JP2005150287A - Nitride-based iii-v group semiconductor device and its manufacturing method, method of manufacturing nitride-based iii-v group semiconductor substrate, and lot of nitride-based iii-v group semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride-based III-V group semiconductor device which has excellent device characteristics and has a good productivity and its manufacturing method, and further provide a method of manufacturing a nitride-based III-V group semiconductor substrate used for the same, and a lot of the nitride-based III-V group semiconductor substrates. <P>SOLUTION: The nitride-based III-V group semiconductor device is in the form of a chip, and includes an epitaxial layer having a device structure on the nitride-based III-V group semiconductor substrate, with at least one set of parallel side faces of the epitaxial layer as cleavage planes. About the substrate, a low index crystal plane closest to the substrate surface is inclined against the substrate surface, that is, the low index plane has an off-angle, and the off-angle direction in which the low index plane is inclined is parallel to one of equivalent cleavage planes of the substrate. The cleavage planes of the epitaxial layer are on the same plane as the cleavage plane of the substrate parallel to the off-angle direction of the substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a group III-V nitride semiconductor device and a method for manufacturing the same, a method for manufacturing a group III-V nitride semiconductor substrate, and a lot of a group III-V nitride semiconductor substrate.

  Nitride-based semiconductor materials such as gallium nitride (GaN), indium gallium nitride (InGaN), and gallium aluminum nitride (GaAlN) have a sufficiently large forbidden band and a direct transition type between bands. Application to is actively studied. In addition, application to electronic devices is also expected due to the high saturation drift velocity of electrons and the use of two-dimensional carrier gas by heterojunction.

  Silicon (Si), gallium arsenide (GaAs), etc., which are already widely used in the world, are homoepitaxially grown on an epitaxial growth layer for making semiconductor devices on a substrate made of the same kind of material as Si substrate and GaAs substrate, respectively. Have been used. In homoepitaxial growth on the same kind of substrate, crystal growth proceeds in a step flow mode from the initial stage of growth, so that there are few crystal defects and a flat epitaxial growth surface is easily obtained. When growing a mixed crystal layer such as AlGaInP with a close lattice constant on a GaAs substrate, the surface morphology of the epitaxial layer tends to be rough, but it is specified from the low index plane based on the plane orientation of the underlying substrate. By intentionally inclining in the direction (this is generally referred to as turning off), the occurrence of crystal defects is small, and a flat epitaxial growth surface can be obtained.

  On the other hand, nitride-based semiconductors are difficult to grow in bulk crystals, and recently, a GaN free-standing substrate of a level that can withstand practical use has been developed and is in use. Currently, the base substrate for GaN growth, which is widely used in practice, is sapphire, and metal organic vapor phase epitaxy (MOVPE), molecular beam vapor phase epitaxy (MBE), Nitride-based semiconductor for producing semiconductor devices in another growth furnace after GaN is heteroepitaxially grown by a vapor phase growth method such as hydride vapor phase epitaxy (HVPE) and continuously or once taken out of the GaN. A method of growing an epitaxial layer is generally used.

Since the sapphire base substrate has a lattice constant different from that of GaN, a single crystal film cannot be grown by directly growing GaN on the sapphire base substrate. For this reason, the low-temperature buffer layer technology (Patent Document 1) devised for the purpose of hetero-growth Si or the like on the sapphire base substrate is applied to the growth of GaN, and once at a low temperature of about 500 ° C. on the sapphire base substrate. A method has been devised in which a buffer layer of AlN or GaN is grown, and lattice distortion is relaxed by this low-temperature growth buffer layer, and then GaN is grown thereon (Patent Document 2). By using this low-temperature grown nitride layer as a buffer layer, single crystal epitaxial growth of GaN on a sapphire base substrate became possible. However, even with this method, it is difficult to shift the lattice between the base substrate and the crystal. At the beginning of the growth, the crystal growth proceeds in the three-dimensional island growth mode instead of the above-described step flow mode. For this reason, the GaN thus obtained has a dislocation density of 10 ⁹ to 10 ¹⁰ cm ⁻² . This defect becomes an obstacle in manufacturing a GaN-based semiconductor device, particularly an LD (laser diode) or an ultraviolet light emitting LED.

Recently, a GaN layer with a reduced dislocation density is epitaxially grown thickly on a dissimilar substrate such as a sapphire substrate, and the GaN layer is peeled off from the substrate after growth, and the resulting GaN layer is used as a self-supporting GaN substrate. Various methods have been proposed. For example, Patent Document 3, after a thick film of GaN layer grown on a sapphire base substrate, which is discloses a method of removing a sapphire base substrate, also in Patent Document 4, ELO (E pitaxial L ateral O vergrowth: after forming a GaN layer on a sapphire base substrate by using a dislocation reduction technique called non-Patent Document 1), the sapphire base substrate is removed by etching or the like, it has been proposed to obtain a GaN free-standing substrate. VAS method (V oid- A ssisted S eparation: Non-Patent Document 2, Patent Document 5), on the underlying substrate such as sapphire, by growing the GaN through the TiN thin film mesh structure, the base substrate and the GaN layer A void is formed at the interface of the GaN substrate, and the GaN substrate can be peeled off and the dislocation can be reduced at the same time.

  When GaN is crystal-grown on a sapphire base substrate, in order to improve the flatness and reproducibility of the surface morphology of the GaN epitaxial layer, a sapphire base substrate that is turned off is often used. The epitaxial layer grown on the base substrate with the off tends to grow crystal with the off in the direction following the base substrate, and therefore the GaN layer grown on the sapphire base substrate with the off is Even after the sapphire base substrate is removed, the substrate is turned off.

In order to manufacture a semiconductor device using this free-standing substrate, an epitaxial layer having a device structure is grown on the free-standing substrate to form a device epitaxial substrate, and then the device epitaxial substrate is cut into chips. However, at this time, it is often cut using the cleavage property of the crystal. In general, the crystal end face obtained by cleaving has an advantage that it is clean and has no cutting margin loss as compared with an end face cut by a dicer or the like. In particular, in a Fabry Perot type laser diode, it is generally performed by cleaving the resonator surface. For example, Patent Document 6 describes an example in which a resonator surface of a III-V nitride semiconductor laser diode is produced by cleavage.
Japanese Patent Publication No.62-29397 Japanese Patent Laid-Open No. 4-297003 Japanese Patent Laid-Open No. 10-256661 JP-A-11-251253 JP 2003-178984 A Japanese Patent Laid-Open No. 10-22526 Appl.Phys.Lett.71 (18) 2638 (1997) Y.Oshima et.al., Jpn.J.Appl.Phys.Vol.42 (2003) pp.L1-L3

  However, problems to be solved remain in III-V nitride semiconductor devices such as III-V nitride semiconductor laser diodes manufactured by such a method.

  As described above, in many cases, a GaN free-standing substrate is necessarily turned off due to the influence of the base substrate used for manufacturing. The fact that the GaN substrate is turned off is not bad at all, and the substrate for epitaxial growth is superior in that the surface flatness of the epitaxial layer is easier to improve than the substrate that is not turned off. There are also many. However, I found that turning off this substrate is a problem when manufacturing semiconductor devices.

  FIG. 3 is an explanatory diagram showing the cleavage plane and cleavage direction of the III-V nitride semiconductor substrate, and FIG. 4 is an explanatory diagram showing the cleavage plane and cleavage direction of the GaAs substrate. A semiconductor device using a cubic (001) plane as a substrate, such as Si or GaAs, has a cleavage plane that is symmetrical four times as shown in FIG. Is possible. However, since the III-V nitride semiconductor crystal generally uses a hexagonal (0001) plane, the cleavage plane appears only in 6-fold symmetry as shown in FIG. In a nitride-based semiconductor crystal, there is one bond in the direction perpendicular to the atomic arrangement plane in both the {10-10} plane and the {11-20} plane, which can be a cleavage plane. However, in actuality, the cleavage of the {11-20} plane is weaker than that of the {10-10} plane, and it is difficult to obtain a clean cleavage plane even when attempting to cleave the {11-20} plane. . Therefore, it can be said that the cleaved surface that can be effectively used is only the {10-10} plane that appears only six times symmetrically.

  For this reason, when an attempt is made to produce a III-V nitride semiconductor device only by cleavage, the shape of the semiconductor device becomes a triangular prism or a prism having a parallelogram on the upper surface, and does not become a rectangular parallelepiped. Therefore, in order to obtain a rectangular parallelepiped semiconductor device, only a pair of parallel surfaces must be formed by cleavage, and the other pair of surfaces perpendicular to it must depend on a method such as cutting using a dicer. This causes problems inherent in hexagonal III-V nitride semiconductor crystals that did not occur in conventional cubic semiconductors.

  FIG. 2A shows an ideal rectangular parallelepiped semiconductor device, and FIG. 2B shows a semiconductor produced by cleaving a substrate with OFF, and the cleavage plane is tilted from a plane perpendicular to the surface of the semiconductor device. It is a schematic diagram which shows an example of a device.

  When a substrate with OFF is cleaved, the cleavage plane is not perpendicular to the substrate surface depending on the off direction of the substrate. For this reason, as shown in FIG. 2A, the shape of the semiconductor device which should ideally be a rectangular parallelepiped is slightly inclined from the plane perpendicular to the semiconductor device surface 13 as shown in FIG. It will be distorted. If this is an LED device or an electronic device, it will not be a big problem, but it becomes a big problem in a Fabry-Perot type laser diode having a cleavage plane as a resonator surface.

  In a Fabry-Perot laser diode, light emitted by current injection is oscillated by reflection between opposing resonator surfaces. At this time, if the resonator surface is inclined from the surface of the semiconductor device, the rate at which the light reflected by one resonator surface returns to the other resonator decreases. As a result, the laser device characteristics are deteriorated such that the oscillation threshold current increases and the light emission output decreases.

  Also in the case of a GaAs semiconductor laser diode, if the resonator surface is inclined, the aforementioned laser device characteristics are deteriorated. However, since the cleavage plane appears symmetrically four times, if the off direction is parallel to the cleavage direction, a pair of cleavage planes perpendicular to the surface of the semiconductor device is always provided in addition to the pair of cleavage planes inclined from the surface of the semiconductor device. Will exist. On the other hand, in the group III-V nitride semiconductor crystal, the cleavage plane appears 6 times symmetrical, so that the off direction is the same as the cleavage direction and a resonator is not produced using a cleavage plane parallel to the off direction. As long as other cleaved surfaces, the resonator surface is always inclined.

  Conventionally, however, the turn-off of the group III-V nitride semiconductor substrate has not been discussed so much, and attention has not been paid to the relationship between the off direction and the cleavage plane of the semiconductor device.

  This can be easily seen from the fact that the sapphire base substrate is not uniform in the off direction and the off size, and is different for each manufacturer who purchases the sapphire base substrate. If the off-direction and off-size of the sapphire base substrate vary, the off-direction and off-size of the GaN substrate produced using this will also vary.

  For this reason, conventional group III-V nitride semiconductor devices, particularly group III-V nitride semiconductor laser diodes, have problems of large variations in device characteristics and poor yield.

  The present invention solves the above-mentioned problems, and has excellent device characteristics and good productivity, a group III-V nitride semiconductor device, a method for manufacturing the same, and a method for manufacturing a group III-V nitride semiconductor substrate used therefor An object of the present invention is to provide a lot of III-V nitride semiconductor substrates.

  The present invention has a chip shape and has an epitaxial layer of a device structure on a group III-V nitride semiconductor substrate, and at least one parallel side surface of the epitaxial layer is a cleavage plane. In the III-V nitride-based semiconductor device, the substrate has a low index plane that is a crystal plane closest to the substrate surface and is tilted off with respect to the substrate surface, and the low index plane tilt The off direction which is the direction is parallel to one of the equivalent cleavage planes of the substrate, and the cleavage plane of the epitaxial layer is the same as the cleavage plane of the substrate parallel to the off direction of the substrate It is in the group III-V nitride semiconductor device characterized by being in the plane.

  The device structure of the epitaxial layer may be a laser diode structure, and the cleavage plane of the epitaxial layer may be a resonator surface of the laser diode.

  The present invention also provides an epitaxial layer having a device structure grown on a group III-V nitride semiconductor substrate, and the epitaxial layer is cleaved together with the substrate so that at least one set of parallel side surfaces of the epitaxial layer is present. In the method of manufacturing a group III-V nitride semiconductor device for forming a group III-V nitride semiconductor device which is a cleavage plane, the substrate has a low index plane which is a crystal plane closest to the substrate surface, And an off direction which is the direction of the low index plane is parallel to one of the equivalent cleavage planes of the substrate, After growing the epitaxial layer on the substrate, cleaving the epitaxial layer together with the substrate at a position of the cleavage plane of the substrate parallel to an off direction of the substrate, and a cleavage plane of the epitaxial layer; A method for producing a group III-V nitride semiconductor device is characterized in that a group III-V nitride semiconductor device is formed in which the cleavage plane of the substrate parallel to the off direction of the substrate is the same plane. .

  The device structure of the epitaxial layer may be a laser diode structure, and the cleavage plane of the epitaxial layer may be a resonator surface of the laser diode.

  The present invention also provides a self-supporting III-V group consisting of a group III-V nitride semiconductor crystal by epitaxially growing a group III-V nitride semiconductor crystal on the base substrate, removing the base substrate after completion of the growth. A method of manufacturing a nitride semiconductor substrate, wherein the base substrate is turned off in an off direction such that the off direction of the III-V nitride semiconductor substrate described below is parallel to the cleavage plane. In the III-V nitride semiconductor substrate, the low index plane which is the crystal plane closest to the substrate surface is tilted off with respect to the substrate surface, and the low index plane In the method of manufacturing a group III-V nitride semiconductor substrate, the off direction, which is the direction of inclination, is parallel to one of the equivalent cleavage planes of the substrate.

  As the base substrate, a sapphire base substrate in which the C-axis of the crystal is inclined in the M-axis direction is used, and a group III-V nitride semiconductor crystal is epitaxially grown on the C surface of the sapphire base substrate. By removing the base substrate and manufacturing a self-supporting group III-V nitride semiconductor substrate made of a group III-V nitride semiconductor crystal, a low index surface, which is the crystal plane closest to the substrate surface, is obtained. III-V group nitriding in which the off direction, which is the direction of inclination of the low index plane, is parallel to one of the equivalent cleavage planes of the substrate. A physical semiconductor substrate may be obtained.

  The present invention also relates to a lot of III-V group nitride semiconductor substrates composed of a plurality of group III-V nitride semiconductor substrates.

  As described above, according to the present invention, device characteristics can be improved and stabilized, and reliability can be improved. In addition, the process steps of the semiconductor device are facilitated, and the yield of non-defective products of the semiconductor device is improved in combination with the above-described effect of improving the device characteristics.

  The inventors of the present invention provide a group III-V nitride-based semiconductor substrate with an off direction that is aligned with the cleavage direction of the substrate, and which cleavage direction is one of the three cleavage directions in the substrate. If a group III-V nitride semiconductor device, particularly a group III-V nitride semiconductor laser diode, having a cleavage plane parallel to the off direction is formed, the semiconductor device can be identified. It has been found that the cleavage plane can always be formed perpendicular to the surface of the semiconductor device, so that the device characteristics can be improved and stabilized, and the reliability can be improved.

  An embodiment of a III-V nitride semiconductor device according to the present invention is as follows.

  A semiconductor laser diode having a chip shape and having an epitaxial layer of a laser diode structure on a GaN substrate, wherein at least one parallel side surface of the epitaxial layer of the semiconductor laser diode is a resonator surface of the laser diode And the GaN substrate is turned off, and the off direction is parallel to one of the equivalent cleavage surfaces of the GaN substrate, The cleavage plane of the epitaxial layer is a group III-V nitride semiconductor laser diode that is in the same plane as the cleavage plane of the GaN substrate parallel to the off direction of the GaN substrate.

  An embodiment of a method for producing a group III-V nitride semiconductor device according to the present invention is as follows.

  An epitaxial layer having a laser diode structure is grown on the GaN substrate, the epitaxial layer is cleaved together with the GaN substrate, and at least one set of parallel side surfaces of the epitaxial layer is a resonator surface of the laser diode, and a cleavage plane In the method of manufacturing a group III-V nitride semiconductor device for forming a group III-V nitride semiconductor device, the GaN substrate is turned off, and the off direction is equivalent to that of the GaN substrate. And preparing a parallel one of the cleavage planes, growing the epitaxial layer on the GaN substrate, and then the position of the cleavage plane of the GaN substrate parallel to the off-direction of the GaN substrate And cleaving the epitaxial layer together with the GaN substrate, and the cleavage plane of the epitaxial layer and a front surface parallel to the off direction of the GaN substrate. And the cleavage plane of the GaN substrate is the production method of the III-V nitride semiconductor laser diode to form a group III-V nitride-based semiconductor device having the same surface.

  Here, the GaN substrate is turned off means that the low index plane, which is the crystal plane closest to the GaN substrate surface, is tilted with respect to the GaN substrate surface, The direction of the slope of the low index plane.

  Further, in order to align the off direction of the III-V nitride semiconductor substrate with the cleavage direction of the substrate, the thickness of the III-V nitride semiconductor on the C surface of the sapphire base substrate that is off in the M-axis direction. A method for producing a group III-V nitride semiconductor substrate has been devised in which a film is epitaxially grown and only the group III-V nitride semiconductor layer is peeled off after crystal growth. By doing so, the off direction and the cleavage direction of the substrate can be naturally matched.

  A group of group III-V nitride semiconductor substrates may be formed by combining a plurality of the group III-V nitride semiconductor substrates with the off direction and the cleavage direction of the substrate as one set.

  Conventionally, even in the case of GaN substrates included in the same lot, the off direction of the substrate was not specified as one of the equivalent directions, so the cleavage surface of the semiconductor device was also selected in consideration of the substrate off. Although there were large wafer-to-wafer variations in device characteristics and yield at the time of semiconductor device creation, according to the present invention, the off direction of all the substrates is aligned in a direction parallel to a specific cleavage direction. Variations between wafers can be greatly reduced.

  In general, a semiconductor crystal substrate is often circular, and a notch called an orientation flat (orientation flat) is provided in a part of the circle in order to indicate a crystal orientation. However, some of the substrates for light emitting devices have a rectangular shape. The rectangular substrate is not particularly provided with an orientation flat, but in this case as well, a pair of end faces are parallel to the cleavage direction aligned with the off direction, and this is always on the long side (or short side) of the rectangle. If determined in such a manner, it is possible to prevent the cleavage plane from being inclined when the semiconductor device is manufactured. In the case where the substrate is square, a side indicating the off direction may be specified by notching the corner of the substrate.

  The “self-supporting” substrate in the present invention refers to a substrate having a strength that can retain its shape and does not cause inconvenience in handling. In order to have such strength, the thickness of the self-supporting substrate is preferably 200 μm or more.

The group III-V nitride semiconductor in the present invention includes a semiconductor represented by In _x Ga _y Al _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). . Of these, semiconductors such as GaN and AlGaN are preferably used. This is because the properties required for the substrate material such as strength and manufacturing stability are satisfied.

  The group III-V nitride semiconductor substrate according to the present invention has a hexagonal C-plane, particularly a chemically, mechanically and thermally stable group III plane on the surface, from the viewpoint of easy fabrication of semiconductor devices. It is desirable to have a substrate.

  The inclination of the crystal axis in the substrate plane can be evaluated using a value obtained by X-ray diffraction measurement.

  The means for growing the III-V nitride semiconductor substrate of the present invention is preferably HVPE (hydride vapor phase epitaxy). The HVPE method is used because the crystal growth rate is high and it is suitable for manufacturing a substrate.

An embodiment of a method for producing a group III-V nitride semiconductor substrate according to the present invention will be described below.
A self-standing GaN substrate was fabricated using the VAS method. The substrate manufacturing procedure and conditions are as follows.

An undoped GaN layer was grown to 300 nm on the C-plane of a commercially available single crystal sapphire base substrate having a diameter of 2 inches by MOVPE using TMG and NH ₃ as raw materials. As the sapphire base substrate, a substrate that is off by 0.3 ° in the M-axis direction parallel to the orientation flat, with the A plane being the orientation flat surface. The growth pressure is normal pressure. First, a low temperature buffer layer is epitaxially grown on a sapphire base substrate at a temperature of 600 ° C. and a low temperature buffer layer is epitaxially grown to 20 nm, and then the temperature of the base substrate is raised to 1100 ° C. did. The carrier gas is a mixed gas of hydrogen and nitrogen. The crystal growth rate was 4 μm / h. By this method, 10 so-called GaN templates having a GaN layer on a sapphire base substrate were prepared.

Next, a 20 nm thick metal Ti film was deposited on the GaN layer of these GaN templates using an EB vaporizer, and this was put in an electric furnace at a temperature of 1000 ° C. in an H ₂ stream containing 20% NH _3. A heat treatment was performed for 20 minutes to change the metal Ti film into a mesh-like TiN film, and at the same time, many voids were formed in the GaN layer.

Next, a GaN template in which voids were formed in the GaN layer was placed in an HVPE furnace, and the GaN template was used as a base substrate, and GaN was deposited thereon by 550 μm. The raw materials used for HVPE growth were NH ₃ and GaCl, and N ₂ was used as a carrier gas. The growth conditions are normal pressure and a substrate temperature of 1040 ° C. The GaN layer was peeled from the sapphire base substrate with the void layer as a boundary in the temperature lowering process after the growth was completed, and a self-supporting GaN substrate having a (0001) Ga surface as the surface was obtained.

  The obtained GaN substrate was mirror-polished on the front and back surfaces to finish a substrate having a thickness of 350 μm. All of the GaN substrates were transparent and had a flat mirror surface, and the surface roughness was all 10 nm or less when Ra was scanned in a 500 μm range using a surface step meter. The GaN substrate was subjected to orientation flat processing such that the outer shape was ground into a circular shape, and the (1-100) plane of GaN that had a positional relationship parallel to the orientation flat position of the sapphire base substrate was used as the orientation flat surface. The surface accuracy of the orientation flat is measured by X-ray diffraction measurement on the orientation flat surface, and finished with high accuracy by further correcting the deviation from the (1-100) surface, and finally the (1-100) surface ± 0. The processing accuracy was .02 °.

  When a GaN crystal is epitaxially grown on a sapphire base substrate with the surface turned off, the grown GaN also grows off with the sapphire base substrate off. Therefore, when the orientation flat processing is performed on the GaN substrate in the manner described above, the off-direction can be unified to the [11-20] direction parallel to the orientation flat surface in all ten GaN substrates.

  In order to investigate the inclination direction of the C axis with respect to the surface of the GaN substrate thus fabricated, X-ray diffraction measurement was performed on the substrate surface. As a result, it was found that the C-axis inclination vector measured at the center of the substrate was inclined by an average of 0.36 ° in the [11-20] direction parallel to the orientation flat of the substrate.

  Next, an example of a III-V nitride semiconductor device and a manufacturing method thereof according to the present invention will be described.

  Using the GaN substrate produced in Example 1, a laser diode chip was produced.

  FIG. 1 is a schematic cross-sectional view showing the structure of a III-V nitride semiconductor laser diode according to one embodiment of the present invention.

On a self-supporting n-type GaN substrate 10 made of a single crystal obtained by the method of Example 1, a Si-doped (n = 5 × 10 ¹⁷ cm ⁻³ ) n-type GaN buffer layer 9 is 2 μm, Si-doped (n = n-type Al ₀ of ^{5 × 10 17 cm -3).} 07 Ga 0.93 n cladding layer 8 to 1.0 .mu.m, the n-type GaN SCH layer 7 of Si-doped ^{(n = 1 × 10 17 cm} -3) 0. 1 μm, Si-doped or undoped In _0.2 Ga _0.8 N / In _0.05 Ga _0.95 N multiple quantum well layer 6 of 30 A / 50 A × 3, Mg-doped (p = 2 × 10 ¹⁹ cm ⁻³ ) p-type Al _0.2 Ga _0.91 N overflow prevention layer 5 is 0.02 μm, Mg-doped (p = 2 × 10 ¹⁹ cm ⁻³ ) p-type GaN optical confinement layer 4 is 0.1 μm, Mg-doped (p = 2 × 10 ¹⁹ cm ⁻³ ) p-type Al _0.07 Ga _0.93 N clad layer 3 of 0.5 μm, Mg-doped (p = 2 × 10 ¹⁹ cm ⁻³ ) p-type The GaN contact layer 2 was formed in order with a thickness of 0.05 μm to produce an LD structure. Thereafter, a ridge structure having a width of 4 μm and a depth of 0.4 μm was formed on the p side by dry etching, and current confinement was performed. Further, a Ni / Au electrode was formed on the ridge to form a p-type ohmic electrode 1. A Ti / Al electrode was formed on the entire surface of the back surface of the self-standing GaN substrate to form an n-type ohmic electrode 11. The end face serving as a resonator was cleaved with a (1-100) plane parallel to the orientation flat surface of the n-type GaN substrate 10, and a highly reflective coating film made of TiO ₂ / SiO ₂ was applied to both end faces. . The semiconductor device length was 500 μm. When this semiconductor device was energized, it oscillated continuously at room temperature with a threshold current density of 4.6 kA / cm ² and a threshold voltage of 5.4 V. The lifetime of the semiconductor device was as good as 5000 hours when driven at 25 ° C. and 30 mW. In all 10 GaN substrates fabricated in Example 1, good characteristics were obtained with 80% or more of the laser diode chips fabricated from the GaN substrate. It is considered that the yield of semiconductor devices is greatly improved because the method of manufacturing a III-V nitride semiconductor device of the present invention reduces variations in device characteristics and stabilizes the process.
[Comparative Example 1]
First, an epitaxial layer having a laser diode structure was formed on a GaN substrate in the same manner as in Example 2. Thereafter, when this is made into a chip, the surface serving as the resonator is cleaved and separated by a (10-10) plane that intentionally forms an angle of 60 ° with the orientation flat surface of the GaN substrate. Was made.
The resonator plane obtained by cleaving at the (10-10) plane is inclined about 0.4 °, which is the same as the off-size of the GaN substrate, with respect to the chip surface. It was clarified by SEM observation of the side surface of the chip that it was as shown in b).

The characteristics of the laser diode chip fabricated in this way are the characteristics of the laser diode obtained in Example 2, with a threshold current density required for continuous oscillation at room temperature of 4.9 kA / cm ² and a threshold voltage of 6.2 V. It was clearly worse than that. Further, the lifetime of the semiconductor device was 900 hours when driven at 25 ° C. and 30 mW, and the reliability deteriorated in response to the deterioration of the device characteristics.

  In a conventional GaN substrate lot composed of a plurality of GaN substrates, since the cleavage direction could not be aligned only in a specific direction among the three equivalent directions, a semiconductor device having a method of making as in the above comparative example, It can be said that 2/3 of the semiconductor devices manufactured as in Example 2 were mixed, and as a result, device characteristics and yield variations between wafers were increased.

  The present invention has been described above based on the embodiments. However, these are exemplifications, and various modifications can be made to combinations of the respective processes, and such modifications are also within the scope of the present invention. It will be understood by those skilled in the art.

  For example, in this embodiment, the orientation flat surface attached to the GaN substrate is a (1-100) plane parallel to the orientation flat surface of the sapphire base substrate, but which cleavage direction is the off direction of the GaN substrate relative to the orientation flat? As long as it can be specified, the present invention conforms to the present invention, and the orientation flat surface is not necessarily the (1-100) surface. For example, even if the orientation flat of the GaN substrate is the (10-10) plane or the (01-10) plane and the off direction of the substrate is defined based on this, the effect of the present invention can be obtained. Further, the {11-20} plane perpendicular to the off direction of the substrate can be an orientation flat surface. The relative position of the orientation flat attached to the GaN substrate relative to the orientation flat of the sapphire base substrate is not an important problem in this patent. It is important for the sapphire base substrate to be off in the M-axis direction so that the off direction of the GaN substrate matches the cleavage direction, and the orientation flat of the sapphire base substrate is in the off direction of the substrate. Which position is attached to is not a problem. (It seems awkward, but since the orientation sapphire of sapphire is used as a mark for specifying the off direction of the grown GaN substrate, in the direction of the M axis in the sapphire base substrate, the off state is attached to the orientation flat. However, in order to avoid confusion, if the orientation flat of the sapphire base substrate is the (11-20) plane and the off direction of the sapphire base substrate is the [1-100] direction, it grows on this. The off direction of the GaN substrate obtained in this way is the [11-20] direction, and it is desirable that the (1-100) plane parallel to this be the orientation flat surface. Then, the orientation flat of the sapphire base substrate, the off direction of the sapphire base substrate, the orientation flat of the GaN substrate, the off direction of the GaN substrate, and the cleavage direction of the GaN substrate are all aligned in parallel. Mistakes in direction are reduced.

In this embodiment, an example in which a sapphire base substrate is used as the base substrate for manufacturing the substrate of the present invention has been described. Conventionally, a substrate for forming a GaN-based epitaxial layer such as GaAs, SiC, Si, ZrB ₂ , ZnO or the like All the substrates with reported examples are applicable. At that time, when it is necessary to turn off the GaN substrate, the off direction of the base substrate is selected so that the off direction of the GaN substrate is the same as the cleavage direction in consideration of the consistency between the base substrate and GaN. There must be. For example, when using a GaAs or Si substrate, it is necessary to use a substrate whose surface is (111) plane and turned off in the [1-10] direction, and when using a SiC substrate, [11− 20] It is necessary to use a substrate turned off in the direction.

  In this embodiment, an example of a circular GaN substrate with an orientation flat is described, but means for specifying the orientation of the substrate corresponding to the orientation flat, for example, a notch indicating the cleavage direction or IF (index flat) can also be used. It is. It is also possible to apply to a rectangular or square core substrate that is not circular. For example, in the case of a rectangular substrate, it may be determined that the long side is a cleavage plane parallel to the off direction of the substrate, and in the case of a square substrate, one side is a cleavage plane parallel to the off direction of the substrate. The orientation can be specified by chamfering the corner of the substrate.

  In this embodiment, an example of a self-supporting GaN substrate has been described. However, the present invention can also be applied to a self-supporting AlGaN substrate.

It is a cross-sectional schematic diagram which shows the structure of the III-V nitride semiconductor laser diode concerning one Example of this invention. (A) is an ideal rectangular parallelepiped-shaped semiconductor device, and (b) is an example of a semiconductor device produced by cleaving a substrate with OFF, and the cleavage plane is inclined from a plane perpendicular to the surface of the semiconductor device. It is a schematic diagram shown. It is explanatory drawing which shows the cleavage surface and cleavage direction of a III-V group nitride semiconductor substrate. It is explanatory drawing which shows the cleavage surface and cleavage direction of a GaAs substrate.

Explanation of symbols

1 P-type ohmic electrode 2 p-type GaN contact layer 3 p-type Al _0.07 Ga _0.93 N clad layer 4 p-type GaN optical confinement layer 5 p-type Al _0.2 Ga _0.91 N overflow prevention layer 6 In _0.2 Ga _0.8 N / In _0.05 Ga _0.95 N multiple quantum well layer 7 n-type GaN SCH layer 8 n-type Al _0.07 Ga _0.93 N clad layer 9 n-type GaN buffer layer 10 n-type GaN substrate 11 n-type ohmic electrode

Claims (7)

A group III-V having a chip shape, having an epitaxial layer of a device structure on a group III-V nitride semiconductor substrate, and at least one parallel side surface of the epitaxial layer being a cleavage plane In nitride-based semiconductor devices,
The substrate has a low index plane that is the crystal plane closest to the substrate surface and is tilted off with respect to the substrate surface, and an off direction that is a direction of the tilt of the low index plane is equivalent to the substrate. Parallel to one of the cleavage planes,
A group III-V nitride semiconductor device, wherein a cleavage plane of the epitaxial layer is flush with a cleavage plane of the substrate parallel to an off direction of the substrate.   2. The III-V nitride semiconductor according to claim 1, wherein the device structure of the epitaxial layer is a laser diode structure, and the cleavage plane of the epitaxial layer is a resonator surface of the laser diode. device. An epitaxial layer having a device structure is grown on a group III-V nitride semiconductor substrate, the epitaxial layer is cleaved together with the substrate, and at least one parallel side surface of the epitaxial layer is a cleavage plane. In a method for manufacturing a group III-V nitride semiconductor device for forming a group V nitride semiconductor device,
The substrate has a low index plane that is the crystal plane closest to the substrate surface and is tilted off with respect to the substrate surface, and an off direction that is a direction of the tilt of the low index plane is equivalent to the substrate. A substrate parallel to one of the cleavage planes is prepared, and the epitaxial layer is grown on the substrate, and then the substrate is cleaved at a position of the cleavage plane parallel to the off-direction of the substrate. And the epitaxial layer is cleaved to form a group III-V nitride semiconductor device in which the cleavage plane of the epitaxial layer and the cleavage plane of the substrate parallel to the off direction of the substrate are the same plane. A method for producing a group III-V nitride semiconductor device.   4. The group III-V nitride semiconductor according to claim 3, wherein the device structure of the epitaxial layer is a laser diode structure, and a cleavage plane of the epitaxial layer is a resonator surface of the laser diode. Device manufacturing method.   A group III-V nitride semiconductor crystal is epitaxially grown on the base substrate, the base substrate is removed after the growth is completed, and a self-supporting group III-V nitride semiconductor substrate made of group III-V nitride semiconductor crystal is obtained. A method of manufacturing, wherein the base substrate is a substrate that is turned off in an off direction such that an off direction and a cleavage plane of a group III-V nitride semiconductor substrate described below are parallel, In the III-V nitride semiconductor substrate, the low index plane, which is the crystal plane closest to the substrate surface, is tilted off with respect to the substrate surface, and the off direction is the direction of the tilt of the low index plane. A method for producing a group III-V nitride semiconductor substrate, characterized in that the direction is parallel to one of the equivalent cleavage planes of the substrate.   A III-V nitride semiconductor crystal is epitaxially grown on a sapphire base substrate having a hexagonal C-plane as its surface, and after completion of the growth, the sapphire base substrate is removed to form a self-supporting layer consisting of a group III-V nitride semiconductor crystal. A method of manufacturing a group III-V nitride-based semiconductor substrate, wherein the sapphire base substrate uses a crystal whose C-axis is inclined in the M-axis direction, and the group III-V nitride-based semiconductor substrate is used. The low index plane that is the crystal plane closest to the substrate surface is tilted off with respect to the substrate surface, and the off direction that is the direction of the tilt of the low index plane is the equivalent cleavage of the substrate. A method for producing a group III-V nitride semiconductor substrate, characterized by being parallel to one of the planes.   The group III-V nitride semiconductor substrate lot composed of a plurality of group III-V nitride semiconductor substrates, wherein each of the substrates constituting the lot is III- according to claim 5 or 6. A lot of group III-V nitride semiconductor substrates, which is a group III-V nitride semiconductor substrate obtained by a method for manufacturing a group V nitride semiconductor substrate.

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