JP5005900B2 - Semiconductor element - Google Patents

Description

  The present invention relates to a semiconductor element comprising a single crystal material layer and a boron phosphide-based semiconductor layer formed on the surface of the single crystal material layer.

Conventionally, a boron phosphide-based semiconductor layer has been formed on a substrate made of, for example, a cubic zinc blende crystal type gallium phosphide (GaP) or silicon carbide (SiC) single crystal (the following patent documents) 1). For example, a compound semiconductor LED is composed of a laminated structure including these substrates, a boron phosphide-based semiconductor layer formed on the substrate, and a group III nitride semiconductor layer provided to be bonded to the substrate. (See Patent Document 2 below). Further, a boron phosphide-based semiconductor layer such as monomeric boron phosphide (BP) is formed using silicon single crystal (silicon) as a substrate (see Patent Document 3 below). Also disclosed is a technique for constructing an LED from a laminated structure including a silicon substrate, a monomeric BP layer, and a group III nitride semiconductor layer provided thereon (see Patent Document 4 below). ).
JP-A-2-288388 JP-A-2-275682 US Pat. No. 6,194,744 B1 US Pat. No. 6,690,021

However, for example, even if a boron phosphide-based semiconductor layer is grown on a (111) crystal surface using silicon as a substrate, only a growth layer containing a large amount of twins and stacking faults can be obtained ( Non-patent document 1 below). Further, for example, even when a BP layer of a monomer is grown on the (0.0.0.1.) Crystal plane using hexagonal 6H type SiC as a substrate, it contains a large amount of crystal defects such as twins. Only a growth layer is obtained (see Non-Patent Document 2 below). Even when a laminated structure including a 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 cannot be stably manufactured. There is.
T. Udagawa and G. Shimaoka, J. Ceramic Processing Res., (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 semiconductor element that can improve various characteristics as an element by using the boron phosphide-based semiconductor layer.

1) In order to achieve the above object, a first invention provides a semiconductor element comprising a single crystal material layer and a boron phosphide-based semiconductor layer formed on the surface of the single crystal material layer. The single crystal material layer is made of hexagonal crystal, and its {1.1. -2.0. } On the surface of crystalline surfaces, the boron phosphide-based semiconductor layer made of hexagonal crystal provided et al is, the boron phosphide-based semiconductor layer is <1 the single crystal material layer. -1.0.0. > Parallel to the direction <1. -1.0.0. > The direction is oriented and the surface is {1.1. -2.0. } The crystal plane is composed of crystals.

2 ) 2nd invention comprises the said single-crystal material layer by a sapphire ((alpha) -alumina single crystal) in the structure of invention mentioned in said 1) term .

3 ) The third invention is the structure of the invention described in the above item 1) or 2) , wherein the boron phosphide-based semiconductor layer is composed of monomeric boron phosphide (BP). It is.

4 ) According to a fourth aspect of the present invention, there is provided a hexagonal group III nitride semiconductor layer on the boron phosphide-based semiconductor layer in the configuration of the invention described in any one of the above items 1) to 3 ). Is.

According to the onset bright, and the single crystal material layer, a semiconductor device comprising a the single crystal material layer boron phosphide-based semiconductor layer formed on the surface of said single crystal material layer comprises a hexagonal That {1.1. -2.0. } Because the boron phosphide-based semiconductor layer composed of hexagonal crystal is provided on the surface composed of a crystal plane, the boron phosphide-based semiconductor layer excellent in crystallinity with a small density of crystal defects such as twins and stacking faults Can be formed. Therefore, a high-performance semiconductor element can be provided by using a boron phosphide-based semiconductor layer having excellent crystallinity.

According to the onset bright, a boron phosphide-based semiconductor layer of hexagonal crystal, the hexagonal single crystal material layer <1. -1.0.0. > Direction, <1. -1.0.0. > The surface is oriented with the directions parallel, and {1.1. -2.0. } Since it is composed of a crystal having a crystal plane, a hexagonal boron phosphide-based semiconductor layer excellent in crystallinity with a small crystal defect density such as twins can be obtained stably. Therefore, a high-performance semiconductor element can be stably provided by using such a hexagonal boron phosphide-based semiconductor layer having excellent crystallinity.

According to the onset bright, a single crystal material layer hexagonal, sapphire composed of (alpha-alumina single crystal) of the sapphire {1.1. -2.0. } Since a hexagonal boron phosphide-based semiconductor layer is provided on the surface composed of crystal planes, <1. -1.0.0. > Direction, <1. -1.0.0. > Oriented with the directions parallel and the surface {1.1. -2.0. } Effective in stably forming a hexagonal boron phosphide-based semiconductor layer having a crystal plane.

According to the onset bright, a boron phosphide-based semiconductor layer of hexagonal crystal, so it was decided to consist monomer boron phosphide (BP), stably a boron phosphide-based semiconductor layer of hexagonal crystal form can do.

According to the onset bright, since there is provided a group III nitride semiconductor layer of hexagonal crystal in the boron phosphide-based semiconductor layer, due to good lattice matching crystal Group III nitride semiconductor layer of hexagonal Therefore, it is possible to provide a compound semiconductor light emitting device that can be formed as a layer having excellent properties, has high luminance, and has excellent electrical characteristics such as reverse voltage. Moreover, if the hexagonal group III nitride semiconductor layer is used as an electron transit layer (channel layer), a Schottky junction field effect transistor (FET) can be formed, and high electron mobility can be expressed. An FET having excellent high frequency characteristics can be obtained.

  According to the present invention, in a semiconductor element comprising a single crystal material layer and a boron phosphide-based semiconductor layer formed on the surface of the single crystal material layer, the single crystal material layer is formed of hexagonal crystals and {1 .1. -2.0. } A boron phosphide-based semiconductor layer made of hexagonal crystal is provided on the surface made of crystal face.

The boron phosphide-based semiconductor layer is a crystal layer made of a III-V group compound semiconductor material containing boron (element symbol: B) and phosphorus (element symbol: P) as essential constituent elements. The hexagonal single crystal material layer includes sapphire (α-Al ₂ O ₃ single crystal), a group III nitride semiconductor single crystal such as wurtzite crystal type (Wurtzite) AlN, zinc oxide (ZnO) single crystal, Examples thereof include bulk single crystals such as 2H type (wurtzite crystal type) or 4H type or 6H type silicon carbide (SiC). Among them, a sapphire (α-alumina single crystal) substrate can be most suitably used for forming the hexagonal boron phosphide-based semiconductor layer according to the present invention.

  The surface on which the boron phosphide-based semiconductor layer is provided is {1.1. -2.0. } It is preferable to compose from a crystal plane. In particular, the {1.1. -2.0. } It is preferably provided on a crystal plane, that is, a surface commonly referred to as an A plane. Sapphire {1.1. -2.0. } By using the crystal plane (plane A), a hexagonal boron phosphide-based semiconductor layer can be stably obtained instead of the usual zincblende crystal type (zinc-blend). This is the same as {1.1. -2.0. } It is considered that atoms constituting a crystal in a non-polar crystal plane such as a crystal plane are conveniently arranged to provide a hexagonal boron phosphide-based semiconductor layer having a high covalent bond.

  Sapphire {1.1. -2.0. The crystal plane is determined by CZ (Czochralski) method, Bernoulli method, EFG (edge-defined film-fed growth) method, etc. (BRIAN R. PAMPLIN edi., “CRYSTAL GROWTH”, 1975, Perg. ) Grown on a bulk single crystal, or an alumina single crystal film grown by physical means such as chemical vapor deposition (CVD) or sputtering. It may be the A side.

The hexagonal boron phosphide-based semiconductor layer can be formed by vapor phase growth means such as a halogen method, a hydride method, or a metal organic chemical deposition (MOCVD) method. 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. Regardless of the combination of the boron source and the phosphorus source, in order to form a hexagonal boron phosphide-based semiconductor layer, it is desirable that the growth temperature is 700 ° C. or higher and 1200 ° C. or lower. According to these growth means, {1.1. -2.0. } On the surface consisting of crystal faces, the surface is {1.1. -2.0. } A hexagonal boron phosphide-based semiconductor layer having a crystal plane can be formed.

A hexagonal boron phosphide-based semiconductor layer is formed of, for example, {1.1. -2.0. } When forming on a crystal surface, when a source of phosphorus is first supplied to the surface, and then a group III element material such as boron is supplied, it is uniformly oriented in a specific crystal orientation. A hexagonal boron phosphide-based semiconductor layer can be formed. For example, {1.1. -2.0. } A phosphine (molecular formula PH ₃ ) is supplied to the surface consisting of crystal planes in advance of triethylboron ((C ₂ H ₅ ) ₃ B), and formation of a boron phosphide-based semiconductor layer is started by MOCVD. In particular, sapphire <1. -1.0.0. > Direction, <1. -1.0.0. > A hexagonal boron phosphide-based semiconductor layer having a parallel direction can be obtained. The investigation of whether the formed boron phosphide-based semiconductor layer is a hexagonal crystal layer and the investigation of the orientation relationship of the hexagonal boron phosphide-based semiconductor layer with respect to the surface of the hexagonal single crystal material layer For example, it can be performed by analysis means such as electron diffraction or X-ray diffraction.

  The surface is {1.1. -2.0. } The crystal plane and <1. -1.0.0. > Direction of the hexagonal single crystal material layer <1. -1.0.0. The hexagonal boron phosphide-based semiconductor layer parallel to the> direction is, for example, {1.1. -2.0. } Since it is on the surface composed of crystal planes and oriented in a direction excellent in lattice matching, it is characterized by few crystal defects such as twins and stacking faults. In particular, when a hexagonal boron phosphide-based semiconductor layer is composed of a monomeric boron phosphide (BP) layer having an orientation relationship with the above surface, it is approximately 50 nm from the junction interface with the hexagonal single crystal material layer. Thus, a hexagonal boron phosphide-based semiconductor layer containing almost no twins can be obtained in a region exceeding 100 nm. Since the density of twins is reduced, the density of grain boundaries due to twins can be observed by a general cross-sectional TEM technique using a transmission electron microscope (abbreviation: TEM).

A hexagonal boron phosphide-based semiconductor layer having excellent crystallinity, for example, a semiconductor layer made of a BP layer of hexagonal monomer forms, for example, a group III nitride semiconductor layer having excellent crystallinity. Can be used as a foundation for As the group III nitride semiconductor layer provided by being bonded to the hexagonal boron phosphide-based semiconductor layer, for example, wurtzite crystal type GaN, AlN, indium nitride (InN), and aluminum nitride that is a mixed crystal thereof are used. gallium indium (compositional formula _{Al X Ga Y in Z N:} 0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1) is. Further, for example, a wurtzite crystal type gallium nitride phosphide (composition) containing nitrogen (element symbol: N) and a group V element such as phosphorus (element symbol: P) other than nitrogen and arsenic (element symbol: As). Formula GaN _1-Y P _Y : 0 ≦ Y <1).

The hexagonal monomer BP layer is particularly useful as a base for forming a group III nitride semiconductor layer having a lattice constant approximating the a-axis. For example, the a-axis of hexagonal monomer BP is about 0.319 nanometers (nm), which coincides with the a-axis of hexagonal GaN. Therefore, a GaN layer having excellent crystallinity can be formed on the hexagonal monomer BP layer due to good lattice matching. If a group III nitride semiconductor layer having excellent crystallinity is used, a pn junction type heterostructure that provides high intensity light emission can be formed. For example, a heterojunction light-emitting portion for LED use in which a GaN layer is a clad layer and a Ga _x In _1-X N (0 <X <1) layer is a light-emitting layer can be configured. By using a light emitting portion composed of a group III compound semiconductor layer having excellent crystallinity, a compound semiconductor light emitting device having high luminance and excellent electrical characteristics such as reverse voltage can be provided.

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

  Example 1 An LED is constructed using a BP layer of a hexagonal monomer bonded and provided on the surface of a bulk crystal of sapphire (1.1.-2.0.). The contents of the present invention will be specifically described by taking the case as an example.

  FIG. 1 schematically shows a planar configuration of the LED 10 according to the first embodiment. FIG. 2 is a schematic sectional view of the LED 10 taken along the broken line A-A ′ shown in FIG. 1.

  The laminated structure 100 for producing the LED 10 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 101. On the surface of the (1.1.-2.0.) Crystal plane of the substrate 101, an undoped n-type hexagonal monomer having a layer thickness of about 290 nm using a general MOCVD method. The BP layer was formed as a hexagonal boron phosphide-based semiconductor layer 102.

  A general TEM analysis shows that the surface of the hexagonal monomer BP layer forming the hexagonal boron phosphide-based semiconductor layer 102 is a (1.1.-2.0.) Crystal plane. It was done. Further, from the electron diffraction pattern, <1. -1.0.0. > Direction of the hexagonal monomer BP layer 102. -1.0.0. It was shown to be oriented parallel to the> direction. Furthermore, in the observation by the cross-sectional TEM technique, the presence of twins was hardly observed in the hexagonal monomer BP102 layer. In addition, in the region inside the hexagonal monomer BP layer, which is higher than about 50 nm from the bonding interface with the sapphire substrate 101, the disorder on the lattice arrangement was hardly confirmed.

  On the surface composed of the (1.1.-2.0.) Crystal face of the hexagonal monomer BP layer forming the hexagonal boron phosphide-based semiconductor layer 102, a wurtzite crystal type hexagonal crystal layer is formed. An n-type GaN layer (layer thickness = 2100 nm) 103 was grown. According to an analysis using a general TEM, an internal region of the hexagonal GaN layer 103 in the vicinity of the junction interface with the hexagonal monomer BP layer that forms the hexagonal boron phosphide-based semiconductor layer 102 is formed in the internal region. Almost no twins or stacking faults were observed.

On the (1.1.-2.0.) Surface of the hexagonal n-type GaN layer 103, a lower cladding layer (layer thickness = 150 nm) 104 made of hexagonal n-type Al _0.15 Ga _0.85 N, Ga _{A 0.85} In _0.15 N well layer / Al _0.01 Ga _0.99 N barrier layer having one period and a light emitting layer 105 having a multi-quantum well structure consisting of five periods, and an upper clad composed of p-type Al _0.10 Ga _0.90 N having a layer thickness of 50 nm The layers 106 were stacked in this order to form a light emitting portion having a pn junction DH structure. A p-type GaN layer (layer thickness = 80 nm) was further deposited as a contact layer 107 on the surface of the upper cladding layer 106, and the formation of the multilayer structure 100 was completed.

  A p-type ohmic electrode 108 made of a gold (element symbol: Au) / nickel oxide (NiO) alloy is formed in a partial region of the p-type contact layer 107. One n-type ohmic electrode 109 is formed on the surface of the exposed n-type GaN layer 103 after the layers such as the lower cladding layer 104 and the light emitting layer 105 in the region where the electrode 109 is provided are removed by dry etching means. did. From this, LED10 was comprised.

  A light emission characteristic was investigated by passing a device drive current of 20 mA in the forward direction between the p-type and n-type ohmic electrodes 108 and 109 of the LED 10. The wavelength of the main light emitted from the LED 10 was about 460 nm. The light emission luminance in the chip state was about 1.6 candela (cd). Further, by providing the n-type GaN layer 103 provided with the group III nitride semiconductor layers 104 to 106 and the n-type ohmic electrode 109 constituting the light emitting portion of the pn junction type DH structure on the hexagonal BP layer, Therefore, the reverse voltage when the reverse current was 10 μA was a high value exceeding 15V. Further, due to the crystallinity of the group III nitride semiconductor layer, almost no local breakdown was observed.

1 is a schematic plan view of an LED described in Example 1. FIG. It is a cross-sectional schematic diagram of LED along the broken line A-A 'shown in FIG.

Explanation of symbols

10 Compound semiconductor LED
100 Laminated structure for LED 101 Sapphire substrate (hexagonal single crystal material layer)
102 Hexagonal boron phosphide semiconductor layer (hexagonal monomer BP layer)
103 Hexagonal group III nitride semiconductor layer (GaN layer)
104 lower clad layer 105 light emitting layer 106 upper clad layer 107 contact layer 108 p-type ohmic electrode 109 n-type ohmic electrode

Claims (4)

In a semiconductor element comprising a single crystal material layer and a boron phosphide-based semiconductor layer formed on the surface of the single crystal material layer,
The single crystal material layer is made of hexagonal crystal, and its {1.1. -2.0. } On the surface of crystalline surfaces, the boron phosphide-based semiconductor layer is provided, et al is made of hexagonal,
The boron phosphide-based semiconductor layer is <1. -1.0.0. > Parallel to the direction <1. -1.0.0. > The direction is oriented and the surface is {1.1. -2.0. } It is composed of a crystal as a crystal plane,
The semiconductor element characterized by the above-mentioned. The semiconductor element according to claim 1, wherein the single crystal material layer is a layer made of sapphire (α-alumina single crystal). The semiconductor element according to claim 1, wherein the boron phosphide-based semiconductor layer is composed of monomeric boron phosphide (BP). 4. The semiconductor element according to claim 1, wherein a hexagonal group III nitride semiconductor layer is provided on the boron phosphide-based semiconductor layer. 5.

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