JP2010232549A - Nitride-based semiconductor device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride-based semiconductor device and a method of manufacturing the device, which can form a nitride-based semiconductor layer (an active layer of InGaN) at a high temperature on a substrate of an oxide, making it possible to achieve a high-quality nitride-based semiconductor layer. <P>SOLUTION: A nitride-based semiconductor device 10 includes a substrate 11 consisting of an oxide single crystal having a wurtzite structure, an oxide interfacial layer 12 formed on the substrate and consisting of an oxide including zinc (Zn) and at least either an element of group II or an element of group III, and an InGaN semiconductor layer 13 formed on the oxide interfacial layer. The oxide interfacial layer 12 is formed between the substrate 11 of the oxide and the InGaN semiconductor layer 13 of the nitride. Since the oxide interfacial layer 12 which is thermally stable and has an even thin thickness is interposed on the interface between the oxide single crystal substrate 11 and the InGaN semiconductor layer 13, the InGaN semiconductor layer 13 can be formed at a high temperature on the oxide single crystal substrate 11, and thus the InGaN semiconductor layer of a high quality can be obtained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nitride-based semiconductor device such as a semiconductor light-emitting device having a nitride-based semiconductor layer formed by growing on a substrate made of an oxide single crystal, and a method for manufacturing the same.

  Conventionally, a semiconductor light emitting element using InGaN is known as a semiconductor light emitting element emitting blue light (emission wavelength of 480 nm or less) (see, for example, Patent Document 1).

  By the way, in order to obtain longer wavelength green light emission with a semiconductor light emitting device using InGaN, it is conceivable to narrow the forbidden band width of the active layer by increasing the In composition ratio. However, when the In composition ratio is increased, phase separation occurs, and it becomes difficult to obtain an active layer having a uniform In composition, resulting in a decrease in luminous efficiency. Further, when a piezoelectric field is generated due to the crystal structure, there is a problem that the light emission recombination probability is lowered and the light emission efficiency is further lowered. In addition, since the lattice constant differs greatly from that of the substrate, there are a large number of threading dislocations, and there is a problem that the light emission efficiency is lowered and good reliability cannot be obtained.

  In order to suppress these, it is possible to use a substrate lattice-matched to an active layer of a nitride-based semiconductor such as InGaN or a cladding layer having a close lattice constant. Zinc oxide (ZnO) is suitable as a material for such a substrate and cladding layer.

When an InGaN layer is grown directly on a substrate made of zinc oxide (ZnO) single crystal, the interface between the ZnO single crystal substrate (oxide layer) and the InGaN layer (nitride layer) reacts, resulting in a steep interface. Therefore, there is a problem that a good crystal cannot be obtained as an active layer of a semiconductor light emitting device. The reason why InGaN layers with good crystallinity cannot be obtained is that In and Ga are interdiffused in the ZnO single crystal substrate, and Zn is interdiffused in the InGaN layer, and the steepness of the interface cannot be obtained. For example, a reaction layer (Ga ₂ ZnO ₄ ) is formed at the interface between the crystal substrate and the InGaN layer. By growing the InGaN layer at a low temperature, the diffusion of In and Ga and the formation of the reaction layer (Ga ₂ ZnO ₄ ) are suppressed. However, since the stacking fault is formed, the crystallinity of the InGaN layer is deteriorated. .

Conventionally, a technique for forming an InGaN layer on a ZnO single crystal substrate is known (see, for example, Non-Patent Document 1). In the prior art disclosed in Non-Patent Document 1, amorphous Al ₂ O ₃ is deposited at a low temperature (100 ° C.) by ALD (Atomic Layer Deposition) method before depositing nitride on the ZnO substrate by MOCVD method, Thereafter, heat treatment is performed at a high temperature (1100 ° C.) to recrystallize Al ₂ O ₃ and simultaneously form ZnAl ₂ O ₄ . That is, ZnO and amorphous Al ₂ O ₃ are reacted to convert a part of amorphous Al ₂ O ₃ into ZnAl ₂ O ₄ .

Japanese Patent Laid-Open No. 06-061527

MRS Symp.Proc.Vol.1035 L11-23 2007 Fall Meeting Nov. 26-30

By the way, in the conventional technique disclosed in Non-Patent Document 1, only a partial transition layer of amorphous Al ₂ O ₃ deposited on a ZnO single crystal substrate at a low temperature by the ALD method is crystallized into Al ₂ ZnO _4. If Al ₂ O ₃ having a different crystal structure or amorphous is present thereon, information such as the lattice constant of the ZnO single crystal substrate cannot be transmitted to the upper nitride semiconductor layer, particularly the InGaN layer. For this reason, an InGaN layer with good crystal quality cannot be formed, and threading dislocations and phase separation occur.
Accordingly, an object of the present invention is to form a nitride semiconductor layer (an active layer made of InGaN) on a ZnO substrate at a high temperature, and to obtain a high-quality nitride semiconductor layer and a nitride semiconductor device thereof It is to provide a manufacturing method.

  As a result of intensive studies, the inventors of the present invention are made of an oxide (for example, aluminum oxide), a nitride, or a metal (for example, an aluminum single layer) on a substrate composed of an oxide single crystal having a wurtzite structure. After depositing the precursor or nitride, the substrate and the precursor were reacted by heat treatment at a high temperature, and it was found that the interface reaction layer was formed as a crystal. This interface reaction layer is a thermally stable oxide interface layer. After forming this oxide interface layer, it was found that an upper layer (an active layer made of InGaN) can be grown on the oxide interface layer at a high temperature, and a high-quality nitride-based semiconductor layer can be obtained. The present invention has been made based on the above-described findings.

In order to solve the above problems, a nitride-based semiconductor device according to the first aspect of the present invention includes a substrate made of an oxide single crystal having a wurtzite structure, zinc (Zn) formed on the substrate, and And an oxide interface layer made of an oxide containing at least one of a group II element and a group III element, and gallium indium nitride [In x Ga 1-x N (0 <X <1)] and an active layer.
As used herein, “a substrate made of an oxide single crystal having a wurtzite structure” is a zinc oxide magnesium beryllium cadmium typified by zinc oxide (ZnO) [Zn 1-abc Mg a Be b
Cd c (0 ≦ a <1, 0 ≦ b <1, 0 ≦ c <1, a + b + c <1)] In addition to single crystal substrate, zinc magnesium oxide on sapphire (α-Al ₂ O ₃ ) substrate Beryllium cadmium [Zn 1-abc Mg a Be b Cdc (0 ≦ a <1, 0 ≦ b <1, 0 ≦ c <1, a + b + c <1)] epitaxially grown, LiGaO ₂ or MgAlO on a substrate made of an oxide of ₃ zinc oxide magnesium beryllium cadmium [Zn 1-abc Mg a Be b Cd c (0 ≦ a <1,0 ≦ b <1,0 ≦ c <1, a + b + c <1 )] Is included.

  In the nitride-based semiconductor device according to another aspect of the present invention, a pseudo lattice matching layer made of a nitride containing at least one of aluminum, gallium, or indium is formed between the oxide interface layer and the active layer. It is characterized by being.

  In the nitride semiconductor device according to another aspect of the present invention, the substrate is made of zinc magnesium beryllium cadmium [Zn 1-abc Mg a Be b Cdc (0 ≦ a <1, 0 ≦ b <1, 0 ≦ c <1, a + b + c <1)].

  In the nitride-based semiconductor device according to another aspect of the present invention, the oxide interface layer includes beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba) as group II elements. ) Or cadmium (Cd).

  In the nitride semiconductor device according to another aspect of the present invention, the oxide interface layer includes boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (as a group III element). Tl), scandium (Sc), yttrium (Y), lutetium (Lu), ytterbium (Yb), thulium (Tm), erbium (Er), or holmium (Ho).

  The nitride semiconductor device according to another aspect of the present invention is characterized in that the oxide interface layer has a thickness of one molecular layer (ML) or more and a critical thickness or less with respect to the substrate.

  The method for manufacturing a nitride-based semiconductor device according to the second aspect of the present invention includes a precursor made of any one of a predetermined nitride, oxide and metal on a substrate made of an oxide single crystal having a wurtzite structure. A precursor deposition step for depositing a body; and after depositing the precursor, a heat treatment is performed so that at least a part of the precursor deposited on the substrate reacts with the substrate to form an oxide interface layer. Forming an oxide interface layer, and forming an active layer made of gallium indium nitride [In x Ga 1-x N (0 <x <1)] on the oxide interface layer; , Provided.

According to the present invention, a thermally stable oxide interface layer is formed between a substrate made of oxide and an active layer made of nitride, whereby a nitride system is formed on the oxide substrate at a high temperature. A semiconductor layer can be formed, and a high-quality nitride semiconductor layer can be obtained.
Since no nucleation layer is formed between the oxide single crystal substrate and the nitride active layer, all semiconductor layers on the substrate can be epitaxially grown, so the threading dislocation density in the upper nitride semiconductor layer Is equivalent to or less than that in the oxide single crystal substrate, and a high-quality nitride-based semiconductor layer can be obtained.

Sectional drawing which shows schematic structure of the nitride-type semiconductor element which concerns on 1st Embodiment. Sectional drawing which shows schematic structure of the nitride-type semiconductor element which concerns on 2nd Embodiment. Sectional drawing which shows schematic structure of the semiconductor laser diode which concerns on 3rd Embodiment. Sectional drawing which shows schematic structure of the semiconductor laser diode which concerns on 4th Embodiment.

  Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. In the description of each embodiment, the same parts are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
FIG. 1 shows a schematic configuration of a nitride semiconductor device 10 according to the first embodiment.
The nitride-based semiconductor element 10 includes a substrate 11 made of an oxide single crystal, an oxide interface formed on the substrate and containing zinc (Zn) and at least one of a group II element and a group III element. A layer 12 and an InGaN semiconductor layer 13 formed on the oxide interface layer.
In this example, the oxide interface layer 12 is formed between a substrate 11 made of an oxide single crystal and an InGaN semiconductor layer 13 that is a nitride. The InGaN semiconductor layer 13 is a nitride-based semiconductor layer including an active layer made of gallium indium nitride [In x Ga 1-x N (0 <x <1)].

  The substrate 11 has a wurtzite structure and uses a substrate having a substrate orientation that is less susceptible to the influence of a piezoelectric field. The plane orientation of the substrate 11 is any one of the m plane (1_100), a plane (11_20), c plane (0001), r plane (11_22), (10_1_1) plane, or equivalent plane orientation. It is. The plane orientation of the oxide substrate 11 may be a c-plane (0001) and an oxygen polar (O-polar) plane.

  The oxide interface layer 12 is a crystal (oxide single crystal) and is uniformly formed in the plane of the substrate 11.

(Example)
Example 1
The oxide interface layer 12 is an oxide single crystal layer having a spinel structure. The spinel structure has a structure represented by a general chemical formula AB ₂ X ₄ .
The oxide interface layer 12 is, for example, an Al ₂ ZnO ₄ single crystal layer, a Ga ₂ ZnO ₄ single crystal layer, an In ₂ ZnO ₄ single crystal layer, a B ₂ ZnO ₄ single crystal layer, or a ScAlMgO ₄ lattice-matched to ZnO. (SCAM).

The oxide interface layer 12 may have a superlattice structure. For example, the oxide interface layer _{12, M1M2O 3 (ZnO) m} ( although, M1 is, Ga, Fe, Sc, In , Lu, Yb, Tm, Er, at least one of Ho and Y, M2 is, Mn , Fe, Ga, In, and Al, and m is a natural superlattice homologous thin film made of a complex oxide represented by (1 is a natural number of 1 or more including 1). For example, InGaO ₃ (ZnO) ₅ .
The oxide interface layer 12 is an oxide single crystal layer having a perovskite structure. The perovskite structure has a structure represented by the general chemical formula ABO ₃ .

The oxide interface layer 12 has a thickness of one molecular layer (ML) or more and a critical thickness or less with respect to the substrate 11.
For example, the thickness of the oxide interface layer 12 is not less than one molecular layer (ML) and not more than 50 nm, and more preferably, the thickness of the oxide interface layer 12 is not less than one molecular layer (ML) and not more than 20 nm. . If the film thickness is thinner than one molecular layer (ML), the heat resistance is poor, which is not preferable. If the film thickness is greater than 20 nm, the lattice constant of the oxide single crystal substrate 11 is not transmitted to the upper layer, which is not preferable. More preferably, the thickness of the oxide interface layer 12 is not less than one molecular layer (ML) and not more than 5 nm.

  “Molecular layer” herein refers to a layer unit having a minimum thickness in which a group III atom and a group V atom are arranged two-dimensionally, and is used synonymously with a mono-layer (ML). When the oxide interface layer 12 is made of, for example, aluminum oxide, the monomolecular layer (ML) is about 0.25 nm. Further, the “critical film thickness” referred to here is the maximum film thickness at which the oxide interface layer 12 does not crack when the oxide interface layer 12 is grown on the lower substrate 11. It is the maximum film thickness that can maintain the lattice constant.

In addition, the oxide interface layer 12 may be a superlattice layer made of a plurality of oxides having a thickness of one molecular layer (ML) or more and different from the critical thickness of the substrate 11. For example, the oxide interface layer 12 may be a superlattice layer made of Ga ₂ O ₃ and In ₂ O ₃ having a thickness of one molecular layer (ML) or more and a critical thickness or less with respect to the substrate 11.
Furthermore, it is preferable that the threading dislocation density in the InGaN semiconductor layer 13 is approximately the same as the threading dislocation density in the substrate 11 (10 ⁵ cm ⁻² or less).

The manufacturing method of the nitride semiconductor device 10 shown in FIG. 1 includes the following steps.
(Step 1) A step of depositing a precursor made of any of nitride, oxide and metal on the substrate 11.
(Step 2) A step of forming the oxide interface layer 12 by reacting at least a part of the precursor deposited on the substrate 11 with the substrate 11 by performing a high temperature heat treatment after depositing the precursor.
(Step 3) A step of forming an InGaN semiconductor layer 13 made of gallium indium nitride [In x Ga 1-x N (0 <x <1)] on the oxide interface layer 12.

As a manufacturing method of such a nitride-based semiconductor element 10, there are manufacturing method 1, manufacturing method 2, manufacturing method 3, and manufacturing method 4 described below.
(Production method 1)
A thin atomic layer is uniformly formed on the substrate 11 by irradiating the substrate 11 with each metal raw material (Al, Ga, In, B, etc.) by resistance heating, electron beam evaporation, sputtering or the like. Thereafter, an oxide interface layer 12 which is a uniform oxide single crystal layer (Al ₂ ZnO ₄ , Ga ₂ ZnO ₄ , In ₂ ZnO ₄ , B ₂ ZnO _4, etc.) is formed by high-temperature heat treatment, and nitriding is performed thereon. An InGaN semiconductor layer 13 which is a physical semiconductor layer is formed (see FIG. 1).

(Manufacturing method 2)
Sputtering oxides such as Al ₂ O ₃ (aluminum oxide), Ga ₂ O ₃ (gallium oxide), In ₂ O ₃ (indium oxide), B ₂ O ₃ (boron oxide), PLD (pulse laser) Deposition), oxygen plasma cell-assisted MBE (molecular beam epitaxy), CVD (chemical vapor deposition) method, etc. are deposited on the substrate 11, and then the oxide interface is a uniform oxide single crystal layer by high-temperature heat treatment A layer 12 is formed, and an InGaN semiconductor layer 13 is formed thereon.

(Manufacturing method 3)
Sputtering polycrystalline and amorphous GaAlO ₃ (ZnO) ₅ , InAlO ₃ (ZnO) ₅ , BAlO ₃ (ZnO) ₅ , InGaO ₃ (ZnO) ₅ , BGaO ₃ (ZnO) ₅ , BInO ₃ (ZnO) ₅ After depositing on the substrate 11 by PLD, oxygen plasma cell assist MBE, CVD method or the like, a uniform oxide single crystal layer is formed by high-temperature heat treatment, and an InGaN semiconductor layer 13 is formed thereon.

(Manufacturing method 4)
Constituent elements are deposited on a substrate 11 in a laminated structure composed of a plurality of layers, and then a uniform oxide interface layer 12 is formed by high-temperature heat treatment, and an InGaN semiconductor layer 13 is formed thereon.

(Manufacturing method 4a)
After the In ₂ O ₃ layer and the Ga ₂ O ₃ layer are alternately laminated on the oxide substrate 11, a uniform oxide interface layer 12 made of InGaO ₃ (ZnO) ₅ is formed by high-temperature heat treatment, and on that, Then, the InGaN semiconductor layer 13 is formed.
GaAlO ₃ (ZnO) ₅ , InAlO ₃ (ZnO) ₅ , BAlO ₃ (ZnO) ₅ , BGaO ₃ (ZnO) ₅ , and BInO ₃ (ZnO) ₅ can be formed similarly.
In each manufacturing method mentioned above, heat processing temperature is 800 degreeC or more and 1600 degrees C or less.
The step of forming the oxide layer and the step of forming the upper nitride semiconductor layer include a plurality of vacuum chambers (for example, a vacuum chamber for oxide and a vacuum chamber for nitride) connected by a vacuum transfer system without being taken out to the atmosphere. It is preferable to form with the apparatus which has.
In the step of forming the oxide layer, the oxide single crystal layer may be directly epitaxially grown on the substrate without high-temperature heat treatment by sputtering, PLD, oxygen plasma cell assist MBE, CVD method or the like.

According to 1st Embodiment comprised as mentioned above, there exist the following effects.
Formation of a reaction layer at the interface between the substrate 11 and the InGaN semiconductor layer 13 can be suppressed.
By forming the thermally stable oxide interface layer 12 at the interface between the substrate 11 and the InGaN semiconductor layer 13, the InGaN semiconductor layer 13 can be formed on the substrate 11 at a high temperature, and a high-quality InGaN semiconductor layer ( Nitride semiconductor layer) is obtained.

  By forming a thin (thickness or less) uniform layer between the substrate 11 and the InGaN semiconductor layer 13, the upper nitride semiconductor layer can be epitaxially grown while maintaining the lattice constant of the substrate. it can.

-Although the oxide interface layer 12 is a crystal, it can be formed directly by epitaxial growth, or by depositing an amorphous film or a polycrystalline film at a low temperature and then heat-treating it to form a crystal. And a uniform oxide single crystal layer can be obtained.
In each of the above-mentioned manufacturing methods, the substrate and the oxide interface layer are evaporated by surrounding the oxide sintered body made of the constituent elements during the high temperature heat treatment for single crystallization and performing the high temperature heat treatment. Can be suppressed.

(Second Embodiment)
FIG. 2 shows a schematic configuration of the nitride-based semiconductor device according to the second embodiment.
The nitride semiconductor element 10A is characterized in that, in the nitride semiconductor element 10 according to the first embodiment shown in FIG. 1, between the substrate 11 and the InGaN semiconductor layer 13, specifically, the oxide interface layer 12 and The pseudo-lattice matching layer 14 is formed between the InGaN semiconductor layer 13 and the InGaN semiconductor layer 13. The pseudo lattice matching layer 14 is made of gallium or indium nitride.

According to 2nd Embodiment comprised in this way In addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.
Since the nitride pseudo-lattice matching layer 14 containing at least one of aluminum, gallium, and indium is formed between the substrate 11 and the InGaN semiconductor layer 13, a steep gap is formed between the substrate 11 and the InGaN semiconductor layer 13. A good nitride / oxide interface can be obtained, and an InGaN layer 13 having better crystallinity can be obtained.

(Third embodiment)
FIG. 3 is a cross-sectional view showing a schematic configuration of the nitride-based semiconductor device according to the third embodiment. This nitride-based semiconductor element is configured as a semiconductor laser diode (semiconductor light emitting element).
A semiconductor laser diode 10B shown in FIG. 3 includes a substrate 11A, an oxide epitaxial layer 15 made of an oxide sequentially formed on the substrate 11A, an oxide interface layer 12, a lower contact layer 16, a lower cladding layer 17, an InGaN active layer. A layer 18, an upper cladding layer 19, and an upper contact layer 20. The oxide epitaxial layer 15 is a layer provided to make the surface flatter than the substrate 11A and improve the crystallinity.

  Further, the semiconductor laser diode 10B includes a lower electrode layer 21 formed on the lower contact layer 16, a passivation film 22, and an upper electrode layer 23 formed on the upper contact layer 20. The conductivity types of the lower contact layer 16 and the lower cladding layer 17 are n-type, and the conductivity types of the upper cladding layer 19 and the upper contact layer 20 are p-type.

  In this semiconductor laser diode 10B, an epitaxial wafer for a semiconductor laser diode, which is formed on a substrate 11A and emits light in a long-wavelength visible region such as a green region, includes an oxide epitaxial layer 15, an oxide interface layer 12, a lower contact layer. 16, a lower cladding layer 17, an InGaN active layer 18, an upper cladding layer 19, and an upper contact layer 20. In this embodiment, the epitaxial wafer is formed on the c-plane (0001) and the oxygen-polar (O-polar) plane of the substrate 11A.

The lower contact layer 16 is a layer for realizing ohmic contact with the lower electrode layer 21 formed on the exposed portion of the lower contact layer 16. This lower contact layer 16 is made of nitride aluminum gallium indium nitride [Al _{1 -pq} Ga _p In _q N (0 ≦ p <1, 0 ≦ q <1, p + q ≦ 1)]. For example, the lower contact layer 16 is made of a nitride such as gallium indium nitride (InGaN), aluminum gallium indium nitride (AlInGaN), gallium nitride (GaN), or the like. Here, the lower contact layer 16 has n-type conductivity by doping silicon (Si).

The lower cladding layer 17 is a lattice-matched cladding layer that is lattice-matched so as to have a lattice constant equal to or smaller than that of the InGaN active layer 18, and is refracted more than the InGaN active layer 18 that functions as a core. The ratio is small and plays a role of stably confining light in the active layer 18. The lower cladding layer 17, an aluminum gallium indium nitride _{[Al 1-pq Ga p In} q N (0 ≦ p <1,0 ≦ q <1, p + q ≦ 1)] composed of (nitride). For example, the lower cladding layer 17 is made of a nitride such as gallium indium nitride (InGaN), aluminum indium nitride (AlInN), aluminum gallium indium nitride (AlInGaN), or gallium nitride (GaN).

  The lower cladding layer 17 is not limited to being lattice-matched to the InGaN active layer 18, but may be any layer that is lattice-matched to at least one of the InGaN active layer 18, the buffer layer 15, or the substrate 11A. Here, the lower cladding layer 17 has n-type conductivity by doping silicon (Si).

  The InGaN active layer 18 is formed by growing gallium indium nitride [In x Ga 1-x N (0 <x <1)] crystal (InGaN layer) on the lower cladding layer 17. In the InGaN active layer 18, the composition ratio of indium (In) is set so that the emission wavelength is 480 nm or more. Specifically, the InGaN active layer 18 is composed of an InGaN layer having an In composition (In composition ratio of 20% or more) having an emission wavelength in the green region. In this example, the In composition ratio in the InGaN active layer 18 is about 30%.

  The upper cladding layer 19 is a nitride of gallium indium nitride (InGaN), aluminum indium nitride (AlInN), aluminum gallium indium nitride (AlInGaN), gallium nitride (GaN) or the like lattice-matched to at least one of the InGaN active layer 18 or the substrate 11A. An object is formed by growing on the InGaN active layer 18. Here, the upper cladding layer 19 has p-type conductivity by doping with magnesium (Mg).

  The contact layer 20 is formed on the upper cladding layer 19 by supplying N onto the substrate together with a raw material containing at least one of Ga and In set to an optimum cell temperature. The contact layer 20 has p-type conductivity by supplying magnesium (Mg). That is, the contact layer is p-type doped.

  According to 3rd Embodiment comprised in this way, in addition to the effect which the said 1st Embodiment show | plays, there exist the following effects.

A semiconductor laser diode emitting light in the upper nitride semiconductor layer (green wavelength or other long wavelength visible region) by inserting a thin (thickness or less) uniform oxide interface layer (Epitaxial wafer for use).
High quality In In composition InGaN crystal can be formed, piezo electric field, phase separation, threading dislocation can be suppressed, the characteristics of the light emitting layer (InGaN active layer 18) are improved, and the wavelength is longer than blue ( It is possible to realize a green semiconductor laser diode with a high emission efficiency having an emission wavelength of> 480 nm.
-Since there is no threading dislocation, a highly reliable semiconductor laser diode can be realized.

(Fourth embodiment)
FIG. 4 shows a schematic configuration of the nitride-based semiconductor device according to the fourth embodiment.
In the semiconductor laser diode 10C shown in FIG. 4, a pseudo lattice matching layer 14 is formed between the oxide interface layer 12 and the lower contact layer 16 in the semiconductor laser diode 10B shown in FIG. Other configurations of the semiconductor laser diode 10C are the same as those of the semiconductor laser diode 10B shown in FIG.

According to 4th Embodiment comprised in this way In addition to the effect which the said 3rd Embodiment show | plays, there exist the following effects.
Since the nitride pseudo-lattice matching layer 14 containing at least one of aluminum, gallium, and indium is formed between the substrate 11A and the InGaN semiconductor layer 18, the substrate 11A and the InGaN semiconductor layer 18 are interposed between them. A steep nitride / oxide interface is obtained, and an InGaN layer 18 having better crystallinity is obtained.

In addition, you may change the said embodiment of this invention as follows.
In the first embodiment, zinc oxide magnesium beryllium cadmium typified by zinc oxide (ZnO) as the substrate 11 [Zn 1-abc Mg a Be b Cdc (0 ≦ a <1, 0 ≦ b <1, 0 ≦ c <1, a + b + c <1)], but instead of a substrate made of an oxide single crystal, a substrate 11 is formed on a sapphire (α-Al ₂ O ₃ ) substrate or LiGaO. Zinc magnesium beryllium cadmium on an oxide substrate such as ₂ or MgAlO ₃ [Zn 1-abc Mg a Be b Cdc (0 ≦ a <1, 0 ≦ b <1, 0 ≦ c <1, a + b + c < A substrate obtained by epitaxial growth of 1)] may be used.
-In the said 3rd and 4th embodiment, this invention is applicable also to semiconductor light-emitting devices, such as a semiconductor laser diode which each provided the light guide layer between the upper and lower clad layers and the active layer.

  In the third and fourth embodiments, the lower contact layer 16 and the lower cladding layer 17 have p-type conductivity, and the upper cladding layer 19 and the upper contact layer 20 have n-type conductivity, respectively. The present invention is also applicable to semiconductor light emitting devices such as laser diodes.

  In the third and fourth embodiments, a vertical substrate structure is obtained by using a conductive substrate and imparting conductivity to the oxide interface layer and the oxide epitaxial layer by doping impurities. It is also possible.

  In the third and fourth embodiments, the epitaxial wafer for a semiconductor laser diode is formed on the c-plane (0001) and the oxygen-polar (O-polar) plane of the substrate 11A. The present invention can also be applied to a semiconductor light emitting device such as a semiconductor laser diode formed on the c-plane (0001) of the substrate 11A and on a zinc-polar (Zn-polar) plane. In this case, the flatness is somewhat rough compared to the oxygen-polar (O-polar) c-plane (000_1) substrate. A clean surface with good flatness can be obtained on the (Zn-polar) c-plane. This suppresses the diffusion of Ga in the InGaN active layer 18 into the substrate 11A, so that a steep interface between the substrate 11A and the InGaN active layer 18 is obtained, and a better crystal of the InGaN active layer 18 is obtained. can get. As a result, a semiconductor light emitting device such as a semiconductor laser diode having high emission efficiency and high reliability can be obtained.

  In each of the above embodiments, a slightly inclined surface (a surface having an off angle of 1 ° or less in the m-axis direction or the a-axis direction) may be used. For example, in the first and second embodiments, the oxide interface layer 12 may be formed on the slightly inclined surface of the substrate 11 (a surface whose off-angle is 1 ° or less in the m-axis direction or the a-axis direction). Good. In the third and fourth embodiments, the oxide interface layer 12 may be formed on the slightly inclined surface of the substrate 11A via the oxide epitaxial layer 15.

  In each of the above embodiments, the nonpolar and nonpolar surfaces of the substrate 11 may be used. For example, in each of the above embodiments, the oxide interface layer 12 may be formed on the m-plane (1_100) of the substrate 11.

In the third and fourth embodiments, the present invention can be applied to a semiconductor laser diode without the oxide epitaxial layer 15.
In the third and fourth embodiments, the present invention can be applied to a semiconductor laser diode in which the InGaN active layer 18 has a double hetero structure or a quantum well structure.

  In the third and fourth embodiments, a separate confinement structure (SCH) in which an optical confinement layer is provided between the InGaN active layer 18 and the lower cladding layer 17 and between the InGaN active layer 18 and the upper cladding layer 19, respectively. : Separate Confinement Hetero-structure) The present invention can also be applied to a semiconductor laser diode.

The present invention relates to various electronic devices having the structure of the first embodiment or the second embodiment, for example, a field effect transistor (FET) or HEMT (High Electron Mobility Transistor) using a GaN-based semiconductor. It can also be applied to an electron mobility transistor).
The nitride semiconductor device described in the first embodiment or the second embodiment can also be applied to an interface formation technique (heteroepitaxy) of a heterogeneous semiconductor having high reactivity at the interface.

  In the second and fourth embodiments, the pseudo lattice matching layer 14 is a layer in which a GaN binary material is grown at the initial stage of growth on the substrate 11 and the In composition is gradually increased on the GaN layer ( A pseudo lattice matching layer in which an InGaN gradient composition layer) is formed may be used. In this configuration, a GaN binary material is grown at the early stage of the growth of the pseudo lattice matching layer 14 so that a steep interface is formed between the oxide substrate and the nitride semiconductor layer (InGaN active layer). can get.

  In the third and fourth embodiments, the semiconductor light emitting device configured as a semiconductor laser diode has been described. However, the present invention can also be applied to a semiconductor light emitting device such as a light emitting diode (LED) having a pn junction. .

DESCRIPTION OF SYMBOLS 10,10A ... Nitride based semiconductor element 10B, 10C ... Semiconductor laser diode 11, 11A ... Substrate 12 ... Oxide interface layer 13 ... InGaN semiconductor layer 14 ... Pseudo lattice matching layer 15 ... Oxide epitaxial layer 16 ... Lower contact layer 17 ... Lower clad layer 18 ... InGaN active layer 19 ... Upper clad layer 20 ... Upper contact layer 21 ... Lower electrode 22 ... Passivation film 23 ... Upper electrode

Claims (7)

A substrate made of an oxide single crystal having a wurtzite structure;
An oxide interface layer formed on the substrate and made of an oxide containing zinc (Zn) and at least one of a group II element and a group III element;
An active layer made of gallium indium nitride [In x Ga 1-x N (0 <x <1)] formed on the oxide interface layer;
A nitride-based semiconductor device comprising:   The nitridation according to claim 1, wherein a pseudo lattice matching layer made of a nitride containing at least one of aluminum, gallium, or indium is formed between the oxide interface layer and the active layer. Physical semiconductor device.   The substrate is made of zinc magnesium beryllium cadmium [Zn 1-abc Mg a Be b Cdc (0 ≦ a <1, 0 ≦ b <1, 0 ≦ c <1, a + b + c <1)]. The nitride semiconductor device according to claim 1, wherein the nitride semiconductor device is characterized in that:   The oxide interface layer includes any one of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and cadmium (Cd) as a group II element. The nitride semiconductor device according to any one of claims 1 to 3.   The oxide interface layer includes boron (B), aluminum (Al), gallium (Ga), indium (In), thallium (Tl), scandium (Sc), yttrium (Y), lutetium (group III) as group III elements. 5. The nitride-based semiconductor device according to claim 1, comprising any one of Lu), ytterbium (Yb), thulium (Tm), erbium (Er), and holmium (Ho). .   The nitride system according to any one of claims 1 to 5, wherein the oxide interface layer has a thickness of one molecular layer (ML) or more and a critical thickness or less with respect to the substrate. Semiconductor element. A precursor deposition step of depositing a precursor made of any of a predetermined nitride, oxide and metal on a substrate made of an oxide single crystal having a wurtzite structure;
An oxide interface layer forming step of forming an oxide interface layer by reacting at least a part of the precursor deposited on the substrate with the substrate by performing a heat treatment after depositing the precursor; ,
An active layer forming step of forming an active layer made of gallium indium nitride [In x Ga 1-x N (0 <x <1)] on the oxide interface layer;
A method for manufacturing a nitride-based semiconductor device comprising:

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