JP2005094029A - GaN SYSTEM SEMICONDUCTOR AND MANUFACTURING METHOD - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GaN system semiconductor having a low dislocation area with few crystal defects by epitaxial growth. <P>SOLUTION: The GaN system semiconductor is grown while forming a facet structure, and adjacent facet structures are combined. By the growth of the facet structure, dislocation from the ground is bent, and the low dislocation area is formed. Furthermore, the bent dislocation is collected to the overlap area of each facet side, by growing the facet structure and combining adjacent facet structures. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an epitaxial growth method of a semiconductor crystal, a method of epitaxially growing a group III-V compound semiconductor crystal film on a substrate having different lattice constants and thermal expansion coefficients, and a method of growing the III-V group compound semiconductor film. About. In particular, it is effective for the application of a GaN-based semiconductor epitaxial growth method in which it is difficult to form a semiconductor film with few crystal defects.

  Furthermore, the present invention relates to a GaN-based semiconductor element and a method for manufacturing the same, and more particularly to a GaN-based semiconductor element formed on a GaN semiconductor film with few crystal defects and a method for manufacturing the same.

  Among group III-V compound semiconductors, gallium nitride (GaN), for example, has attracted attention as a blue light emitting element material because it has a large forbidden band of 3.4 eV and is a direct transition type.

As a substrate material for manufacturing a light emitting device using this material, it is desirable to use a bulk crystal of the same substance as the epitaxial layer to be grown. However, in the case of a crystal such as GaN, it is very difficult to produce a bulk crystal due to the high dissociation pressure of nitrogen. Therefore, when manufacturing devices using materials that are very difficult to manufacture bulk crystals, for example, physical properties such as lattice constant, thermal expansion coefficient, and chemical properties such as sapphire (Al ₂ O ₃ ) substrates. A completely different substrate has been used.

  Non-Patent Document 1 reports that when epitaxial growth is performed on such a hetero-substrate, distortion and defects occur in the substrate and the epitaxial layer, and cracks occur particularly when a thick film is grown. Yes. In such a case, not only the performance as a device is extremely deteriorated, but also the growth layer is often destroyed.

In addition, in order to obtain a high-quality epitaxial growth layer with a low dislocation density in the lattice-mismatched epitaxial growth, selective growth of a GaN film is performed on a sapphire substrate in which stripes are formed with a 1 μm SiO ₂ film in the first crystal growth, Patent Document 1 discloses that lattice defects and dislocations are concentrated in a specific region. However, in the example of Patent Document 1, since growth does not occur in the SiO ₂ film portion, a flat growth layer cannot be obtained on the entire surface, and restrictions have been imposed on element formation locations.
JP-A-8-64791 "Japanese Journal of Applied Physics Vol. 32 (1993) pp. 1528-1533" (Jpn.J. Appl. Phys. Vol 32 (1993) pp.1528-1533)

  The object of the present invention is that even if epitaxial growth is performed using a hetero-substrate having a different lattice constant or thermal expansion coefficient, distortion and defects are not generated in the substrate or epitaxial growth layer, and cracks are generated even when a thick film is grown. The object is to provide a growth method for obtaining a difficult epitaxial growth layer.

  Still another object of the present invention is to provide a GaN-based semiconductor film having few crystal defects by utilizing the above-mentioned epitaxial growth for the growth of a GaN-based semiconductor.

  Another object of the present invention is to produce a GaN-based semiconductor device structure (for example, a GaN-based semiconductor light-emitting device structure) on the GaN-based semiconductor film formed by the above epitaxial growth, thereby obtaining excellent device characteristics. The object is to provide a semiconductor device (for example, a GaN-based semiconductor light-emitting device).

  The growth method of a GaN-based semiconductor according to the present invention is characterized by growing while forming a facet structure of a GaN-based semiconductor and combining the adjacent facet structures.

  The method for growing a GaN-based semiconductor according to the present invention includes growing a GaN-based semiconductor while forming a facet structure, bending the dislocations in the GaN-based semiconductor, and collecting the dislocations at a boundary between adjacent facet surfaces. Features.

  The GaN-based semiconductor of the present invention is characterized in that it has a region in which the adjacent facet structures are combined and grown while forming a facet structure of the GaN-based semiconductor.

  The GaN-based semiconductor of the present invention has a region in which the dislocations are gathered at the boundary between the adjacent facet surface by bending the dislocations in the GaN-based semiconductor, while growing the facet structure of the GaN-based semiconductor. It is characterized by.

The method for growing a GaN-based semiconductor according to the present invention includes, in an initial growth stage, limiting a growth region on a substrate with a mask and facilitating facet growth, thereby causing a difference in thermal expansion coefficient between the growing GaN-based semiconductor layer and the substrate crystal; Cracks caused by the difference in lattice constant can be suppressed, and introduction of defects can be suppressed to form a high-quality GaN-based semiconductor.

  Therefore, if the crystal according to the present invention is used, a high-quality semiconductor element, for example, a laser structure or a transistor structure can be produced thereon, and it is expected that the characteristics will be drastically improved.

  Embodiments of the present invention will be described below with reference to the drawings.

  (First Embodiment) A first embodiment of the present invention will be described with reference to FIG. 1 by taking epitaxial growth of a III-V compound semiconductor as an example.

  First, a group III-V compound semiconductor 12 having a property different from that of the substrate material and being the same as the material grown in the next process or having a property similar to that material in lattice constant and thermal expansion coefficient is formed on the substrate. A mask 14 for limiting the growth region on the substrate is formed on the surface by photolithography and wet etching. The shape of the mask was a stripe. At this time, the thickness of the mask 14 was about 10 nm to 2 μm, and the stripe width of the growth region 13 and the mask 14 was usually about 0.1 μm to 10 μm. (FIG. 1 (a)).

  Next, the III-V group compound semiconductor film is epitaxially grown on the growth region. The substrate with the mask 14 is inserted into the reaction tube of the epitaxial apparatus, and the substrate 11 is heated to a predetermined growth temperature while supplying hydrogen gas, nitrogen gas, or a mixed gas of hydrogen and nitrogen and a group V source gas. To do. After the temperature is stabilized, a group III material is supplied to grow a group III-V compound semiconductor 15 in the growth region 13. The crystal growth method is preferably vapor phase epitaxy (VPE: Vapor Phase Epitaxy) using chloride as a group III material, but organometallic compound vapor phase growth (MOCVD) using an organic metal as a group III material. : Metal Organic Vapor Phase Epitaxy) may be used.

  The III-V compound semiconductor 15 does not grow on the mask 14 in the initial stage, but crystal growth occurs only in the growth region 13, and a facet structure is formed in the III-V compound semiconductor 15 on the growth region. The growth conditions of the III-V compound semiconductor 15 at this time are the growth temperature of 650 ° C. to 1100 ° C. so that the facet structure is formed, and the Group V raw material supplying the same amount to 200,000 times the supply amount of the Group III raw material. Perform within the supply range. (FIG. 1 (b)).

  If the epitaxial growth is further continued, the group III-V compound semiconductor 15 grows in a direction perpendicular to the facet structure plane, and thus covers not only the growth region but also the mask 14. And it contacts with the facet structure of the III-V group compound semiconductor 15 of an adjacent growth region (Drawing 1 (c)).

  When the epitaxial growth is further continued, the facet structure is embedded (FIG. 1D), and finally a III-V group compound semiconductor film 15 having a flat surface can be obtained (FIG. 1E).

  Normally, when crystal growth of a III-V group compound semiconductor having a different lattice constant or thermal expansion coefficient is performed on a substrate, dislocations due to crystal defects generated at the interface with the substrate extend in a direction perpendicular to the interface. Even if the epitaxial film is thickened, no reduction in dislocation is observed.

  In the method according to the present embodiment, the facet structure is formed in the growth region by selective growth. This facet appears because the growth rate is slower than the other aspects. Due to the appearance of the facet, the dislocation advances toward the facet, and the dislocation extending perpendicular to the substrate cannot extend in the vertical direction. It was found that crystal defects were bent laterally with facet growth, and as the thickness of the epitaxial film increased, crystal defects decreased in the growth region and appeared at the edge of the crystal or formed a closed loop. . Thereby, reduction of defects in the epitaxial film is measured. By forming and growing the facet structure in this way, crystal defects can be greatly reduced.

  In particular, in the vapor phase growth by the chloride transport method using chloride as a group III material, the growth of the group III-V compound semiconductor 15 is fast, so that the same surface as the substrate surface of the facet structure disappears quickly. Accordingly, dislocations extending perpendicularly to the substrate will soon extend in a direction different from the substrate surface in the facet structure, and dislocations extending perpendicularly in the III-V compound semiconductor 15 can be greatly reduced.

  In addition, the organometallic compound vapor phase growth using an organic metal as the group III material has a slower growth rate than the vapor phase growth by the chloride transport method, but the facet structure of the group III-V compound semiconductor 15 as described above. Of these, the same surface as the substrate surface should disappear quickly. For example, if the area of the mask with respect to the growth region is increased, the supply amount of the growth species from the mask increases, so that the growth of the III-V group compound semiconductor 15 in the growth region can be stopped.

  (Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. 5 by taking epitaxial growth of a III-V compound semiconductor as an example.

  Since FIGS. 5A to 5B are manufactured in the same steps as FIGS. 1A to 1E of the first embodiment, the description thereof is omitted. In the second embodiment, after the III-V group compound semiconductor is epitaxially grown and the growth layer is planarized, a second mask is provided (FIG. 5C), and facets are formed as in the first embodiment. A structure is formed and planarization is performed (FIG. 5D).

  In the second embodiment, the defect density of the group III-V compound semiconductor film formed by repeating the manufacturing steps of FIGS. 1A to 1E can be further reduced.

The first embodiment or the second embodiment is effective for crystal growth of a material having a lattice constant or a thermal expansion coefficient different from that of the substrate. Al ₂ O ₃ , Si, SiC, MgAl ₂ O ₄ , The present invention can be applied to the growth of III-V group compound semiconductors such as GaN, GaAlN, InGaN, and InN on a substrate such as LiGaO ₂ and ZnO.

  In FIG. 1 or FIG. 5, an example is shown in which a mask is formed on the surface of a group III-V compound semiconductor film having the same property as that of the material grown in the next step on the substrate or similar to the material and the lattice constant and thermal expansion coefficient. However, the same effect can be obtained by forming a mask directly on the surface of the substrate 11 and performing the processes of FIGS. 1B to 1E or 5B to 5D.

  Further, in the present embodiment, the growth region using a stripe pattern as the mask 14 has been described. However, the present invention is not limited to this, and if the facet structure appears, the growth region has a rectangular shape, The mask may be round or triangular.

  (Third Embodiment) Next, a third embodiment of the present invention will be described. In the third embodiment, the GaN-based semiconductor film is formed by using the epitaxial growth of the III-V group compound semiconductor described in the first embodiment or the second embodiment for the growth of the GaN-based semiconductor. is there.

  In the third embodiment, the epitaxial growth described in the first embodiment or the second embodiment is used for a GaN-based semiconductor, and the description of the common parts is simplified.

  First, a mask for limiting a growth region on a substrate is formed on a substrate material having a thermal expansion coefficient and a lattice constant different from those of a GaN-based semiconductor by using a photolithography method and a wet etching method.

  Next, epitaxial growth of a GaN-based semiconductor is performed on the growth region. The crystal growth method of a GaN-based semiconductor that grows in a growth region is based on gallium chloride (GaCl), which is a reaction product of gallium (Ga) and hydrogen chloride (HCl), as a group III source and ammonia (NH3) gas as a group V source. A hydride VPE method that is vapor phase growth (VPE: VaporPhase Epitaxy) using a chloride transport method and an organic metal compound vapor phase growth (MOCVD: Metal Organic Vapor Phase Epitaxy) that uses an organic metal as a Ga raw material are used. The growth temperature is 650 ° C. to 1100 ° C., and the supply amount of the group V raw material may be from 1 to 200,000 times the supply amount of the group III raw material.

  In the epitaxial growth of the GaN-based semiconductor layer, as in the first embodiment, the GaN-based semiconductor does not grow on the mask in the initial stage and crystal growth occurs only in the growth region. A facet structure having a plane orientation different from the plane orientation of the substrate is formed.

  If the epitaxial growth is continued, the GaN-based semiconductor grows in a direction perpendicular to the facet structure surface, and thus covers not only the growth region but also the mask. And it contacts the facet structure of the GaN-based semiconductor in the adjacent growth region. When the epitaxial growth is further continued, the facet structure is embedded by the GaN-based semiconductor, and finally, a GaN-based semiconductor film having a flat surface can be obtained.

  Since GaN is difficult to produce bulk crystals, sapphire substrates, SiC substrates, etc. have been used as substrates in conventional GaN-based semiconductor crystal growth, but these substrates have lattice constants and thermal expansion coefficients that are different from those of GaN-based semiconductors. Is different. For this reason, when epitaxial growth of a GaN-based semiconductor is performed, dislocations accompanying crystal defects generated at the interface with the substrate extend in a direction perpendicular to the interface, and even if the epitaxial film is thickened, no reduction in dislocation was observed.

  In the epitaxial growth method according to the present embodiment, a facet structure having a plane orientation different from the substrate plane orientation is formed in a growth region selectively formed by a mask material on a substrate material having a thermal expansion coefficient or lattice constant different from that of a GaN-based semiconductor. A GaN-based semiconductor is epitaxially grown. This facet appears because the growth rate is slower than the other planes, and with the appearance of the facet, dislocations generated from the vicinity of the interface between the substrate and the GaN-based semiconductor proceed toward the facet, and the dislocations extended perpendicular to the substrate. Cannot extend in the vertical direction.

  Therefore, the crystal defects of the GaN-based semiconductor are bent in the lateral direction as the facet grows, and as the film thickness increases due to the epitaxial growth of the GaN-based semiconductor, the crystal defects decrease in the growth region and appear at the end of the crystal. Form a closed loop. Thereby, reduction of defects in the epitaxial film is measured.

  As described above, by growing a GaN-based semiconductor film having a facet structure in a growth region selectively formed on a substrate by a mask, crystal defects in the GaN-based semiconductor film can be greatly reduced.

  Furthermore, after the GaN-based semiconductor film obtained in the third embodiment is grown to a desired thickness, the substrate (such as a sapphire substrate), the mask, and a part of the GaN-based semiconductor are removed. It can be used as a substrate for a GaN-based semiconductor film with few defects. By producing a GaN-based semiconductor element on such a GaN-based semiconductor film, the crystallinity of the laminated structure of the GaN-based semiconductor element can be improved.

  When the GaN-based semiconductor light-emitting element is a GaN-based semiconductor light-emitting element, it is possible to form an electrode on the back surface of the substrate in the GaN-based semiconductor light-emitting element that has been a problem with sapphire substrates and the like.

  Further, when the GaN-based semiconductor light-emitting device is a GaN-based semiconductor laser, it is possible to produce a resonator mirror by cleavage even if a laser structure is formed on a hetero substrate having a cleavage plane different from that of the GaN-based semiconductor.

  The formation of the GaN-based semiconductor film in the third embodiment has been described using the epitaxial growth of the first embodiment for the sake of explanation, but it can also be applied to the second embodiment.

  In the description of the third embodiment, an example is shown in which a mask is directly formed on a substrate surface having a lattice constant or a thermal expansion coefficient different from that of a GaN-based semiconductor. However, after the GaN-based semiconductor is grown on the substrate, the GaN-based semiconductor is formed. A similar effect can be obtained even if a mask is formed on the semiconductor surface.

  Furthermore, as the mask used in this embodiment, the same material, size, and shape as those in the first embodiment or the second embodiment can be applied. In addition, as the GaN-based semiconductor film in the present embodiment, GaN, AlGaN, InGaN and the like can be mentioned, but GaN is most preferable.

  Further, as a GaN-based semiconductor element, in addition to a GaN-based semiconductor light-emitting element such as a GaN-based semiconductor laser and a GaN-based LED, it can be applied to devices such as FETs and HBTs.

  (Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIG.

  In the fourth embodiment, a GaN-based semiconductor thick film is grown on a substrate having a thermal expansion coefficient and a lattice constant different from those of the GaN-based semiconductor by using the epitaxial growth of the first embodiment. A GaN-based semiconductor element is produced on a thick film.

  In the fourth embodiment, a case where a GaN-based semiconductor light-emitting element is used as a GaN-based semiconductor element on a GaN-based semiconductor film will be described.

  First, a mask is formed on the substrate surface, and the mask and the growth region are separated by photolithography and wet etching. As the substrate, a substrate in which a GaN-based semiconductor is formed on a substrate material having a thermal expansion coefficient or a lattice constant different from that of the GaN-based semiconductor is used.

  The shape of the mask and the growth region is a shape in which facets appear in the GaN-based semiconductor in the growth region as described in the first embodiment.

Next, epitaxial growth of a GaN-based semiconductor is performed on the growth region. The GaN-based semiconductor growth method is a hydride VPE method using gallium chloride (GaCl), which is a reaction product of gallium (Ga) and hydrogen chloride (HCl), as a group III material and ammonia (NH ₃ ) gas as a group V material. Although preferred, metal organic chemical vapor deposition (MOVPE) may be used.

  In the epitaxial growth of the GaN-based semiconductor, as in the first embodiment, the GaN-based semiconductor does not grow on the mask in the initial stage, and crystal growth occurs only in the growth region. A facet structure having a plane orientation different from the plane orientation is formed.

  If the epitaxial growth is continued, the GaN-based semiconductor grows in a direction perpendicular to the facet structure surface, and thus covers not only the growth region but also the mask. Then, it contacts the facet structure of the GaN-based semiconductor film in the adjacent growth region. When the epitaxial growth is further continued, the facet structure is embedded by the GaN-based semiconductor, and finally, a GaN-based semiconductor film having a flat surface can be obtained.

  Next, an element structure of a GaN-based semiconductor light-emitting element is fabricated on the GaN-based semiconductor film. After forming the GaN-based semiconductor film, the substrate on which the GaN-based semiconductor film has been formed is set in an MOCVD apparatus, and the n-type GaN layer, the n-type AlGaN clat layer, n at a predetermined temperature, gas flow rate, and V / III ratio. -Type GaN light guide layer, multi-quantum well structure active layer comprising undoped InGaN quantum well layer and undoped InGaN barrier layer, p-type AlGaN layer, p-type GaN light guide layer, p-type AlGaN cladding layer, p-type GaN contact layer in order Form a laser structure.

Next, the substrate on which the laser structure is formed is set in a polishing machine, and the substrate, the SiO ₂ mask, and a part of the GaN-based semiconductor film are polished to expose the GaN-based semiconductor film. An n-type electrode is formed on the exposed surface of the GaN-based semiconductor film, that is, the back surface side of the GaN-based semiconductor light-emitting element, and a p-type electrode is formed on the front surface side.

  The following effects are obtained by the fourth embodiment.

  By growing a GaN-based semiconductor device structure on the GaN-based semiconductor film obtained by the epitaxial growth of the first embodiment, the epitaxial growth in the GaN-based semiconductor device structure that has been a problem in the growth using the conventional sapphire substrate The crystallinity of the film can be improved, and the characteristics of the GaN-based semiconductor element can be improved.

  Furthermore, when the GaN-based semiconductor device is a GaN-based semiconductor light-emitting device, an electrode can be formed on the back surface, so that the electrode is formed on the surface of the GaN-based semiconductor film by a complicated manufacturing process such as dry etching as in the prior art. The device can be manufactured without any problems, and the electrode manufacturing process can be simplified.

  When the GaN-based semiconductor light-emitting device is a GaN-based semiconductor laser, the substrate mirror and the mask are removed after the GaN-based semiconductor thick film with few crystal defects is formed. Can be formed. For this reason, compared with the conventional method in which the resonator mirror surface is formed by a complicated process such as dry etching, the yield can be greatly improved.

  Note that the fourth embodiment is not limited to the above description, and other configurations and growth methods can be adopted as necessary.

  For example, not only the first embodiment but also the second embodiment can be applied to the epitaxial growth of a GaN-based semiconductor film.

  Furthermore, the substrate and the mask were removed after the laminated structure of the GaN-based semiconductor element was formed on the GaN-based semiconductor film. A stacked structure of elements may be manufactured.

  The example in which the substrate and the mask are removed from the GaN-based semiconductor film has been described. However, if only the crystallinity effect of the GaN-based semiconductor element formed on the GaN-based semiconductor film is desired, the substrate and the mask are removed. Instead of this, an electrode may be formed on the surface side of the GaN-based semiconductor element.

  Furthermore, as the mask used in this embodiment, the same material, size, and shape as those in the first embodiment or the second embodiment can be applied. In addition, as the GaN-based semiconductor film in the present embodiment, GaN, AlGaN, InGaN and the like can be mentioned, but GaN is most preferable.

  Further, as a GaN-based semiconductor element, in addition to a GaN-based semiconductor light-emitting element such as a GaN-based semiconductor laser and a GaN-based LED, it can be applied to devices such as FETs and HBTs.

  Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) An embodiment of the present invention will be described with reference to FIG. In this example, a substrate in which a GaN film 12 having a thickness of about 1 μm was previously formed on a (0001) plane sapphire (Al ₂ O ₃ ) substrate 11 was used. A SiO ₂ film was formed on the surface of the GaN film 12 and separated into a mask 14 and a growth region 13 by photolithography and wet etching. The growth region 13 and the mask 14 are stripes having a width of 5 μm and 2 μm, respectively. The stripe direction was the <11-20> direction ((FIG. 1A)).

The GaN film 15 grown in the growth region 13 is a hydride that uses gallium chloride (GaCl), which is a reaction product of gallium (Ga) and hydrogen chloride (HCl), as a group III source and ammonia (NH ₃ ) gas as a group V source. VPE method was used. The substrate 11 is set in a hydride growth apparatus and heated to a growth temperature of 1000 ° C. in a hydrogen atmosphere. After the growth temperature is stabilized, the HCl flow rate is supplied at 20 cc / min, and the NH 3 flow rate is supplied at 1000 cc / min for about 5 minutes, so that the growth region 13 is made of the {1-101} plane of the GaN film 15. A facet structure was grown (FIG. 1 (b)). Further, the epitaxial growth was continued for about 20 minutes, and the facet structure 16 was developed until the mask 14 was covered (FIG. 1C).

  By continuing the epitaxial growth, the facet structure was embedded (FIG. 1D), and finally a GaN film having a flat surface of about 200 μm was formed by the growth for 5 hours (FIG. 1E). After the GaN film 15 was formed, it was cooled to room temperature while supplying ammonia gas and taken out from the growth apparatus.

  In the first embodiment, crystal growth is performed by forming facets whose side walls are {1-101} planes by selective growth that limits the growth region. This facet appears because the growth rate is slower than the other aspects. Before the facets appear, dislocations that extend perpendicular to the substrate cannot extend in this direction due to the appearance of the facets.

  Examining the crystal grown according to the present invention in detail, it was found that the facet was bent in the lateral direction with the appearance of the facet, and emerged at the end of the crystal as the thickness of the epitaxial film increased. Thereby, reduction of defects in the epitaxial film is measured.

It was confirmed that the GaN film 15 formed according to the first example was free of cracks despite the difference in lattice constant and thermal expansion coefficient from the sapphire substrate 11. Moreover, the GaN film on which the thick film was grown had very few defects, and the defect density was about 10 ⁶ cm ² .

  The GaN film grown in this example has very few defects, and device characteristics can be improved by growing high-quality device structures such as lasers, FETs, and HBTs thereon.

  Further, the GaN film 15 can be used as a substrate material by removing the sapphire substrate 11 by polishing or the like.

In the first embodiment, a hydride VPE method is used for epitaxial growth of a GaN film, but the same effect can be obtained by using a metal organic compound vapor deposition method (MOCVD). Although the Al ₂ O ₃ substrate 11 is used, the same effect can be obtained by using a Si substrate, a ZnO substrate, a SiC substrate, a LiGaO ₂ substrate, a MgAl ₂ O ₄ substrate, or the like. Furthermore, although the GaN film 12 is formed in advance on the Al ₂ O ₃ substrate 11, a mask may be formed directly on the substrate 11.

Further, although SiO ₂ is used as the mask 14, it is not limited to this, and an insulator film such as SiN _x may be used. In this embodiment, the width of the mask 14 is set to 2 μm, but the same effect can be obtained as long as the mask can be embedded. Further, the stripes are formed in the <11-20> direction, but if facets are formed, the direction may be perpendicular to the direction <1-100>, and even at an angle inclined from these directions, it depends on the crystal growth conditions. A facet structure can be formed in the growth region. The crystal growth conditions for forming the facet structure vary depending on the material.

  Moreover, although the GaN epitaxial growth has been described, the same effect can be obtained by epitaxially growing an InGaN film, an AlGaN film, or an InN film. Further, the same effect can be obtained by adding impurities to the growing III-V group compound.

  (Second Embodiment) The second embodiment of the present invention will be described with reference to FIG. 1 as in the first embodiment.

In the second example, a crystal in which an Al _0.1 Ga _0.9 N film 12 having a thickness of about 1 μm was previously formed on a (0001) plane SiC substrate 11 was used as the substrate. A SiO ₂ film was formed on the surface of the Al _0.1 Ga _0.9 N film 12 and separated into a mask 14 and a growth region 13 by photolithography and wet etching. The growth region 13 and the mask 14 are stripes having a width of 2 μm and 10 μm, respectively. The stripe direction was <1-100> direction ((FIG. 1A)).

The GaN film 15 grown in the growth region 13 is a hydride that uses gallium chloride (GaCl), which is a reaction product of gallium (Ga) and hydrogen chloride (HCl), as a group III source and ammonia (NH ₃ ) gas as a group V source. VPE method was used. The substrate 11 is set in a hydride growth apparatus and heated to a growth temperature of 1000 ° C. in a hydrogen atmosphere. After the growth temperature is stabilized, the HCl flow rate is supplied at 20 cc / min, and the NH ₃ flow rate is 2000 cc / min for about 5 minutes, so that the growth region 13 is exposed from the {1-101} plane of the GaN film 15. A facet structure was grown (FIG. 1 (b)).

  Further, the epitaxial growth was continued for about 20 minutes, and the GaN facet structure 15 was developed until the mask 14 was covered (FIG. 1C).

By continuing the epitaxial growth, the facet structure was embedded (FIG. 1D), and finally a GaN film having a flat surface of about 200 μm was formed by the growth for 5 hours (FIG. 1E). After the GaN film 15 is formed, it is cooled at room temperature while supplying NH ₃ gas, and taken out from the growth apparatus.

It was confirmed that the GaN film 15 formed according to the second example was free of cracks despite the difference in lattice constant and thermal expansion coefficient from the SiC substrate 11. Moreover, the GaN film on which the thick film was grown had very few defects and a defect density of about 10 ⁶ cm ² .

  The GaN film grown in this example has very few defects, and device characteristics can be improved by growing high-quality device structures such as lasers, FETs, and HBTs thereon.

  Further, the GaN film 15 can be used as a substrate material by removing the SiC substrate 11 by polishing or the like.

In the second embodiment, a hydride VPE method is used for epitaxial growth of a GaN film, but the same effect can be obtained by using an organic metal compound vapor phase growth method (MOCVD). In this embodiment, the SiC substrate 11 is used. However, the same effect can be obtained by using an Si substrate, a ZnO substrate, an Al ₂ O ₃ substrate substrate, a LiGaO ₂ substrate, an MgAl ₂ O ₄ substrate, or the like. Furthermore, although the GaN film 12 having a film thickness is formed in advance on the SiC substrate 11, a mask may be formed directly on the substrate 11.

Further, although SiO ₂ is used as the mask 14, it is not limited to this, and an insulator film such as SiN _x may be used. In this embodiment, the width of the mask 14 is 10 μm, but the same effect can be obtained as long as the mask can be embedded. Further, the stripe is formed in the <1-100> direction, but if a facet is formed, the direction <1-120> may be perpendicular to the direction, and even if the angle is inclined from these directions, it depends on the crystal growth conditions. A facet structure can be formed in the growth region. The crystal growth conditions for forming the facet structure vary depending on the material.

  Further, although AlGaN having an Al composition of 0.1 is used as the film on the substrate 11, this composition may be arbitrary, and the same effect can be obtained by using AlN, InGaN, or the like as this film. Furthermore, although the GaN epitaxial growth has been described, the same effect can be obtained by epitaxially growing an InGaN film, an AlGaN film, or an InN film. The same effect can be obtained by adding impurities to the growing group III-V compound.

  (Third Embodiment) A third embodiment of the present invention will be described with reference to FIG.

In the third embodiment, the (111) -plane MgAl ₂ O ₄ substrate 21 was used as the substrate. A SiO ₂ film 23 was formed on the surface of the substrate 21 and separated into a mask 23 and a growth region 22 by photolithography and wet etching. The growth region 22 and the mask 23 are stripes having a width of 4 μm and 3 μm, respectively. The stripe direction was the <11-20> direction ((FIG. 2A)).

  For the growth of the GaN film, a hydride VPE method suitable for suppressing the deposition of polycrystalline GaN on the mask 23 was used. In this method, gallium chloride (GaCl), which is a reaction product of gallium (Ga) and hydrogen chloride (HCl), is used as the group III material, and ammonia (NH3) gas is used as the group V material.

First, the substrate 21 is set in a growth apparatus, heat-treated at a high temperature of about 1000 ° C. while supplying hydrogen gas, then cooled to 500 ° C., an HCl flow rate is supplied at 0.5 cc / min, and an NH ₃ flow rate is 1000 cc. / By supplying about 5 minutes per minute, the GaN buffer layer 24 having a film thickness of about 20 nm is formed in the crystal growth region 23 (FIG. 2B).

In this state, the temperature is raised to 1000 ° C. while supplying NH ₃ gas. After the growth temperature is stabilized, the HCl flow rate is supplied at 20 cc / min, and the NH ₃ flow rate is supplied at 1500 cc / min for about 5 minutes, so that the GaN {1- A facet structure 25 composed of a 101} plane was grown (FIG. 2C).

Further, the epitaxial growth is continued and the facet structure of the GaN film 25 is developed until the mask 23 is covered, and then the growth is continued while embedding the facet structure. Finally, the surface has a flat surface of about 200 μm after 5 hours of growth. A GaN film 25 was formed (FIG. 2D). After the GaN film 25 is formed, it is cooled to room temperature while supplying NH ₃ gas and taken out from the growth apparatus.

It was confirmed that the GaN film 25 formed by the third example was free of cracks despite the difference in lattice constant and thermal expansion coefficient from the MgAl ₂ O ₄ substrate 21. Moreover, the GaN film on which the thick film was grown had very few defects and was about 10 ⁶ cm ² .

The GaN film grown in this example has very few defects, and device characteristics can be improved by growing high-quality device structures such as lasers, FETs, and HBTs thereon. Further, the GaN film 25 can be used as a substrate material by removing the MgAl ₂ O ₄ substrate 21 by polishing or the like.

In the third embodiment, a hydride VPE method is used for epitaxial growth of a GaN film, but the same effect can be obtained by using an organic metal compound vapor phase growth method (MOCVD). In the embodiment, the MgAl ₂ O ₄ substrate 21 is used, but the same effect can be obtained by using a Si substrate, a ZnO substrate, a SiC substrate, a LiGaO ₂ substrate, an Al ₂ O ₃ substrate, or the like. Further, although the mask is formed directly on the MgAl ₂ O ₄ 21, a GaN film may be formed on the substrate 21 in advance.

Further, although SiO ₂ is used as the mask 14, it is not limited to this, and an insulator film such as SiN _x may be used. Further, although the width of the mask 24 is 10 μm, the same effect can be obtained as long as the mask can be embedded. In this embodiment, the stripes are formed in the <11-20> direction. However, if facets are formed, the direction may be perpendicular to the direction <1-100>, and the crystal growth conditions may be inclined at an angle from these directions. Thus, a facet structure can be formed in the growth region. The crystal growth conditions for forming the facet structure vary depending on the material.

  In this embodiment, since the GaN film is grown after providing the low-temperature buffer layer on the substrate, it is possible to reduce crystal defects.

  Furthermore, in the embodiments, the epitaxial growth of GaN has been described. However, the same effect can be obtained even if an InGaN film, an AlGaN film, or an InN film is epitaxially grown. Further, the same effect can be obtained by adding impurities to the growing III-V group compound.

  (Fourth Embodiment) A fourth embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a schematic diagram in which the shape of the growth region for selective epitaxial growth is round, triangular, and rectangular.

In this example, a crystal substrate in which a GaN film 42 having a thickness of about 1 μm was formed in advance on an Al ₂ O ₃ substrate 41 having a (0001) plane was used as the substrate.

  A SiO2 film was formed on the surface of the GaN film 42 and separated into a mask 43 and a growth region 44 by photolithography and wet etching. There are three types of growth regions 44: a round shape having a diameter of 4 μm (FIG. 3A), a triangular shape having a side of 3 μm (FIG. 3B), and a rectangular shape having a 5 μm square (FIG. 3C). Each mask was used.

The GaN film 45 grown in the formed growth region 44 uses a metal organic compound vapor phase growth method using trimethylgallium (TMGa) and trimethylaluminum (TMAl) as group III materials and ammonia (NH ₃ ) gas as group V materials. It was.

FIG. 4 is a schematic view of a process of forming a group III-V compound semiconductor film by vapor deposition on the substrate on which the growth region of FIG. 3 is formed. The substrate 41 is set in an organometallic compound vapor phase growth apparatus, and the temperature is raised to a growth temperature of 1050 ° C. while supplying hydrogen gas and NH ₃ gas. After the growth temperature is stabilized, the trimethylgallium flow rate is supplied at 5 cc / min, and the NH ₃ flow rate is supplied at 5000 cc / min for about 10 minutes, so that the {1-101} surface of the GaN film 45 is grown on the growth region 44. A facet structure consisting of was grown (FIG. 4 (a)).

  Further, the epitaxial growth was continued for about 30 minutes, and the facet structure of the GaN layer 45 was developed until the mask 43 was covered (FIG. 4B).

  By continuing the epitaxial growth, the facet structure of the GaN layer 45 is embedded (FIG. 4C), and finally, a GaN film 45 having a flat surface of about 100 μm is formed by the growth for 12 hours (FIG. 4 ( d)).

  It was confirmed that the GaN film 45 formed in the three types of growth regions had a flat surface regardless of the shape of the growth region, and the sapphire substrate 41 was not cracked. In this embodiment, the growth region has three shapes, round, triangular, and rectangular. However, the shape that can embed the mask region is the same regardless of the polygonal shape and size. effective.

  The GaN film grown in this example has very few defects, and device characteristics can be improved by growing high-quality device structures such as lasers, FETs, and HBTs thereon.

  Further, the GaN film 45 can be used as a substrate material by removing the sapphire substrate 41 by polishing or the like.

In the fourth embodiment, a hydride VPE method is used for epitaxial growth of a GaN film, but the same effect can be obtained by using a metal organic compound vapor deposition method (MOCVD). Although the Al ₂ O ₃ substrate 41 is used, the same effect can be obtained by using a Si substrate, a ZnO substrate, a SiC substrate, a LiGaO ₂ substrate, a MgAl ₂ O ₄ substrate, or the like. Further, the GaN film 42 having a film thickness is formed in advance on the Al ₂ O ₃ substrate 41, but a mask may be formed directly on the substrate 41.

Further, although SiO ₂ is used as the mask 43, the present invention is not limited to this, and an insulating film such as SiN _x may be used.

  Moreover, although the GaN epitaxial growth has been described, the same effect can be obtained by epitaxially growing an InGaN film, an AlGaN film, or an InN film. Further, the same effect can be obtained by adding impurities to the growing III-V group compound.

  (Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIG.

  As the substrate 51, a (0001) -plane sapphire substrate 51 on which a GaN film 52 having a thickness of 1 μm was formed was used.

A SiO ₂ film was formed on the surface of the substrate 51 and separated into a first mask 53 and a first growth region 54 by photolithography and wet etching. The first growth region 54 and the first mask 53 were in the form of stripes of 2 μm and 5 μm, respectively. The stripe direction was <11-20> (FIG. 5A).

The first GaN film 55 grown in the first growth region 54 is made of gallium chloride (GaCl), which is a reaction product of gallium (Ga) and hydrogen chloride (HCl), as a group III material, as in the first embodiment. And a hydride VPE method using ammonia (NH ₃ ) gas as a group V raw material. The substrate 51 is set in a hydride growth apparatus and heated to a growth temperature of 1000 ° C. in a hydrogen atmosphere. The substrate 51 is changed to an NH ₃ gas atmosphere from a temperature of 650 ° C. After the growth temperature is stabilized, the HCl flow rate is supplied at 10 cc / min, and the NH ₃ flow rate is 4000 cc / min for 60 minutes. From (a) to (e) in FIG. The first GaN film 55 in which the first mask 53 is embedded is formed through the growth step (FIG. 5B). After forming the first GaN film 55, it is cooled to room temperature in an NH ₃ gas atmosphere and taken out from the growth apparatus.

Next, an SiO ₂ film is formed again on the GaN film 55, and a second growth region 56 and a second mask 57 are formed. The respective stripe widths were 2 μm and 5 μm, and the stripe direction was <11-20> (FIG. 5C). A second mask 57 is embedded on the substrate 51 again through the growth steps (a) to (e) of FIG. 1 described in the first embodiment, and a second GaN layer 58 of about 150 μm is formed. A flattened surface obtained by growth was obtained (FIG. 5 (d)).

As a result of examining the defects of the grown second GaN film 58 with a cross-sectional transmission electron microscope, the number of defects was as small as 10 ⁵ cm ² or less. Although the two-stage selective growth has been described here, the defect density can be further reduced by repeating the above steps.

In the fifth embodiment, a hydride VPE method is used for epitaxial growth of a GaN film, but the same effect can be obtained by using a metal organic chemical vapor deposition method (MOCVD). Although the Al ₂ O ₃ substrate 51 is used, the same effect can be obtained by using a Si substrate, a ZnO substrate, a SiC substrate, a LiGaO ₂ substrate, a MgAl ₂ O ₄ substrate, or the like. Further, the mask is formed after the GaN film 52 is grown on the Al ₂ O ₃ substrate 51. However, the present invention is not limited to this, and the first mask 53 may be grown directly without growing the GaN film 52 on the substrate. .

Further, although SiO ₂ is used as the mask 53, the present invention is not limited to this, and an insulator film such as SiN _x may be used. Furthermore, although the mask patterned so that the growth region becomes a stripe is used, the present invention is not limited to this, and a round shape, a rectangular shape, or a triangular shape may be used. Moreover, although the GaN epitaxial growth has been described, the same effect can be obtained by epitaxially growing an InGaN film, an AlGaN film, or an InN film. Further, the same effect can be obtained by adding impurities to the growing III-V group compound.

  In each embodiment of the present invention, an example using a GaN-based group III-V compound semiconductor has been described. However, the present invention is not limited to this, and a group III-V compound semiconductor having a lattice constant or a thermal expansion coefficient different from that of the substrate is not limited thereto. Needless to say, it is applicable to growth.

  (Sixth Embodiment) A sixth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a schematic view for explaining a process of using the epitaxial growth of the present invention for growing a GaN film and manufacturing a GaN-based semiconductor laser on the GaN film.

A sapphire substrate 61 having a (0001) plane on which a GaN film 62 having a thickness of 1 μm was formed was used as the substrate 61 shown in FIG. An SiO ₂ film was formed on the surface of the substrate 61 and separated into a first mask 63 and a first growth region 64 by photolithography and wet etching as in the first to fourth embodiments. The first growth region 64 and the first mask 63 were in the form of stripes of 5 μm and 2 μm, respectively. The stripe direction was tilted 10 degrees from the <11-20> direction (FIG. 6A).

The first GaN film 65 grown in the first growth region 64 is formed of gallium chloride (GaCl), which is a reaction product of gallium (Ga) and hydrogen chloride (HCl) as a group III material, as in the first embodiment. And a hydride VPE method using ammonia (NH ₃ ) gas as a group V raw material. The substrate 61 is set in a hydride growth apparatus and heated to a growth temperature of 1000 ° C. in a hydrogen atmosphere. The substrate 51 is changed to an NH ₃ gas atmosphere from a temperature of 650 ° C. After the growth temperature is stabilized, the HCl flow rate is supplied at 40 cc / min, the NH ₃ flow rate is 1000 cc / min, and the silane (SiH ₄ ) flow rate is 0.01 cc / min for 150 minutes. 1A to 1E described in the embodiment, a first GaN film 65 having a thickness of 200 μm is formed with the first mask 63 buried therein (FIG. 5B). After forming the first GaN film 65, it is cooled to room temperature in an NH ₃ gas atmosphere and taken out from the growth apparatus. The GaN film 65 was n-type and had a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ or more.

Next, the GaN-based semiconductor laser structure was fabricated using metal organic chemical vapor deposition (MOVPE). After the GaN film 65 is formed, it is set in an MOCVD apparatus and heated to a growth temperature of 1050 ° C. in a hydrogen atmosphere. An NH ₃ gas atmosphere is set from a temperature of 650 ° C. An n-type GaN layer 66 having a thickness of 1 μm to which Si is added, an n-type Al _0.15 Ga _0.85 N clat layer 67 having a thickness of 0.4 μm to which Si is added, and an n-type having a thickness of 0.1 μm to which Si is added. GaN light guide layer 68, 10-period multi-quantum well structure active layer 69 composed of 2.5 nm thick undoped In _0.2 Ga _0.8 N quantum well layer and 5 nm thick undoped In _0.05 Ga _0.95 N barrier layer, magnesium A 20 nm thick p-type Al _0.2 Ga _0.8 N layer 70 to which (Mg) is added, a 0.1 μm thick p-type GaN light guide layer 71 to which Mg is added, and a 0.4 μm thickness to which Mg is added A p-type Al _0.15 Ga _0.85 N cladding layer 72 and a 0.5 μm-thick p-type GaN contact layer 73 to which Mg was added were sequentially formed to produce a laser structure. After the p-type GaN contact layer 73 is formed, the p-type GaN contact layer 73 is cooled to room temperature in an HN ₃ gas atmosphere and taken out from the growth apparatus (FIG. 6C). Multiple quantum well structure active layer 69 of undoped In _0.05 Ga _0.95 N barrier layer thickness of the undoped In0.2Ga0.8N quantum well layers and 5nm thick of 2.5nm was formed at a temperature of 780 ° C..

Next, the sapphire substrate 61 having the laser structure is set in a polishing machine, and the sapphire substrate 61, the GaN layer 62, the SiO ₂ mask 63, and the GaN film 65 are polished by 50 μm to expose the GaN film 65. A titanium (Ti) -aluminum (Al) n-type electrode 74 is formed on the exposed GaN layer 65 surface, and a nickel (Ni) -gold (Au) p-type electrode 75 is formed on the p-type GaN layer 73. Is formed (FIG. 6D).

  In the laser structure shown in FIG. 6, an n-type electrode is formed on the back surface, and an element can be formed without forming an n-type electrode on the nitride surface by a complicated manufacturing process such as dry etching as in the prior art. The manufacturing process can be simplified.

  In addition, since sapphire and GaN-based semiconductors have different crystal cleavage planes, it has been difficult to form a resonator mirror having a laser structure on a conventional sapphire substrate by cleavage.

  In contrast, in this embodiment, since the GaN layer 65 with few crystal defects can be grown thickly, even if the sapphire substrate or the mask material is removed, the laser structure of the GaN-based semiconductor formed on the GaN 65 is not affected. In addition, the laser structure on the GaN layer 65 has the advantage that a resonator mirror surface can be formed by cleavage, so it is greatly simplified compared to the conventional method in which the resonator mirror surface is formed by a complicated process such as dry etching. The yield was greatly improved.

In this embodiment, the sapphire substrate 51, the GaN film 62, and the SiO ₂ mask 63 are polished after the laser structure is formed on the GaN layer 65, but before the laser structure is formed, the sapphire substrate 61, the GaN film 62, and the SiO ₂ mask 63 are polished. _{2 Even if the} mask 63 is polished, the same effect can be obtained.

In this embodiment, the n-type electrode is formed by polishing the sapphire substrate 61, the GaN layer 62, the SiO ₂ mask 63, and a part of the GaN film 65. However, dry etching is not performed. The conventional structure can be produced by removing the n-type GaN layer 66 or 65 to form an n-type electrode and forming a resonator mirror surface.

It is process schematic explaining the formation method of the III-V group compound semiconductor of this invention. AlGaN film with a hydride VPE method MgAl ₂ O ₄ substrate, which is formed is a schematic view of a step of forming a GaN film. It is the schematic which formed the shape of the growth area | region which selectively epitaxially grows in round shape, a triangular shape, and a rectangular shape. FIG. 4 is a schematic view of a step of forming a group III-V compound semiconductor film using a vapor phase growth method on a substrate on which the round, triangular, and rectangular growth regions in FIG. 3 are formed. It is the schematic of the GaN film | membrane formed by repeating the growth method of this invention twice. It is the schematic of the process of forming a GaN-type semiconductor laser structure on the GaN film | membrane formed using the growth method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Substrate 12 III-V compound semiconductor film 13 formed on substrate 13 Growth region 14 for growing group III-V compound semiconductor Mask 15 Epitaxially grown group III-V compound semiconductor film 16 Facet structure 21 of group III-V compound semiconductor (0001) plane sapphire substrate 22 GaN film 23 mask 25 epitaxially grown GaN film 31 (111) plane MgAl ₂ O ₄ substrate 32 1 μm GaN film, or AlGaN film 32 Growth region 33 formed on the substrate On the substrate The formed SiO ₂ film mask 34 Epitaxially grown GaN buffer layer 35 GaN film 43 grown by hydride VPE method Mask 44 Growth region 51 (0001) plane sapphire substrate 53 First mask 54 First growth region 55 First GaN layer 56 second growth region 7 the second mask 58 the second GaN layer 65 n-type GaN layer 66 n-type GaN layer 67 n-type Al _0.15 Ga _0.85 N Klatt layer 68 n-type GaN optical guide layer 69 10 cycle multiple quantum well structure active layer 70 p of P-type Al _0.2 Ga _0.8 N layer 71 p-type GaN optical guide layer 72 p-type Al _0.15 Ga _0.85 N clat layer 73 p-type GaN contact layer 74 Ti-Al n-type electrode 75 Ni-Au p-type electrode

Claims (4)

  A method for growing a GaN-based semiconductor, comprising growing a facet structure of a GaN-based semiconductor and combining the adjacent facet structures.   A method for growing a GaN-based semiconductor, comprising growing a GaN-based semiconductor while forming a facet structure, bending the dislocations in the GaN-based semiconductor, and collecting the dislocations at a boundary between adjacent facet surfaces.   A GaN-based semiconductor having a region in which the facet structures adjacent to each other are grown while forming a facet structure of the GaN-based semiconductor.   A GaN-based semiconductor having a region in which dislocations are gathered at a boundary between an adjacent facet surface by growing dislocations in the GaN-based semiconductor while forming a facet structure of the GaN-based semiconductor.

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