JP2002094186A - Semiconductor-laminated structure and light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor-laminated structure in which a III nitride semiconductor laminated structure can be put to crystal growth and which is formed on a conductive substrate. SOLUTION: The laminated-laminated structure uses the conductive substrate 100 which has been difficult to be used in the conventional example by using a strontium titanate(SrTiO3) single-crystal substrate having electric conductivity as a single-crystal substrate. Consequently, the electrical communication between the substrate 100 and a III nitride semiconductor layer 101 can be realized and, at the same time, a light emitting element having a laminated structure can be put to crystal growth on the semiconductor layer 101. Therefore, a light emitting element having such a structure that an electrode is formed on the substrate side can be realized unlike the conventional example in which an insulating substrate, such as the sapphire substrate, etc., is used and, accordingly, the structure is not able to be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laminated structure applicable to various light sources, for example, a light source for an optical pickup such as a DVD or a CD, an LED lamp, a light source for an optical print, a light source for an optical communication, and the like. It relates to a light emitting element.

[0002]

2. Description of the Related Art Conventionally, blue LEDs have lower luminance than red and green and have been difficult to put into practical use. In recent years, a low-temperature AlN buffer layer or a III-nitride semiconductor represented by the general formula InAlGaN has been used. Improvement in crystal growth technology by using a low-temperature GaN buffer layer, and the provision of a low-resistance p-type semiconductor layer using Mg as a dopant, enable practical use of a high-brightness blue LED, and furthermore, have a low output. However, a semiconductor laser having a lifetime exceeding 10,000 hours and continuously oscillating at room temperature has been realized.

At the beginning of the development of the InAlGaN-based laser, problems such as improvement of the quality of crystals on a heterogeneous substrate such as sapphire, formation of an end face of an optical resonator, formation of electrodes, and mounting form were mentioned as problems.

[0004] Among them, the crystal quality is determined by the low temperature buffer,
By selective growth and lateral growth techniques, high-quality crystals can be grown even on a sapphire substrate having a lattice mismatch with GaN of 16.1% and a large difference in thermal expansion coefficient.

[0005] In addition, the formation of an optical cavity facet, which is indispensable for manufacturing a semiconductor laser, is performed by dry etching, sapphire substrate polishing, substrate cleavage, and group III nitride crystal cracking. Can be formed.

[0006] However, the problems of electrode formation and mounting form still remain unsolved. That is, it is difficult to form an electrode on the back surface of a sapphire substrate that is an insulator. Therefore, a conventional mounting mode such as an AlGaAs laser, that is, a mode in which the light emitting unit side is directly mounted on the heat sink cannot be obtained. This means that the heat generated in the light emitting portion must be radiated through the sapphire substrate having poor thermal conductivity, so that the temperature of the semiconductor laser is inevitably increased, and the life of the semiconductor laser at the time of high output operation is significantly shortened. .

Further, since the electrodes corresponding to the p-type and the n-type are formed on the element surface, the chip size is increased by the space of the electrodes. Furthermore, since dry etching for exposing the n-type layer is required for forming the n-side electrode, the laser element manufacturing process is complicated.

To solve these problems, SiC substrates, Si substrates, GaAs
Substrates, ZnO substrates, and the like have been studied, but only SiC substrates have the advantages and disadvantages of each substrate and allow crystal growth until a semiconductor laser can be manufactured.

However, the semiconductor laser fabricated on the SiC substrate has a short lifetime and is far from practical use.
Further, the SiC substrate has a problem of crystal defects such as micropipes on the substrate itself.

Therefore, a substrate having electrical conductivity and excellent enough to replace a sapphire substrate has not yet been proposed, and a semiconductor laser having a high output operation and a long life has not been realized.

[0011] For the method using these different kinds of substrates, G
Attempts have been made to fabricate aN substrates. This is roughly divided into two types: a method of producing a GaN bulk single crystal and a method of producing a GaN thick film single crystal by thick film growth.

However, at present, only a few millimeters of a GaN bulk single crystal have been obtained, and it is far from practical use.

On the other hand, several techniques for manufacturing a GaN substrate from a high-quality GaN thick film having a low defect density have been disclosed.

For example, JP-A-10-326912, JP-A-10-326751, and JP-A-10-3
No. 12971, Japanese Patent Application Laid-Open No. 11-4048,
A technique has been disclosed in which GaN is selectively grown on a heterogeneous substrate using a mask and crystal growth is continued to embed the mask to form a flat GaN thick film over the entire surface of the substrate.

FIG. 16 shows a method of manufacturing a GaN thick film substrate disclosed in Japanese Patent Application Laid-Open No. 10-312971. First,
As shown in FIG. 16A, a heterogeneous substrate 1 such as sapphire is used.
1, a III-V compound semiconductor film 12 such as GaN is laminated, and a mask 1 of several μm width made of SiO ₂ or the like is formed thereon.
Then, a growth region 13 for selectively growing a III-V group compound semiconductor such as GaN is formed.

Next, as shown in FIG. 16B, a facet structure 15 is manufactured by selectively growing a III-V compound semiconductor such as GaN in the growth region 13.

When the growth is further continued, the facet structure 15 laterally grows in the lateral direction and covers the mask 14 as shown in FIG.

When the growth is further continued, as shown in FIG. 16D, the adjacent group III-V compound semiconductors 15 are united and the trench is filled.

As the growth continues, the surface of the group III-V compound semiconductor 15 is flattened as shown in FIG.
A flat group III-V compound semiconductor thick film is formed on the entire surface of the substrate 11.

According to these techniques, threading dislocations generated at the substrate interface are present at a high density in the crystal layer of the portion selectively grown on the heterogeneous substrate, but in the portion laterally grown on the mask in the lateral direction. The density of threading dislocations has been drastically reduced, resulting in high quality crystals. Further, by repeating the selective growth and the lateral growth thereon, a high-quality GaN thick film with few dislocations can be formed on the entire surface of the wafer. Further, according to this technique, even when GaN as thick as 100 μm or more is grown,
Since a crack due to a difference in thermal expansion coefficient from the substrate does not occur, a GaN thick film having a thickness that can be used as a substrate can be grown even if a heterogeneous substrate is removed.

Then, in order to solve the problems of the end face of the optical resonator, the formation of the electrodes, and the heat dissipation, the heterogeneous substrate and the mask are finally removed to form a GaN substrate. The removal of the heterogeneous substrate and the mask material depends on a method utilizing polishing or thermal shock.

Other techniques for producing a GaN thick film substrate include, for example, Japanese Patent Application Laid-Open No. 7-202265 and
JP-A-165498 discloses that a buffer layer made of ZnO is formed on a sapphire substrate, a group III nitride semiconductor is grown thereon, and then the buffer layer is dissolved and removed.
A method for separating and manufacturing a group I nitride semiconductor is disclosed.

Japanese Patent Application Laid-Open No. Hei 10-229218 discloses that a group III nitride semiconductor is grown on a first wafer on which a group III nitride semiconductor is grown on a first substrate and a group III nitride semiconductor is grown on a second substrate. A method of preparing a second wafer, bonding the first and second wafers so that the respective group III nitride semiconductors are in close contact with each other, and polishing and removing the first substrate and the second substrate. Is disclosed.

JP-A-10-312971 and JP-A-11-4048 disclose that a laser structure is formed by laminating a heterogeneous substrate and a GaN substrate from which a mask material has been removed.
A group III nitride semiconductor laser is disclosed.

FIG. 17 shows a configuration example of a semiconductor laser disclosed in Japanese Patent Application Laid-Open No. 11-4048. The nitride semiconductor substrate 40 is formed by growing a Si-doped GaN thickly on a sapphire substrate via a selective growth mask, and then polishing and removing the sapphire substrate and the selective growth mask to form only a Si-doped GaN layer. The substrate is being manufactured. On this GaN substrate 40, a nitride semiconductor layer having a laser structure is grown.

[0026] Laser laminate structure is made of the second buffer layer 41, n-type In _{0. 1} Ga _0.9 crack preventing layer 42 consisting of N, n-type Al _0.2 Ga _0.8 N / GaN superlattice of n-type GaN n-side cladding layer 43, n-type GaN of n-side optical guide layer _{44, In 0. 05 Ga 0.95 n} / In 0.2 G
a _0.8 N active layer 45 having a multiple quantum well structure, p-type Al _0.3 G
a p-side cap layer 46 of a _0.7 N, a p-side light guide layer 47 of p-type GaN, p-type Al _0.2 Ga _0.8 N / Ga
A p-side cladding layer 48 of N superlattice and a p-side contact layer 49 of p-type GaN are sequentially laminated.

Then, a part of the p-side contact layer 49 and a part of the p-side cladding layer 48 are dry-etched to form a ridge stripe having a width of 4 μm. The position where the ridge stripe is formed is the crystal portion immediately above the selective growth mask. Since the sapphire substrate and the selective growth mask have been removed, this alignment is performed by placing a mark serving as a starting point on the GaN substrate side before growing the stacked structure of the nitride semiconductor device. A p-side electrode made of Ni / Au is formed on the ridge stripe, and Ti /
An n-side electrode made of Al is formed. The end face of the laser resonator is formed by cleaving the M-plane of the n-type GaN substrate.

[0028]

As described above, as described above, SiC
Technology using conductive substrates such as a substrate, a Si substrate, a GaAs substrate, a ZnO substrate, and a GaN substrate has been studied,
It has not been put to practical use yet.

JP-A-10-326912, JP-A-10-326751, JP-A-10-312971
Gazette disclosed in Japanese Unexamined Patent Publication No. 11-4048
In the method of manufacturing an N substrate, cracks do not occur even when thick GaN is grown, but the wafer is warped due to a difference in thermal expansion coefficient between GaN and a heterogeneous substrate. For this reason, it is difficult to uniformly polish a heterogeneous substrate having a diameter of about 2 inches over the entire surface. Even if a high-quality GaN thick film is grown on a 2-inch diameter substrate, it is difficult to polish a heterogeneous substrate. It was necessary to divide the substrate into about 10 mm ² , and a large GaN substrate could not be manufactured.

That is, it is difficult to manufacture a large-area GaN substrate by the conventional method of polishing and removing the substrate. Also, due to this warpage, in the process of polishing different kinds of substrates, G
The characteristics of the semiconductor laser were not always good, such as the introduction of defects into the aN layer, the deterioration of crystallinity, and the increase in the threshold current density of the semiconductor laser fabricated thereon.

Further, the first and second wafers disclosed in Japanese Patent Application Laid-Open No. 10-229218 are bonded to each other so that the respective group III nitride semiconductors come into close contact with each other, and then the first substrate and the second substrate are bonded to each other. In the method of removing the second substrate, the substrate and II
GaN due to the difference in thermal expansion coefficient from Group I nitride semiconductor
When the substrate is grown to a large thickness, the wafer is warped, so that in a large-area wafer, the group III nitride semiconductors may not completely adhere to each other over the entire surface of the wafer. In addition, cracks may occur in the process of close contact. Further, since the first substrate and the second substrate are polished and removed, two expensive substrates are used for manufacturing one GaN substrate, which causes a problem of high cost.

In addition, G can be used without polishing and removing a heterogeneous substrate.
Japanese Unexamined Patent Publication No. Hei 7 (Japanese Unexamined Patent Publication No.
In JP-A-202265 and JP-A-7-165498, it takes a very long time to dissolve and remove the thin-film buffer layer made of ZnO, and practical use has been difficult.

On the other hand, in the method of separating different kinds of substrates using thermal shock, the problem of introducing defects due to thermal shock is the same as in polishing, since the bonding strength between the GaN layer and the substrate is strong. It has been difficult to produce a quality GaN substrate.

Accordingly, an object of the present invention is to provide a semiconductor multilayer structure formed on a conductive substrate capable of crystal-growing a group III nitride semiconductor multilayer structure, and to provide a group III nitride semiconductor layer capable of forming an electrode on the back surface of the substrate. And a light-emitting device using the same.

More specifically, a semiconductor laminated structure having a conductive substrate is provided.

Further, the present invention provides a semiconductor laminated structure composed of a hexagonal group III nitride semiconductor layer laminated on a conductive substrate.

Further, the present invention provides a semiconductor laminated structure including a hexagonal group III nitride semiconductor layer laminated on a substrate having conductivity comparable to metal conduction.

Further, there is provided a semiconductor laminated structure comprising a group III nitride semiconductor layer having a flat surface laminated on a conductive substrate.

Further, the present invention provides a light emitting device laminated on a conductive substrate.

Further, the present invention provides a group III nitride semiconductor light emitting device which can easily use the conventional face-down mounting technology.

Further, there is provided a group III nitride semiconductor laser device which can easily use the conventional face-down mounting technology.

[0042]

According to a first aspect of the present invention, there is provided a semiconductor laminated structure comprising a strontium titanate (SrTiO ₃ ) single crystal substrate having electric conductivity and a strontium titanate (SrTiO ₃ ) single crystal substrate. At least one or more layers of Al, B, Ga,
A group III nitride semiconductor layer containing at least one element of In and N is provided.

Therefore, a semiconductor laminated structure having a conductive substrate, which has been difficult in the past, is obtained.
It is possible to realize electrical conduction with the group III nitride laminated structure, and it is possible to crystal-grow a light emitting element laminated structure on this semiconductor laminated structure, which cannot be realized with an insulating substrate such as a conventional sapphire substrate. A light emitting element having a structure in which an electrode is formed on a substrate side, which has been possible, can be realized.

According to a second aspect of the present invention, in the semiconductor laminated structure according to the first aspect, the strontium titanate (SrTiO ₃ ) single crystal substrate has an electrical resistivity of 0.5Ω.
cm or less.

Accordingly, for example, a semiconductor laminated structure capable of manufacturing a semiconductor laser which continuously oscillates at room temperature is obtained.

According to a third aspect of the present invention, in the semiconductor laminated structure of the first or second aspect, the group III nitride semiconductor layer is a hexagonal single crystal.

Accordingly, a semiconductor laminated structure having good crystallinity in which a hexagonal single crystal, which is a stable layer of a group III nitride, is laminated, has the effect of the first or second aspect of the present invention. A light-emitting element using a group III nitride stacked structure having high crystallinity stacked on a conductive substrate can be formed.

According to a fourth aspect of the present invention, in the semiconductor multilayer structure according to the first, second or third aspect, the strontium titanate (SrTiO ₃ ) single crystal substrate has a (111) plane as a main surface. And

Therefore, in addition to the functions and effects of the first, second or third aspect of the present invention, strontium titanate (SrTi
Since the (111) plane of O ₃ ) has a structure similar to the (0001) plane of a hexagonal crystal, the (0001) plane of a hexagonal group III nitride semiconductor single crystal easily grows epitaxially, Further, for example, (0001) of hexagonal GaN
Lattice mismatch between the (111) plane and the SrTiO ₃ plane is Δ
a = 15.5%, which is smaller than the case where the (0001) plane of sapphire or the (001) plane or (110) plane of SrTiO ₃ is used.
The growth on the (111) plane can suppress the introduction of defects due to lattice mismatch, and can grow a high-quality GaN crystal when grown on the (111) plane than when grown on aN.

The fifth aspect of the present invention provides the first to fourth aspects.
In the semiconductor multilayer structure according to any one of the above, the strontium titanate (SrTiO ₃ ) single crystal substrate may
a is doped.

Therefore, by doping La, the charge density can be increased to a level comparable to the metal conduction of 1.2 × 10 ²¹ cm, and the resistivity can be reduced to about 0.0006 Ωcm. Since this value is equal to or less than the resistivity of a substrate used in an AlGaInP-based semiconductor laser or the like, a group III nitride laminated structure is formed on a La-doped strontium titanate (SrTiO ₃ ) single crystal substrate. In the semiconductor laminated structure in which
It is possible to lower the resistivity of the substrate used in semiconductor lasers such as aInP system to the same or less,
A light-emitting element requiring a large current, such as a semiconductor laser, can be manufactured.

The invention according to claim 6 is the invention according to claims 1 to 5
5. The semiconductor multilayer structure according to claim 1, further comprising at least one electrically conductive buffer layer deposited on the strontium titanate (SrTiO ₃ ) single crystal substrate, wherein the buffer layer is formed on the buffer layer. At least one layer of said II grown at a temperature higher than the deposition temperature of the layer.
It has a group I nitride semiconductor layer.

Therefore, it is possible to provide a semiconductor laminated structure in which the conductivity between the substrate and the semiconductor layer is not impaired.

According to a seventh aspect of the present invention, in the semiconductor laminated structure according to the sixth aspect, the same electrical conductivity type as that of the buffer layer is provided between the buffer layer and the group III nitride semiconductor layer. Above the deposition temperature of the buffer layer and
It has at least one intermediate layer grown at a temperature lower than the growth temperature of the group III nitride semiconductor layer.

Therefore, when crystal growth is performed by MOCVD or the like, the exposed substrate surface not covered with the buffer layer can be prevented from being exposed to a reducing atmosphere at a high temperature and decomposed, and the intermediate layer can be laminated. Depending on the surface flattening,
Improvement in crystallinity can be expected.Also, by changing the composition of the intermediate layer and the high-temperature layer, propagation of dislocations at the interface can be suppressed, and a high-temperature layer with better crystallinity can be grown. Further, since the intermediate layer and the buffer layer have the same electric conductivity type, a semiconductor laminated structure having conduction between the substrate and the high-temperature layer can be provided.

According to an eighth aspect of the present invention, in the semiconductor laminated structure according to the sixth or seventh aspect, the buffer layer is made of hexagonal n-type ZnO.

Therefore, when the carrier concentration exceeds (4 to 6) × 10 ¹⁸ cm ⁻³ , the electric conduction mechanism causes metal conduction, so that the n-type ZnO has a high carrier concentration.
By using nO for the buffer layer, the conductivity between the group III nitride laminated structure and the substrate can be improved, and the crystal system is the same hexagonal system as the group III nitride stable layer, and the group III Since the lattice constant is close to that of nitride and is lattice-matched to In _0.22 Ga _0.78 N, a high-quality group III nitride single crystal multilayer structure is grown as in the case of using a group III nitride buffer layer. Can be done.

According to a ninth aspect of the present invention, there is provided a light emitting device comprising the semiconductor laminated structure according to any one of the first to eighth aspects, at least one p-type layer, and at least one n-type layer. With structure.

Therefore, by making the substrate conductive, it is possible to form electrodes on the substrate, which has been difficult in the past.

According to a tenth aspect of the present invention, in the light emitting device according to the ninth aspect, electrodes are formed on both surfaces of the laminated structure.

Therefore, by making the substrate conductive, it is possible to form electrodes on the back surface of the substrate, which has been difficult in the past, thereby enabling the conventional mounting method and the light emitting element side. Face-down mounting on a heat sink material is facilitated, heat radiation efficiency during high-output operation can be increased, and a light-emitting element capable of high-temperature, high-output operation can be realized.

According to an eleventh aspect of the present invention, the light emitting device according to the tenth aspect is a semiconductor laser.

Accordingly, by making the substrate conductive, it is possible to form electrodes on the back surface of the substrate, which has been difficult in the past, thereby facilitating face-down mounting in which the semiconductor laser side is mounted on a heat sink material. Therefore, the heat radiation efficiency at the time of large output operation can be increased, and as a result, a semiconductor laser capable of high temperature and large output operation can be realized.

[0064]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a cross-sectional view showing an example of a basic semiconductor laminated structure of the present embodiment. Schematically, the structure is such that a hexagonal Al _0.15 Ga _0.85 N layer 101 is stacked as a group III nitride semiconductor layer on a (111) plane of a strontium titanate (SrTiO ₃ ) single crystal substrate 100.

The details will be described below.

The group III nitride semiconductor layer laminated on the substrate 100 may be either single crystal or polycrystal. Particularly, if the group III nitride has a single crystal laminated structure in which the group III nitride is epitaxially grown, Thus, a semiconductor laser having a structure in which electrodes are formed on the substrate side, which cannot be realized with an insulating substrate such as a sapphire substrate, can be realized.

The SrTiO ₃ crystal constituting the semiconductor laminated structure of the present embodiment will be considered. The strontium titanate (SrTiO ₃ ) single crystal has a cubic perovskite crystal structure (lattice constant a = 3.9) as shown in FIG.
05Å), and has several beneficial features as a substrate for epitaxial growth of a group III nitride semiconductor as follows.

1. As described later, the lattice constant of the crystal structure on a specific crystal plane is closer to that of a hexagonal group III nitride than to a sapphire substrate. 2. As will be described later, the crystal structure at a specific crystal plane is similar to that of hexagonal group III nitride. 3. The melting point is as high as 2080 ° C., and no phase transition is observed in the temperature range from the melting point to 110K. 4. High electrical conductivity is obtained by doping with impurities.

Therefore, the strontium titanate (SrTiO ₃ ) substrate 100 doped with impurities can be used to grow a group III nitride crystal thereon, and furthermore, it has an electric conductivity not found in an insulating substrate such as sapphire. It becomes a conductive substrate which also has conductivity.

First, the (111) SrTiO ₃ crystal will be considered. [1] (111) SrTiO ₃ crystal. The (111) crystal of SrTiO ₃ has the structure shown in FIGS. The (111) plane crystal of SrTiO ₃ has two types of planes, an A plane in which Sr and O atoms are mixed as shown in FIG. 3 and a B plane in which only Ti atoms are present as shown in FIG. Are stacked in the order of ABABABA.

Here, attention is paid to the side A. Sr atoms and O atoms on the A plane form a hexagon as shown in FIG.
When the length of the side of this hexagon is estimated, a = 2.76 °.

On the other hand, as an example of hexagonal group III nitride, G
On the (0001) plane of aN, Ga atoms (or N
Atoms) form a hexagon, and a = 3.189 °.

When the SrTiO ₃ crystal and the GaN crystal are compared, they form the same hexagon, and the lengths of the sides are similar. Considering that Sr atoms and O atoms forming a hexagon on the SrTiO ₃ (111) A plane are bonded to Ga atoms or N atoms on the (0001) plane of the group III nitride, Lattice irregularity Δa
Δa = [a (GaN) −a (substrate)] / a (substrate) (where a (GaN) is the lattice constant of the GaN crystal and a
When (substrate) is defined by the lattice constant of the substrate, Δa = 15.5% with respect to the lattice constant a of SrTiO ₃ (111).

This lattice mismatch shows a smaller value than 16.1% of the lattice mismatch between the GaN and the sapphire substrate described above. Therefore, hexagonal GaN easily grows on the (111) SrTiO ₃ crystal plane.

[2] Regarding (001) SrTiO ₃ crystal. The (001) crystal of SrTiO ₃ has a structure as shown in FIGS. That is, the A surface where Sr atoms and O atoms are mixed, and the B surface where Ti atoms and O atoms are mixed.
.. Are stacked in the order of ABABA. Attention is paid to the surface A at this time, and it is understood that the Sr atoms and the O atoms form a hexagon. Focusing on the B-plane, it can be seen that Ti atoms and O atoms form a hexagon.

The hexagon is distorted as shown in FIGS. 5 and 6, and when the length of the side of the hexagon is estimated, a
1 = 3.905 ° and a2 = 2.76 °.

[0077] Thus, a SrTiO ₃ (001) plane, the size of the lattice mismatch of the hexagonal GaN (0001) plane, using the above-described defining equation, with respect to the lattice constant a1 of SrTiO ₃ (001), Δa = -18.3%, SrTiO
₃ Δa = 15.5 for lattice constant a2 of (001)
%. a1 is larger than the sapphire substrate,
Since the directions of the lattice irregularities are opposite to each other and the magnitudes thereof are substantially the same, the magnitude of the lattice irregularity in the case of GaN on the sapphire substrate is isotropic and Δa = 16.1%. This indicates that the strain between the substrate and the GaN crystal plane may be reduced.

[3] Regarding (110) SrTiO ₃ crystal. The crystal of the (110) plane of SrTiO ₃ has a structure as shown in FIGS. That is, two types of planes, that is, an A plane in which Sr atoms, Ti atoms, and O atoms are mixed, and a B plane including only O atoms are stacked in the order of ABABA.
Focusing on the surface A at this time, it can be seen that the Sr atoms and the Ti atoms form a hexagon.

This hexagon is distorted, and when the lengths of the sides of the hexagon are estimated, a1 = 3.905 ° and a2 = 3.
382Å.

[0080] Thus, a SrTiO ₃ (110) plane, the size of the lattice mismatch of the hexagonal GaN (0001) plane, using the above-described defining equation, with respect to the lattice constant a1 of SrTiO ₃ (110), Δa = -18.3%, SrTiO
_{3 For} a lattice constant a2 of (110), Δa = -5.7
%. Although the lattice irregularity of the lattice constant a1 is larger than that of the sapphire substrate, the lattice irregularity of the lattice constant a2 is -5.7.
%, And it is possible to grow crystals.

Here, GaN was considered as an example of hexagonal group III nitride, but BN (a = 3.
905), AlN (a = 3.111), InN (a
= 3.533 °), and the mixed crystal can be similarly grown.

In the case of cubic group III nitride,
For example, since the lattice constant of cubic GaN is about 4.5 °, the lattice mismatch with the lattice constant of 3.905 ° of SrTiO ₃ is Δa = 15%. This value is used for the GaAs substrate or S
Compared with the i-substrate, GaAs has a lattice constant of 5.653.
Å, the lattice irregularity is Δa = -20.4%, Si has a lattice constant of 5.4309 °, the lattice irregularity is Δa = 16-16.5%, and SrTiO ₃ is smaller. Therefore, cubic GaN
Can be grown as a crystal. Other cubic crystals III
Crystal growth of group nitride can be performed similarly.

SrTiO_ThreeWith respect to the electrical conductivity of
rTiO_ThreeDoped with impurities has electrical conductivity
Is shown. For example, 0.05 wt% of Nb is doped.
The resistivity is 0.08Ωcm, 0.5wt%
The resistivity of the material becomes 0.0065 Ωcm. Ma
In addition, the one doped with 5.0 at% of La is 1.2 × 1
0 ^{twenty one}cm^ThreeHigh charge density and conductivity comparable to metal conduction
Shows conductivity.

Next, as a preferred example in the present embodiment, the strontium titanate (SrTiO ₃ ) single crystal substrate 100 has an electric resistivity of 0.5 Ωcm or less.

Strontium titanate (SrTiO ₃ )
Further, for example, those doped with about 0.001 wt% or more of Nb and those doped with about 0.04 wt% or more of La have a resistivity of 0.5 Ωcm or less.

The case where the group III nitride semiconductor multilayer structure of the present embodiment is applied to a light emitting device will be considered. The resistance of the element is
In a device fabricated on a substrate such as sapphire, the resistance of the group III nitride semiconductor laminated structure and the resistance of the electrode become the resistance of the element. However, in the case of an element in which an electrode is formed on the back surface of the substrate, the electric resistance of the substrate is also included in the element resistance. Therefore, when the electric resistance of the substrate is high, the voltage drop at the substrate cannot be ignored, which leads to an increase in the operating voltage. Also, when the substrate resistance is high, the heat generated by the substrate significantly deteriorates the element performance. Therefore, the lower the resistance of the substrate, the better. A group III nitride semiconductor laser fabricated on a conventional insulating substrate,
At present, the resistance of an element that continuously oscillates at room temperature is about several Ω to about ten and several Ω.

Since the electrical resistance of the laminated structure constituting the semiconductor laser is about several Ω, the resistance of the substrate is several Ω or less, specifically, about 5 Ω or less in order to realize continuous oscillation at room temperature.
Desirably, it should be 1 Ω or less, more preferably 0.1 Ω or less.

The resistivity ρ is expressed as ρ = R · S / l, where R is the substrate resistance, S is the substrate area, and l is the substrate thickness.

Usually, the thickness of the substrate is 100 μm to 300 μm.
m, so that the element area is about 300 × 300 μm ² and R = 5Ω, the resistivity ρ is ρ = 0.5Ωc
m. For R = 1Ω, ρ = 0.03 to 0.09
For about Ωcm and R = 0.1Ω, ρ = 0.003 to 0.
It becomes about 009 Ωcm.

Therefore, as in the preferred example of this embodiment,
By using a strontium titanate (SrTiO ₃ ) single crystal substrate 100 having a resistivity ρ of 0.5Ωcm or less, a semiconductor laminated structure capable of manufacturing a semiconductor laser that continuously oscillates at room temperature is obtained.

As a preferred example of the present embodiment, II
The group I nitride semiconductor is a single crystal, and the crystal system is hexagonal.

In the group III nitride semiconductor, a cubic crystal having a zinc blende structure and a hexagonal crystal having a wurtzite structure grow depending on the substrate structure on which the crystal is grown. Among them, the cubic system has a metastable structure, and hexagonal crystals are often mixed depending on crystal growth conditions. The hexagonal system having a wurtzite structure is a stable layer, and a high-quality semiconductor laminated structure with good crystallinity can be formed. As described above, the hexagonal group III nitride single crystal layer, which is a stable layer, is formed from strontium titanate (SrTiO ₃ ) having electrical conductivity.
A structure in which at least one layer is stacked over the single crystal substrate 100 is preferable.

In the preferred embodiment of the present invention, the single crystal substrate is made of strontium titanate (SrTiO ₃ ) having a (111) plane as a main surface and having electrical conductivity.

As described above, the (111) plane of strontium titanate (SrTiO ₃ ) has a hexagonal crystal (0
Since it has a structure similar to the (001) plane, the (0001) plane of the hexagonal group III nitride semiconductor single crystal is easily epitaxially grown. For example, the lattice mismatch between the (0001) plane of hexagonal GaN and the (111) plane of SrTiO ₃ is Δa = 15.5%, and the (0)
(001) plane, (001) plane of SrTiO ₃ or (11) plane.
0) Smaller than when using a plane. Therefore, the introduction of defects due to lattice mismatch is suppressed more than when hexagonal GaN is grown on these substrates, and a high-quality GaN crystal can be grown.

Further, as a preferred example of the present embodiment,
Strontium titanate (SrTiO ₃ ) single crystal substrate 1
00 is strontium titanate (SrTiO ₃ ) doped with La.

Strontium titanate (SrTiO ₃ )
Shows electrical conductivity when doped with impurities. A typical impurity is Nb. The Nb doping is about 0.001 wt% doping, the resistivity is about 0.5 Ωcm, and the doping about 1 wt% can reduce the resistivity to about 0.003 Ωcm. This value is substantially equal to the resistivity of a substrate used in a semiconductor laser such as an AlGaInP system.

On the other hand, La used in the present embodiment
Doped strontium titanate (SrTiO
₃ ) can reduce the resistivity further than that doped with Nb. La is doped with about 0.04 wt% and has a resistivity of about 0.5 Ωcm and about 3.7
With a doping of 3 wt% (5.0 at%), the charge density becomes 1.
Equivalent to metal conduction of 2 × 10 ²¹ cm, resistivity is about 0.0
006 Ωcm.

This value is equal to or less than the resistivity of a substrate used in a semiconductor laser such as an AlGaInP-based semiconductor laser. As described above, the resistivity of the substrate is about 0.5 Ωcm in order to continuously oscillate the group III nitride semiconductor laser at room temperature.
It must be: Therefore, the doping amount of La is about 0.04 wt% or more, preferably about 0.1 wt%.
(About 0.1 Ωcm) or more, more preferably about 0.5
wt% (about 0.01 Ωcm), more desirably,
It is preferably about 1.0 w% (about 0.003 Ωcm) or more.

Therefore, in a semiconductor multilayer structure in which a group III nitride multilayer structure is formed on a strontium titanate (SrTiO ₃ ) single crystal substrate 100 doped with La, the substrate resistance is changed to a substrate used in a semiconductor laser of AlGaInP type or the like. Can be reduced to a value equal to or less than the resistivity of the light emitting element, and the effect in manufacturing a light emitting element requiring a large current, such as a semiconductor laser, is great.

A configuration example covering these preferred examples will be described with reference to FIG. The semiconductor laminated structure of the present embodiment
SrTiO ₃ substrate 10 doped with 5.0 at% of La
It has a structure in which a single layer of a hexagonal Al _0.15 Ga _0.85 N layer 101 is stacked as a group III nitride semiconductor layer on the (111) plane of 0. The C axis of the Al _0.15 Ga _0.85 N layer 101 is S
The single crystal is grown so as to be perpendicular to the main surface of the rTiO ₃ substrate 100, and the (0001) plane is the main surface. The Al _0.15 Ga _0.85 N layer 101 is doped with Si and has n-type electric conductivity.

The surface of Al _0.15 Ga _0.85 N layer 101 and SrT
It was confirmed that when an electrode was formed on the back surface of the iO ₃ substrate 100 and a voltage was applied, a current flowed and there was continuity.

In the semiconductor laminated structure of the present embodiment, a laminated structure of a light emitting element can be further grown thereon, and electrodes of the light emitting element can be formed on the back surface of the substrate.

Note that the Al _0.15 Ga _0.85 N layer 101
It was grown by the E method.

A second embodiment of the present invention will be described with reference to FIG. In the present embodiment, at least one electrically conductive buffer layer 20 deposited on a strontium titanate (SrTiO ₃ ) single crystal substrate 200 in the semiconductor multilayer structure described in the first embodiment is used.
1 and the buffer layer 201
Is a semiconductor laminated structure having at least one group III nitride semiconductor layer 202 grown by crystal growth at a temperature higher than the deposition temperature.

The buffer layer 201 may be deposited as amorphous, polycrystalline, microcrystalline, or the like, as long as the high-temperature layer laminated thereon becomes a single crystal.
It does not need to be a Group I nitride. Also, the buffer layer 201
Has electrical conductivity, the substrate 200 and the semiconductor layer 20
The electrical conductivity between the two is not impaired.

A more specific configuration example will be described. The semiconductor laminated structure of the present embodiment has a structure in which an n-type Al _0.07 Ga _0.93 N buffer layer 201 and a group III nitride semiconductor layer are formed on a (111) plane of a SrTiO ₃ substrate 200 doped with 5.0 at% of La. It has a structure in which a single n-type GaN layer 202 is stacked.

The GaN layer 202 is a single crystal grown so that the C axis is perpendicular to the main surface of the substrate and the (0001) plane is the main surface.

The laminated structure was laminated by the MOCVD method.
The buffer layer is at 520 ° C. and the GaN layer 202 is at 1050 ° C.
Was laminated. In addition, Al _0.07 Ga _0.93 N buffer layer 2
01, the GaN layer 202 is doped with Si and has n-type electrical conductivity.

In such a configuration, the GaN layer 202
It was confirmed that when electrodes were formed on the front surface and the back surface of the SrTiO ₃ substrate 200 and a voltage was applied, a current flowed and there was continuity.

In the semiconductor laminated structure of the present embodiment, it is possible to crystal-grow a laminated structure of a light emitting element thereon, and it is also possible to form electrodes of the light emitting element on the back surface of the substrate.

A third embodiment of the present invention will be described with reference to FIG. In the present embodiment, the buffer layer 30 in the semiconductor laminated structure described in the second embodiment is used.
1 and the group III nitride semiconductor layer 303, having the same electrical conductivity type as the buffer layer 301, at a temperature higher than the deposition temperature of the buffer layer 301 and lower than the growth temperature of the group III nitride semiconductor layer 303. This is a semiconductor multilayer structure having at least one intermediate layer 302 grown by crystal.

The intermediate layer 302 prevents the exposed surface of the substrate 300 which is not covered with the buffer layer 301 from being decomposed by exposure to a reducing atmosphere at a high temperature when crystal growth is performed by MOCVD or the like. One of the purposes. By laminating the intermediate layer 302, flattening of the surface and improvement of crystallinity are expected.

Although the composition of the intermediate layer 302 is not particularly limited, an intermediate layer having good crystallinity can be grown using InGaN which can grow a crystal at a low temperature. Also, the middle layer 3
By changing the composition of the high-temperature layer to 02, the propagation of dislocations at the interface is suppressed, and a high-temperature layer with better crystallinity grows.

A more specific configuration example will be described. The semiconductor laminated structure of the present embodiment has an n-type Al _0.07 Ga _0.93 N buffer layer 301 on a (111) plane of a SrTiO ₃ substrate 300 doped with 5.0 at% of La, and a hexagonal In _0.1 as an intermediate layer. Ga _{0 .9} N layer 302 are stacked one layer further GaN layer 303 of hexagonal thereon has one layer stacked structure.

The crystal growth was performed by MOCVD. Al _0.07
The Ga _0.93 N buffer layer 301 has an In _0.1 G
The a _0.9 N layer 302 is at 800 ° C. and the GaN layer 303 is at 10 ° C.
Lamination was performed at 50 ° C. The GaN layer 303 is a single crystal grown so that the C-axis is perpendicular to the main surface of the substrate, and the (0001) plane is the main surface. The surface morphology is flat with few irregularities. Al _0.07 Ga _0.93 N buffer layer 301, In _0.1 Ga _{0 .9} N layer 302, GaN layer 303
Is doped with Si and has n-type electrical conductivity.

In such a configuration, the GaN layer 303
It was confirmed that an electrode was formed on the front surface and the back surface of the SrTiO ₃ substrate 300, and when a voltage was applied, a current flowed and there was continuity.

In the semiconductor laminated structure of the present embodiment, it is possible to crystal-grow a laminated structure of a light emitting element thereon, and it is also possible to form an electrode of the light emitting element on the back surface of the substrate.

A fourth embodiment of the present invention will be described with reference to FIG. In the present embodiment, in the laminated structure as in the second or third embodiment, the buffer layer is made of hexagonal n-type ZnO.

The n-type ZnO has a carrier concentration of (4 to 6)
If it exceeds × 10 ¹⁸ cm ^-3 , the electric conduction mechanism causes metal conduction, so that the conductivity between the group III nitride laminated structure and the substrate is improved when n-type ZnO having a high carrier concentration is used for the buffer layer. . ZnO having a carrier concentration of 1 × 10 ¹⁹ cm ⁻³ or more can be easily deposited, and can be easily deposited by a sputtering method or the like.

The crystal system is also the same hexagonal system as the group III nitride stable layer, and has a lattice constant close to that of the group III nitride.
Since lattice matching is _achieved with In _0.22 Ga _0.78 N, high-quality III
A group nitride single crystal laminated structure can be crystal-grown.

A specific configuration example of the present embodiment will be described with reference to FIG. The semiconductor laminated structure of the present embodiment is represented by L
SrTiO ₃ substrate 400 doped with 5.0 at% a
The n-type ZnO buffer layer 401 and _one hexagonal In _0.1 Ga _0.9 N layer 402 as an intermediate layer are stacked on the (111) plane, and a hexagonal GaN layer 403 is further formed thereon. It has a laminated structure. The GaN layer 403 is grown such that the C axis is perpendicular to the main surface of the substrate, and (000
1) The surface is laminated with the main surface.

Further, a selective growth mask 404 made of SiO ₂ is formed on the GaN layer 403, and a GaN layer 405 is formed thereon. Selective growth mask 4
04 is formed in a stripe pattern at a period of 10 μm, and has an opening having a width of 3 μm.

The GaN layer 405 has a selective growth mask 404.
Selective growth on the surface of the GaN layer 403 exposed at the opening of the substrate, laterally growing the surface of the selective growth mask 404 laterally, the adjacent crystals are united, and the crystal growth is continued, so that the flat GaN surface is obtained. It is a layer 405.
The GaN layer 405 was grown by about 20 μm.

Incidentally, ZnO having a carrier concentration of 1 × 10 ¹⁹ cm ⁻³ was deposited by sputtering. The group III nitride crystal was grown by MOCVD. In _0.1 Ga _0.9 N layer 4
02 is 800 ° C, other group III nitrides are 1050 ° C
Was laminated. In addition, the In _0.1 Ga _0.9 N layer 402 and the Ga
The N layer 403 and the GaN layer 405 are doped with Si and have n-type electric conductivity.

The GaN layer 405 formed on the selective growth mask 404 made of SiO ₂ has another dislocation density of 1
While it was about 0 ¹⁰ cm ^-2 , it was reduced to about 10 ⁷ cm ^-2 . Also, the surface of the GaN layer 405 and SrTiO ₃
When an electrode was formed on the back surface of the substrate 400 and a voltage was applied, current flowed, and it was confirmed that there was continuity.

A fifth embodiment of the present invention will be described with reference to FIG. The present embodiment is applied to a light emitting element having a semiconductor multilayer structure including the semiconductor multilayer structure as in the first to fourth embodiments described above and including at least one p-type layer and at least one n-type layer. It is an example.

The light-emitting element of this embodiment may be any light-emitting element such as a light-emitting diode, a semiconductor laser, and a superluminescent diode, and the electrodes corresponding to the p-type layer and the n-type layer of the light-emitting element. When a current is applied to the pn junction, any current may be injected into the pn junction and light may be emitted by recombination of carriers.

The structure of the light emitting device is not particularly limited.
A group III nitride semiconductor multilayer structure having at least one mold layer, at least one pn junction, a current is injected into the pn junction, and light is emitted by recombination of carriers. If so, a homojunction, a single heterojunction, a double heterojunction, a quantum well structure, a multiple quantum well structure, or any other structure may be used.

A specific configuration example of the present embodiment will be described with reference to FIG. This specific example shows a configuration example of a light emitting diode as a light emitting element, and FIG. 12 is a cross-sectional view of the light emitting diode taken along a plane perpendicular to a substrate. The structure of this light-emitting diode is such that n is formed on a (111) plane of a SrTiO ₃ substrate 500 doped with 5.0 at% of La.
-Type Al _0.07 Ga _0.93 N buffer layer 501, n-type In _{0. 1} Ga _0.9 N layer 502 of hexagonal are laminated one layer as an intermediate layer, further n hexagonal as the n-type cladding layer thereon
Type Al _0.15 Ga _0.85 N layer 503 and In _{0.15 serving as} an active layer
Ga _0.85 N layer 504, p-type Al serving as p-type cladding layer
_It has a structure in which a _0.15 Ga _0.85 N layer 505 and a p-type GaN layer 506 to be a p-type contact layer are sequentially laminated.

The stacked structure is grown so that the C axis is perpendicular to the main surface of the substrate 500, and the (0001) plane is the main surface. P-type GaN layer 5 on the top of the stacked structure
On p. 06, a p-side ohmic electrode 507 is formed. Then, leaving the laminated structure in a stripe shape,
The n-side ohmic electrode 508 is formed on the exposed surface of the substrate 500 by dry etching to 0.

Note that the laminated structure to be a light emitting diode is M
The crystal was grown by OCVD. The n-side ohmic electrode 508 is formed by evaporating Ti / Al on the substrate surface, and the p-side ohmic electrode 507 is formed of Ni / Au.
Was formed by vapor deposition on p-GaN.

In the light emitting diode, by injecting a current into the p-side ohmic electrode 507 and the n-side ohmic electrode 508, carriers are injected into the active layer to emit light.

A specific effect of this embodiment is that, since the substrate 500 is conductive and has low resistance, an electrode is formed directly on the substrate 500 without forming a conventionally required n-type contact layer. Can be. Therefore, it is possible to reduce the amount of raw material and process time required for laminating the n-type contact layer.

A sixth embodiment of the present invention will be described with reference to FIG. This embodiment relates to a light-emitting element such as the above-described fifth embodiment, in which electrodes are formed on both surfaces of the laminated structure, that is, on the surface of the laminated structure laminated on the substrate and the back surface of the substrate. Here is an example of application to

The light-emitting element of this embodiment may be any light-emitting element such as a light-emitting diode, a semiconductor laser, and a superluminescent diode. When a current is applied, a current is injected into the pn junction, and light may be emitted as a result of recombination of carriers.

The layer structure is not particularly limited either, and the laminated structure forming the light emitting device is a group III nitride semiconductor laminated structure having at least one p-type layer and at least one n-type layer. If the structure has one pn junction, a current is injected into the pn junction, and light is emitted by recombination of carriers, a homojunction, a single heterojunction, a double heterojunction, a quantum well structure, a multiple A quantum well structure or any other structure may be used.

FIG. 13 shows a specific configuration example of this embodiment.
It will be described with reference to FIG. In this specific example, the light emitting element emits light.
FIG. 13 shows a configuration example of a diode, and FIG.
FIG. 4 shows a cross-sectional view of a plane perpendicular to the substrate of the iodine. Book
In the structure of the light emitting diode of the embodiment, La is 5.0 at.
% Doped SrTiO_Three(111) of the substrate 600
N-type Al_0.07Ga_0.93N buffer layer 601, middle
Hexagonal n-type In as interlayer_0.1Ga_0.9N layer 602
One layer is laminated, and an n-type clad layer is further formed thereon.
Orthogonal n-type Al_0.15Ga_0.85N layer 603, active layer
In_0.15Ga _0.85N layer 604, becomes p-type cladding layer
p-type Al_0.15Ga_0.85N layer 605, p-type contact layer
Has a structure in which p-type GaN layers 606 are sequentially stacked.

The stacked structure is grown so that the C axis is perpendicular to the main surface of the substrate, and the (0001) plane is the main surface. A p-side ohmic electrode 607 is provided on the p-type GaN layer 606 above the stacked structure,
An n-side ohmic electrode 608 is formed on the back surface.
The dimensions of the light emitting diode are 300 μm (vertical) x 300 μm
(Width) × 200 μm (height).

[0139] The layered structure of the light emitting diode is M
The crystal was grown by OCVD. The n-side ohmic electrode 608 is formed by evaporating Ti / Al on the substrate surface, and the p-side ohmic electrode 607 is formed of Ni / Au.
Was formed by vapor deposition on p-GaN.

In the light emitting diode, by injecting a current into the p-side ohmic electrode 607 and the n-side ohmic electrode 608, carriers are injected into the active layer to emit light.

As a special effect of the present embodiment, the substrate resistance R is as small as about 0.013 Ω because the resistivity of the substrate 600 is about 0.0006 Ωcm. for that reason,
Even if the electrode 608 is formed on the back surface of the substrate 600, there is almost no voltage drop in the substrate 600, and high output operation can be performed with low power consumption. Conventional face-down mounting is also possible.

A seventh embodiment of the present invention will be described with reference to FIG. This embodiment includes a semiconductor laser as a light emitting device having a semiconductor multilayer structure including the semiconductor multilayer structure as in the above-described first to fourth embodiments and including at least one p-type layer and at least one n-type layer. It is an example of application to

In the semiconductor laser of this embodiment, the electrodes are formed on the front side and the back side of the substrate, respectively. In this semiconductor laser, when a current is applied to the electrodes corresponding to the p-type and n-type layers, the current is injected into the active layer, light is emitted by recombination of carriers, and light is reflected and amplified by the laser resonator surface. Occurs, and stimulated emission light is extracted to the outside.

The layer structure of the semiconductor laser is not particularly limited, and the laminated structure forming the semiconductor laser has at least one p-type layer and at least one n-type layer.
It has a layered structure of group I nitride semiconductor and has an active layer.Current is injected into this active layer, light is emitted by recombination of carriers, light reflection and amplification are caused by the laser cavity surface, and stimulated emission light is generated. As long as the structure can be taken out, a homojunction, a single heterojunction, a double heterojunction, a quantum well structure, a multiple quantum well structure, or any other structure may be used.

A specific configuration example of the semiconductor laser according to the present embodiment will be described with reference to FIGS. FIG. 14 is a perspective view of the semiconductor laser, and FIG. 15 is a cross-sectional view taken along a plane perpendicular to the light emission direction.

The semiconductor laser according to the present embodiment is the fourth embodiment.
Formed on the semiconductor multilayer structure manufactured in the embodiment.
You. That is, SrTiO doped with 5.0 at% of La
_ThreeOn the (111) plane of the substrate 700, an n-type ZnO buffer
Layer 701, n-type In of intermediate layer _0.1Ga_0.9N layer 702, high
An n-type GaN layer 703 of a thermal layer is sequentially laminated, and further
And SiO_TwoForming a selective growth mask 704 made of
GaN layer 70 exposed at the opening of selective growth mask 704
Selective growth and surface of selective growth mask 704
Semiconductor consisting of n-type GaN layer 705 formed by Lall growth
Semiconductor laser stacked structure is fabricated on
You.

The semiconductor laser structure has an n-type Al _0.2 Ga _0.8
N clad layer 706, n-type GaN light guide layer 707, I
n _0.05 Ga _0.95 N / In _0.15 Ga _0.85 N quantum well active layer 708, p-type GaN light guide layer 709, p-type Al _0.2 Ga
_The stacked structure 7000 including the _0.8 N cladding layer 710 and the p-type GaN cap layer 711 is combined with the p-type GaN cap layer 71.
A portion of the p-type Al _0.2 Ga _0.8 N cladding layer 710 is etched while leaving it in the form of a stripe to form a current-confined ridge waveguide structure 720. The current constriction ridge waveguide structure 720 is formed on the selective growth mask 704 along the stripe direction of the mask.

An insulating film 712 made of SiO ₂ is formed on the surface of the laminated structure. Insulating film 7 on ridge 720
12 has an opening. A p-side ohmic electrode 713 is formed on the surface of the p-type GaN cap layer 711 exposed at the opening. SrTiO ₃ substrate 70
An n-side ohmic electrode 714 is formed on the back surface of the zero.

Optical resonator surfaces 7001 and 7002 are formed perpendicular to the ridge 720 and the active layer 708. The optical resonator surfaces 7001 and 7002 have a current constriction ridge waveguide structure 72.
It is formed by dry-etching the laminated structure 7000 perpendicularly to 0 and substantially perpendicular to the active layer.

It is to be noted that a laminated structure 7000 serving as a laser structure is provided.
Was grown by MOCVD. Further, the n-side ohmic electrode 714 is formed by evaporating Ti / Al on the back surface of the substrate, and the p-side ohmic electrode 713 is formed of Ni-Au by p-G
It was formed by vapor deposition on aN.

In such a configuration, by injecting current into the p-side ohmic electrode 713 and the n-side ohmic electrode 714, carriers are injected into the active layer 708, light emission and light amplification occur, and the optical resonator Faces 7001, 70
02, laser beams 7101 and 7102 are emitted.

As a special effect of the present embodiment, since the resistivity of the substrate 700 is about 0.0006 Ωcm, the substrate resistance R is very small at about 0.0013 Ω. Therefore, even if the electrode 714 is formed on the back surface of the substrate 700,
There is almost no voltage drop at 0, and high output operation is possible with low power consumption. In addition, since conventional face-down mounting in which the semiconductor laser side is mounted on a heat sink is also possible,
The heat radiation characteristics are improved, and high output operation is possible.

[0153]

According to the semiconductor laminated structure according to the first aspect of the present invention, strontium titanate (S) having electrical conductivity is provided.
Since a single crystal substrate of rTiO ₃ ) is used, a semiconductor laminated structure having a conductive substrate, which has been difficult in the past, is obtained. As a result, electrical conduction between the substrate and the group III nitride laminated structure is reduced. It is possible to crystallize a stacked structure of a light emitting element on this semiconductor stacked structure, and it is possible to realize a structure in which electrodes are formed on the substrate side, which cannot be realized with an insulating substrate such as a sapphire substrate. A light-emitting element can be realized.

According to the second aspect of the present invention, for example, a semiconductor laminated structure capable of manufacturing a semiconductor laser which continuously oscillates at room temperature is obtained.

According to the third aspect of the present invention, a semiconductor laminated structure having good crystallinity in which hexagonal single crystals, which are stable layers of a group III nitride, are laminated, is provided. In addition to the effects of the invention, a light-emitting element using a group III nitride laminated structure having high quality crystallinity laminated on a conductive substrate can be formed.

According to the invention described in claim 4, according to claim 1,
In addition to the functions and effects of the invention described in 2 or 3, the (111) plane of strontium titanate (SrTiO ₃ ) has a structure similar to the (0001) plane of the hexagonal crystal. Group III nitride semiconductor single crystal (000
1) The plane is easily epitaxially grown, and for example, the (0001) plane of hexagonal GaN and the (11) plane of SrTiO ₃
1) The lattice mismatch with the plane is Δa = 15.5%, and the (0001) plane of sapphire and the (00) plane of SrTiO ₃
Since growth is smaller than when 1) or (110) planes are used, growing crystals on the (111) plane suppresses the introduction of defects due to lattice mismatching when growing hexagonal GaN on these substrates. GaN crystals of high quality can be grown.

According to the fifth aspect of the present invention, in the semiconductor laminated structure according to any one of the first to fourth aspects, L
The charge density is 1.2 × 10 ²¹ c by doping a.
m can be increased to a level comparable to metal conduction, and the resistivity can be reduced to about 0.0006 Ωcm. Since this value is equal to or lower than the resistivity of a substrate used in a semiconductor laser such as an AlGaInP-based semiconductor laser, La-doped strontium titanate (SrTi
In a semiconductor multilayer structure in which a group III nitride multilayer structure is formed on an O ₃ ) single crystal substrate, the substrate resistance can be reduced to a value equal to or lower than the resistivity of a substrate used in a semiconductor laser such as an AlGaInP system. In addition, a light-emitting element requiring a large current, such as a semiconductor laser, can be manufactured.

According to the sixth aspect of the present invention, there is provided the semiconductor laminated structure according to any one of the first to fifth aspects, wherein the conductivity between the substrate and the semiconductor layer is not impaired. be able to.

According to the seventh aspect of the present invention, in the semiconductor laminated structure according to the sixth aspect, when crystal growth is performed by MOCVD or the like, the exposed substrate surface not covered with the buffer layer is exposed to a reducing atmosphere at a high temperature. Decomposition due to exposure to water can be suppressed, and by laminating the intermediate layer, surface flattening and improvement in crystallinity can be expected, and by changing the composition of the intermediate layer and the high-temperature layer, It is possible to suppress the propagation of dislocations at the interface and grow a high-temperature layer with better crystallinity. Further, since the intermediate layer and the buffer layer have the same electric conduction type, the substrate and the high-temperature layer It is possible to provide a semiconductor laminated structure having conduction between them.

According to the eighth aspect of the present invention, in the semiconductor laminated structure according to the sixth or seventh aspect, the n-type ZnO has an electric conduction property when the carrier concentration exceeds (4 to 6) × 10 ¹⁸ cm ^−3. Since the mechanism causes metal conduction, the conductivity between the group III nitride laminated structure and the substrate can be improved by using n-type ZnO having a high carrier concentration for the buffer layer. It has the same hexagonal system as the stable layer of group nitride, has a lattice constant close to that of group III nitride, and has an In _0.22
Since lattice matching is _achieved with Ga _0.78 N, a high-quality group-III nitride single crystal laminated structure can be grown as in the case of using a group III nitride buffer layer.

According to the light emitting device of the ninth aspect,
A semiconductor laminated structure according to any one of claims 1 to 8, a laminated structure including at least one p-type layer and at least one n-type layer, wherein the substrate is made conductive. In addition, it is possible to form an electrode on a substrate, which has been difficult in the past.

According to the tenth aspect, the ninth aspect is provided.
Regarding the light emitting device described, by making the substrate conductive, it is possible to form electrodes on the back surface side of the substrate, which was difficult in the past, thereby enabling the conventional mounting method and the light emitting device side. This facilitates face-down mounting of the light-emitting device on a heat sink material, increases the heat dissipation efficiency during high-output operation, and can realize a light-emitting element capable of high-temperature and high-output operation.

According to the eleventh aspect, by making the substrate conductive, it is possible to form an electrode on the back surface of the substrate, which has been difficult in the prior art.
Face-down mounting, in which the semiconductor laser side is mounted on a heat sink material, is facilitated, and the radiation efficiency during high-power operation can be increased. As a result, a semiconductor laser capable of high-temperature, high-power operation can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a plane perpendicular to a substrate of a semiconductor multilayer structure according to a first embodiment of the present invention.

FIG. 2 is a crystal structure diagram of the SrTiO ₃ .

FIG. 3 is a view showing an arrangement of atoms on an A-plane of a (111) crystal of SrTiO ₃ .

FIG. 4 is a diagram showing an arrangement of atoms on a B-plane of a (111) crystal of SrTiO ₃ .

FIG. 5 is a view showing the arrangement of atoms on the A-plane of the (001) crystal of SrTiO ₃ .

FIG. 6 is a diagram showing an arrangement of atoms on a B-plane of a (001) crystal of SrTiO ₃ .

FIG. 7 is a diagram showing the arrangement of atoms on the A-plane of the (110) crystal of SrTiO ₃ .

FIG. 8 is a diagram showing an arrangement of atoms on a B-plane of a (110) crystal of SrTiO ₃ .

FIG. 9 is a cross-sectional view of a plane perpendicular to a substrate having a semiconductor multilayer structure according to a second embodiment of the present invention.

FIG. 10 is a cross-sectional view of a plane perpendicular to a substrate having a semiconductor multilayer structure according to a third embodiment of the present invention.

FIG. 11 is a cross-sectional view of a plane perpendicular to a substrate having a semiconductor multilayer structure according to a fourth embodiment of the present invention.

FIG. 12 is a cross-sectional view of a light-emitting element according to a fifth embodiment of the present invention, taken along a plane perpendicular to a substrate.

FIG. 13 is a cross-sectional view of a plane perpendicular to a substrate of a light-emitting element according to a sixth embodiment of the present invention.

FIG. 14 is a perspective view of a semiconductor laser according to a seventh embodiment of the present invention.

FIG. 15 is a cross-sectional view taken along a plane perpendicular to the light emission direction of the semiconductor laser.

FIG. 16 is a process chart showing a conventional method for manufacturing a GaN thick film substrate.

FIG. 17 is a cross-sectional view of a conventional semiconductor laser taken along a plane perpendicular to the light emission direction.

[Explanation of symbols]

100, 200, 300, 400, 500, 600, 7
00 SrTiO ₃ substrate 201, 301, 401, 501, 601, 701
Buffer layer 202, 302, 303, 402, 403, 405, 5
02,504,602,603,604,605,70
2,703,705,706,710,711 Group III nitride semiconductor layer 503 N-type layer 505 P-type layer 507,607,713 Electrode 508,608,714 Electrode

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference) 5F041 CA34 CA40 CA41 CA46 CA48 CA57 CA65 CA82 CA92 DA04 FF16 5F045 AA04 AA19 AB14 AB17 AB22 AD09 AD12 AD14 AF01 CA12 DA53 DA54 DA55 DA63 DA64 5F073 AA13 AA45 AA55 AA73 CB05

Claims (11)

[Claims] 1. A strontium titanate (SrTiO ₃ ) single crystal substrate having electrical conductivity, and at least one or more Al, B, Ga layers laminated on the strontium titanate (SrTiO ₃ ) single crystal substrate by crystal growth. , I
A semiconductor multilayer structure comprising: a group III nitride semiconductor layer containing at least one element of n and N. 2. The strontium titanate (SrTi)
2. The semiconductor multilayer structure according to claim 1, wherein the O ₃ ) single crystal substrate has an electric resistivity of 0.5 Ωcm or less. 3. The semiconductor multilayer structure according to claim 1, wherein said group III nitride semiconductor layer is a hexagonal single crystal. 4. The strontium titanate (SrTi)
4. The semiconductor multilayer structure according to claim 1, wherein the O ₃ ) single crystal substrate has a (111) plane as a main surface. 5. The strontium titanate (SrTi)
5. The semiconductor multilayer structure according to claim 1, wherein the O ₃ ) single crystal substrate is doped with La. 6. The strontium titanate (SrTi)
O ₃ ) at least one electrically conductive buffer layer deposited on a single-crystal substrate, and at least one of the at least one layer of crystals grown on the buffer layer at a temperature higher than the deposition temperature of the buffer layer. 6. The semiconductor multilayer structure according to claim 1, further comprising a group III nitride semiconductor layer. 7. The group III nitride semiconductor layer between the buffer layer and the group III nitride semiconductor layer, having the same electrical conductivity type as the buffer layer and higher than the deposition temperature of the buffer layer. 7. The semiconductor multilayer structure according to claim 6, further comprising at least one intermediate layer formed by crystal growth at a temperature lower than the growth temperature. 8. The buffer layer is made of hexagonal n-type ZnO.
The semiconductor multilayer structure according to claim 6, wherein: 9. A light-emitting device comprising a semiconductor laminated structure according to claim 1, a laminated structure comprising at least one p-type layer and at least one n-type layer. element. 10. The light emitting device according to claim 9, wherein electrodes are formed on both surfaces of the laminated structure. 11. The light emitting device according to claim 10, wherein the light emitting device is a semiconductor laser.