
[Brief description of the drawings]
FIG. 1 is a sectional view of a semiconductor laser device according to a first embodiment of the present invention.
FIG. 2 is a manufacturing process diagram of the semiconductor laser element according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a median lifetime with respect to a distance from a region immediately above a growth mask to a mesa stripe.
FIG. 4 is a cross-sectional view of a semiconductor light emitting element according to a second embodiment of the present invention.
FIG. 5 is a manufacturing process diagram of the semiconductor light-emitting element according to the second embodiment of the present invention.
FIG. 6 is a sectional view of a semiconductor laser device according to a third embodiment of the present invention.
FIG. 7 is a top view of a semiconductor light emitting element according to a fourth embodiment of the present invention.
FIG. 8 is a manufacturing process diagram of a conventional semiconductor light emitting device.
FIG. 9 is a view showing a structure of a conventional semiconductor light emitting device.
FIG. 10 is a diagram showing the surface density of crystal transition with respect to the distance from the growth suppression structure.
[Explanation of symbols]
100 sapphire substrate 101,601 GaN buffer layer 102,602,401 n-GaN continuous layer 103,603,402 n-GaN buffer layer 104,604 n-Al 0.1 Ga 0.9 N cladding layer 105,605 MQW active layer 106, 606, 405 p-Al 0.1 Ga 0.9 N cladding layer 107, 607 406 p-GaN contact layer 110, 610 Mesa stripe 111, 611, 408, 711 p-type electrode 112, 612, 407, 712 n-type electrode 150, 151, 650, 651 Selective growth mask 152, 153, 652, 653 Directly above region 400 Sapphire substrate 403 In 0.2 Ga 0.8 N strain relaxation layer 404 In 0.45 Ga 0.55 N single quantum well active layer 410 Mesa 450 Trench structure 451, 751 Directly above Region 600 SiC substrate 710 S

Claims (1)

  1. On the substrate, the growth suppression structure formed on the substrate, the GaN continuous film semiconductor layer formed on the substrate and the growth suppression structure, the GaN continuous film semiconductor layer, and the GaN continuous film semiconductor layer A light emitting diode having an active layer for generating light,
    In the active layer, a light emitting region that generates light by current injection is formed in a region other than the region directly above the growth suppression structure,
    The light emitting region is formed at a position 30 μm or more away from the region immediately above the growth suppressing structure ,
    The active layer is removed in a region between the light emitting region and the region immediately above the growth suppressing structure.
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