JP2007073872A - Semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor element provided with a boron phosphide-based semiconductor layer which can reduce leakage of an element driving current, improve photoelectric conversion efficiency as a light-emitting element, improve an opposite direction voltage, cause a gate electrode to have high voltage resistance as an electric field effect transistor, and improve the pinch-off characteristic of a drain current. <P>SOLUTION: In the semiconductor element 10 provided with the boron phosphide-based semiconductor layer 102; the semiconductor layer 102 consists of a hexagonal system, and an electrode 109 is provided on the surface of the semiconductor layer 102 having the hexagonal system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor device including a boron phosphide-based semiconductor 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). A compound semiconductor LED is configured by using a laminated structure including these substrates, a boron phosphide-based semiconductor layer formed thereon, and a group III nitride semiconductor layer provided to be bonded thereto. (See Patent Document 2 below).
JP-A-2-288388 JP-A-2-288371

For example, in the case of configuring an LED using a boron phosphide-based semiconductor layer formed on a single crystal substrate, an ohmic electrode has been conventionally used as a cubic zinc-blende crystal type (zinc−). (blende) boron phosphide layer (see, for example, Patent Document 3 below). Even in a conventional laser diode (abbreviation: LD), an ohmic electrode is provided in contact with a cubic boron phosphide layer (see Patent Document 4 below).
JP-A-2-275682 JP-A-4-84486

However, for example, even when a cubic boron phosphide-based semiconductor layer is grown on a (111) crystal surface using silicon as a substrate, a cubic crystal growth layer containing a large amount of twins and stacking faults. (See 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. It is known that it becomes a cubic crystal growth layer (see Non-Patent Document 2 below).
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), 285-288.

  For example, when an ohmic electrode is provided in contact with a cubic boron phosphide-based semiconductor layer containing a large amount of such crystal defects, an operating current (element driving current) for driving the element is twin crystal or the like. For example, there is a problem that LEDs with a high reverse voltage and high photoelectric conversion efficiency cannot be stably produced because they leak unnecessarily through the crystal defects. Even if a Schottky contact-type electrode is provided on the surface of a cubic boron phosphide-based semiconductor layer having many crystal defects, only a gate electrode having a high leakage current and a low breakdown voltage can be formed. Moreover, the pinch-off characteristic of the drain current is also deteriorated, and there is a problem that the FET having excellent high-frequency characteristics cannot be stabilized even if it is stabilized.

  The present invention has been made to overcome the problems of the prior art, can reduce the leakage of element driving current, can increase the photoelectric conversion efficiency as a light emitting element, can also increase the reverse voltage, and the field effect. An object of the present invention is to provide a semiconductor element including a boron phosphide-based semiconductor layer, which can increase the breakdown voltage of the gate electrode as a type transistor and can improve the pinch-off characteristics of the drain current.

  1) To achieve the above object, according to a first aspect of the present invention, there is provided a semiconductor element including a boron phosphide-based semiconductor layer, wherein the boron phosphide-based semiconductor layer is composed of a hexagonal crystal, and the hexagonal boron phosphide-based semiconductor is provided. An electrode is provided on the surface of the layer.

  2) The second aspect of the present invention is the structure of the invention described in the above item 1), wherein the surface of the boron phosphide-based semiconductor layer is a (1.1.-2.0.) Crystal plane.

  3) According to a third invention, in the configuration of the invention described in the above item 1) or 2), the boron phosphide-based semiconductor layer is formed of phosphorus phosphide (BP) composed of hexagonal monomer boron phosphide (BP). It is a boron fluoride layer.

  4) The fourth invention is the structure of the invention described in the above item 3), wherein the boron phosphide layer is a conductive n-type, and an ohmic electrode is provided on the surface of the boron phosphide layer. It is.

  5) A fifth aspect of the invention is the structure of the invention described in the above item 3), wherein the boron phosphide layer is a conductive p-type, and an ohmic electrode is provided on the surface of the boron phosphide layer. It is.

  6) According to a sixth aspect of the present invention, in the configuration of the invention described in the above item 3), the boron phosphide layer has a high resistance, and a Schottky contact electrode is provided on the surface of the boron phosphide layer. Is.

  7) A seventh invention is such that in the configuration of the invention described in the above item 6), the Schottky contact electrode is used as a gate electrode.

  8) An eighth invention is the above-described constitution of the invention according to any one of items 4) to 7), wherein the boron phosphide layer is an undoped layer to which no impurity is intentionally added. is there.

  9) According to a ninth aspect of the present invention, in the structure according to any one of the above items 1) to 3), the boron phosphide-based semiconductor layer is a hexagonal crystal having a small polarity or a nonpolar single layer. A crystal layer or a single crystal substrate is formed as a base layer.

  8) The tenth invention is configured as a light emitting element in the configuration of the invention described in any one of items 1) to 5), 8) and 9).

  8) The eleventh invention is configured as a field effect transistor in the configuration of the invention described in any one of the above items 1) to 3) and 6) to 9).

  According to the present invention, in a semiconductor device including a boron phosphide-based semiconductor layer, the boron phosphide-based semiconductor layer is a hexagonal crystal, and the surface of the hexagonal boron phosphide-based semiconductor layer having few crystal defects such as twins is formed. Since the electrode is provided, as a result, an ohmic electrode or a Schottky contact electrode with less element operating current leaking through crystal defects can be formed. Accordingly, a light-emitting element such as a light-emitting diode (LED) or a laser diode (LD) with high photoelectric conversion efficiency, and a field effect transistor (FET) provided with a high breakdown voltage gate electrode and improved drain current pinch-off characteristics are provided. be able to.

  In addition, according to the present invention, the electrode is provided on the hexagonal boron phosphide-based semiconductor layer whose surface is a (1.1.-2.0.) Crystal plane, that is, a twin crystal or the like. Since the electrode is provided on the boron phosphide-based semiconductor layer having few crystal defects and excellent crystallinity, it is possible to form an electrode with little leakage of element operating current. It is possible to provide an FET including a light emitting element and a gate electrode having a high breakdown voltage and improved drain current pinch-off characteristics.

  In particular, according to the present invention, the electrode is provided on the surface of a hexagonal monomer boron phosphide (BP) layer having a particularly small crystal defect density, so that an ohmic electrode or a Schottky contact with a small leakage current is provided. Therefore, it is possible to easily provide a light-emitting element with high photoelectric conversion efficiency and a FET having a high breakdown voltage gate electrode and improved drain current pinch-off characteristics.

  In particular, since the ohmic electrode impurity is provided on the surface of the BP layer having sufficient conductivity even if it is undoped without being doped, the light emitting element can be simply configured.

  In addition, since the boron phosphide-based semiconductor layer is formed using a hexagonal, low-polarity or nonpolar single-crystal layer or a single-crystal substrate as an underlayer, the hexagonal boron phosphide-based semiconductor layer is further increased. It can be stably formed as a layer having few crystal defects, and the electrode formed on the surface thereof can be made to have much fewer crystal defects.

  The present invention relates to a semiconductor element including a boron phosphide-based semiconductor layer, wherein the boron phosphide-based semiconductor layer is a hexagonal crystal, and an electrode is provided on the surface of the hexagonal boron phosphide-based semiconductor layer. .

  The hexagonal boron phosphide-based semiconductor layer according to the present invention includes hexagonal crystals such as sapphire (α-Al 2 O 3 single crystal), hexagonal 4H-type or 6H-type silicon carbide (SiC), zinc oxide (ZnO), or GaN. A single crystal layer or a single crystal substrate is formed as a base layer. In particular, a hexagonal boron phosphide-based semiconductor layer can be efficiently formed on the surface of a single crystal layer or a single crystal substrate having a small or nonpolar crystal plane. This is because atoms are arranged conveniently on the surface of the hexagonal single crystal layer or single crystal substrate that has a small or nonpolar crystal plane to provide a hexagonal boron phosphide-based semiconductor layer. It is.

  A nonpolar crystal plane suitable for providing a hexagonal boron phosphide-based semiconductor layer is, for example, a single crystal of a hexagonal compound material formed by combining element A and element B, and element A And the element B are exposed at the same surface density. For example, 2H SiC or Wurtzite GaN or aluminum nitride (AlN) {1.1. -2.0. } It is a crystal plane. Moreover, for example, {1.1. -2.0. } It is a crystal plane.

A hexagonal boron phosphide is formed on a hexagonal crystal plane having a small polarity or nonpolarity by vapor phase growth means such as a halogen method, a hydride method, or a metal organic chemical deposition (MOCVD) method. A system semiconductor layer is formed. 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. For example, monomeric boron phosphide (BP) and multimeric B ₁₂ P ₂ (B ₆ P). Further, for example, boron phosphide / aluminum (composition formula B _1-X Al _X P: 0 ≦ X ≦ 1). The MOCVD method is suitable for forming a boron phosphide-based semiconductor layer containing Al.

If the boron phosphide-based semiconductor layer formed on the crystal plane of a hexagonal single crystal layer or a single crystal substrate with little or no polarity is made of a material with low ion bonding properties, hexagonal phosphorous A boron fluoride based semiconductor layer can be formed stably. A boron phosphide-based semiconductor layer with a small ion bondability has a small difference in the degree of ionic bond with a nonpolar hexagonal single crystal layer or single crystal substrate, or a crystal defect such as a twin crystal. A high-quality hexagonal boron phosphide-based semiconductor layer can be stably formed. Among boron phosphide-based semiconductors, monomeric boron phosphide (BP) has a small ionic bond degree (fi) of 0.006 (JC Phillips, “Semiconductor Bond Theory” (physics). Series 38), Yoshioka Shoten Co., Ltd., issued July 25, 1985, 3rd printing, page 51), a suitable material for stably providing a hexagonal boron phosphide-based semiconductor layer. In addition, since the fi of boron arsenide (BAs) is as small as 0.002 (see “Semiconductor Bonding Theory” above, page 51), boron arsenide phosphide which is a mixed crystal with BP (composition formula BAs _1-Y P _Y : 0 <Y ≦ 1), a hexagonal boron phosphide-based semiconductor layer can be stably formed.

  In particular, a boron phosphide-based semiconductor layer having a small ionic bond grown so that the surface has a (1.1.-2.0.) Crystal plane has few twins and stacking faults. It can be suitably used as a semiconductor layer for providing the film.

  Whether or not the formed boron phosphide-based semiconductor layer is a hexagonal crystal layer can be investigated by an analysis means such as electron diffraction or X-ray diffraction. According to a general electron diffraction analysis, for example, a monomer BP bonded to a nonpolar (1.1.-2.0.) Crystal plane of a hexagonal GaN single crystal layer is hexagonal. It can be seen that this is a wurtzite crystal type crystal layer. It can also be seen that the surface of the hexagonal BP crystal layer has a nonpolar (1.1.-2.0.) Crystal plane.

A shaft of BP wurtzite crystal type hexagonal monomeric is approximately 0.319 nanometers (nm), of the hexagonal a group III nitride semiconductor _{Al X Ga 1-X N (} 0 ≦ It substantially coincides with the a axis of X ≦ 1). Therefore, if the hexagonal boron phosphide-based semiconductor layer is composed of monomeric BP, a group III nitride semiconductor layer having excellent crystallinity is formed on the layer due to good lattice matching. Can be formed. Since the boron phosphide-based semiconductor layer formed on a small polarity or nonpolar hexagonal crystal is excellent in crystallinity, it can contribute to providing a group III nitride semiconductor layer excellent in crystallinity as an upper layer.

If a group III nitride semiconductor layer having excellent crystallinity is used, for example, a pn junction type heterostructure made of a group III nitride semiconductor layer can be formed. For example, an n-type Ga _x In _1-X N (0 ≦ X ≦ 1) layer is a light emitting layer, and n-type and p-type Al _x Ga _1-X N (0 ≦ X ≦ 1) layers are clad. A double hetero (DH) junction type light emitting part for LED use as a layer can be configured. Since the light-emitting portion can be composed of a group III compound semiconductor layer having excellent crystallinity, it is possible to provide a compound semiconductor light-emitting element that emits light with high brightness and is excellent in electrical characteristics such as reverse voltage.

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. That is, it is a group III nitride semiconductor having an a-axis that approximates a hexagonal monomer BP. 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). It is a group III nitride semiconductor having an a-axis that approximates the hexagonal monomer BP, such as the formula GaN _1-Y P _Y : 0 ≦ Y <1).

  The ohmic electrode provided in the hexagonal boron phosphide-based semiconductor layer can be composed of various metal materials and conductive oxide materials. For example, for boron phosphide-based semiconductor layers exhibiting n-type conductivity, alloys such as gold (element symbol: Au) / germanium (element symbol: Ge) alloy, gold (Au) / tin (element symbol: Sn) alloy, etc. N-type ohmic electrodes can be formed. Further, an n-type ohmic electrode can be formed from an alloy containing a rare earth element, for example, a lanthanum (element symbol: La) / aluminum (Al) alloy. Further, an n-type ohmic electrode can be formed from an oxide material such as zinc oxide (ZnO).

For the p-type boron phosphide-based semiconductor layer, a p-type ohmic electrode can be formed from a gold (Au) / zinc (element symbol: Zn) alloy, a gold (Au) / beryllium (element symbol: Be) alloy, or the like. In addition, a p-type ohmic electrode can be formed from an indium (In) / tin (Sn) composite oxide film (English abbreviation: ITO). The low contact resistance ohmic electrode is preferably formed by a low resistance layer having a carrier concentration of about 1 × 10 ¹⁸ cm ⁻³ or more. Whether it is a doping layer intentionally added with impurities or an undoped layer without intentionally adding impurities, the layer provided with the ohmic electrode is preferably a low resistance layer. In the case of the monomeric BP layer, n-type and p-type low-resistance layers that are convenient for forming electrodes can be easily obtained by undoping.

  Both the n-type and p-type ohmic electrodes are optimally provided in a hexagonal boron phosphide-based semiconductor layer with few crystal defects and excellent crystallinity. Also, for example, a group III nitride semiconductor having excellent crystallinity in which one ohmic electrode is provided in a hexagonal boron phosphide-based semiconductor layer with good crystallinity and the other ohmic electrode is formed with that layer as a base. Even if it is provided in contact with the layer, it can contribute to providing a semiconductor element with good characteristics.

  The Schottky contact electrode formed on the hexagonal boron phosphide-based semiconductor layer can be composed of transition metals such as titanium (element symbol: Ti). Moreover, it can form from platinum (element symbol: Pt). If the hexagonal boron phosphide-based semiconductor layer having excellent crystallinity according to the present invention is used, a gate electrode or the like with less leakage current can be formed. In particular, when a Schottky contact electrode is provided in a high-resistance boron phosphide-based semiconductor layer, a gate electrode with low leakage current and excellent withstand voltage can be formed. For this reason, it is possible to contribute to the production of a high-frequency Schottky junction type FET having a small gate leakage current and excellent mutual conductance. The high-resistance boron phosphide-based semiconductor layer is an undoped or high-resistance hexagonal crystal layer that is electrically compensated by doping one or both of n-type and p-type impurities. It can be conveniently constructed from a monomeric BP layer.

  With respect to the hexagonal boron phosphide-based semiconductor layer, a metal electrode that forms ohmic contact or Schottky contact can be formed by a general vacuum deposition method, electron beam deposition method, sputtering method, or the like. An oxide material such as ITO or ZnO can be formed by a general physical film forming means such as a sputtering method or a wet film forming method such as a sol-gel method.

  (Example 1) The case where the compound semiconductor LED provided with the ohmic electrode on the BP layer of the hexagonal monomer bonded to the (1.1.-2.0.) Crystal plane of sapphire is provided. The present invention will be described specifically by way of examples.

  FIG. 1 schematically shows a planar configuration of the LED 10 according to the first embodiment. FIG. 2 is a schematic sectional view taken along the broken line A-A ′ of the LED 10 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. The surface of the substrate 101 with the (1.1.-2.0.) Crystal plane is 750 ° C. at a surface of (1.1.-2.0.) Crystal plane using a general MOCVD method. An n-type hexagonal monomer BP layer (layer thickness = 2000 nm) 102 was formed by undoping. The carrier concentration of the n-type BP layer 102 was measured to be 2 × 10 ¹⁹ cm ⁻³ .

An undoped n-type hexagonal GaN layer (layer thickness = 1200 nm) 103 was grown on the surface of the hexagonal BP layer 102 having the (1.1.-2.0.) Crystal plane. According to the analysis using a general TEM (transmission electron microscope), the number of twins and stacking faults in the hexagonal BP layer 102 was as small as less than 1 × 10 ⁴ cm ⁻² . Further, since the hexagonal BP layer 102 having excellent crystallinity was joined and provided, almost no twins or stacking faults were observed in the hexagonal GaN layer 103.

On the (1.1.-2.0.) Surface of the hexagonal n-type GaN layer 103, a lower cladding layer (layer thickness = 280 nm) 104 made of hexagonal n-type Al _0.15 Ga _0.85 N, Ga _{The 0.85} In _0.15 N well layer (layer thickness = 3 nm) / Al _0.01 Ga _0.99 N barrier layer (layer thickness = 8 nm) is one period, the light emitting layer 105 having a multi-quantum well structure consisting of five periods, and the layer thickness is 85 nm. The upper clad layer 106 made of p-type Al _0.10 Ga _0.90 N is stacked in this order to constitute a light emitting portion of a pn junction type DH structure. On the surface of the upper cladding layer 106, a p-type GaN layer (layer thickness = 80 nm) was further deposited as a contact layer 107, 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 was formed in a partial region of the p-type contact layer 107.

  One n-type ohmic electrode 109 is exposed after removing the layers 103 to 107 above the hexagonal n-type BP layer 102 in the region where the n-type ohmic electrode 109 is provided by dry etching means. It was formed on the surface of the hexagonal n-type BP layer 102. The n-type ohmic electrode 109 was formed from a gold (Au) / germanium (Ge) alloy film (Au 90 wt%: Ge 10 wt% alloy) formed by a general vacuum deposition method.

  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 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 102 having excellent crystallinity, a reverse voltage (reverse voltage) When the directional current was 10 μA, the value was higher than 15V. Furthermore, there was almost no local break down.

  (Example 2) The present invention will be specifically described with reference to an example in which a semiconductor LED is formed by providing both n-type and p-type ohmic electrodes on an n-type and p-type hexagonal monomer BP layer. To do.

  FIG. 3 schematically shows a planar configuration of the LED 20 according to the second embodiment. FIG. 4 is a schematic sectional view taken along the broken line B-B ′ of the LED 20 shown in FIG. 3.

As described in Example 1 above, the laminated structure 200 for producing the LED 20 is made of sapphire (α-alumina single crystal) having a (1.1.-2.0.) Crystal plane (commonly referred to as A plane) as a surface. Crystal) was formed as a substrate 201. As described in Example 1 above, the surface of the substrate 201 having a (1.1.-2.0.) Crystal plane is formed by using a general MOCVD method at 750 ° C. ( 1.1.-2.0.) An n-type hexagonal monomer BP layer (layer thickness = 2000 nm) 202 was formed undoped as a crystal plane. The carrier concentration of the n-type BP layer 202 was 2 × 10 ¹⁹ cm ⁻³ . According to analysis using a general TEM, the number of twins and stacking faults in the hexagonal BP layer 202 was as small as less than 1 × 10 ⁴ cm ⁻² .

As described in Example 1 above, an undoped n-type hexagonal GaN layer (layer thickness =) is formed on the surface of the hexagonal BP layer 202 (1.1.-2.0.). 1200 nm) 203, lower clad layer (layer thickness = 280 nm) 204 made of hexagonal n-type Al _0.15 Ga _0.85 N with a surface of (1.1.-2.0.) Crystal plane, layer thickness of Ga _0.85 In _0.15 N The well layer (layer thickness = 3 nm) / Al _0.01 Ga _0.99 N barrier layer (layer thickness = 8 nm) is one period, the light emitting layer 205 having a multi-quantum well structure consisting of the five periods, and the p-type having a layer thickness of 85 nm. The upper clad layer 206 made of Al _0.10 Ga _0.90 N was laminated in this order to form a light emitting portion of a pn junction type DH structure.

  A p-type hexagonal undoped monomer BP layer (layer thickness) is further formed on the surface of the hexagonal and n-type upper cladding layer 206 having a crystal plane of (1.1.-2.0.). = 200 nm) was deposited as the contact layer 207. According to general cross-sectional TEM observation, in the hexagonal undoped monomer BP layer forming the contact layer 207, plane defects such as twins and stacking faults and dislocations were hardly confirmed.

  At the center of the surface of the p-type contact layer 207, a p-type ohmic electrode 208 made of a gold (Au) / zinc (Zn) alloy (Au 95 wt%: Zn 5 wt% alloy) having a circular planar shape is formed. did.

  One n-type ohmic electrode 209 is an exposed hexagonal crystal after the layers 203 to 207 above the hexagonal n-type BP layer 202 in the region where the n-type ohmic electrode 209 is provided are removed by dry etching means. The n-type BP layer 202 was formed in a circumferential shape in plan view. The n-type ohmic electrode 209 was formed from a gold (Au) / germanium (Ge) alloy film (Au 90 wt%: Ge 10 wt% alloy) by a general vacuum deposition method.

  In each case, a device driving current of 20 mA was passed in the forward direction between the p-type and n-type ohmic electrodes 208 and 209 provided in the hexagonal monomer BP layers 207 and 202, and the light emission characteristics were investigated. The wavelength of the main light emitted from the LED 20 was about 460 nm. The light emission luminance in the chip state was about 1.6 candela (cd). Further, by providing the group III nitride semiconductor layers 204 to 206 and the ohmic electrodes 208 and 209 constituting the light emitting part of the pn junction type DH structure on the hexagonal BP layers 202 and 207 having excellent crystallinity, the reverse voltage When the reverse current was 10 μA, the value was higher than 18V. Furthermore, there was almost no local break down.

  Example 3 A GaN-based FET is formed by providing a high resistance and n-type hexagonal monomer BP layer with a Schottky contact gate electrode and ohmic contact source and drain electrodes, respectively. The present invention will be specifically described with reference to FIG.

  FIG. 5 schematically shows a cross-sectional structure of the GaN-based FET 30 according to the third embodiment. Components identical to those shown in FIGS. 1 and 2 are given the same reference numerals and shown in FIG.

As described in Example 1 above, the laminated structure 300 for manufacturing the FET 30 is a sapphire (α-alumina single crystal) having a (1.1.-2.0.) Crystal plane (commonly referred to as A plane) as a surface. Crystal) was formed as a substrate 301. A high resistance undoped monomer BP layer (layer thickness = 720 nm) 302 is formed on the surface of the (1.1.-2.0.) Crystal plane of the substrate 301 by using a general MOCVD method. Formed at ° C. The carrier concentration of the high-resistance BP layer 302 was less than 1 × 10 ¹⁷ cm ⁻³ . According to the analysis using a general TEM, the number of twins and stacking faults in the BP layer 302 was as small as less than 1 × 10 ⁴ cm ⁻² .

On the surface of the high-resistance BP layer 302, there are an electron transit layer 303 made of an undoped n-type hexagonal GaN layer (layer thickness = 48 nm), and the surface is a (1.1.-2.0.) Crystal plane. An electron supply layer (layer thickness = 28 nm) 304 made of hexagonal n-type Al _0.25 Ga _0.75 N was stacked in this order. Both the electron transit layer 303 and the electron supply layer 304 were formed by MOCVD.

A Schottky contact electrode formation layer 305 for providing the gate electrode 307 is bonded to the surface of the hexagonal n-type electron supply layer 304 having a (1.1.-2.0.) Crystal surface. Provided. The Schottky contact electrode forming layer 305 was composed of a high-resistance hexagonal monomer BP having a layer thickness of 12 nm and a carrier concentration of less than 5 × 10 ¹⁶ cm ⁻³ . After the Schottky contact electrode formation layer 305 is formed, the Schottky contact electrode formation layer 305 is left only in the central region in plan view where the Schottky contact gate electrode 307 is formed, and is present in other regions. The Schottky contact electrode forming layer was removed by a general dry etching means.

Next, an n-type hexagonal monomer BP layer (layer thickness) is formed so as to cover the entire surface of both the remaining Schottky contact electrode forming layer 305 and the electron supply layer 304 exposed in the periphery thereof. = 100 nm, carrier concentration = 2 × 10 ¹⁹ cm ⁻³ ) was deposited as the contact layer 306. According to general cross-sectional TEM observation, in the hexagonal monomer BP layer forming the contact layer 306, plane defects such as twins and stacking faults and dislocations were hardly confirmed.

  Thereafter, in order to provide the gate electrode 307, the contact layer 306 made of a hexagonal n-type BP layer covering the Schottky contact electrode forming layer 305 was removed by a general dry etching means. A Schottky contact gate made of titanium (Ti) is formed on the surface of the Schottky contact electrode formation layer 305 of the recess portion 308 exposed by removing the contact layer 306 by a general electron beam evaporation means. An electrode 307 was provided.

  In addition, an ohmic contact source electrode 309 was formed on the surface of one hexagonal BP layer forming the contact layer 306 that was left facing both sides with the gate electrode 307 interposed therebetween. Also, a drain electrode 310 was provided on the surface of the contact layer 306 made of the other hexagonal BP layer, which is located opposite to the gate electrode 307, thereby producing a GaN-based FET 30. The ohmic electrodes constituting the source electrode 309 and the drain electrode 310 were formed from a gold (Au) / germanium (Ge) alloy film (Au 95 wt%: Ge 5 wt% alloy) by a general vacuum deposition method.

  Since both the ohmic electrodes of the source electrode 309 and the drain electrode 310 are provided in the contact layer 306 made of the hexagonal monomer BP with few twins and stacking faults, the source provided in the region where the crystal defect density is high as in the prior art. The inconvenience that the drain current flows in a short-circuited manner and in a concentrated manner between the partial region of the electrode and the region of the drain electrode opposed thereto can be solved. For this reason, an FET having characteristics such as that an element driving current can be passed through the electron transit layer 303 with a uniform current density is provided.

  Further, since the Schottky contact gate electrode 307 is provided so as to be in contact with the Schottky contact electrode formation layer 305 made of the high-resistance hexagonal monomer BP and containing almost no twins or stacking faults, the leakage current As a result, a GaN-based FET provided with a gate electrode 307 having a high withstand voltage and a low withstand voltage is provided.

1 is a schematic plan view of an LED described in Example 1. FIG. It is a cross-sectional schematic diagram along the broken line A-A 'of LED shown in FIG. 3 is a schematic plan view of an LED described in Example 2. FIG. FIG. 3 is a schematic sectional view taken along a broken line B-B ′ of the LED shown in FIG. 2. 6 is a schematic cross-sectional view of an LED FET described in Example 3. FIG.

Explanation of symbols

10 LED
DESCRIPTION OF SYMBOLS 100 LED use laminated structure 101 Sapphire substrate 102 Hexagonal BP layer 103 Hexagonal 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 20 LED
200 LED use laminated structure 201 Sapphire substrate 202 Hexagonal BP layer 203 Hexagonal GaN layer 204 Lower cladding layer 205 Light emitting layer 206 Upper cladding layer 207 Contact layer 208 p-type ohmic electrode 209 n-type ohmic electrode 30 FET
300 FET Use Laminated Structure 301 Sapphire Substrate 302 High Resistance BP Layer 303 Electron Traveling Layer 304 Electron Supply Layer 305 Schottky Contact Electrode Formation Layer 306 Contact Layer 307 Gate Electrode 308 Recess Portion 309 Source Electrode 310 Drain Electrode

Claims (11)

In a semiconductor device comprising a boron phosphide-based semiconductor layer,
The boron phosphide-based semiconductor layer is made of hexagonal crystal, and an electrode is provided on the surface of the hexagonal boron phosphide-based semiconductor layer.
The semiconductor element characterized by the above-mentioned.   The semiconductor element according to claim 1, wherein a surface of the boron phosphide-based semiconductor layer is a (1.1.-2.0.) Crystal plane.   3. The semiconductor element according to claim 1, wherein the boron phosphide-based semiconductor layer is a boron phosphide layer made of hexagonal monomer boron phosphide (BP).   The semiconductor element according to claim 3, wherein the boron phosphide layer is a conductive n-type, and an ohmic electrode is provided on a surface of the boron phosphide layer.   4. The semiconductor element according to claim 3, wherein the boron phosphide layer is a conductive p-type, and an ohmic electrode is provided on the surface of the boron phosphide layer.   The semiconductor element according to claim 3, wherein the boron phosphide layer has a high resistance, and a Schottky contact electrode is provided on a surface of the boron phosphide layer.   The semiconductor element according to claim 6, wherein the Schottky contact electrode is a gate electrode.   The semiconductor element according to claim 4, wherein the boron phosphide layer is an undoped layer to which impurities are not intentionally added.   4. The semiconductor element according to claim 1, wherein the boron phosphide-based semiconductor layer is formed using a hexagonal, low-polarity or nonpolar single crystal layer or single crystal substrate as a base layer. 5.   The semiconductor device according to any one of claims 1, 2, 3, 4, 5, 8, and 9 configured as a light emitting device.   The semiconductor device according to claim 1, configured as a field effect transistor.

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