JP3700664B2 - Boron phosphide-based semiconductor layer, manufacturing method thereof, and semiconductor element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a boron phosphide-based semiconductor layer and a semiconductor element using the boron phosphide-based semiconductor layer. In particular, the boron phosphide-based semiconductor layer having excellent surface flatness and continuity is vapor-phase grown on the surface of a crystal substrate. For technology.
[0002]
[Prior art]
Conventionally, boron phosphide-based semiconductor layers containing boron (B) and phosphorus (P) as constituent elements have been used to form various semiconductor elements. For example, a semiconductor layer made of boron phosphide (BP) which is a typical monomer as a boron phosphide-based semiconductor is used to form an n-type base layer of an npn heterobipolar transistor (HBT). (See J. Electrochem. Soc., 125 (4) (1978), pages 633-637). Further, in a blue laser diode (LD), it is used as a contact layer for forming an ohmic electrode having a low contact resistance (see Japanese Patent Laid-Open No. 10-242567). Further, it is used as a buffer layer for constituting a light emitting diode (LED) that emits light of a short wavelength such as near ultraviolet or blue (see US Pat. No. 6,069,021).
[0003]
The boron phosphide-based semiconductor layer for constituting the semiconductor element as described above has been conventionally formed by vapor phase growth means. Conventional vapor growth means include, for example, boron trichloride (BCl_Three) And phosphorus trichloride (PCl)_Three) As a starting material (see “The Crystal Growth Society of Japan”, Vol. 24, No. 2 (1997), page 150), borane (BH)_Three) Or diborane (B₂H₆) And phosphine (PH_Three) And the like as raw materials (see J. Crystal Growth, 25/25 (1974), pages 193 to 196), molecular beam epitaxy (J. Solid State Chem., 133 (1997)) 269-272), and metal organic chemical vapor deposition (MOCVD) method (Inst. Phys. Conf. Ser., No. 129 (IOP Publishing Ltd. (UK, 1993), pp. 157-162)) Can be illustrated.
[0004]
In vapor phase growth of a boron phosphide-based semiconductor layer, a single crystal of a semiconductor material is exclusively used for the substrate. Conventionally, silicon (Si) single crystal (silicon) has been used as a practical substrate (see (1) J. Electrochem. Soc., 125 (1978) and (2) US Pat. No. 6,069,021). Silicon carbide (SiC) (see Japanese Patent Laid-Open No. 10-242568), gallium phosphide (GaP) (see Japanese Patent Laid-Open No. 10-242568), gallium nitride (GaN) (see Japanese Patent Laid-Open No. 10-247745), etc. The single crystal is used.
[0005]
[Problems to be solved by the invention]
However, the lattice constants of the single crystal material forming the substrate and, for example, boron phosphide (BP) are significantly different. The lattice constant of silicon single crystal is 5.431 Å, while that of cubic zinc blende BP is 4.538 （(Akira Teramoto, “Introduction to Semiconductor Devices” (March 30, 1995, ( The first edition issued by Baifukan Co., Ltd.), page 28). Therefore, the degree of lattice mismatch is as large as about 16.5% (Katsufusa Shono, “Semiconductor Technology (above)” (June 25, 1992, 9th edition, Tokyo University Press), 97- (See page 98).
[0006]
Thus, on a crystal substrate with a large degree of lattice mismatch, the boron phosphide-based semiconductor layer causes island-like growth in a growth mode similar to Volmer-Weber (Thin Film and Surface Physics Subcommittee of the Japan Society of Applied Physics) Ed., "Thin Film Handbook" (March 25, 1991, Kyoritsu Shuppan Co., Ltd., first edition, first edition), page 59). For this reason, it has been difficult to obtain a continuous boron phosphide-based semiconductor layer.
[0007]
If there is means for vapor-phase growth of a boron phosphide-based semiconductor layer having excellent continuity without cracks, the forward voltage (so-called Vf) is low due to, for example, the development of normal pn junction characteristics. LEDs and threshold voltages (so-called V_th) Can be easily provided. The present invention provides a vapor phase growth method for obtaining a boron phosphide-based semiconductor layer having excellent continuity even on a crystal substrate having a large degree of lattice mismatch. In addition, a semiconductor element configured using the boron phosphide-based semiconductor layer is provided.
[0008]
[Means for Solving the Problems]
That is, the present invention
(1) In a method for producing a boron phosphide-based semiconductor layer in which a boron phosphide-based semiconductor layer containing boron (B) and phosphorus (P) as constituent elements is vapor-phase grown on the surface of a crystal substrate, A boron phosphide-based semiconductor layer characterized in that particles containing either boron or phosphorus are formed in advance on the surface of the substrate, and then a boron phosphide-based semiconductor layer is vapor-phase grown on the surface of the crystal substrate. Production method.
(2) The method for producing a boron phosphide-based semiconductor layer according to (1) above, wherein the diameter of the particles containing either boron or phosphorus is 1 nm or more and 30 nm or less.
(3) The method for producing a boron phosphide-based semiconductor layer according to (1) or (2) above, wherein the crystal substrate is made of an n-type or p-type conductive single crystal.
(4) The production of a boron phosphide-based semiconductor layer according to any one of (1) to (3) above, wherein the particles containing either boron or phosphorus are formed of polycrystals. Method.
(5) The above-mentioned (1) to (1), wherein the particles containing either boron or phosphorus are formed from a polycrystalline material containing an amorphous material in a region of a bonding interface with the surface of the crystal substrate. 4. The method for producing a boron phosphide-based semiconductor layer according to any one of 4).
(6) The boron phosphide-based semiconductor layer is vapor-phase grown on the surface of the crystal substrate at a temperature that exceeds the temperature for forming particles containing either boron or phosphorus and is 1200 ° C. or lower. The method for producing a boron phosphide-based semiconductor layer according to any one of (1) to (5) above.
(7) The same vapor phase growth as that for forming particles containing either boron or phosphorus using the same raw material as the boron raw material or phosphorus raw material used to form particles containing either boron or phosphorus. The method for producing a boron phosphide-based semiconductor layer according to any one of (1) to (6) above, wherein the boron phosphide-based semiconductor layer is vapor-phase grown by means.
(8) The method for producing a boron phosphide-based semiconductor layer as described in (7) above, wherein the vapor phase growth means is a metal organic chemical vapor deposition (MOCVD) method.
(9) A boron phosphide-based semiconductor layer manufactured using the method for manufacturing a boron phosphide-based semiconductor layer described in any one of (1) to (8) above.
(10) A semiconductor device using the boron phosphide-based semiconductor layer according to (9).
It is.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a boron phosphide-based semiconductor includes boron and phosphorus as constituent elements, for example, B_αAl_βGa_γIn_{1- α - β - γ}P_{1- δ}As_δ(0 <α ≦ 1, 0 ≦ β <1, 0 ≦ γ <1, 0 <α + β + γ ≦ 1, 0 ≦ δ <1), for example, B_αAl_βGa_γIn_{1- α - β - γ}P_{1- δ}N_δ(0 <α ≦ 1, 0 ≦ β <1, 0 ≦ γ <1, 0 <α + β + γ ≦ 1, 0 ≦ δ <1). To describe an example of the first embodiment of the present invention, first, for example, triethyl boron ((C₂H_Five)_ThreeB) is uniformly adsorbed on the surface of the crystal substrate. In particular, boron-containing compounds that are liquid at room temperature, such as boron dioxide (B (OCH_Three)_ThreeIf melting point = −29 ° C., boiling point = + 68 to + 69 ° C.), etc., this is uniformly sprayed on the surface of the crystal substrate. Thereafter, the temperature of the crystal substrate is raised, the additional group is removed, and solidified as particles containing boron. The temperature of the crystal substrate is set to a temperature suitable for solidifying the boron-containing particles. In this way, before the continuous film of the boron phosphide-based semiconductor layer is vapor-phase grown, particles containing boron or phosphorus can be deposited on the surface of the substrate in advance.
[0010]
Particles containing phosphorus can be formed in the same manner. For example, a phosphine (PH) is formed on the surface of a crystal substrate placed inside an MOCVD growth furnace._Three) Is adsorbed. Thereafter, if the temperature of the crystal substrate is raised to a temperature of 400 ° C. or more and below the practical heat resistant temperature of the crystal substrate, the pH adsorbed on the surface of the crystal substrate is increased._ThreeThe molecules can be pyrolyzed to form particles containing phosphorus. For example, (C₂H_Five)_ThreeB and PH_ThreeThere is also a means for causing particles containing both boron and phosphorus formed by vapor-phase reaction by simultaneously circulating them to fly toward the surface of the crystal substrate and adhere to the surface.
[0011]
The size of the particles containing boron or phosphorus provided on the crystal substrate is preferably 1 nm or more and 30 nm or less in terms of particle diameter (particle diameter). Particles whose particle diameter is extremely large exceeding 30 nm generally have a high elevation from the surface of the crystal substrate. In a boron phosphide-based semiconductor layer that grows on particles as “nuclei”, the presence of large particles results in a disadvantage that the flatness of the surface of the boron phosphide-based semiconductor layer is impaired. Further, in the case of fine particles having a particle diameter of less than 1 nm, the boron phosphide-based semiconductor layer grows only around the fine particles, which hinders obtaining a continuous film and becomes inconvenient.
[0012]
Furthermore, if the density of the particles present on the surface of the crystal substrate is low, a continuous boron phosphide-based semiconductor layer cannot be stably obtained. In order to stably obtain a continuous boron phosphide-based semiconductor layer, for example, particles having an average particle diameter of 10 nm are about 1 × 10 × 10.⁸/ Cm²It is desirable to exist on the surface of the crystal substrate at the above density. More desirably, the particles are present at a high density so as to almost completely cover the surface of the crystal substrate. More preferably, the surface of the crystal substrate is almost completely covered with particles that flatten the top plate. The particles that are substantially parallel to the surface of the crystal substrate and have a flat top plate contribute particularly to obtaining a boron phosphide-based semiconductor layer having a flat surface. As the total concentration of boron raw material or phosphorus raw material supplied to the surface of the crystal substrate is increased, particles having a larger particle diameter can be generated at higher density. The composition of the particles present on the surface of the crystal substrate can be investigated by, for example, a composition analysis method such as Auger electron analysis or electron microscope analysis. The particle diameter and particle density can be measured using, for example, an atomic force microscope (AFM).
[0013]
If particles containing either boron or phosphorus according to the present invention are formed on the surface of a crystal substrate, a continuous boron phosphide-based semiconductor layer can be formed on a single crystal substrate having a large degree of lattice mismatch. . For example, a group III-V compound semiconductor single crystal such as gallium arsenide (GaAs), a group III nitride semiconductor single crystal such as aluminum nitride (AlN), or a silicon (Si) single crystal can be used as the substrate. Insulating α-alumina (α-Al₂O_Three) A single crystal or a perovskite crystal type oxide single crystal can be used as a substrate. When an n-type or p-type conductive single crystal is used as a substrate, an ohmic electrode of positive or negative polarity of either polarity can be laid on the back surface of the substrate as a back electrode, contributing to the simple construction of light emitting elements such as LEDs. it can. A single crystal substrate having a low resistivity of 1 mΩ · cm or less contributes to an LED having a low forward voltage.
[0014]
The particles containing either boron or phosphorus according to the present invention may be composed of polycrystalline particles. Polycrystalline particles refer to crystal grains formed by, for example, single crystals having different orientations joined together via crystal grain boundaries. Polycrystalline particles may be composed of a collection of single crystals having different crystal types. For example, there is a polycrystalline particle composed of a single crystal having the same crystal type as the crystal forming the substrate and a single crystal having a different crystal type. Polycrystalline particles can be formed by setting the substrate temperature to be lower than the substrate temperature when the single crystal particles are formed. As an example of the second embodiment of the present invention, (C₂H_Five)_ThreeIn a MOCVD growth furnace using B as a boron source (C₂H_Five)_ThreeOn the surface of the silicon single crystal substrate held at a low temperature below the boiling point of B (= + 95 ° C.), (C₂H_Five)_ThreeHydrogen associated with B (H₂). After waiting for a while, the temperature of the silicon single crystal substrate is desirably raised to about 450 ° C. to about 650 ° C. Then, after waiting for a while, polycrystalline grains containing boron are formed on the surface of the crystal substrate. In this case, the longer the standby time at high temperature, the larger the polycrystalline grains can be obtained. In polycrystalline grains, lattice mismatch between the crystal substrate and the boron phosphide-based semiconductor layer is absorbed by crystal grain boundaries or stacking faults contained therein, and a high-quality boron phosphide-based semiconductor layer with few crystal defects can be obtained. It is effective to obtain. The constituents of the crystal grains can be analyzed by, for example, an electron diffraction technique using a transmission electron microscope (TEM).
[0015]
In the third embodiment of the present invention, in particular, after boron or phosphorus-containing particles are deposited on the surface of the crystal substrate, the temperature of the crystal substrate is suddenly increased, so that the junction boundary region with the crystal substrate is not formed. Form crystal grains. For example, (C₂H_Five)_ThreeAfter forming boron-containing particles at 350 ° C. in a MOCVD growth furnace using B as a boron raw material, the particle is rapidly raised to 650 ° C. at a rate of 100 ° C. per minute to make the boundary region of the crystal substrate amorphous. To form crystal grains. The amorphous layer present in the region in the vicinity of the bonding interface with the crystal substrate relaxes the lattice mismatch with the crystal substrate, and can provide a boron phosphide-based semiconductor layer with excellent crystallinity with less distortion. According to an electron diffraction technique using a transmission electron microscope (TEM), it is possible to identify the presence or absence of an amorphous material in a region near a bonding interface with a crystal substrate.
[0016]
Particles containing boron or phosphorus formed in advance on the surface of the crystal substrate act as growth nuclei, and are effective in providing a continuous boron phosphide-based semiconductor layer. In order to grow a boron phosphide-based semiconductor layer using these particles as nuclei, the temperature of the crystal substrate when growing the boron phosphide-based semiconductor layer exceeds the temperature at which particles containing either boron or phosphorus are formed, It is suitable that the temperature is 1200 ° C. or lower. Growing a boron phosphide-based semiconductor layer at the same temperature at which the particles are formed is disadvantageous in many cases because it results in a polycrystalline boron phosphide-based semiconductor layer with irregular alignment. A preferable temperature is a temperature of 750 ° C. or higher and 1200 ° C. or lower. High temperature exceeding 1200 ° C is, for example, B₆P or B₁₃P₂Such a boron phosphide multimer is generated, which is inconvenient for obtaining a compositionally uniform boron phosphide-based semiconductor layer. As an example of the fourth embodiment of the present invention, particles containing boron and phosphorus are formed in advance on the surface of a p-type silicon single crystal at 450 ° C. and then increased to 1050 ° C. at a rate of 75 ° C. per minute. And a method of forming a continuous film of monomeric boron phosphide (BP) by MOCVD.
[0017]
Means for forming a boron phosphide-based semiconductor layer using boron or phosphorus-containing grains as growth nuclei include pre-brown halogen vapor phase epitaxy, hydride vapor phase epitaxy, molecular beam epitaxy, and There are vapor phase growth means such as metal organic chemical vapor deposition (MOCVD). If the particles provided on the surface of the crystal substrate and the boron phosphide-based semiconductor layer on the particles are formed by the same vapor phase growth means using the same boron raw material or phosphorus raw material, it is advantageous for simple configuration. It becomes. In particular, in MOCVD means, particles caused by halogen species in halogen vapor phase growth means using chloride or bromide as a raw material (see J. Appl. Phys., 42 (1) (1971), pages 420 to 424). There is an advantage that etching (etching) can be avoided. This is a convenient way to form a boron phosphide-based semiconductor layer without reducing the density of particles formed on the crystal substrate surface. As an example of the fifth embodiment of the present invention, a particle containing boron or phosphorus and a boron phosphide-based semiconductor layer are formed as (C₂H_Five)_ThreeA means for forming B by the MOCVD method using the same boron raw material can be mentioned. PH_ThreeIs a means for forming particles and a boron phosphide-based semiconductor layer by atmospheric pressure (substantially atmospheric pressure) or reduced pressure MOCVD.
[0018]
Various semiconductor elements can be formed by forming a boron phosphide-based semiconductor layer provided with grains containing boron or phosphorus as growth nuclei. For example, an n-type boron phosphide-based semiconductor layer formed through particles containing boron and phosphorus formed on an n-type silicon carbide (SiC) single crystal substrate can be used as a barrier (cladding) layer in an LED. Insulating sapphire (α-Al₂O_ThreeSingle-crystal) An oxygen-doped high-resistance boron phosphide-based semiconductor layer formed through particles containing boron and phosphorus formed on the substrate surface can be used as a high-resistance buffer layer for field effect transistor (FET) applications. Various specifications such as layer thickness and resistance of the boron phosphide-based semiconductor layer provided via boron or phosphorus-containing particles are determined in view of the function to be performed by the layer. For example, from a monomeric boron phosphide layer having a forbidden band width of about 3 eV at room temperature, a clad layer that also serves as a light-emitting reflective layer capable of reflecting light of a specific wavelength with high reflectivity by adjusting the layer thickness (See Japanese Patent Application No. 2002-18188).
[0019]
[Action]
When the boron phosphide-based semiconductor layer is vapor-phase grown on the surface of the crystal substrate, particles containing either boron or phosphorus previously formed on the surface of the crystal substrate cause the subsequent growth of the boron phosphide-based semiconductor layer. Act as a growth nucleus to promote.
[0020]
In particular, a polycrystalline particle containing boron or phosphorus has an effect of providing a boron phosphide-based semiconductor layer having few crystal defects and excellent crystallinity regardless of the presence of a lattice mismatch between the crystal substrate and the boron phosphide-based semiconductor layer. Have
[0021]
In particular, when a particle containing boron or phosphorus is formed from a polycrystalline body containing an amorphous material in a region of a bonding interface with the surface of the crystalline substrate, the amorphous material is formed from the crystalline substrate and the boron phosphide-based semiconductor layer. It exerts the effect of relaxing the lattice mismatch with and providing a boron phosphide-based semiconductor layer with excellent crystallinity.
[0022]
【Example】
(First embodiment)
The present invention will be specifically described by taking as an example the case where a boron phosphide semiconductor layer is vapor-phase grown after previously forming particles containing either boron or phosphorus on a crystal substrate.
[0023]
In the first embodiment, a general halogen vapor phase growth apparatus (for example, Electronic Communication Society “Semiconductor / Transistor Research Group / Material No. SSD74-89 (1975-03)” (March 25, 1975) The particles containing boron and phosphorus were formed on the surface of a Si single crystal substrate having a p-type {111} plane by using a boron-phosphorous particle 102. Boron trichloride (BCl) as raw material_Three) And phosphorus trichloride (PCl)_Three)It was used. BCl_ThreeWas bubbled with hydrogen gas and then supplied to the reactor of the vapor phase growth apparatus. BCl_ThreeWas maintained at 0 ° C., and the flow rate of the hydrogen gas for foaming accompanied with the vapor was adjusted to 15 milliliters (ml) per minute. PCl_ThreeThe flow rate of hydrogen gas for foaming was set to 30 ml per minute. These raw materials are hydrogen (H₂) Along with the carrier gas, it was circulated in the reactor of the vapor phase growth apparatus. The flow rate of the hydrogen carrier gas was 2 liters (l) per minute. BCl_Three, PCl_ThreeThe hydrogen gas and the carrier gas accompanied by the vapor were continuously circulated for 1 minute to form particles 102 containing boron and phosphorus on the surface of the substrate 101.
[0024]
FIG. 1 is a copy of an atomic force microscope image of the particles 102 formed on the surface of the substrate 101 made of a Si single crystal held at 450 ° C. under the above conditions. From observations using a general cross-sectional TEM technique and an atomic force microscope, it was analyzed that the particles 102 formed on the surface of the substrate 101 consisted of non-stoichiometric boron phosphide rich in boron. The average height was about 25 nm. The highest was about 28 nm and the lowest height was about 20 nm. Moreover, the horizontal cross-sectional shape of the particle | grains 102 was substantially circular, and the diameter (particle diameter) was about 20 nm. The density of the particles 102 on the surface of the substrate 101 having a diameter of 2 inches is about 10 from surface observation by an atomic force microscope.⁷Piece / cm²I was asked.
[0025]
After forming the particles 102, the Si single crystal substrate 101 was taken out of the halogen vapor phase growth furnace. Next, the boron phosphide layer was vapor-phase grown by using MOCVD means different from the halogen vapor phase growth method using the particles 102 as growth nuclei. FIG. 2 schematically shows an outline of the MOCVD apparatus used in the first embodiment. At one end of the MOCVD reactor 11 of the MOCVD apparatus, an introduction hole 12 for supplying a boron raw material or a phosphorus raw material for forming particles is provided. Further, a discharge hole 13 for discharging a boron raw material or a phosphorus raw material to the outside of the furnace is provided at the other opposite end of the MOCVD reaction furnace 11. In addition, a substrate support table 14 that can be carried into and out of the furnace is placed inside the MOCVD reaction furnace 11.
[0026]
First, after placing the Si single crystal substrate 101 with the particles 102 formed on the surface thereof on the substrate support 14, the substrate support 14 was inserted into the MOCVD reactor 11. Next, the temperature of the substrate support 14 is increased from room temperature to 1050 ° C. at a slow rate of 20 ° C. per minute by a high-frequency induction heating method using a high-frequency induction coil 15 disposed around the outer periphery of the MOCVD reactor 11. I let you. Thereafter, triethylboron ((C₂H_Five)_ThreeB) and phosphine (PH) as a phosphorus raw material_Three) To hydrogen (H₂) It was circulated in the MOCVD reactor 11 together with the carrier gas. (C₂H_Five)_ThreeB was supplied after foaming with hydrogen gas. (C₂H_Five)_ThreeThe temperature of B was maintained at 25 ° C., and the flow rate of the hydrogen gas for foaming accompanied with the vapor was adjusted to 45 milliliters (ml) per minute. PH_ThreeThe flow rate (concentration 100%) was set to 400 ml per minute. The flow rate of the hydrogen carrier gas was 8 liters (l) per minute. While maintaining the pressure inside the MOCVD reactor 11 at approximately atmospheric pressure,₂H_Five)_ThreeHydrogen gas accompanied by B vapor, PH_ThreeThen, hydrogen carrier gas was continuously circulated for 8 minutes, and an undoped p-type monomer boron phosphide layer was vapor-phase grown on the Si single crystal substrate 101 using the particles 102 as growth nuclei. The layer thickness of the boron phosphide layer was about 240 nm. The boron phosphide layer became a continuous film with no protrusions and excellent surface flatness. The carrier (hole) concentration is about 2 × 10.¹⁹cm^-3As a result, a low resistance p-type boron phosphide semiconductor layer was obtained.
[0027]
(Second embodiment)
In the second embodiment, the present invention will be described by taking as an example the case where polycrystalline grains are previously formed on a crystal substrate by halogen vapor phase epitaxy and then the boron phosphide semiconductor layer is vapor phase grown by MOCVD. The contents of will be specifically described.
[0028]
Different from the first embodiment, the temperature-related conditions were different, and boron or phosphorus-containing particles were formed on a Si single crystal substrate by halogen vapor phase epitaxy. In the second embodiment, a BCl gas and a hydrogen carrier gas are used under the same conditions as in the first embodiment toward the surface of the Si single crystal substrate maintained at about 23 ° C. at room temperature._ThreeAnd PCl_ThreeAnd droplets of boron raw material and phosphorus raw material were deposited on the surface of the substrate. Thereafter, the supply of the raw material into the halogen vapor phase growth apparatus was stopped, and the temperature of the substrate was increased to 650 ° C. at a rate of temperature increase of 20 ° C. per minute to solidify the droplets. Analysis by a general cross-sectional TEM technique revealed that the particles solidified under these conditions were polycrystalline containing flat, generally spherical boron and / or phosphorus having a diameter of approximately 5 nm, or both. . Further, in the measurement using an atomic force microscope, the particles were distributed almost uniformly on the surface of the substrate having a diameter of 2 inches with an average distance of about 10 nm.
[0029]
However, in the Auger electron analysis, fine precipitates with a diameter of several tens of nanometers mainly consisting of phosphorus oxide were confirmed on the surface. The in-plane density of the precipitate is about 100 / cm.²It was about. In the vapor phase growth according to the second embodiment, as in the case of the first embodiment, boron or phosphorus-containing particles and the boron phosphide layer are formed by different vapor phase growth means. Therefore, after forming the grains, it was necessary to take out the silicon single crystal substrate from the apparatus and place it again in the MOCVD reactor in which the boron phosphide layer is vapor-grown. Therefore, the silicon single crystal substrate on which the particles are formed is exposed to the atmosphere, and at this time, it is thought that precipitates are formed by oxidizing the particles containing boron or phosphorus.
[0030]
Next, in accordance with the same means as in the first embodiment, a boron phosphide semiconductor layer was formed by atmospheric pressure MOCVD using the polycrystalline particles as growth nuclei. The obtained boron phosphide semiconductor layer was a continuous film with no visible cracks.
[0031]
(Third embodiment)
In the third embodiment, an example in which the boron phosphide semiconductor layer is vapor-phase grown after previously forming particles containing amorphous in the region of the bonding interface with the crystal substrate on the crystal substrate will be described. The contents of the invention will be specifically described.
[0032]
A boron raw material and a phosphorus raw material were deposited on the surface of the silicon single crystal substrate at 450 ° C. by the same means as in the first example. Thereafter, the substrate temperature was rapidly increased to 1050 ° C. at a heating rate of 150 ° C. per minute. By this temperature raising operation, particles containing boron or phosphorus, in which the region of the bonding interface with the silicon single crystal substrate was made amorphous, were formed. Thereafter, the monomeric boron phosphide semiconductor layer was vapor-phase grown by the same means as in the first example.
[0033]
FIG. 6 shows the dependence of the reflectance of the boron phosphide semiconductor layer vapor-grown on the silicon single crystal substrate of the third embodiment with respect to the wavelength of light. The reflectance of blue band light having a wavelength of about 450 nm is about 30% and about 33% in the case of the boron phosphide semiconductor layer fabricated in the first and second embodiments, respectively. In the three examples, the highest was about 43%. From this, it was shown that the particles containing amorphous are effective in providing a boron phosphide layer having particularly excellent surface flatness.
[0034]
(Fourth embodiment)
In the fourth embodiment, the content of the present invention will be described more specifically by taking as an example a case where a boron phosphide semiconductor layer is vapor-phase grown after previously forming amorphous particles on a crystal substrate. .
[0035]
FIG. 3 schematically shows a cross-sectional structure of an epitaxial multilayer structure 1A according to the fourth embodiment. In addition, about the same component as shown in FIG.1 and FIG.2, the same code | symbol is attached | subjected and the description is abbreviate | omitted.
[0036]
In the fourth embodiment, the layer thickness is approximately 240 nm, and the carrier (hole) concentration is approximately 2 × 10, which is manufactured by the same method as in the third embodiment.¹⁹cm^-3On the p-type boron phosphide layer 103, trimethylgallium ((CH_Three)_ThreeGa) / Ammonia (NH_Three) / Hydrogen (H₂) N-type Ga using normal atmospheric pressure MOCVD_0.90In_0.10The N layer was stacked as the light emitting layer 104. The layer thickness of the light emitting layer 104 is set to about 65 nm, and the carrier (electron) concentration is about 4 × 10.¹⁸cm^-3Set to. Wurtzite crystal type Ga forming the light emitting layer 104_0.90In_0.10The a-axis lattice constant of the N layer is about 3.216Å, and the {110} crystal plane lattice plane of the zinc phosphite crystal-type monomer boron phosphide (lattice constant ≒ 4.538Å) as the underlayer It was decided to coincide with the interval (≈3.209 mm).
[0037]
On the light emitting layer 104, (C₂H_Five)_ThreeB / PH_Three/ H₂An n-type monomeric boron phosphide (BP) layer 105 was laminated undoped at 850 ° C. using system atmospheric pressure MOCVD. The layer thickness of the n-type BP layer 105 was about 240 nm, which is substantially the same as the layer thickness 103 of the p-type BP layer. Carrier (electron) concentration is about 8 × 10¹⁸cm^-3It was.
[0038]
In the fourth embodiment, in particular, the p-type boron phosphide layer 103 was vapor-phase grown using amorphous particles as growth nuclei, so that it became a continuous film and had excellent surface flatness. For this reason, both the light emitting layer 104 and the n-type boron phosphide layer 105 grown by vapor phase growth using the same layer 103 as an underlayer became a continuous film having a flat mirror surface.
[0039]
(5th Example)
In the fifth embodiment, the contents of the present invention are described by taking as an example the case where both the particles on the crystal substrate surface and the boron phosphide semiconductor layer are formed by MOCVD using the same boron source and phosphorus source. This will be specifically described.
[0040]
In the fifth embodiment, using the MOCVD apparatus shown in FIG. 2, particles containing boron or phosphorus containing amorphous are formed on a p-type silicon single crystal substrate having a (111) plane. Boron raw materials include (C₂H_Five)_ThreeB was used. The phosphorus raw material is PH_ThreeIt was. (C₂H_Five)_ThreeB was supplied into the MOCVD reactor 11 from the introduction hole 12 in association with hydrogen gas for bubbling the boron raw material maintained at a constant temperature of 25 ° C. The flow rate of hydrogen gas for foaming was 5 ml / min. PH_ThreeThe flow rate of (concentration 100%) was 400 ml per minute. The flow rate of hydrogen gas for transporting these raw materials into the MOCVD reactor 11 was 16 liters per minute (l). The temperature of the Si single crystal substrate 101 was set to 450 ° C., and the boron raw material and the phosphorus raw material were circulated toward the surface of the substrate 101 together with the hydrogen carrier gas at the above flow rate for 1.5 minutes. Thus, particles 102 containing boron and phosphorus were formed. In surface observation using a general atomic force microscope, the average particle diameter of the particles 102 was measured to be about 10 nm. The surface density of the particles 102 existing on the surface of the substrate 101 is about 10⁸/ Cm²I was asked.
[0041]
After stopping the supply of the boron raw material into the MOCVD reactor 11, the PH_ThreeAnd the hydrogen carrier gas in the MOCVD reactor 11 while maintaining the above flow rates, the temperature of the substrate 101 was rapidly increased from 450 ° C. to 1050 ° C. at a rate of 150 ° C. per minute. Next, according to the same procedure as in the fourth example, using the particle 102 as a growth nucleus, the p-type boron phosphide layer, the light emitting layer, and the n-type boron phosphide layer similar to those in the fourth example The same MOCVD apparatus used for forming was used, and lamination was performed by the MOCVD method.
[0042]
The surfaces of the p-type boron phosphide layer, the light emitting layer, and the n-type boron phosphide layer grown by vapor phase through the particles 102 were all flat. If the particles and the boron phosphide-based semiconductor layer are formed by the same vapor phase growth means using the same raw material, the particles and the boron phosphide-based semiconductor layer provided therebetween are provided by different vapor phase growth means. As a result, it was taught that a boron phosphide layer excellent in surface flatness and continuity can be easily formed while avoiding complexity. In addition, in the first to fourth examples, precipitates mainly composed of phosphorous oxide scattered on the surface can be almost confirmed by the Auger analysis and the scanning electron microscope observation. There wasn't.
[0043]
(Sixth embodiment)
In the sixth embodiment, an example in which an LED is formed using a boron phosphide-based semiconductor layer obtained by vapor-phase growth using amorphous particles on a crystal substrate as growth nuclei will be described. Will be described in detail.
[0044]
FIG. 4 shows a schematic plan view of an LED 1B according to the sixth embodiment. FIG. 5 schematically shows a cross-sectional structure of the LED 1B along the broken line X-X ′ in FIG. 4 and 5, the same components as those shown in FIGS. 1 to 3 are given the same reference numerals, and descriptions thereof are omitted.
[0045]
The LED 1B described in the sixth example is configured by providing an ohmic electrode on the laminated structure 1A described in the fifth example. At the center of the surface of the n-type boron phosphide layer 105, Au.Ge/nickel (Ni) / Au in which an ohmic electrode made of a gold-germanium (Au.Ge) alloy is disposed on the side in contact with the layer 105. A surface electrode 106 having a three-layer multi-layer structure was provided. The surface electrode 106 also serving as a pedestal (pad) electrode for connection was a circular electrode having a diameter of about 120 μm. Also, an ohmic electrode made of aluminum (Al) was disposed as the back electrode 107 on substantially the entire back surface of the p-type Si single crystal substrate 101. The thickness of the Al vapor deposition film was about 2 μm. Thus, an LED 1B having a pn junction type DH structure in which the n-type light emitting layer 104 is sandwiched between the p-type and n-type boron phosphide layers 103 and 105 is configured. Since both the p-type and n-type boron phosphide layers 103 and 104 have a band gap of about 3 eV at room temperature, they can be effectively used as a clad layer for the light-emitting layer 104.
[0046]
When an operating current of 20 milliamperes (mA) was passed between the front electrode 106 and the back electrode 107 in the forward direction, blue-violet light having a wavelength of about 440 nm was emitted from the LED 1B. The luminance in a chip state measured using a general integrating sphere was 9 millicandela (mcd), and an LED 1B having high emission intensity was provided. In addition, since both the n-type light emitting layer 104 and the p-type boron phosphide layer 103 are formed of a pn junction from a continuous film having excellent surface flatness, good rectification characteristics are manifested, and the forward voltage (Vf However, the forward current = 20 mA) was about 3 V, and the reverse voltage (VR, reverse current = 10 μA) was 5 V or more.
[0047]
【The invention's effect】
According to the present invention, there is provided a method for producing a boron phosphide-based semiconductor layer in which a boron phosphide-based semiconductor layer containing boron and phosphorus as constituent elements is vapor-phase grown on a surface of a crystal substrate. Since particles containing either boron or phosphorus on the surface were previously formed, and then the boron phosphide-based semiconductor layer was vapor-phase grown, the above-mentioned action as a “growth nucleus” was utilized. This is effective for vapor phase growth of a boron phosphide-based semiconductor layer having excellent surface flatness and continuity.
[0048]
In addition, according to the present invention, since the particles containing either boron or phosphorus are made of polycrystalline in particular, a continuous film of a boron phosphide-based semiconductor layer having excellent surface flatness is vapor-phase grown. Can be effective.
[0049]
Further, according to the present invention, since the particles containing either boron or phosphorus are composed of a polycrystalline body containing an amorphous body in the region of the bonding interface with the surface of the crystalline substrate, the crystal forming the substrate Is particularly effective for vapor phase growth of a boron phosphide-based semiconductor layer having excellent surface flatness and continuity.
[0050]
Further, according to the present invention, the boron phosphide-based semiconductor layer is formed at a substrate temperature of 1200 ° C. or lower, exceeding the temperature at which particles containing either boron or phosphorus are formed. This is effective for vapor phase growth of an excellent boron phosphide-based semiconductor layer.
[0051]
Further, according to the present invention, the boron phosphide-based semiconductor layer is vapor-phase grown by the same means as the boron raw material or the phosphorus raw material used to form the particles containing either boron or phosphorus. Therefore, it is effective to easily form a boron phosphide-based semiconductor layer having a flat surface and excellent continuity.
[0052]
Further, according to the present invention, since the semiconductor element is configured using the boron phosphide-based semiconductor layer having excellent surface flatness and continuity brought about by the action of the particles of the present invention, for example, A pn junction that exhibits good rectification can be configured, and an LED with high emission intensity that is excellent in forward and reverse voltage characteristics can be provided.
[Brief description of the drawings]
FIG. 1 is a copy of an atomic force microscope image showing particles containing boron or phosphorus formed on a substrate surface according to a first embodiment of the present invention.
FIG. 2 is a schematic view showing the configuration of an MOCVD apparatus.
FIG. 3 is a schematic cross-sectional view of a multilayer structure according to a fourth embodiment of the present invention.
FIG. 4 is a schematic plan view of an LED according to a sixth embodiment of the present invention.
5 is a schematic sectional view taken along a broken line X-X ′ of the LED shown in FIG. 4;
FIG. 6 is a graph showing the dependency of the reflectance of the boron phosphide layer according to the third embodiment of the present invention on the wavelength of light.
[Explanation of symbols]
1A Laminated structure
1B LED
11 MOCVD reactor
12 Introduction hole
13 Discharge hole
14 Substrate support stand
15 High frequency induction coil
16 Boron material container
17 Phosphorus raw material container
101 Crystal substrate
102 Particles containing boron or phosphorus
103 p-type boron phosphide layer
104 Light emitting layer
105 n-type boron phosphide layer
106 Surface electrode
107 Back electrode

Claims (11)

In a method for producing a boron phosphide-based semiconductor layer, in which a boron phosphide-based semiconductor layer containing boron (B) and phosphorus (P) as constituent elements is vapor-grown on a surface of a crystal substrate, the surface of the crystal substrate A method for producing a boron phosphide-based semiconductor layer, wherein particles containing either boron or phosphorus are previously formed, and then a boron phosphide-based semiconductor layer is vapor-phase grown on the surface of the crystal substrate. 2. The method for producing a boron phosphide-based semiconductor layer according to claim 1, wherein the diameter of the particle containing either boron or phosphorus is 1 nm or more and 30 nm or less. 3. The method for manufacturing a boron phosphide-based semiconductor layer according to claim 1, wherein the crystal substrate is made of an n-type or p-type conductive single crystal. The method for producing a boron phosphide-based semiconductor layer according to any one of claims 1 to 3, wherein the particles containing either boron or phosphorus are formed of polycrystals. 5. The method according to claim 1, wherein the particles containing either boron or phosphorus are formed from a polycrystalline body including an amorphous body in a region of a bonding interface with the surface of the crystal substrate. A method for producing a boron phosphide-based semiconductor layer described in the item. 2. The boron phosphide-based semiconductor layer is vapor-phase grown on the surface of the crystal substrate at a temperature exceeding a temperature for forming particles containing either boron or phosphorus and at a temperature of 1200 ° C. or less. 6. The method for producing a boron phosphide-based semiconductor layer according to any one of items 1 to 5. By using the same raw material as the boron raw material or phosphorus raw material used to form the particles containing either boron or phosphorus, by the same vapor phase growth means as forming the particles containing either boron or phosphorus, The method for producing a boron phosphide-based semiconductor layer according to claim 1, wherein the boron phosphide-based semiconductor layer is vapor-phase grown. 8. The method for producing a boron phosphide-based semiconductor layer according to claim 7, wherein the vapor growth means is a metal organic chemical vapor deposition (MOCVD) method. A boron phosphide-based semiconductor layer produced using the method for producing a boron phosphide-based semiconductor layer according to claim 1. A semiconductor device using the boron phosphide-based semiconductor layer according to claim 9. LED using the semiconductor element according to claim 10.

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