JP4864435B2 - Compound semiconductor laminated structure, compound semiconductor device and lamp - Google Patents

Description

  The present invention relates to a compound semiconductor comprising a crystal substrate, a boron phosphide (BP) based semiconductor layer formed thereon, and a group III nitride semiconductor layer provided with the boron phosphide based semiconductor layer as an underlayer. The present invention relates to a laminated structure, a compound semiconductor element, and a lamp.

Conventionally, cubic sphalerite crystal type boron phosphide (BP) is a group III-V for forming a light emitting diode (LED) emitting a short wavelength visible light such as blue band light. It is used as a compound semiconductor material (see, for example, Patent Document 1). Further, it is used as a buffer layer for constituting a laminated structure for a light emitting device (see, for example, Patent Document 2). Further, it is used as a contact layer for providing an ohmic contact electrode for constituting a light emitting element (see, for example, Patent Document 3).
JP-A-2-288388 JP-A-3-87019 JP-A-3-34537

Alternatively, a heterojunction of boron phosphide and a wurtzite crystal group III-nitride semiconductor is used as a light emitting layer. For example, a technology example is disclosed in which a light emitting layer of a laser diode (LD) emitting blue band light is formed from a heterojunction of p-type boron phosphide and n-type aluminum nitride / gallium (AlGaN) (for example, (See Patent Document 4).
Japanese Unexamined Patent Publication No. 4-34536

However, a group III nitride semiconductor layer such as gallium nitride (GaN) is a phosphide containing boron (element symbol: B) such as monomeric boron phosphide and phosphorus (element symbol: P) as main constituent elements. There is a problem that it cannot be easily formed on a boron-based semiconductor layer. This is due to a chemical reaction with a nitrogen (element symbol: N) source such as ammonia (molecular formula: NH ₃ ) used to form a group III nitride semiconductor layer, and boron phosphide as an underlayer. This is because the semiconductor layer is transformed into a nitride layer. The surface of the modified boron phosphide-based semiconductor layer has severe irregularities, and when it is used as a base layer, a flat group III nitride semiconductor layer cannot be deposited. For this reason, it is difficult to stably obtain a compound semiconductor multilayer structure composed of a semiconductor layer excellent in surface flatness suitable for constituting a compound semiconductor element.

  The present invention has been proposed in view of the above, and it is possible to prevent a boron phosphide-based semiconductor layer as an underlayer from being altered by a nitrogen source and to stack a semiconductor layer having excellent surface flatness, An object of the present invention is to provide a compound semiconductor multilayer structure, a compound semiconductor element, and a lamp having desired characteristics.

1) In order to achieve the above object, the first invention is provided with a crystal substrate, a boron phosphide (BP) based semiconductor layer formed thereon, and the boron phosphide based semiconductor layer as an underlayer. In addition, in the compound semiconductor stacked structure including the group III nitride semiconductor layer containing gallium (Ga) , aluminum (Al) and gallium (gallium) are interposed between the boron phosphide-based semiconductor layer and the group III nitride semiconductor layer. A first intermediate layer made of a III-V group compound semiconductor containing Ga) and phosphorus (P) is provided.

2 ) In the second invention, in addition to the structure of the invention described in the above item 1 ), the first intermediate layer is formed of aluminum gallium phosphide (composition formula: Al _Y Ga _1-YP (0 < Y <1)).

3 ) In the third invention, in addition to the structure of the invention described in the above item 1) or 2) , the group III nitride is provided between the first intermediate layer and the group III nitride semiconductor layer. A second intermediate layer made of a group III nitride semiconductor containing a group III element constituting the metal semiconductor layer is provided.

4 ) In the fourth invention, in addition to the structure of any one of the above-mentioned items 1) to 3 ), the boron phosphide-based semiconductor layer contains 50% of boron as a group III constituent element. It is characterized by containing phosphorus at a composition ratio of 50% or more as a group V constituent element.

5 ) The fifth invention is a compound semiconductor device, characterized in that it is configured using the compound semiconductor multilayer structure according to any one of items 1) to 4 ) above. Yes.

6 ) A sixth invention is a lamp, characterized in that it is configured using the compound semiconductor multilayer structure described in the above item 5 ).

  According to the present invention, since the group III nitride semiconductor layer is deposited on the boron phosphide-based semiconductor layer with the first intermediate layer interposed therebetween, even when the group III nitride semiconductor layer is grown. Alteration of the boron phosphide-based semiconductor layer is prevented, and therefore a compound semiconductor stacked structure including a boron phosphide-based semiconductor layer that maintains desired original chemical and electrical properties can be provided.

In particular, when the first intermediate layer includes gallium (Ga), aluminum (Al), or phosphorus (P), for example, Al _Y Ga _1-YP (0 <Y <1), boron phosphide-based Deterioration of the semiconductor layer is efficiently avoided, and a compound semiconductor multilayer structure with good surface flatness can be provided by using a high-quality boron phosphide-based semiconductor layer.

  According to the present invention, the second intermediate layer is further disposed on the first intermediate layer provided on the boron phosphide-based semiconductor layer, and the group III nitride semiconductor layer is provided on the second intermediate layer. Due to the stacked structure, the boron phosphide-based semiconductor layer is further prevented from being altered during the growth of the group III nitride semiconductor layer, and a flat and continuous group III nitride semiconductor layer is stably grown. Therefore, it is possible to provide a compound semiconductor multilayer structure including a group III nitride semiconductor layer that is excellent in flatness and continuity.

In addition, according to the present invention, a compound semiconductor element is formed using a compound semiconductor stacked structure including a boron phosphide-based semiconductor layer without alteration and a group III nitride semiconductor layer excellent in flatness and continuity. Since it is configured, for example, in a short wavelength LED including a light emitting layer including a Ga _Z In _1-Z N (0 ≦ Z ≦ 1) layer, particularly excellent in optical characteristics such as light emission intensity, Moreover, it is possible to provide an LED that is excellent in electrical characteristics with no local breakdown voltage failure.

  The compound semiconductor multilayer structure of the present invention includes a crystal substrate, a boron phosphide (BP) based semiconductor layer formed thereon, and a group III nitride semiconductor provided with the boron phosphide based semiconductor layer as an underlayer. And a group III-V compound semiconductor containing a group III element and phosphorus (P) constituting the group III nitride semiconductor layer between the boron phosphide-based semiconductor layer and the group III nitride semiconductor layer A first intermediate layer is provided.

The boron phosphide-based semiconductor layer includes boron as a group III constituent element in a composition ratio of 50% or more, considering that the effect of providing the first intermediate layer deposited thereon is remarkably exhibited. It is desirable to contain phosphorus as a group constituent element at a composition ratio of 50% or more. In addition, it is desirable to be a binary or ternary mixed crystal having three or less kinds of constituent elements, which is easier to form than a multi-element mixed crystal such as a quaternary mixed crystal. For example, monomeric boron phosphide (BP), boron phosphide / gallium (composition formula B _Q Ga ₁ -QP (Q ≧ 0.5)), boron phosphide / aluminum (composition formula B _Q Al _{1− Q} P (Q ≧ 0.5)) can be exemplified.

  The first intermediate layer is made of a material that does not change due to the nitrogen source used by the lower boron phosphide-based semiconductor layer to grow the group III nitride semiconductor layer. In particular, it is preferable to use a III-V group compound semiconductor material that does not form a nitride due to contact with a nitrogen source. When the first intermediate layer is made of a material that can be easily nitrided, the nitrogen source penetrates into the boron phosphide-based semiconductor layer, so that the alteration of the boron phosphide-based semiconductor layer, in particular, the group V constituent element is replaced with nitrogen. It is not possible to reliably avoid the alteration caused by this. From this situation, the first intermediate layer includes not only arsenic (element symbol: As), which is easily replaced by nitrogen, but also phosphorus (P), which is more difficult to replace, as a group V constituent element in a high temperature environment. It is preferable to comprise a compound semiconductor.

  Further, the first intermediate layer includes phosphorus (P) as a group V constituent element for the above reasons, and also includes a group III-V group including a group III constituent element forming a group III nitride semiconductor layer deposited thereon. It is preferable to comprise a compound semiconductor material. The first intermediate layer containing a group III constituent element forming the group III nitride semiconductor layer can provide a “growth nucleus” that promotes the growth of the group III nitride semiconductor layer, so that the group III nitride semiconductor layer can be efficiently grown. Can contribute. For example, in a stacked structure in which a gallium nitride (GaN) layer is deposited on the first intermediate layer, it is preferable that the first intermediate layer be made of gallium phosphide (GaP).

Further, when the first intermediate layer is made of a III-V group compound semiconductor material containing aluminum (Al), it is suitable for obtaining a first intermediate layer having excellent adhesion to the boron phosphide-based semiconductor layer. . For example, when an aluminum nitride gallium (compositional formula Al _Q Ga _{1 -QN} (0 ≦ Q ≦ 1)) layer is provided as an upper layer, an aluminum gallium phosphide (compositional formula Al _Y Ga ₁ -YN (0 < When Y <1)) is used, the adhesion with the lower boron phosphide-based semiconductor layer is excellent, and the growth of the Al _Q Ga _{1 -QN} (0 ≦ Q ≦ 1) layer as the upper layer can be promoted. The first intermediate layer can be configured.

  In the above description, the first intermediate layer is provided between the boron phosphide-based semiconductor layer and the group III nitride semiconductor layer. However, in the present invention, the first intermediate layer and the group III nitride are further provided. You may comprise so that a 2nd intermediate | middle layer may be provided in the middle with a semiconductor layer.

The second intermediate layer can be preferably configured from a group III nitride semiconductor layer containing a group III element constituting the group III nitride semiconductor layer, and has a function of promoting the growth of the group III nitride semiconductor layer. Yes. For example, when a gallium nitride phosphide (compositional formula GaN _1-Q P _Q (0 ≦ Q <1)) layer is deposited as the group III nitride semiconductor layer, the second intermediate layer is preferably made of gallium nitride (GaN). Can be configured. Nitrogen (N) and Group III constituent elements of the same type as the Group III nitride semiconductor layer contained in the second intermediate layer serve as “growth nuclei” that induce and promote the growth of the Group III nitride semiconductor layer. Take a role.

  In the following description, the second intermediate layer will be described together with the first intermediate layer. However, in the compound semiconductor multilayer structure of the present invention, the first intermediate layer is always formed, and the second intermediate layer is It is appropriately formed on the first intermediate layer.

The first and second intermediate layers are formed by metal organic chemical vapor deposition (MOCVD) method, halogen vapor phase epitaxy (VPE) method, hydride (hydride) VPE method, molecular beam epitaxy (MBE). It is formed by vapor phase growth means such as a method. In order to form the III-V group compound semiconductor layer forming the first intermediate layer while suppressing evaporation of highly volatile phosphorus (P), the MOCVD method is used rather than the MBE method in which the growth is performed in a high vacuum. The halogen VPE method and the hydride VPE method are suitable. In order to form the first or second intermediate layer containing aluminum (Al) as a group III constituent element, an MOCVD method in which an organoaluminum compound having an appropriate vapor pressure can be used as an aluminum source is suitable. In addition, according to the MOCVD method, the group III nitride semiconductor layer can be vapor-phase grown using ammonia (NH ₃ ) or hydrazine (N ₂ H ₄ ) as a nitrogen source. Therefore, the MOCVD means which can be generally used for vapor phase growth of the boron phosphide-based semiconductor layer, the first intermediate layer, the second intermediate layer, and the group III nitride semiconductor layer is a compound semiconductor including them. This is convenient for easily constructing the laminated structure.

In order to form a group III nitride semiconductor layer composed of, for example, an Al _Q Ga _1-Q N (0 ≦ Q ≦ 1) layer by atmospheric pressure (substantially atmospheric pressure) or low pressure MOCVD, for example, trimethylgallium (Molecular formula: (CH ₃ ) ₃ Ga), triethylgallium (molecular formula: (C ₂ H ₅ ) ₃ Ga) or the like is used as a gallium (Ga) source (Ga source). An organic gallium compound to which such an aliphatic hydrocarbon group is added can be suitably used as a gallium (Ga) source. Further, organometallic (MO) compounds such as trimethylaluminum (molecular formula: (CH ₃ ) ₃ Al) and triisobutylaluminum (molecular formula: (i-C ₄ H ₉ ) ₃ Al) are used as raw materials for aluminum (Al) (Al source). ). Trimethylaluminum ((CH ₃ ) ₃ Al) is used as an aluminum source in forming the first or second intermediate layer containing aluminum (Al), or the group III nitride semiconductor layer provided on the intermediate layer. Is preferred.

As the nitrogen source, ammonia (molecular formula: NH ₃ ), hydrazine (molecular formula: N ₂ H ₄ ), or the like can be used. Dimethylhydrazine (molecular formula: (CH ₃ ) ₂ H ₂ N ₂ ) having an asymmetric molecular structure having a lower thermal decomposition temperature can also be used as a nitrogen (N) source for growing a group III nitride semiconductor layer. The first intermediate layer effectively acts to prevent such a nitrogen source and the boron phosphide-based semiconductor layer from coming into direct contact.

  When obtaining a laminated structure for a compound light emitting device such as LED or LD, the conductivity type of the first and second intermediate layers, and the conductivity type of the group III nitride semiconductor layer provided on any of the intermediate layers are: It is desirable to be the same as the boron phosphide-based semiconductor layer. When the boron phosphide-based semiconductor layer is provided on a conductive and low-resistance semiconductor crystal substrate, it is desirable that the conductivity type of the boron phosphide-based semiconductor layer be the same as that of the semiconductor crystal substrate. The conductivity type of the first and second intermediate layers and the group III nitride semiconductor layer is added by adding a group II, group IV or group VI element as an impurity when the layers are vapor-grown by, for example, MOCVD. And control.

  As an impurity for obtaining the p-type first intermediate layer, group II elements beryllium (Be), zinc (Zn), and magnesium (Mg) are desirable. As impurities for obtaining the n-type first intermediate layer, group IV silicon (Si), germanium (Ge), tin (Sn), group VI selenium (Se), and tellurium (Te) are desirable.

  Examples of impurities for obtaining the p-type second intermediate layer and the p-type group III nitride semiconductor layer include Be and Mg. Further, Si and Ge can be exemplified as impurities for obtaining the n-type second intermediate layer and the n-type group III nitride semiconductor layer. There is also a technical means for forming a p-type or n-type second intermediate layer or group III nitride semiconductor layer by implanting calcium (Ca), Si, or Ge by an ion implantation method. According to the means for doping p-type or n-type impurities during phase growth, a p-type or n-type second intermediate layer or group III nitride semiconductor layer can be obtained more conveniently.

  In the case of forming a compound semiconductor laminated structure for use in a light receiving element, for example, a pin type photodiode (PD), the first and second intermediate layers do not necessarily have a low resistance p-type or n-type. There is no need to form a conductive layer. In the case of PD applications, the boron phosphide-based semiconductor layer, the first and second intermediate layers, and the group III nitride semiconductor layer need not have the same conductivity type. As an example, an n-type boron phosphide-based semiconductor layer, a high-resistance first intermediate layer called π-type or ν-type deposited thereon, and a p-type Group III nitride deposited thereon A compound semiconductor multilayer structure for pin use is configured using the physical semiconductor layer. For example, the first intermediate layer, which has high resistance for PD use, is preferably so-called “undope” that does not intentionally add impurities, and is highly pure. The ratio of the raw material of the group III constituent element and the raw material of the group V constituent element supplied to the region where the vapor phase growth is performed when the undoped and high resistance first intermediate layer is vapor grown by, for example, the MOCVD method It is convenient to grow the film after adjusting so as to obtain a high resistance layer.

A compound semiconductor multilayer structure for use in a two-dimensional electron field effect transistor (TEGFET) includes, for example, a high-resistance boron phosphide-based semiconductor layer, a first high-resistance intermediate layer thereon, and an electron transit layer thereon. for example the _{Ga Z in 1-Z n (} 0 ≦ Z ≦ 1) layer of the electron mobility of large n-type to form a sequentially deposited compound semiconductor multilayer structure. Also, for example, a high resistance boron phosphide-based semiconductor layer, a high resistance first intermediate layer thereon, a high resistance second intermediate layer on the high resistance first intermediate layer, and an electron transit layer thereon For example, an n-type Ga _Z In _1-Z N (0 ≦ Z ≦ 1) layer having a high electron mobility is sequentially deposited. The high-resistance first or second intermediate layer for use in a field effect transistor (FET) may be composed of an undoped layer. Further, it may be formed by doping the p-type impurity and the n-type impurity so that electrons and holes are mutually electrically compensated.

  The first intermediate layer preferably has a layer thickness capable of uniformly covering the surface of the boron phosphide-based semiconductor layer without a gap. Desirably, it is 1 nanometer (nm) or more, more preferably 2 nm or more. Further, the higher the temperature (growth temperature) for growing the second intermediate layer or the group III nitride semiconductor layer on the first intermediate layer is, the larger the layer thickness of the first intermediate layer is. Is preferred. At high temperatures, thermal decomposition of the nitrogen source used to grow the group III nitride semiconductor layer occurs more significantly, and the released nitrogen (N) diffuses deeper into the first intermediate layer. For this reason, it is preferable that the higher the growth temperature, the thicker the first intermediate layer is to reduce the amount of nitrogen atoms entering the lower boron phosphide-based semiconductor layer.

  For example, when a growth temperature is set to 1,000 ° C. to 1,150 ° C. and a gallium nitride (GaN) layer is grown by bonding directly to the first intermediate layer, the maximum thickness of the first intermediate layer is 250 nm. Is preferable. If the thickness exceeds 250 nm, it is difficult to stably obtain the first intermediate layer having excellent surface flatness. For example, when the second intermediate layer is provided on the first intermediate layer at a low temperature of about 350 ° C. to 650 ° C., it is preferable that the first intermediate layer has a maximum thickness of 50 nm. The layer thickness of the first intermediate layer can be controlled by adjusting the growth time under growth conditions that give a known growth rate. The actual thickness of the first intermediate layer can be measured using, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

  The second intermediate layer preferably has a layer thickness that can uniformly cover the surface of the first intermediate layer without any gap. Desirably, it is 1 nanometer (nm) or more, more preferably 2 nm or more. The second intermediate layer preferably has a larger layer thickness as the temperature for growing the group III nitride semiconductor layer on the second intermediate layer is higher. At high temperatures, the degree to which nitrogen (N) released due to thermal decomposition of the nitrogen source used for growing the group III nitride semiconductor layer diffuses into the first intermediate layer becomes more prominent. For this reason, the higher the growth temperature of the group III nitride semiconductor layer, the thicker the second intermediate layer, and the nitrogen atoms entering the lower boron phosphide-based semiconductor layer through the first intermediate layer. It is preferable to reduce the amount of. For example, when a GaN layer is stacked on the second intermediate layer at a high temperature of 1,100 ° C., the thickness of the second intermediate layer is preferably 20 nm or more and 100 nm or less.

  Growing the second intermediate layer at a lower temperature is effective in avoiding thermal alteration of the first intermediate layer. For example, by depositing the second intermediate layer on the first intermediate layer at a low temperature of about 350 ° C. to 650 ° C., the phosphorus (P) volatilization of the group V constituent element from the first intermediate layer is better suppressed. Is done. Therefore, the stoichiometric composition of the first intermediate layer can be maintained. Further, if the second intermediate layer is grown at a low temperature, the penetration of nitrogen (N) constituting the second intermediate layer into the first intermediate layer can be better suppressed. Therefore, nitrogen (N) penetrating into the lower boron phosphide-based semiconductor layer can be reduced through the first intermediate layer, and the boron phosphide-based semiconductor layer is more reliably transformed into a nitride layer. Can be avoided.

If a laminated structure including a boron phosphide-based semiconductor layer in which alteration is prevented by providing the first and second intermediate layers, a compound semiconductor element having excellent characteristics can be configured. For example, compound semiconductor light emission that emits short-wavelength visible light or ultraviolet light from a laminated structure including a light-emitting portion including a light-emitting layer made of a GaN-based group III nitride semiconductor on the first or second intermediate layer An element can be configured. The light-emitting layer, the radiative recombination efficient direct transition example, it is preferable to constitute a gallium indium nitride _{(Ga Z In 1-Z N} (0 ≦ Z ≦ 1)).

  Since the compound semiconductor light-emitting device of the present invention has high emission intensity, it is possible to provide a white lamp suitable for a lighting fixture or the like by combining with a specific fluorescent material.

  First Example Taking as an example the case where a first intermediate layer according to the present invention is provided on a silicon single crystal (silicon) substrate to form a compound semiconductor laminated structure (hereinafter referred to as “laminated structure”). The present invention will be specifically described.

FIG. 1 is a diagram schematically showing a cross-sectional structure of the laminated structure of the first embodiment. The laminated structure 10 was formed using an n-type silicon single crystal to which phosphorus (P) was added as the substrate 100. On the (111) surface of the substrate 100, an undoped n-type boron phosphide / gallium (composition formula B _0.98 Ga _0.02 P) having a layer thickness of about 700 nm and a carrier concentration of about 8 × 10 ²⁰ cm ^−3. ) The mixed crystal layer 101 was deposited as a boron phosphide-based semiconductor layer. The boron phosphide / gallium mixed crystal layer 101 uses trimethylgallium (molecular formula: (CH ₃ ) ₃ Ga) as a gallium (Ga) source and triethyl boron (molecular formula: (C ₂ H ₅ ) ₃ B) as boron (B). The substrate was grown at 900 ° C. by a normal pressure (substantially atmospheric pressure) MOCVD method using a phosphine (molecular formula: PH ₃ ) as a phosphorus (P) source.

A first intermediate layer 102 made of n-type aluminum gallium phosphide (composition formula: Al _0.50 Ga _0.50 P) doped with silicon (Si) is formed on the boron phosphide / gallium mixed crystal layer 101 by MOCVD. Was provided. The thickness of the first intermediate layer 102 was about 15 nm, and the carrier concentration was about 3 × 10 ¹⁸ cm ⁻³ . The first intermediate layer 102 was grown at 750 ° C. using trimethylaluminum (molecular formula: (CH ₃ ) ₃ Al) as an aluminum (Al) source in addition to (CH ₃ ) ₃ Ga and PH ₃ .

On the first intermediate layer 102, a Si-doped n-type gallium nitride indium (composition formula: Ga _0.88 In _0.12 N) mixed crystal layer 103a having a layer thickness of about 1.5 nm and a layer thickness of about 1.5 nm are formed. A superlattice structure layer 103 in which Si-doped n-type gallium nitride / indium (composition formula: Ga _0.99 In _0.01 N) mixed crystal layers 103b are alternately stacked for five periods is provided as a group III nitride semiconductor layer. These gallium nitride / indium mixed crystal layers 103a and 103b include trimethylindium (molecular formula: (CH ₃ ) ₃ In) as an indium (In) source in addition to (CH ₃ ) ₃ Ga, and ammonia (molecular formula: NH ₃ ). As a nitrogen (N) source, it was grown at 750 ° C. in the same manner as the first intermediate layer 102 by the atmospheric pressure MOCVD method. According to the SIMS analysis, a situation in which a large amount of nitrogen atoms are diffused into the boron phosphide / gallium mixed crystal layer 101 is not recognized, and the superlattice structure layer 103 is grown by providing the first intermediate layer 102. It was suggested that alteration of the boron phosphide / gallium mixed crystal layer 101 due to the nitrogen source at the time was prevented. Further, the GaInN-based superlattice structure layer 103 is a continuous film because it is provided via the first intermediate layer 102.

The superlattice structure layer 103 is hetero-junctioned with the superlattice structure layer 103, has a layer thickness of about 15 nm, and a carrier concentration of about 1 × 10 ¹⁹ cm ^−3. Formula: B _0.99 Al _0.01 P) mixed crystal layer 104 was provided. The boron phosphide / aluminum mixed crystal layer 104 was grown at 1025 ° C. by an atmospheric pressure MOCVD method using (C ₂ H ₅ ) ₃ B, (CH ₃ ) ₃ Al, and PH ₃ as raw materials.

Thus, the first intermediate layer 102 made of Al _0.50 Ga _0.50 N is provided, the boron phosphide / gallium mixed crystal layer 101 made of B _0.98 Ga _0.02 P is used as the n-type lower cladding layer, and the GaInN-based superlattice structure layer Laminated structure for light emitting device use of pn junction type double hetero (DH) junction structure having 103 as an n-type light emitting layer and boron phosphide / aluminum mixed crystal layer 104 made of B _0.99 Al _0.01 P as a p-type upper cladding layer Body 10 was formed.

  (Second Example) The content of the present invention is specifically described by taking as an example the case of manufacturing a nitride semiconductor light emitting diode (LED) as a compound semiconductor element using the laminated structure 10 of the first example. I will explain it.

  FIG. 2 is a diagram schematically showing a cross-sectional structure of the LED of the second embodiment. This LED 1A is formed using the laminated structure 10 of the first embodiment. That is, a gold (Au) film is deposited on substantially the entire back surface of the substrate 100 made of an n-type silicon single crystal of the laminated structure 10 by using a general vacuum deposition method, and an n-type ohmic electrode is formed. 106 was formed. The film thickness of the gold film forming the n-type ohmic electrode 106 was about 2000 nm.

  An alloy film 107a of nickel (Ni) and zinc (Zn) was formed on the surface of the boron phosphide / aluminum mixed crystal layer 104, which is the outermost layer of the laminated structure 10, by a general electron beam evaporation method. . Next, an Au film 107b was deposited on the Ni / Zn alloy film 107a having a thickness of about 100 nm to form a metal film having a total thickness of about 1500 nm. Next, patterning is applied to the metal film using a known photolithography technique, and the metal film is left in a circular shape in plan view only in the central region of the surface of the boron phosphide / aluminum mixed crystal layer 104. Thus, the p-type ohmic electrode 107 was formed. Thereafter, the laminated structure 10 was cut into individual elements (chips), and an LED 1A having a pn junction DH structure using the GaInN-based superlattice structure layer 103 as an n-type light emitting layer was produced.

  When a forward current of 20 mA was passed between the n-type and p-type ohmic electrodes 106 and 107, blue band light having a wavelength of about 450 nm was emitted from the LED 1A. Further, the LED 1A includes a light emitting layer of a superlattice structure layer 103 made of a group III nitride semiconductor layer that is formed by using the first intermediate layer and is excellent in flatness and continuity. The light emission intensity measured using a sphere before molding with resin reached about 5 milliwatts (mW). Further, there was no local breakdown voltage, and the forward voltage (Vf) when the forward current was 20 mA was a low value of 3.3V. Moreover, the reverse voltage when the reverse current was 10 microamperes (μA) was a high value of 8V. Therefore, by providing the first intermediate layer of the present invention, a blue LED having high emission intensity, low power consumption and high electrical withstand voltage is provided.

(Comparative Example) On the other hand, as a comparative example, an LED having the same electrode configuration as that of the second example was manufactured from the laminated structure substantially the same as that of the first example except that the first intermediate layer was not provided. did. That is, the same n-type silicon single crystal as in the first embodiment is used as a substrate, and a boron phosphide / gallium (composition formula B _0.98 Ga _0.02 P) mixed crystal layer, a GaInN-based superlattice structure layer, boron phosphide is formed thereon. LED was produced using the laminated structure of a pn junction type double hetero (DH) junction structure formed by laminating aluminum (B _0.99 Al _0.01 P) mixed crystal layers. As a result of measuring the energization current and the like of the LED 1A of the second embodiment, the emission intensity of the LED of the comparative example not provided with the first intermediate layer according to the present invention is about 3.9 milliwatts (mW). ), The forward voltage was 3.4V, and the reverse voltage was 6.8V. Therefore, both the light emission intensity and the reverse voltage were inferior to the LED 1A of the second embodiment provided with the first intermediate layer according to the present invention.

  (Third Embodiment) The content of the present invention is specifically described by taking a case where a laminated structure is formed by providing first and second intermediate layers according to the present invention on a silicon carbide (SiC) single crystal substrate. I will explain it.

FIG. 3 is a diagram schematically showing a cross-sectional structure of the laminated structure of the third embodiment. In forming the laminated structure 20, an n-type 6H crystalline SiC single crystal to which nitrogen (N) was added was used for the substrate 200. An undoped n-type boron phosphide (BP) layer 201 having a layer thickness of about 240 nm and a carrier concentration of about 2 × 10 ²⁰ cm ⁻³ is formed on the (0001) surface of the substrate 200. Deposited as a semiconductor layer. The n-type boron phosphide layer 201 has a normal pressure (approximately) using triethyl boron (molecular formula: (C ₂ H ₅ ) ₃ B) as a boron (B) source and phosphine (molecular formula: PH ₃ ) as a phosphorus (P) source. Atmospheric pressure) Grown at 850 ° C. by MOCVD means.

On the n-type boron phosphide layer 201, a first intermediate layer 202 made of n-type aluminum gallium phosphide (compositional formula Al _0.30 Ga _0.70 P) doped with germanium (Ge) was provided by MOCVD means. . The thickness of the first intermediate layer 202 was about 5 nm, and the carrier concentration was about 3 × 10 ¹⁸ cm ⁻³ . The first intermediate layer 202 includes trimethylgallium (molecular formula: (CH ₃ ) ₃ Ga) as a gallium (Ga) source, trimethylaluminum (molecular formula: (CH ₃ ) ₃ Al) as an aluminum (Al) source, and phosphine ( Growth was performed at 720 ° C. using a molecular formula: PH ₃ ) as a phosphorus (P) source.

On the first intermediate layer 202, a second intermediate layer 205 made of a Ge-doped n-type aluminum nitride / gallium mixed crystal (composition formula: Al _0.10 Ga _0.90 N) having a thickness of about 5 nm was provided. The carrier concentration of the Al _0.10 Ga _0.90 N layer of the second intermediate layer 205 was set to about 1 × 10 ¹⁸ cm ⁻³ . The second intermediate layer 205 is grown at 850 ° C. by atmospheric pressure MOCVD using (CH ₃ ) ₃ Ga, (CH ₃ ) ₃ Al, and ammonia (molecular formula: NH ₃ ) as a nitrogen (N) source. I let you.

On the second intermediate layer 205, a Si-doped n-type gallium nitride indium (composition formula: Ga _0.88 In _0.12 N) mixed crystal layer having a layer thickness of about 1.5 nm, as in the first embodiment. 203a and a superlattice structure layer 203 in which Si-doped n-type gallium nitride indium (composition formula: Ga _0.99 In _0.01 N) mixed crystal layer 203b having a layer thickness of about 1.5 nm is alternately stacked for five periods. Provided as a group III nitride semiconductor layer. These gallium nitride / indium mixed crystal layers 203a and 203b are formed by atmospheric pressure MOCVD using (CH ₃ ) ₃ Ga, (CH ₃ ) ₃ In and NH ₃ , compared with the case of the second intermediate layer 205 described above. It was grown at a low temperature of 720 ° C. Since it was grown through the second intermediate layer 205, the gallium nitride / indium mixed crystal layers 203a and 203b all had excellent surface flatness.

An undoped p-type boron phosphide (BP) layer that is heterojunctioned with the superlattice structure layer 203 and has a layer thickness of about 10 nm and a carrier concentration of about 2 × 10 ¹⁹ cm ^−3. 204 was provided. The p-type boron phosphide layer 204 was grown at 1025 ° C. by atmospheric pressure MOCVD using (C ₂ H ₅ ) ₃ B and PH ₃ as raw materials.

Accordingly, the first intermediate layer 202 made of Al _0.50 Ga _0.50 N and the second intermediate layer 205 made of Al _0.10 Ga _0.90 N are provided, and the n-type boron phosphide layer 201 is used as a lower cladding layer, and GaInN A stacked structure 20 for a light emitting device having a pn junction type double hetero (DH) junction structure including the n-type light emitting layer as the superlattice structure layer 203 and the p-type boron phosphide layer 204 as the upper cladding layer was formed.

  (Fourth Example) A nitride semiconductor light-emitting diode (LED) as a compound semiconductor element was manufactured using the laminated structure 20 of the third example in the same manner as in the second example.

  FIG. 4 is a diagram schematically showing a cross-sectional structure of the LED of the fourth embodiment. This LED 2A is formed using the laminated structure 20 of the third embodiment. That is, a nickel (Ni) film is deposited on substantially the entire back surface of the substrate 200 made of an n-type 6H crystalline SiC single crystal of the laminated structure 20 by using a general vacuum deposition method, and n A shaped ohmic electrode 206 was formed. The thickness of the nickel film forming the n-type ohmic electrode 206 was about 2000 nm.

  An alloy film 207a of nickel (Ni) and zinc (Zn) was formed on the surface of the p-type boron phosphide layer 204, which is the outermost layer of the laminated structure 20, by a general electron beam evaporation method. Next, an Au film 207b was deposited on the Ni / Zn alloy film 207a having a thickness of about 100 nm to form a metal film having a total thickness of about 1500 nm. Next, using a known photolithography technique, patterning is performed on the metal film, and the metal film is left in a circular shape in plan view only in the plane region at the center of the surface of the p-type boron phosphide layer 204, A p-type ohmic electrode 207 was formed. Thereafter, the laminated structure 20 was cut into individual elements (chips), and an LED 2A having a pn junction DH structure using the GaInN-based superlattice structure layer 203 as an n-type light emitting layer was produced.

  When a forward current of 20 mA was passed between the n-type and p-type ohmic electrodes 206 and 207, blue band light having a wavelength of about 450 nm was emitted from the LED 2A. The light emission intensity measured using a general integrating sphere before molding with resin reached about 8 milliwatts (mW). The LED 2A includes a light emitting layer of a superlattice structure layer 203 made of a group III nitride semiconductor layer having excellent flatness and continuity formed by using the second intermediate layer in addition to the first intermediate layer. Therefore, the emission intensity was higher than that of the LED 1A described in the second example. Moreover, there was no local breakdown voltage (local breakdown), and the forward voltage (Vf) when the forward current was 20 mA was a low value of 3.3V. Further, the reverse voltage when the reverse current was 10 microamperes (μA) was higher than that of the LED 1A of the second example and became 10V. This is because, by providing the second intermediate layer 205 in addition to the first intermediate layer 202, the boron phosphide-based semiconductor layer 201 is prevented from being altered and the superlattice structure layer is formed of a continuous film having excellent flatness. It was considered that this was caused by the formation of 203 light emitting layers. Therefore, a blue LED having high emission intensity, low power consumption and high electrical withstand voltage is provided.

It is a figure which shows typically the cross-section of the laminated structure of 1st Example. It is a figure which shows typically the cross-section of LED of 2nd Example. It is a figure which shows typically the cross-section of the laminated structure of 3rd Example. It is a figure which shows typically the cross-section of LED of 4th Example.

Explanation of symbols

10 Laminated structure 100 Substrate 101 Boron phosphide / gallium mixed crystal layer 102 First intermediate layer 103 Superlattice structure layer 103a Gallium nitride / indium mixed crystal layer 103b Gallium nitride / indium mixed crystal layer 104 Boron phosphide / aluminum mixed crystal Layer 106 n-type ohmic electrode 107 p-type ohmic electrode 107a Ni / Zn alloy film 107b Au film 20 laminated structure 200 substrate 201 n-type boron phosphide layer 202 first intermediate layer 203 superlattice structure layer 203a gallium nitride / indium mixed Crystal layer 203a Gallium nitride / indium mixed crystal layer 204 p-type boron phosphide layer 205 second intermediate layer 206 n-type ohmic electrode 207 p-type ohmic electrode 207a Ni / Zn alloy film 207b Au film

Claims (6)

A crystal substrate, a boron phosphide (BP) based semiconductor layer formed thereon, and a group III nitride semiconductor layer containing gallium (Ga) provided with the boron phosphide based semiconductor layer as an underlayer In the compound semiconductor laminated structure,
A first intermediate layer made of a III-V group compound semiconductor containing aluminum (Al), gallium (Ga), and phosphorus (P) between the boron phosphide-based semiconductor layer and the group III nitride semiconductor layer. Is provided,
A compound semiconductor multilayer structure characterized by the above. 2. The compound semiconductor stacked structure according to claim 1 , wherein the first intermediate layer is made of aluminum gallium phosphide (composition formula: Al _Y Ga _1-YP (0 <Y <1)). A second intermediate layer made of a group III nitride semiconductor containing a group III element constituting the group III nitride semiconductor layer is provided between the first intermediate layer and the group III nitride semiconductor layer. The compound semiconductor multilayer structure according to claim 1 or 2 . The boron phosphide-based semiconductor layer contains boron as a group III constituent element in the composition ratio of 50% or more, the phosphorus as a group V constituent element comprising a composition ratio of 50% or more, any one of claims 1 to 3 1 The compound semiconductor multilayer structure according to Item. Compound semiconductor device according to claim 1 is constructed by using the compound semiconductor multilayer structure according to any one of 4, it is characterized. A lamp comprising the compound semiconductor device according to claim 5 .

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