JP3995790B2 - Crystal manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a crystal manufacturing method for obtaining a high-performance and high-reliability device by growing a high-quality crystal on a substrate having a different lattice constant and manufacturing a light-emitting element or an electronic device on the crystal.To the lawIn particular, a highly efficient and reliable gallium nitride (GaN) blue light emitting deviceTheHow to make crystals to makeTo the lawRelated.
[0002]
[Prior art]
  An opto-electric integrated circuit (OEIC) is a device for processing a large amount of information at high speed by integrating an optical element and a Si-based LSI, and has been expected and studied as an indispensable device in the advanced information society. It was. In optical devices, the main purpose was to develop a technique for producing an AlGaAs laser on a Si substrate. However, due to a large difference in lattice constant and thermal expansion coefficient between the AlGaAs crystal and the Si substrate, a high-quality AlGaAs crystal cannot be manufactured and has not been completed.
[0003]
  For Si-based LSIs, SOI and SIMOX have been proposed as ultra-high speed, low power consumption next generation integrated circuits, and their development is urgently needed.
[0004]
  Since gallium nitride (GaN) blue light-emitting elements do not have large bulk crystals due to their large decomposition pressure, GaN crystals are manufactured using different materials such as sapphire as a substrate.
[0005]
  Since these substitute substrates have a large difference in lattice constant or thermal expansion coefficient from the nitride semiconductor, it is difficult to epitaxially grow a good crystal having a small crystal defect or crystal dislocation density directly on the substrate. For example, when a sapphire substrate is used as a substitute substrate for a nitride semiconductor (GaN), the nitride semiconductor (GaN) layer grown on the substrate has 10⁹-10^Tencm^-2It is known that threading dislocations exist.
[0006]
  As a solution to this problem, FIG. 7 shows the 58th JSAP Scientific Lecture Proceedings 2p-Q-14, No. 1 (1997) p265 shows a first conventional example.
[0007]
  In the figure, 700 is a sapphire substrate, 701 is SiO.₂Pattern, 702 is SiO₂703 is a GaN single crystal film grown by MOCVD. BookConventionalIn the example, SiO such that crystal growth starts from the opening.₂By using the growth suppression effect by the pattern, SiO₂Only in the upper GaN single crystal 704, the defect density 10^Five-10⁶/ Cm²Is obtained and SiO₂The defect density was reduced by about four orders of magnitude compared to the crystal without using a pattern.
[0008]
  FIG. 8 shows the 58th JSAP Scientific Lecture Proceedings 2p-Q-15, No. 8; 1 (1997) p266, the second reportedConventionalIt is an example. In the figure, 800 is a sapphire substrate, and 801 is a GaN single crystal grown by MOCVD. 802 is SiO₂Pattern, 803 is SiO₂804 is a GaN crystal grown by the Hide-VPE method. BookConventionalIn the example as well, the defect density of 6 × 10 6 is near the surface of the GaN crystal 804 grown by the Hide-VPE method.⁷/ Cm²As a result, the defect density was reduced by about three orders of magnitude compared to the conventionally obtained crystal. By using such a GaN single crystal film shown in the conventional example as a growth substrate for a GaN-based semiconductor device, high performance of the electronic device is expected.
[0009]
[Problems to be solved by the invention]
  However, even with the above-described conventional example, the quality of the obtained GaN single crystal substrate has not been sufficient yet. For example, in the case of a semiconductor laser device, if there is no defect near the light emitting region, an innovative improvement in the product life is brought about.^Five/ Cm²The following are required: In this sense, the above-described reduction in defect density was insufficient. Desirably, the defect density is the same as that of other III-V semiconductor substrates such as GaAs.^Four/ Cm²The following are required:
[0010]
  In the first conventional example, the high-quality crystal with a reduced defect density is SiO 2.₂The other regions are limited to the pattern, and the other regions have the same crystal quality as the conventional one, and are difficult to use as a crystal growth substrate.
[0011]
  In the second conventional example, a relatively thick film is grown as an epitaxial growth film by several tens of μm by the Hide-VPE method.₂Since the influence of the pattern is alleviated and the defects are uniformly distributed, there is no such problem, but the defect density is inferior to the first conventional example. An object of the present invention is to solve such a conventional problem.
[0012]
[Means for Solving the Problems]
  In a crystal manufacturing method of growing a nitride semiconductor crystal on a substrate including a first patterned mask made of a substance having a growth-inhibiting effect, an island-shaped nitride semiconductor that is not a continuous film from the opening of the first patterned mask A step of growing a crystal, a step of forming a second patterned mask made of a substance having a growth-inhibiting effect on the upper surface of the island-shaped nitride semiconductor crystal, and further crystal growth from the side surface of the island-shaped nitride semiconductor crystal And a step of covering the second patterned mask.
[0013]
  Note that the second patterned mask is preferably formed using the same material as the first patterned mask. The substrate is preferably a GaN substrate.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
  [Reference implementationForm 1]
  With reference to FIG.Reference implementation closely related to the inventionForm1The crystal growth method is explained.
[0015]
  First, trimethylgallium (TMG) and ammonia (NH) are placed on a sapphire substrate 100 having a C-plane as a surface, which is installed in a predetermined growth furnace._Three) Is used as a raw material, and the GaN layer 101 is grown to a thickness of 4 μm.
[0016]
  Next, in order to form a first patterned mask, a 200 nm thick SiO2 film is formed on the GaN layer 101 by sputtering as a growth inhibitor.₂A film was formed. SiO₂The film forming method is not limited to the sputtering method, and other methods such as a vacuum deposition method and a CVD method may be used. Moreover, as a growth inhibitory substance, SiO₂Besides Al₂O_ThreeTiO₂Oxides such as SiN_xBut you can. Next, SiO 2 is formed by a normal photoresist method.₂The film is formed into a periodic stripe pattern having a stripe width of 7 μm and a pitch of 10 μm, and the first SiO₂A mask 102 was formed. The stripe direction is preferably the <1-100> direction of the crystal of the GaN layer 101.
[0017]
  Using such a substrate, the GaN crystal film 103 was grown by the MOVPE method (metal organic chemical vapor deposition method). Trimethylgallium (TMG) and ammonia (NH) in a predetermined growth furnace_Three) Was used as a raw material, and a GaN crystal film 103 having a thickness of 3 μm was grown at a growth temperature of 1050 ° C. The GaN crystal film 103 started to grow from the opening of the first mask, and grew smoothly over almost the entire surface of the substrate due to the anisotropy that the growth rate in the horizontal direction was faster than the direction perpendicular to the substrate.
[0018]
  However, the defect density is 10 directly above the first mask.^FivePiece / cm²The defect density was still 10 directly above the sapphire substrate at the mask opening.⁷Piece / cm²Met. In the conventional example, the laser element is formed avoiding such a place, but it is insufficient in terms of reliability and yield.
[0019]
  Next, a second mask was formed on the GaN crystal film 103. Same method as the first mask formationof200 nm thick SiO 2 by sputtering₂A film is formed, and the second SiO 2 is formed into a periodic stripe pattern having a stripe width of 8 μm and a pitch of 10 μm by a photoresist method.₂A mask 104 was formed. At this time, it is important that the position of the second mask substantially coincides with the opening of the first mask.
[0020]
  Next, using such a substrate, the GaN single crystal film 105 was grown by the MOVPE method (metal organic chemical vapor deposition method). Trimethylgallium (TMG) and ammonia (NH) in a predetermined growth furnace_Three) Was used as a raw material to grow GaN having a thickness of 3 μm at a growth temperature of 1050 ° C. The GaN single crystal film 105 thus grown has a defect density of 1500 / cm over the entire surface.²The crystallinity was greatly improved.
[0021]
  the abovereferenceEmbodiment1In the case where both the first mask and the second mask have a stripe width of 4 μm and a pitch of 10 μm and are arranged at positions shifted from each other by a half pitch (when the second mask width is smaller than the lack of the first mask). The defect density is 5000 pieces / cm²Thus, compared with the case of the conventional first mask alone, a sufficient crystal defect reduction effect was observed. This reduction effect is somewhat smaller than when the second mask width is larger than the lack of the first mask, and both masks completely cover the crystal threading dislocations extending directly from the sapphire substrate 100. The density was increased, and it was confirmed that it was important to form the second mask so as to completely cover the lacking portion of the first mask.
[0022]
  However, if the width of the second mask is smaller than the lack of the first mask, a certain degree of defect reduction (about 5000 / cm2) is achieved.²It has been found by X-ray diffraction measurement that the c-axis orientation of the GaN continuous film is improved together with the effect of). When the second mask width is larger than the lacking portion of the first mask, the ω value (half-value width) of X-ray diffraction indicating variation in orientation was about 4 to 6 minutes. By using theCIt was confirmed that variation in crystal orientation (ω value) was reduced to 2 minutes. Accordingly, when an LED or a semiconductor laser is manufactured in a shape in which the second mask width is smaller than the lacking portion of the first mask, light emission is performed as compared with the case where the second mask width is larger than the lacking portion of the first mask. Although efficiency is somewhat inferior,CIt was found that the luminous efficiency and uniformity of the laser threshold current can be improved, and the production yield of the device can be improved. Therefore, it is important to select the relationship between the lack of the first mask and the width of the second mask in accordance with the required characteristics of the light emitting element. Further, if the first mask and the second mask are formed of the same material, the vapor deposition apparatus can be unified, and the quality of the crystal film can be stabilized by the same growth suppression effect (emission efficiency is given priority). In this case, when the width of the second mask is selected to be larger than the lack of the first mask and priority is given to the uniformity of characteristics and the yield, the width of the second mask is greater than the lack of the first mask. Should be chosen smaller).
[0023]
  [ActualProcessingstate1]
  Figure 2Embodiment 1 of the present inventionIndicates.Embodiment 1The aboveReference implementationCompared to Embodiment 1, the GaN crystal film 203 grown using the first mask is not a continuous film, but the second mask is different in that it is formed on the upper surface of the GaN crystal film 203 grown in an island shape. is there.
[0024]
  First, the GaN layer 201 is formed on the sapphire substrate 200.thickness4μmIn,Reference implementationGrowing as in Form 1.BookFruitProcessingstate1In the case of the first SiO₂The first GaN crystal film 203 grown using the mask 202 had a thickness of 1 μm, a width of 7 μm, and a pitch of 10 μm. Next, the second SiO₂When the second GaN single crystal film 205 (thickness) was grown using the mask 204 (thickness 200 μm), the defect density was 800 / cm2.²The following were obtained and good crystals were obtained. This is an effect that the GaN single crystal film 205 grows only from the side face 206 with few defects of the first GaN crystal.
[0025]
  [Reference implementationForm2]
  Referring to FIG.Reference implementation closely related to the present inventionForm2Is explained.Reference implementationIn Form 1, it was necessary to perform GaN crystal growth on the patterned mask in two steps.Reference embodiment 2In this case, only one time is required, which is advantageous in terms of cost.Also in this reference embodiment 2,First, on the sapphire substrate 300 on which the GaN layer 301 is formed.Reference implementationSiO as in the case of Form 1 by sputtering.₂A film is formed to 200 nm. This is etched in a stripe pattern with a width of 4 μm and a pitch of 8 μm by a normal photoresist method, and the first SiO 2 is etched.₂A mask 302 is formed. Then, similarly to such a substrate, SiO₂A film is formed, and a stripe-shaped second lower SiO 2 having a width of 2 μm and a pitch of 8 μm is formed on the first mask.₂A mask 303 is formed. Then normalFoLower SiO by trisograph method₂Except mask 303FoCover with a resist film. This method, for example, AZ of ShipleyFoSpin coat the photoresist and lower SiO₂Only the mask 303 portion may be exposed and developed to remove the resist film. Furthermore, SiO₂A second upper SiO 2 formed in a stripe shape having a width of 5 μm and a pitch of 8 μm.₂A mask 304 is formed. Then the above mentionedFoThe resist film is removed with a solvent such as acetone. This second lower SiO₂Mask 303 and second upper SiO₂The mask 304 forms a second mask and forms an L shape. Using such a substrate, GaN was grown by the MOVPE method. Trimethylgallium (TMG) and ammonia (NH) in a predetermined growth furnace_Three) Was used as a raw material, and a GaN single crystal film 305 having a thickness of 3 μm was grown at a growth temperature of 1050 ° C. Growth is the first SiO₂Starting from the opening of the mask 302, the second top SiO₂Growth in the direction perpendicular to the substrate stops at 304 of the mask, and then grows in a direction parallel to the substrate, and the second upper SiO 2₂Growth also started in the direction perpendicular to the substrate from the opening of the mask 304, and finally it grew uniformly over the entire surface of the substrate. Dislocations in the direction perpendicular to the substrate generated from the interface between the GaN layer 301 and the sapphire substrate 300 are the second upper SiO immediately above.₂The dislocation in the direction parallel to the substrate is stopped by the mask 304 and the second lower SiO 2₂Stop by mask 303. Therefore, the obtained GaN single crystal film 305 has a defect density of 600 / cm.²It was the following and extremely good quality.
[0026]
  [Reference implementationForm3]
  Referring to FIG.Reference implementation closely related to the present inventionForm3Is explained. First, on the sapphire substrate 400 on which the GaN layer 401 is formed.Reference implementationSiO as in the case of Form 1 by sputtering.₂A film is formed to a thickness of 200 nm. This is etched in a stripe shape with a width of 4 μm and a pitch of 8 μm by a normal photoresist method, and the first SiO₂A mask 402 is manufactured. Next, using the same method as described above, the second lower SiO 2 having a width of 2 μm and a pitch of 8 μm is formed on the GaN layer 401.₂A mask 403 is formed in a stripe shape. Then normalFoLower SiO by trisograph method₂Except mask 403FoCover with a resist film. This method, for example, AZ of ShipleyFoSpin coat the photoresist and lower SiO₂Only the mask 403 portion is exposed and developed to remove the resist film. Furthermore, SiO₂Striped second upper SiO 2 with a width of 5 μm and a pitch of 8 μm₂A mask 404 is formed on the second lower SiO.₂It is formed on the mask 403. After this,FoThe resist film is removed with a solvent such as acetone. This mask second lower SiO₂Mask 403 and second upper SiO₂The mask 404 forms a T-shape as a second mask. Using such a substrate, GaN was grown by the MOVPE method. Trimethylgallium (TMG) and ammonia (NH) in a predetermined growth furnace_Three) Was used as a raw material, and a GaN single crystal film 405 having a thickness of 3 μm was grown at a growth temperature of 1050 ° C. Growth is the first SiO₂Starting from the opening of the mask 402, the second top SiO₂The mask 404 stops the growth in the direction perpendicular to the substrate, and then grows in the direction parallel to the substrate, so that the second upper SiO 2₂The growth started from the opening of the mask 404 in the direction perpendicular to the substrate, and finally, the growth grew uniformly over the entire surface of the substrate. The dislocation in the direction perpendicular to the substrate generated from the interface between the GaN layer 401 and the sapphire substrate 400 is the second upper SiO 2 immediately above.₂Stopping at the mask 404, the dislocation in the direction parallel to the substrate is the second lower SiO.₂Stop by mask 403. Therefore, the obtained GaN single crystal film 405 has a defect density of 800 / cm.₂It was very good quality.
[0027]
  [Reference implementationForm4]
  Refer to FIG.Reference implementation closely related to the present inventionForm4Is explained. First, in order to form a first patterned mask, a 200 nm-thick SiO2 film is formed by sputtering as a growth inhibitor on the sapphire substrate 500 having a C-plane on which the GaN layer 501 is formed.₂A film was formed. SiO₂The film growth method is not limited to the sputtering method, and other methods such as a vacuum deposition method and a CVD method may be used. Moreover, as a growth inhibitory substance, SiO₂Besides Al₂O_ThreeTiO₂Oxides such as SiN_xBut you can. Next, SiO 2 is formed by a normal photoresist method.₂The film is provided with openings in stripes with a width of 3 μm and a pitch of 10 μm, and the first SiO₂A mask 502 was formed. The stripe direction was preferably <1-100> with respect to the GaN layer 501.
[0028]
  Using such a substrate, GaN was grown by the MOVPE method. Trimethylgallium (TMG) and ammonia (NH) in a predetermined growth furnace_Three) Was used as a raw material to grow GaN having a thickness of 0.5 μm at a growth temperature of 1050 ° C. GaN 503 grows only on the edge of the first mask, and the first SiO₂The mask 502 was not filled. Since this edge portion is a unique point having a low potential for crystal growth, GaN 503 has a very high quality without defects.
[0029]
  Next, a second mask was formed on such a substrate. 200 nm thick SiO 2 by the same sputtering method as the first mask formation₂Then, the second SiO is formed into a stripe shape having a width of 5 μm and a pitch of 10 μm by a photoresist method.₂A mask 504 was formed.
[0030]
  Next, using such a substrate, a GaN single crystal film 505 was grown by the MOVPE method. Trimethylgallium (TMG) and ammonia (NH) in a predetermined growth furnace_Three) Was used as a raw material to grow GaN having a thickness of 3 μm at a growth temperature of 1050 ° C. The GaN single crystal film 505 thus grown has a defect density of 1000 / cm over the entire surface.₂The crystallinity was greatly improved.
[0031]
  Here, it is important that the light shielding portion of the second mask closes the opening of the first mask.
[0032]
  [Reference implementationForm5]
  Refer to FIG.Reference implementation closely related to the present inventionForm5Is explained. FIG.InThe GaN single crystal film 605 from the sapphire substrate 600 isIn FIG.The sapphire substrate 100 corresponds to the GaN single crystal film 105.
[0033]
  This figure6606 is an n-GaN contact layer, and 607 is n-Al._0.1Ga_0.9N clad layer, 608 is an n-GaN guide layer, 609 is a five-layer In layer_0.2Ga_0.8N quantum well layer and 6 layers of In_0.05Ga_0.95Multiple quantum well structure active layer composed of N barrier layer, 610 is Al_0.2Ga_0.8N evaporation prevention layer, 611 is a p-GaN guide layer, 612 is p-Al_0.1Ga_0.9N-cladding layer, 613 is a p-GaN contact layer, 614 is a p-type electrode, 615 is an n-type electrode, and 616 is SiO₂It is an insulating film.
[0034]
  BookReference embodiment 5In this case, the surface of the sapphire substrate 600 may have other plane orientations such as a-plane, r-plane, and m-plane. Further, not only a sapphire substrate but also a GaN substrate, SiC substrate, spinel substrate, MgO substrate, Si substrate, and GaAs substrate can be used. In particular, in the case of a GaN substrate, since a difference in lattice constant with a gallium nitride-based semiconductor material deposited on the substrate is smaller than that of a sapphire substrate, a good crystalline film can be obtained, and furthermore, it is easy to cleave. There is an advantage that the vessel can be easily formed. The n-type cladding layer and the p-type cladding layer are made of Al._0.1Ga_0.9An AlGaN ternary mixed crystal having an Al composition other than N may be used. In this case, when the Al composition is increased, the energy gap difference and the refractive index difference between the active layer and the clad layer are increased, and carriers and light are confined in the active layer, thereby further reducing the oscillation threshold current and improving the temperature characteristics. Further, if the Al composition is reduced to such an extent that the confinement of carriers and light is maintained, the mobility of carriers in the cladding layer increases, so that there is an advantage that the element resistance of the semiconductor laser element can be reduced. Further, these clad layers may be quaternary mixed crystal semiconductors containing other elements in trace amounts, and n-Al_0.1Ga_0.9N clad layer 607 and p-Al_0.1Ga_0.9The N-clad layer 612 may not have the same mixed crystal composition.
[0035]
  The energy gap of the n-GaN guide layer 608 and the p-GaN guide layer 611 is such that the energy gap of the quantum well layer constituting the multiple quantum well structure active layer 609 is n-Al._0.1Ga_0.9N clad layer 607, p-Al_0.1Ga_0.9As long as the material has a value between the energy gaps of the N-clad layer 612, other materials such as InGaN, AlGaN ternary mixed crystal, and the like may be used regardless of GaN. Further, it is not necessary to dope the donor or acceptor over the entire guide layer, only a part on the multiple quantum well structure active layer 609 side may be undoped, and further the entire guide layer may be undoped. In this case, there is an advantage that the number of carriers present in the guide layer is reduced, light absorption by free carriers is reduced, and the oscillation threshold current can be further reduced.
[0036]
  In constituting the multiple quantum well structure active layer 609_0.2Ga_0.8N quantum well layer and In_0.05Ga_0.95The composition of the N barrier layer may be set according to the required laser oscillation wavelength. If it is desired to increase the oscillation wavelength, the In composition of the quantum well layer should be increased, and if it is desired to be shortened, the In composition of the quantum well layer should be decreased. To do. Further, the quantum well layer and the barrier layer may be a quaternary or higher mixed crystal semiconductor containing a trace amount of other elements in the InGaN ternary mixed crystal. Furthermore, the barrier layer may simply be GaN.
[0037]
  Also bookReference implementationForm5Then, Al is in contact with the multiple quantum well structure active layer 609._0.2Ga_0.8The N evaporation preventing layer 610 is formed in order to prevent the multiple quantum well structure active layer 609 from evaporating while the growth temperature is raised. Therefore, if the multi-quantum well structure active layer is protected, Al_0.2Ga_0.8It can be used as the N evaporation preventing layer 610, and AlGaN ternary mixed crystals or GaN having other Al compositions may be used. This Al_0.2Ga_0.8The N evaporation prevention layer 610 may be doped with Mg. In this case, the p-GaN guide layer 611 or the p-Al_0.1Ga_0.9There is an advantage that holes are easily injected from the N clad layer 612. Further, when the In composition of the quantum well layer constituting the multi-quantum structure active layer is small, Al_0.2Ga_0.8Since the quantum well layer does not evaporate without forming the N evaporation prevention layer 610, in particular, Al_0.2Ga_0.8Even without forming the N evaporation prevention layer 610, the presentReference implementationForm5Of gallium nitride based semiconductor laser devicesIsNot damaged.
[0038]
  Next, the gallium nitride based semiconductor laser manufacturing method will be described with reference to FIG. In the following description, the case where the MOVPE method is used is shown, but any growth method capable of epitaxially growing GaN may be used, and other vapor phase growth methods such as MBE and HVPE can also be used.
[0039]
  First, the prescribed growth furnaceWithin the reference implementationForm 1alikeProductionWasOn the board,Trimethylgallium (TMG) and ammonia (NH_Three) And silane gas (SiH)_Four) Is used as a raw material, and an n-GaN contact layer 606 doped with Si having a thickness of 3 μm is grown at a growth temperature of 1050 ° C. Further, trimethylaluminum (TMA) was continuously added to the raw material, and the 0.4 μm Si-doped n-Al was maintained at a growth temperature of 1050 ° C._0.1Ga_0.9An N clad layer 607 is grown. Subsequently, TMA is removed from the raw material, and an n-GaN guide layer 608 doped with Si having a thickness of 0.1 μm is grown with the growth temperature kept at 1050 ° C.
[0040]
  Next, the growth temperature is lowered to 750 ° C., and TMG and NH_Three, And trimethylindium (TMI) as a raw material, In_0.05Ga_0.95N barrier layer (thickness 5 nm) / In_0.2Ga_0.8After five periods of growth of the N quantum well layer (thickness 2 nm), In_0.05Ga_0.95A multi-quantum well structure active layer 609 (total thickness 40 nm) is formed by growing an N barrier layer (thickness 5 nm). Continue to TMG, TMA and NH_ThreeAs a raw material, the growth temperature remains at 750 ° C. and the thickness is 20 nm._0.2Ga_0.8An N evaporation prevention layer 610 is grown.
[0041]
  Next, the growth temperature is again increased to 1050 ° C., and TMG and NH_Three, And bisethylcyclopentadienylmagnesium (FtCp₂A Mg-doped p-GaN guide layer 611 having a thickness of 0.1 μm is grown using Mg) as a raw material. Subsequently, TMA was added to the raw material, and the growth temperature remained at 1050 ° C., and the Mg-doped p-Al having a thickness of 0.4 μm_0.1Ga_0.9An N cladding layer 612 is grown. Subsequently, TMA is removed from the raw material, and a p-GaN contact layer 613 doped with Mg having a thickness of 1050 ° C. is grown to maintain a growth temperature of 1050 ° C.HaComplete. After this,HaAnnealing is performed in a nitrogen gas atmosphere at 800 ° C. to reduce the resistance of the Mg-doped p-type layer.
[0042]
  In addition, a normal photolithographAndUsing a dry etching technique, etching is performed from the outermost surface of the p-GaN contact layer 613 in a stripe shape having a width of 200 μm until the n-GaN contact layer 606 is exposed to produce a mesa structure. Next, the same photolithograph as aboveAndUsing dry etching technique, the remaining p-GaN contact layer 613, p-Al_0.1Ga_0.9The N clad layer 612 is etched. At this time, the striped ridge structure should be separated from both ends of 200 μm by 3 μm or more.Reference implementationForm5Then, a striped ridge structure was formed at a distance of 10 μm from the end of the mesa structure on the side where the n-type electrode 615 is formed. If the striped ridge structure is arranged so as to be close to the n-type electrode 615 in this way, the electrical resistance of the element is reduced and the operating voltage is reduced. In addition, since the etching is stopped so as not to reach the multi-quantum well structure active layer 609 during the dry etch sigma, the etching damage to the active layer is suppressed, and the reliability is lowered and the oscillation threshold current is reduced. Is prevented from increasing.
[0043]
  Subsequently, 200 nm thick SiO2 is formed on the side surface of the ridge and the surface of the p-type layer other than the ridge.₂An insulating film 616 is formed as a current blocking layer. This SiO₂A p-type electrode 614 made of nickel and gold is formed on the surfaces of the insulating film 616 and the p-GaN contact layer 613, and an n-type electrode 615 made of titanium and aluminum is formed on the surface of the n-GaN contact layer 606 exposed by etching. Gallium nitride LD waferHaComplete.
[0044]
  After this,HaCleavage is performed in a direction perpendicular to the ridge stripe to form a laser resonance surface, which is further divided into individual chips. Then, each chip is mounted on the stem andYaboEach electrode and the lead terminal are connected by bonding to complete a gallium nitride based semiconductor laser device.
[0045]
  The semiconductor laser device fabricated as described above has good laser characteristics with an oscillation wavelength of 410 nm and an oscillation threshold of 20 mA. In addition, due to the reduction of crystal defects,Life span10^FiveThe laser device was extremely reliable in terms of time (60 ° C.). In addition, the ratio of laser elements having crystal defects was extremely reduced, and an element yield of 80% or more was obtained.
[0046]
  BookReference implementationForm5Then, the thicknesses of the quantum well layer and the barrier constituting the multi-quantum well structure active layer 609 are 2 nm and 5 nm, respectively. However, if the thicknesses of the quantum well layer and the barrier layer are 10 nm or less,Reference implementationForm5Regardless of this, the same effect can be obtained with other layer thicknesses. The number of quantum well layers in the multiple quantum well structure active layer 609 may be four or three, or a single quantum well structure active layer.
[0047]
  More booksReference implementationForm5In this case, since sapphire, which is an insulator, is used as a substrate, an n-type electrode 615 is formed on the surface of the n-GaN contact layer 606 exposed by etching, but GaN, SiC, Si, GaAs having n-type conductivity is formed. For example, the n-type electrode 615 may be formed on the back surface of the substrate. In this case, the stripe-shaped ridge structure having a width of 200 μm may be separated from both ends of the semiconductor laser element chip by 3 μm or more. Also, the p-type and n-type configurations may be reversed.
[0048]
【The invention's effect】
  As described above, the gallium nitride crystal according to the present invention has a crystal defect density of 10 by forming a material having a growth inhibiting effect on a different surface with a reverse mask pattern so as to prevent the growth of threading dislocations.^Fourcm²Very few crystals were obtained: A gallium nitride semiconductor laser manufactured using such a crystal has high reliability and has a very high yield and can be produced at low cost.
[Brief description of the drawings]
FIG. 1 shows the present invention.Embodiment 1 closely related toIt is sectional drawing of the gallium nitride semiconductor base | substrate which shows.
FIG. 2 of the present inventionEmbodiment 1It is sectional drawing of the gallium nitride semiconductor base | substrate which shows.
FIG. 3Embodiment 2 closely related toIt is sectional drawing of the gallium nitride semiconductor base | substrate which shows.
FIG. 4 The present inventionEmbodiment 3 closely related toIt is sectional drawing of the gallium nitride semiconductor base | substrate which shows.
FIG. 5 shows the present invention.Embodiment 4 closely related toIt is sectional drawing of the gallium nitride semiconductor base | substrate which shows.
FIG. 6Embodiment 5 closely related toIt is sectional drawing of the gallium nitride semiconductor base | substrate which shows.
[Fig. 7]First1 is a cross-sectional view showing a conventional GaN crystal film of FIG.
[Fig. 8]First2 is a cross-sectional view showing a conventional GaN crystal film of FIG.
[Explanation of symbols]
100, 200, 300, 400, 500, 600 Sapphire substrate
101, 201, 301, 401, 501, 601 GaN layer
102, 202, 302, 402, 502, 602 First SiO₂mask
103, 203, 603 GaN crystal film
104, 204, 504 Second SiO₂mask
105, 205, 305, 405, 505, 605 GaN single crystal film
206 Side surface of GaN crystal film 203 crystal
303, 403, second lower SiO₂mask
304, 404 Second upper SiO₂mask
503 GaN
604 Second SiO₂mask
606 n-GaN contact layer
607 n-Al_0.1Ga_0.9N clad layer
608 n-GaN guide layer
609 Active layer with multiple quantum well structure
610 Al_0.2Ga_0.8N evaporation prevention layer
611 p-GaN guide layer
612 p-Al_0.1Ga_0.9N clad layer
613 p-GaN contact layer
614 p-type electrode
615 n-type electrode
616 SiO₂Insulation film
700,800 sapphire substrate
701,802 SiO₂pattern
702, 803 opening
703 GaN single crystal film
704 SiO₂GaN single crystal on
801 GaN single crystal grown by MOCVD
804 GaN crystal grown by hydride-VPE method

Claims (3)

In a crystal manufacturing method for growing a nitride semiconductor crystal on a substrate including a first patterned mask made of a substance having a growth inhibiting effect,
Growing an island-shaped nitride semiconductor crystal that is not a continuous film from the opening of the first patterned mask;
Forming a second patterned mask made of a material having a growth-inhibiting effect on the upper surface of the island-shaped nitride semiconductor crystal;
A crystal manufacturing method comprising a step of further growing a crystal from a side surface of the island-shaped nitride semiconductor crystal and covering the second patterned mask. Crystal manufacturing method according to claim 1, wherein the second patterned mask of the same material as the first patterned mask is formed. Crystal manufacturing method according to claim 1 or 2, wherein the substrate is a GaN substrate.

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