JP2007096200A - Compound semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor element using a boron phosphide semiconductor layer which semiconductor element makes the boron phosphide semiconductor layer superior in crystallinity with a smaller density of such a crystal defect as twin crystal and stacking fault. <P>SOLUTION: The compound semiconductor element has the boron phosphide semiconductor layer 12 joined to the surface 11A of a single crystal material 11. The single crystal material 11 has a hexagonal crystal structure, in which [0. 0. 0. 1. ] crystal faces 11B are arranged in almost parallel with a direction of an increase in the layer thickness of the hexagonal crystal structure. In the boron phosphide semiconductor layer 12, [0. 0. 0. 2. ] crystal faces 12B are arranged in almost perpendicular to the surface 11A of the single crystal material 11, and a distance given by consecutive n [0. 0. 0. 2. ] crystal faces 12B (n is a positive integer of 2 or larger, and n=6 is assumed here) is almost equal to the length of the c axis of the single crystal material 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a compound semiconductor element comprising a boron phosphide-based semiconductor layer provided bonded to the surface of a single crystal material.

Conventionally, a cubic zinc blende crystal boron phosphide-based semiconductor layer is made of, for example, a cubic zinc blende crystal gallium phosphide (GaP) single crystal or silicon carbide (SiC) single crystal. It is formed on a substrate (see Patent Document 1 below). Using a stacked structure including these substrates, a boron phosphide-based semiconductor layer formed thereon, and a group III nitride semiconductor layer provided in contact therewith, for example, a compound semiconductor light emitting diode (LED (See Patent Document 2 below).
JP-A-2-288388 JP-A-2-275682

Further, a zinc-blende crystal type cubic boron phosphide-based semiconductor layer such as monomeric boron phosphide (BP) is formed on a silicon single crystal (silicon) as a substrate (described below). (See Patent Document 3). In addition, a technique for forming an LED from a laminated structure including a silicon substrate, a monomeric BP layer on the substrate, and a group III nitride semiconductor layer provided on the BP layer is disclosed ( See Patent Document 3 below).
US Pat. No. 6,690,021

However, for example, a cubic boron phosphide-based semiconductor layer formed on the surface of the (111) crystal plane using silicon as a substrate contains crystal defects such as twins and stacking faults. Is known (see Non-Patent Document 1 below). Also, for example, a cubic monomer BP layer formed on a (0.0.0.1.) Crystal plane using hexagonal 6H-type SiC as a substrate also has crystal defects such as twins. It is reported that it is contained (see Non-Patent Document 2 below). Even when a stacked structure including a cubic boron phosphide-based semiconductor layer containing a large amount of such crystal defects is used, for example, an LED having a high reverse voltage and a high photoelectric conversion efficiency can be stably produced. There is a problem that cannot be produced.
T. Udagawa and G. Shimaoka, J. Ceramic Processing and Research, (South Korea), Vol. 4, No. 2, 2003, pp. 80-83. T. Udagawa et al., Appl. Surf. Sci., (USA), 244, 2004, pp. 285-288.

  The present invention has been made to overcome the above-mentioned problems of the prior art, and the boron phosphide-based semiconductor layer can have excellent crystallinity with a small density of crystal defects such as twins and stacking faults, An object of the present invention is to provide a compound semiconductor element that can improve various characteristics as an element by using the boron phosphide-based semiconductor layer.

  1) To achieve the above object, according to a first aspect of the present invention, there is provided a compound semiconductor device comprising a boron phosphide-based semiconductor layer bonded to the surface of a single crystal material, wherein the single crystal material is hexagonal. Almost parallel to the increasing direction of the layer thickness {0.0.0.1. } The crystal planes are arranged, and the boron phosphide-based semiconductor layer has {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } The distance of n consecutive crystal planes (n is a positive integer greater than or equal to 2) is set to be approximately equal to the length of the c-axis of the single crystal material.

  2) A second aspect of the present invention is the above-described {0.0.0.2. } The number n of crystal faces is 6 or less.

  According to the present invention, in a compound semiconductor device comprising a boron phosphide-based semiconductor layer provided bonded to the surface of a single crystal material, the single crystal material is hexagonal and substantially parallel to the increasing direction of the layer thickness { 0.0.0.1. } The crystal planes are arranged and the boron phosphide-based semiconductor layer is {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } Since the distance of n consecutive crystal planes (n is a positive integer of 2 or more) is substantially equal to the length of the c-axis of the single crystal material, a hexagonal boron phosphide-based semiconductor Since the layer has excellent long-term consistency with a hexagonal single crystal material, it has few crystal defects and excellent crystallinity, and the compound semiconductor uses the hexagonal boron phosphide-based semiconductor layer. This is effective for improving the characteristics of the element.

  Further, according to the present invention, the boron phosphide-based semiconductor layer {0.0.0.2. } Since the number n of crystal planes is 6 or less, a high-quality hexagonal boron phosphide-based semiconductor layer with few misfit dislocations can be obtained. It is effective to bring.

  The present invention relates to a compound semiconductor device comprising a boron phosphide-based semiconductor layer provided bonded to the surface of a single crystal material, the single crystal material being hexagonal and substantially parallel to the increasing direction of the layer thickness {0. 0.0.1. } The crystal planes are arranged and the boron phosphide-based semiconductor layer is {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } The distance of n consecutive crystal planes (n is a positive integer of 2 or more) is approximately the length of the c-axis of the single crystal material (interval of {0.0.0.1.} Crystal planes). It is trying to be equivalent.

The hexagonal boron phosphide-based semiconductor layer according to the present invention is a hexagonal crystal layer containing boron (element symbol: B) and phosphorus (element symbol: P) as essential constituent elements. For example, hexagonal monomer boron phosphide (BP), which contains boron (B) and another group III element as a constituent element, for example, hexagonal boron phosphide aluminum mixed crystal (composition formula B _1-X Al _X P: 0 <X <1), boron gallium phosphide mixed crystal (composition formula B _1-X Ga _X P: 0 <X <1) and boron phosphide indium mixed crystal (composition formula B _{1- X} In _X P: 0 <X <1). In a mixed crystal containing boron (B) and another group III element as a constituent element, a preferred composition ratio of the group III element different from boron (B) (X in the above composition formula) is 0. 40 or less. This is because when the composition ratio (= X) exceeds 0.40, a cubic boron phosphide-based semiconductor layer rather than a hexagonal crystal is easily formed.

Further, the hexagonal boron phosphide-based semiconductor layer according to the present invention contains, for example, a hexagonal boron arsenide phosphide (composition formula BP ₁ ) containing a group V element different from phosphorus (P) and phosphorus (P). _-Y As _Y : 0 <Y <1) and boron nitride phosphide (compositional formula BN _Y P _1-Y : 0 <Y <1). Taking into account the simplicity of crystal growth and the complexity of composition control, the hexagonal boron phosphide-based semiconductor layer is preferably composed of monomeric boron phosphide (BP).

Examples of the hexagonal single crystal material bonded to the hexagonal boron phosphide-based semiconductor layer according to the present invention include group III nitrides such as sapphire (α-Al ₂ O ₃ single crystal) and wurtzite crystal type GaN. Examples include semiconductors, zinc oxide (ZnO), bulk single crystals or single crystal layers such as 2H type (wurtzite crystal type) or 4H type or 6H type silicon carbide (SiC) in terms of Ramsdell.

  In the present invention, there is a hexagonal single crystal material composed of these bulk single crystals or single crystal layers, and in particular, substantially in parallel with the increasing direction (growth direction) of the layer thickness {0.0.0.1. } Use a hexagonal single crystal material with crystal planes arranged. Therefore, the surface of this single crystal material is, for example, {1.0. -1.0. } Crystal plane or {1.1. -2.0. } It becomes a crystal plane. Here, the increasing direction of the layer thickness is the stacking direction of the layers, and may be expressed as a vertical direction in the following description. Further, substantially in parallel with the increasing direction of the layer thickness of the single crystal material {0.0.0.1. } Although crystal planes are arranged, the term “substantially parallel” means that the crystal plane is preferably within a range of ± 10 degrees with respect to the vertical direction. If it is out of this range, many twins and crystal defects are generated in the layer laminated thereon.

  As described above, in the present invention, {1.0. -1.0. } Crystal plane or {1.1. -2.0. } A hexagonal boron phosphide-based semiconductor layer is provided on the crystal plane. For example, a single crystal material made of a hexagonal silicon carbide single crystal of 2H type, 4H type, or 6H type {1.0. -1.0. } Crystal plane or {1.1. -2.0. } A hexagonal boron phosphide-based semiconductor layer is provided on the surface of the crystal plane. Further, a single crystal material made of wurtzite crystal type hexagonal aluminum nitride (AlN) or a wurtzite crystal type hexagonal GaN, {1.0. -1.0. } Crystal plane or {1.1. -2.0. } A hexagonal boron phosphide-based semiconductor layer is provided on the surface of the crystal plane. Further, a single crystal material made of sapphire (α-alumina single crystal), {1.0. -1.0. } Crystal plane (common name, M plane or m plane) and {1.1. -2.0. } It is preferable to provide a hexagonal boron phosphide-based semiconductor layer on the surface composed of a crystal plane (commonly referred to as A-plane or a-plane).

  The hexagonal boron phosphide-based semiconductor layer has a {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } The distance of n consecutive crystal planes (n is a positive integer of 2 or more) is approximately the length of the c-axis of the single crystal material (interval of {0.0.0.1.} Crystal planes). It is trying to be equivalent. That is, the boron phosphide-based semiconductor layer {0.0.0.2. } The distance of n consecutive crystal planes and the length of the c-axis of the single crystal material are matched periodically. As described above, the hexagonal boron phosphide-based semiconductor layer has {0.0.0.2. } The crystal planes are arranged substantially perpendicular to the surface of the single crystal material, and the term “substantially perpendicular” means that the crystal plane is preferably within a range of ± 10 degrees with respect to the vertical direction. If it is out of this range, many twins and crystal defects are generated in the layer laminated thereon.

A hexagonal boron phosphide-based semiconductor layer is formed on a surface having a suitable crystal plane as described above, such as a halogen method, a hydride method, or a metal organic chemical deposition (abbreviation: MOCVD) method. It can be formed by vapor phase growth means. For example, it can be formed by MOCVD using triethyl boron (molecular formula (C ₂ H ₅ ) ₃ B) as a boron (B) source and triethyl phosphorus (molecular formula (C ₂ H ₅ ) ₃ P) as a phosphorus (P) source. Further, it can be formed by a halogen CVD method using boron trichloride (molecular formula BCl ₃ ) as a boron source and phosphorus trichloride (molecular formula PCl ₃ ) as a phosphorus source. Alternatively, the film can be formed by a growth means for forming a film in a vacuum environment such as a gas source molecular beam epitaxial (abbreviation: GS-MBE) method or a chemical beam epitaxial (abbreviation: CBE) method.

  When a hexagonal boron phosphide-based semiconductor layer is formed on the surface of the above-mentioned preferred crystal plane of the hexagonal single crystal material by, for example, atmospheric pressure (substantially atmospheric pressure) or low pressure MOCVD method, a) The growth temperature is 750 ° C. or more and 850 ° C. or less, and (b) the concentration ratio (so-called V / III ratio) of the phosphorus (P) source to the boron (B) source supplied to the growth reaction system, When the growth rate of the boron phosphide-based semiconductor layer (C) is 20 nm / min or more and 30 nm / min or less in the range of 400 or more and 500 or less, the increase direction of the layer thickness (on the surface of the single crystal material described above) On the other hand, a hexagonal boron phosphide-based semiconductor layer in which {0002} crystal planes are regularly arranged at regular intervals in parallel to the vertical direction) can be formed.

The growth rate of the hexagonal boron phosphide-based semiconductor layer is such that if the concentration of a group III constituent element source such as boron (B) supplied per unit time to the growth reaction system is increased, It is increased in proportion to the concentration. Further, when the concentration of a group III constituent element such as boron supplied to the growth reaction system per unit time is constant, the growth rate is increased as the growth temperature is increased. At a low temperature of less than 750 ° C., the thermal decomposition of the boron (B) source and the phosphorus (P) source does not occur sufficiently in the first place, so that the growth rate decreases rapidly and the above-mentioned preferable growth rate cannot be obtained. On the other hand, a growth temperature exceeding 850 ° C. is not preferable because a multimeric boron phosphide crystal such as a composition formula B ₆ P may be rapidly generated.

For example, when a hexagonal BP layer is formed by MOCVD using phosphine (molecular formula PH ₃ ) as a phosphorus source and triethyl boron ((C ₂ H ₅ ) ₃ B) as a boron source, the growth temperature is set to 800 ° C. The concentration ratio of the raw material supplied to the growth reaction system, that is, the PH ₃ / (C ₂ H ₅ ) ₃ B ratio is set to 450, and the growth rate is set to 25 nm per minute.

  The hexagonal single crystal material was arranged on the surface composed of the above-mentioned preferred crystal planes in parallel to the surface in a direction perpendicular to the surface {0.0.0.2. } To stably form a hexagonal boron phosphide-based semiconductor layer consisting of crystal planes, after desorbing excess material adsorbed on the surface, growth of the boron phosphide-based semiconductor layer is started. Is preferred. For example, a hexagonal single crystal material is heated in vacuum to a temperature above a preferred temperature for growing a hexagonal boron phosphide-based semiconductor layer, for example, to a temperature above 850 ° C., It is preferable to grow the boron phosphide-based semiconductor layer after desorbing molecules adsorbed on the surface of the hexagonal single crystal material. The hexagonal boron phosphide-based semiconductor layer is preferably grown on the cleaned surface while desorbing adsorbed molecules and maintaining the surface state of the cleaned hexagonal single crystal material. From this point of view, an MBE method or a CBE method for growing in a high vacuum environment is suitable as a means for growing a hexagonal boron phosphide semiconductor layer. Further, a low pressure chemical vapor deposition (CVD) method in which growth is performed in a reduced pressure environment is suitable.

As described above, on the surface of the cleaned hexagonal single crystal material having a suitable crystal plane as described above, the length of the c-axis of the hexagonal single crystal material is long-period. A matching hexagonal boron phosphide-based semiconductor layer can be formed stably. FIG. 1 schematically shows long-period matching according to the hexagonal boron phosphide-based semiconductor layer of the present invention. In the figure, a hexagonal single crystal material 11 is represented by {1.0. -1.0. } The pattern of long-period matching in the case of using sapphire having a crystal plane as the surface 11A and the hexagonal boron phosphide-based semiconductor layer 12 bonded to the surface 11A as a B _0.98 Al _0.02 P layer is illustrated. . As shown in FIG. -1.0. } Inside the sapphire whose crystal plane is the surface 11A, {0.0.0.1. The crystal planes 11B are regularly arranged perpendicular to the surface 11A and parallel to each other. In addition, in the hexagonal boron phosphide-based semiconductor layer 12 bonded to the surface 11A of the hexagonal single crystal material with the bonding surface 12A, {0.0.0.1. } Parallel to the crystal plane 11B, {0.0.0.2. } There are a total of six crystal faces 12B arranged. That is, in the bonding system 10 of the single crystal material 11 and the boron phosphide-based semiconductor layer 12, the surface 11A of the cleaned sapphire has a c-axis length (1) of sapphire as shown in FIG. .30 nm) (“c-axis length” in FIG. 1), a total of six {0.0.0.2. } The crystal face 12B is arranged.

  In other words, on the hexagonal single crystal material 11, the length of the c-axis and n (n is a positive integer of 2 or more, for example, 2, 3, 4, 5 or 6) {0.0 0.2. } A hexagonal boron phosphide-based semiconductor layer in which the total length (= (n−1) × d) of the distance d between the crystal planes 12B is equal, that is, in a state of long-period matching Can be formed. d is two adjacent {0.0.0.2. } Since it is given with an interval of crystal planes, {0.0.0.2. } The crystal face needs at least two faces. That is, n is 2 or more.

Sapphire {1.0. -1.0. } A B _0.98 Al _0.02 P mixed crystal layer or a B _0.99 Ga _0.01 P mixed crystal layer bonded to a crystal surface has a long-period matching structure as described above {0.0. .2. } The number of crystal faces is 6, that is, n is 6, but {1.0. -1.0. } N is 2 in the case of a BP layer bonded to the surface of the crystal plane. Also, AlN {1.0. -1.0. } N is 2 even in the BP layer bonded to the surface of the crystal plane. Further, a single crystal material made of GaN or AlN {1.1. -2.0. } N is 2 even in the BP layer bonded to the crystal plane.

If the surface of the hexagonal single crystal material provided with the hexagonal boron phosphide-based semiconductor layer is not sufficiently cleaned, for example, oxygen (element symbol: O) remaining on the surface or water (molecular formula H {0.0.0.2. Due to adverse effects of adsorbed molecules such as ₂ O). } As shown in FIG. 1, the hexagonal boron phosphide-based semiconductor layer whose crystal planes are regularly arranged is hindered from being obtained sufficiently stably. Extra molecules such as carbon monoxide (molecular formula CO), carbon dioxide (molecular formula CO ₂ ) and nitrogen (molecular formula N ₂ ), which are not raw material molecules for growing a hexagonal boron phosphide-based semiconductor layer, are hexagonal crystals. Similarly, even when the surface remains adsorbed on the surface of the single crystal material, the hexagonal boron phosphide-based semiconductor layer having the long-period matching structure described above cannot be obtained sufficiently stably. is there.

  The inconvenience in stably obtaining the hexagonal boron phosphide-based semiconductor layer that fulfills the above-mentioned long-period matching is that the hexagonal boron phosphide-based semiconductor layer is formed by the adsorbed extra molecules {0.0 0.2. } This is because the orderly and regular arrangement of crystal planes is disturbed. As another cause, {0.0.0.2. } A crystal face having a plane index different from the crystal face may be formed. Another cause is that the hexagonal boron phosphide-based semiconductor crystal does not grow on the region where the adsorbed molecules remain. Therefore, when the hexagonal boron phosphide-based semiconductor layer having a long-period matching structure is bonded and provided, a treatment for cleaning the surface of the hexagonal single crystal material is important.

  In the MBE method or the CBE method for forming a film in a vacuum environment, the presence of adsorbed molecules on the surface of a hexagonal single crystal material can be detected from, for example, a high-speed reflection electron diffraction (abbreviation: RHEED) pattern. When molecules adsorbed on the surface remain, the RHEED image is not a spot or streak (light stripe) shape that should originally result from the surface of a hexagonal single crystal material, but a ring. It becomes a (ring) shape or a halo pattern. The molecular species adsorbed on the surface of the hexagonal single crystal material can be identified by an analysis means such as infrared absorption spectroscopy or ultraviolet absorption spectroscopy.

  Further, when the hexagonal boron phosphide-based semiconductor layer is bonded to the surface of the hexagonal single crystal material, the growth rate is set to less than 20 nm per minute or increased to exceed 30 nm per minute. In either case, it will hinder the stable and stable acquisition of a hexagonal boron phosphide-based semiconductor layer that matches periodically. If the growth rate is a low rate of less than 20 nm per minute, for example, {0.0.0.2. } Phosphorus (P) atoms constituting the crystal plane are volatilized and a long-period matching structure is sufficient {0.0.0.2. } This is because there is a numerical loss of crystal planes. On the other hand, when the growth rate is higher than 30 nm per minute, it is sufficient to provide a long-period matching structure {0.0.0.2. } Beyond the number of crystal faces (that is, n in the present invention), {0.0.0.2. } This is because a crystal plane is formed.

  The hexagonal boron phosphide-based semiconductor layers {0.0.0.2] arranged so as to form long-period matching at a distance corresponding to the length of the c-axis of the surface of the hexagonal single crystal material. . } The number of crystal planes, that is, n in the present invention can be examined from, for example, a lattice image obtained by electron diffraction analysis using a transmission electron microscope (abbreviation: TEM) or a cross-sectional TEM technique. When the long-period matching structure according to the present invention is formed, the diffraction spot from the {0.0.0.1} crystal plane of the hexagonal single crystal material on the electron diffraction image is a hexagonal phosphide. The boron-based semiconductor layer {0.0.0.2. } Appears with an interval equal to (n−1) times the diffraction spot from the crystal plane (the total of the intervals between n {0.0.0.2.} Crystal planes in total).

  In particular, when a long-period matching structure in which n is 8 or less, more preferably 6 or less, a hexagonal boron phosphide-based semiconductor layer excellent in crystallinity with few misfit dislocations can be obtained. Hexagonal boron phosphide-based semiconductor in the direction perpendicular to the c-axis of the hexagonal single-crystal material generated in the vicinity of the junction interface between the hexagonal boron phosphide-based semiconductor layer and the hexagonal single-crystal material The density of mismit dislocations inside the layer increases in proportion to the value of n described above. According to the results of the present inventors, a long-period matching structure in which n is 6 or less does not lead to local electrical breakdown, and high-quality hexagonal phosphide with a low density of misfit dislocations. It has been found that a boron based semiconductor layer is provided.

Since the hexagonal boron phosphide-based semiconductor layer having a long-period matching structure in which n is 2 or more and 6 or less has a low misfit dislocation density, a high-quality growth layer is formed because of its good crystallinity. It can be used effectively as a foundation for For example, SiC, zinc oxide (ZnO), GaN, AlN, indium nitride (InN), and a nitride of these mixed crystals are preferably provided on the hexagonal boron phosphide-based semiconductor layer having a long-period matching structure. It is a growth layer made of a group III nitride semiconductor such as aluminum, gallium, and indium (compositional formula Al _x Ga _y In _z N: 0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1). In addition, the group III nitride semiconductor layer includes other group V elements such as nitrogen (element symbol: N) and phosphorus other than nitrogen (element symbol: P) and arsenic (element symbol: As). Examples thereof include growth layers made of gallium nitride phosphide (compositional formula GaN _1-Y P _Y : 0 ≦ Y <1) and gallium arsenide nitride (compositional formula GaN _1-Y As _Y : 0 ≦ Y <1).

A III-nitride as described above, which has a long-period matching structure and is formed from a hexagonal boron phosphide-based semiconductor layer with few misfit dislocations as a base and has low crystal defect density such as twins and dislocations. If a semiconductor layer is used, a pn junction type heterostructure that provides high intensity light emission can be formed. For example, an LED having an Al _X Ga _Y N (0 ≦ X, Y ≦ 1, X + Y = 1) layer as a clad layer and a Ga _X In _1-X N (0 <X <1) layer as a light emitting layer. The double hetero (DH) junction type light emission part for light emitting element use etc. can be comprised.

  Further, not only a compound semiconductor light emitting device but also a Group III nitride semiconductor layer with reduced crystal defect density and excellent crystallinity is used as an electron transit layer (channel layer), a Schottky contact MESFET. Can be configured. The channel layer can be composed of, for example, an undoped high-purity n-type GaN layer to which impurities are not intentionally added. In a group III nitride semiconductor layer with a reduced crystal defect density, high electron mobility is manifested, which is advantageous for obtaining a MESFET having excellent high-frequency characteristics.

  (Example) Contents of the present invention, taking as an example a case where an LED is constructed using a hexagonal monomer BP layer formed on a surface of a sapphire bulk crystal as a hexagonal single crystal material. Will be described in detail.

  FIG. 2 schematically shows a planar configuration of the LED 20 according to the present embodiment. FIG. 3 shows a schematic cross-sectional view of the LED 20 along the broken line A-A ′ shown in FIG. 2.

  The laminated structure 200 for manufacturing the LED 20 was formed using sapphire (α-alumina single crystal) having a (1.1.-2.0.) Crystal plane (commonly referred to as A plane) as the substrate 201. Prior to forming the hexagonal boron phosphide-based semiconductor layer 202 on the surface of the substrate 201, the sapphire substrate 201 is heated to 1200 ° C. under a vacuum of about 0.01 atm in a general low-pressure MOCVD apparatus. The adsorbed material on the surface of the substrate 201 was desorbed to clean the surface.

  Next, an undoped n-type hexagonal monomer BP layer 202 having a layer thickness of about 490 nm is formed on the surface of the cleaned sapphire substrate 201 by using a general low pressure MOCVD method. A boron phosphide-based semiconductor layer was formed. According to a general cross-sectional TEM analysis, {0.0.0.2. } It was revealed that the crystal planes were arranged perpendicular to the cleaned surface of the sapphire substrate 201 and parallel to each other. On the surface of the sapphire substrate 201, {0.0.0.2. Of the hexagonal BP layers 202 arranged at intervals corresponding to the c-axis length of the sapphire. } The number of crystal faces was 6, that is, n in the present invention was 6.

  In addition, in the observation by the cross-sectional TEM technique and the electron diffraction means, the presence of twins was hardly observed in the hexagonal monomer BP layer 202. In addition, in the region inside the hexagonal monomer BP layer 202 that is higher than about 30 nm from the bonding interface with the sapphire substrate 201, {0.0.0.2. } Almost no disorder in the arrangement of crystal planes can be confirmed, {0.0.0.2. } It was confirmed that the crystal planes were regularly arranged in parallel with each other.

  {0.0.0.2. } On the surface of the hexagonal monomer BP layer 202 in which the crystal planes are arranged in parallel to the increasing direction of the layer thickness, the wurtzite crystal type doped with germanium (element symbol: Ge) is hexagonal. An n-type GaN layer (layer thickness = 1900 nm) 203 was grown as a hexagonal group III nitride semiconductor layer. According to an analysis using a general TEM, the n-type GaN layer 203 grown using the hexagonal monomer BP layer 203 as a base is {0.0.0.1. } The crystal plane is {0.0.0.2. Of the hexagonal monomer BP layer 202. } It was a single crystal layer arranged parallel to the crystal plane. Also, almost no twins or stacking faults were observed in the internal region of the hexagonal GaN layer 203.

On the (1.1.-2.0.) Surface of the hexagonal n-type GaN layer 203, a lower cladding layer (layer thickness = 150 nm) 204 made of hexagonal n-type Al _0.15 Ga _0.85 N, Ga _{A 0.85} In _0.15 N well layer and an Al _0.01 Ga _0.99 N barrier layer having one period, and a light emitting layer 205 having a multi-quantum well structure consisting of five periods, and an upper portion made of p-type Al _0.10 Ga _0.90 N having a layer thickness of 50 nm The clad layer 206 was laminated in this order to constitute a light emitting portion having a pn junction type DH structure. A p-type GaN layer (layer thickness = 80 nm) was further deposited as a contact layer 207 on the surface of the upper cladding layer 206, and the formation of the multilayer structure 200 was completed.

  A p-type ohmic electrode 208 made of a gold (element symbol: Au) / nickel oxide (NiO) alloy was formed in a partial region of the p-type contact layer 207. One n-type ohmic electrode 209 is formed on the surface of the exposed n-type GaN layer 203 after the layers such as the lower cladding layer 204 and the light emitting layer 205 in the region where the electrode 209 is provided are removed by dry etching. did. From this, LED20 was comprised.

  A 20 mA element drive current was passed in the forward direction between the p-type and n-type ohmic electrodes 208 and 209 of the LED 20 to investigate the light emission characteristics. The wavelength of the main light emitted from the LED 20 was about 460 nm. The luminous intensity in the chip state was about 1.8 candela (cd). Further, the layers 204 to 206 made of a group III nitride semiconductor constituting the light emitting portion of the pn junction type DH structure and the n-type GaN layer 203 provided with the n-type ohmic electrode 209 are provided on the hexagonal BP layer 202. As a result, since the group III nitride semiconductor layer having excellent crystallinity could be formed, the reverse voltage when the reverse current was 10 μA was a high value exceeding 15V. Furthermore, due to the good crystallinity of the group III nitride semiconductor layer, the LED 20 is provided in which almost no local breakdown is observed.

It is a schematic diagram for demonstrating a long-period matching joining system. It is a plane schematic diagram of LED as described in an Example. FIG. 3 is a schematic cross-sectional view of an LED along a broken line A-A ′ shown in FIG. 2.

Explanation of symbols

10 Long-Period Matching Junction System 11 Hexagonal Single Crystal Material 11A Surface of Hexagonal Single Crystal Material 11B Hexagonal Single Crystal Material {0.0.0.1. } Crystal plane 12 Hexagonal boron phosphide-based semiconductor layer 12A Bonding surface of boron phosphide-based semiconductor layer 12B Hexagonal boron phosphide-based semiconductor layer {0.0.0.2. } Crystal face 20 Compound semiconductor LED
200 Laminated structure for LED 201 sapphire substrate 202 BP layer (hexagonal boron phosphide-based semiconductor layer)
203 GaN layer (hexagonal group III nitride semiconductor layer)
204 Lower clad layer 205 Light emitting layer 206 Upper clad layer 207 Contact layer 208 p-type ohmic electrode 209 n-type ohmic electrode d of hexagonal boron phosphide-based semiconductor layer {0.0.0.2. } Crystal spacing

Claims (2)

In a compound semiconductor element comprising a boron phosphide-based semiconductor layer provided bonded to the surface of a single crystal material,
The single crystal material is hexagonal and substantially parallel to the increasing direction of the layer thickness {0.0.0.1. } The crystal faces are arranged,
The boron phosphide-based semiconductor layer has {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } The distance of n consecutive crystal planes (n is a positive integer of 2 or more) is approximately equal to the length of the c-axis of the single crystal material.
The compound semiconductor element characterized by the above-mentioned.   Above {0.0.0.2. } The compound semiconductor device according to claim 1, wherein the number n of crystal faces is 6 or less.

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