JP2015002297A - Magnetic semiconductor element, and method for manufacturing magnetic semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic semiconductor element using a group III nitride magnetic semiconductor, capable of solving a problem relating to stability and a Curie temperature of ferromagnetism.SOLUTION: A magnetic semiconductor element 11 includes a semiconductor region 13, and a group III nitride semiconductor region 15. The group III nitride semiconductor region 15 is provided on a principal surface 13a of the semiconductor region 13. A junction J0 is formed on the principal surface 13a of the semiconductor region 13. The semiconductor region 13 has the principal surface 13a composed of a hexagonal group III nitride semiconductor, and the principal surface 13a includes one of a semipolar surface and a nonpolar surface. In this manner, a first group III nitride semiconductor layer 17 of the magnetic semiconductor element 11 is provided on the semipolar surface or the nonpolar surface. The first group III nitride semiconductor layer 17 provided on the semipolar surface and the nonpolar surface is excellent in intake to a crystal of at least any magnetic metal of transition metal and rear-earth metal, and also excellent in crystallinity in containing the magnetic metal.

Description

  The present invention relates to a magnetic semiconductor element and a method for manufacturing the magnetic semiconductor element.

  Patent Document 1 discloses a magnetic material containing an amorphous group III-V semiconductor material as a main component. Patent Document 2 discloses a group III-V compound semiconductor that transmits light.

JP 2008-112845 A WO2003 / 105162

  Patent Document 1 describes GaN crystals containing Mn and oxygen as impurities and GaN crystals containing Mn and Si as impurities as semiconductor materials exhibiting ferromagnetism. These GaN crystals have been proposed as semiconductor crystals that exhibit ferromagnetism at room temperature. However, the material applied to the magnetic semiconductor element is desired not only to be a semiconductor crystal exhibiting ferromagnetism at room temperature, but also to have a higher ferromagnetic-paramagnetic transition temperature (Curie temperature). In order to improve the Curie temperature and obtain good ferromagnetism, it is realized to increase the concentration of the magnetic ions added to the crystal and the carrier concentration. Adding a high concentration of magnetic ions in a semiconductor crystal causes problems such as phase separation of the semiconductor crystal and an increase in crystal defects in the semiconductor crystal. These defects eventually lead to deterioration of the characteristics of the magnetic semiconductor element through deterioration of the electrical, optical, and magnetic characteristics of the semiconductor crystal. Patent Document 1 discloses an amorphous compound semiconductor, specifically, GaN, AlN, AlInN, and AlGaN.

  In Patent Document 2, single crystal ferromagnetic III-V in which ferromagnetic properties are realized by mixing a rare earth metal element with a III-V group compound semiconductor that transmits light from infrared light to ultraviolet light. A group compound semiconductor is disclosed.

  According to the knowledge of the inventors, when a magnetic metal such as Gd, Cr, or Dy is added to a GaN-based semiconductor in crystal growth on the c-plane of GaN, a GaN-based magnetic semiconductor such as GaGdN, GaCrN, GaDyN, or GaMnN is It is desired to improve the stability of ferromagnetism without exhibiting clear ferromagnetism and exhibiting the behavior of a mixture of ferromagnetism and paramagnetism. There is a possibility that the magnetic metal added to the GaN-based semiconductor is clustered in the GaN-based semiconductor crystal. There is also a problem that the amount of magnetic metal doping cannot be increased.

  According to the inventors' investigations, when crystal growth is performed on the c-plane of a group III nitride such as GaN, for example, a magnetic metal such as Gd, Cr, or Dy is a group III nitride of group III nitride. It cannot fit in the site (Ga site) and is not successfully substituted with the host group III element. Also, it seems that the efficiency of taking a magnetic metal into the crystal is low on the c-plane of GaN as the base for crystal growth. It is desired that the Curie temperature can be improved and the Curie temperature can be adjusted. In other words, it is desired to solve the above-mentioned problem related to the c-plane of the GaN-based semiconductor.

  The present invention has been made in view of the above circumstances, and can provide a magnetic semiconductor element using a group III nitride magnetic semiconductor that can solve the above-described problems related to the stability of ferromagnetic and the Curie temperature. is there. It is another object of the present invention to provide a method for manufacturing a magnetic semiconductor element that can eliminate the problems associated with the stability and Curie temperature of ferromagnetism.

  The magnetic semiconductor element according to the present invention includes (a) a semiconductor region having a main surface made of a hexagonal group III nitride semiconductor, and (b) a first III provided on the main surface of the semiconductor region. A group III nitride semiconductor layer, wherein the group III nitride semiconductor of the first group III nitride semiconductor layer contains a first metal element, and the first group III nitride semiconductor layer includes the first group III nitride semiconductor layer. The metal element includes at least one of a transition metal and a rare earth metal, and the main surface includes at least one of a semipolar surface and a nonpolar surface.

  According to this magnetic semiconductor element, the first group III nitride semiconductor layer of the magnetic semiconductor element is provided on the semipolar surface or the nonpolar surface. The first group III nitride semiconductor layer provided on the semipolar plane and the nonpolar plane is excellent in incorporating at least one of transition metal and rare earth metal into the crystal of the magnetic metal, and added with a magnetic metal. Excellent crystallinity.

  In the magnetic semiconductor device according to the present invention, the transition metal is at least one of Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Mn, Y, Zr, Nb, Mo, Ag, and Cd. And the rare earth element may be at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. According to this magnetic semiconductor element, the above transition metals and rare earth elements can be applied.

  In the magnetic semiconductor element according to the present invention, the first group III nitride semiconductor layer preferably includes V, Cr, Mn, Nd, Eu, Gd, Dy, and Er as the first metal element. According to this magnetic semiconductor element, the first group III nitride semiconductor layer on the semipolar plane and the nonpolar plane is excellent in incorporation of these metals into the crystal, and when the magnetic metal is included. Excellent crystallinity.

  In the magnetic semiconductor element according to the present invention, the first group III nitride semiconductor layer may have ferromagnetism at room temperature. In the magnetic semiconductor device according to the present invention, the Curie temperature of the first group III nitride semiconductor layer is 300 Kelvin (K) or more.

  In the magnetic semiconductor element according to the present invention, the main surface preferably includes a group III nitride semiconductor crystal plane inclined at an angle of 5 degrees or more with respect to the c-plane of the semiconductor region. According to this magnetic semiconductor element, it is excellent in incorporation of magnetic metals such as transition metals and rare earth metals into crystals.

  In the magnetic semiconductor device according to the present invention, the content of the metal element in the first group III nitride semiconductor layer may be 3% or more. According to this magnetic semiconductor element, the properties resulting from the metal element contained in the first group III nitride semiconductor layer appear relatively clearly.

  The magnetic semiconductor element according to the present invention can further include a second group III nitride semiconductor layer provided on the semiconductor region. The group III nitride semiconductor of the second group III nitride semiconductor layer contains a second metal element, and the second group III nitride semiconductor layer includes a transition metal and a rare earth metal as the second metal element. The second group III nitride semiconductor layer has ferromagnetism, and the coercive force of the second group III nitride semiconductor layer is that of the first group III nitride semiconductor layer. Different from coercive force. According to this magnetic semiconductor element, the second group III nitride semiconductor layer on the semipolar plane and the nonpolar plane is excellent in the incorporation of these metals into the crystal, and when the magnetic metal is added. Excellent crystallinity.

  In the magnetic semiconductor device according to the present invention, the first group III nitride semiconductor layer preferably has either p-type conductivity or n-type conductivity. According to this magnetic semiconductor element, a dopant is added to a group III nitride semiconductor in order to impart either p-type conductivity or n-type conductivity. Depending on the addition of the dopant, the carrier concentration can be changed, whereby the ferromagnetic properties can be adjusted.

  The magnetic semiconductor device according to the present invention further includes a third group III nitride semiconductor layer provided between the first group III nitride semiconductor layer and the second group III nitride semiconductor layer. it can. The third group III nitride semiconductor layer does not have magnetism.

  In the magnetic semiconductor device according to the present invention, the first group III nitride semiconductor layer is different from the material of the third group III nitride semiconductor layer, and the second group III nitride semiconductor layer is the first group III nitride semiconductor layer. 3 may be different from the material of the group III nitride semiconductor layer. According to this magnetic semiconductor element, a heterojunction can be applied in the laminated structure.

  In the magnetic semiconductor device according to the present invention, the semiconductor region may include a GaN substrate. Alternatively, in the magnetic semiconductor element according to the present invention, the semiconductor region may include a silicon substrate and a group III nitride semiconductor layer provided on the silicon substrate.

  In the magnetic semiconductor element according to the present invention, the magnetic semiconductor element includes a magnetic sensor. According to this magnetic semiconductor element, it is possible to provide a magnetic sensor including a group III nitride semiconductor layer excellent in the ability to take in metal elements such as transition metals and rare earth metals. Alternatively, in the magnetic semiconductor element according to the present invention, the magnetic semiconductor element includes a magnetic memory. According to this magnetic semiconductor element, it is possible to provide a magnetic memory including a group III nitride semiconductor layer having an excellent ability to take in metal elements such as transition metals and rare earth metals.

  In the magnetic semiconductor device according to the present invention, the first group III nitride semiconductor layer includes a transition metal as the first metal element, and the first group III nitride semiconductor layer includes a rare earth metal as the first metal element. Is provided. According to this magnetic semiconductor element, a group III nitride semiconductor layer containing both transition metal and rare earth metal can be used.

  In the magnetic semiconductor device according to the present invention, the main surface includes a semipolar surface. Alternatively, in the magnetic semiconductor element according to the present invention, the main surface includes a nonpolar surface.

  The invention according to the present invention is a method for producing a magnetic semiconductor element, which comprises (a) a step of preparing a substrate having a main surface made of a hexagonal group III nitride semiconductor, and (b) And a step of growing a first group III nitride semiconductor layer on the main surface of the substrate, wherein the group III nitride semiconductor of the first group III nitride semiconductor layer contains a metal element. The first group III nitride semiconductor layer includes at least one of a transition metal and a rare earth metal as the metal element, and in the step of growing the semiconductor layer, the first group III nitride semiconductor layer A group III source material of group III constituent element, a nitrogen source material of group V constituent element, and a source material of metal element are supplied to the growth reactor, and the main surface includes one of a semipolar plane and a nonpolar plane.

  According to the method of manufacturing the magnetic semiconductor element, the first group III nitride semiconductor layer is grown on the main surface having semipolarity or nonpolarity. The growth of the first group III nitride semiconductor layer on the semiconductor main surface including the semipolar plane and the nonpolar plane is excellent in the ability to incorporate at least one of the transition metal and the rare earth metal into the crystal. Moreover, it is excellent in crystallinity when it contains a magnetic metal.

  The invention according to the present invention is a method of growing a magnetic semiconductor film, which comprises: (a) a main surface made of a hexagonal group III nitride semiconductor, and a growth furnace on the main surface. A step of growing a first group III nitride semiconductor layer, wherein the group III nitride semiconductor of the first group III nitride semiconductor layer contains a metal element, and the first group III nitride semiconductor The layer includes at least one of a transition metal and a rare earth metal as the metal element, and in the step of growing the semiconductor layer, a group III material of a group III constituent element of the first group III nitride semiconductor layer, a group V configuration An elemental nitrogen raw material and a metal element raw material are supplied to the growth furnace, and the main surface includes one of a semipolar surface and a nonpolar surface.

  According to the method for growing the magnetic semiconductor film, the first group III nitride semiconductor layer is grown on the main surface having semipolarity or nonpolarity. The growth of the first group III nitride semiconductor layer on the semiconductor main surface including a semipolar plane and a nonpolar plane is excellent in incorporating a transition metal and / or a rare earth metal into a crystal of a magnetic metal, In addition, the crystallinity is excellent when a magnetic metal is added.

  As described above, according to the present invention, it is possible to solve the problems related to the stability of the ferromagnetism and the Curie temperature, and to provide a magnetic semiconductor element using a group III nitride magnetic semiconductor. In addition, according to the present invention, it is possible to provide a method of manufacturing a magnetic semiconductor element that can eliminate the problems related to the stability of ferromagnetic and the Curie temperature.

FIG. 1 is a drawing schematically showing the structure of a magnetic semiconductor element according to the present embodiment. FIG. 2 is a drawing showing major steps in the method of growing a magnetic semiconductor film for Example 1. FIG. 3 is a drawing schematically showing the structure of the magnetic semiconductor device according to the first embodiment. FIG. 4 is a drawing showing main steps in a method for producing a magnetic semiconductor element for Example 2. FIG. 5 shows a Schottky barrier diode structure for a magnetic sensor. FIG. 6 is a diagram showing connections for measuring current-voltage characteristics of a Schottky barrier diode of a magnetic sensor. FIG. 7 is a diagram showing a change in resistance of the n-GaGdN layer by applying a magnetic field. FIG. 8 is a drawing showing main steps in a method for producing a magnetic semiconductor element for Example 3. FIG. 9 is a drawing showing an epitaxial film structure for Example 3. FIG. 10 is a drawing showing main steps in a method for producing a magnetic semiconductor element for Example 4. FIG. 11 is a drawing showing an epitaxial film structure for Example 4.

  Subsequently, an embodiment relating to a magnetic semiconductor element using a group III nitride magnetic semiconductor, a method of manufacturing the magnetic semiconductor element, and a method of manufacturing a magnetic semiconductor film will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

  FIG. 1 is a drawing schematically showing the structure of a magnetic semiconductor element according to the present embodiment. The magnetic semiconductor element 11 can be, for example, a magnetic sensor, a magnetic memory, a spin transistor, a circularly polarized laser, or the like. The magnetic semiconductor element 11 includes a semiconductor region 13 and a group III nitride semiconductor region 15. The group III nitride semiconductor region 15 is provided on the main surface 13a of the semiconductor region 13, and forms a junction J0 with the main surface 13a of the semiconductor region 13 in this embodiment. The semiconductor region 13 has a main surface 13a made of a hexagonal group III nitride semiconductor, and has a back surface 13b located on the opposite side of the main surface 13a. The main surface 13a includes one of a semipolar surface and a nonpolar surface. FIG. 1 shows a c-axis vector VC (SEMI) indicating the direction of the c-axis in semipolarity and a c-axis vector VC (NON) indicating the direction of the c-axis in nonpolarity. The main surface 13a showing semipolarity is an angle larger than zero with reference to the c-plane of the hexagonal group III nitride semiconductor, specifically, the (0001) plane or the (000-1) plane. It is inclined at an angle smaller than 90 degrees. An angle range of a plane orientation showing a preferable semipolarity for crystal growth can be, for example, 5 degrees or more and 85 degrees or less. The nonpolar surface of the main surface 13a is provided by defining the crystal orientation so that the c-axis of the hexagonal group III nitride semiconductor extends substantially parallel to the main surface 13a. Examples of the nonpolar surface of the main surface 13a include an a-plane and an m-plane. A main surface obtained by rotating at an arbitrary angle around the c-axis of a hexagonal group III nitride semiconductor from the a-plane or m-plane also exhibits nonpolarity. The angle range of the plane orientation exhibiting preferable nonpolar properties with respect to crystal growth can form an angle in the range of −5 degrees or more and +5 degrees or less with respect to the main surface with respect to the main surface where the c-axis is nonpolar, for example. Thereby, main surface 13a can be provided with a group III nitride semiconductor crystal plane inclined at an angle of 5 degrees or more with respect to the c-plane of semiconductor region 13. This magnetic semiconductor element 11 is excellent in the incorporation of magnetic metals such as transition metals and rare earth metals into crystals.

  The plane orientation of the main surface 13a is inherited by the crystal plane orientation of the group III nitride semiconductor grown on the main surface 13a, and is also inherited by the upper surface 15a of the group III nitride semiconductor region 15. When group III nitride semiconductor region 15 includes a plurality of semiconductor layers, the plane orientation of the junction of these semiconductor layers corresponds to the plane orientation of main surface 13a. Therefore, the characteristics of the semipolar plane and the nonpolar plane in the growth of the group III nitride semiconductor are inherited by the group III nitride semiconductor layer that is sequentially grown on the main surface 13a.

  The group III nitride semiconductor region 15 can include, for example, a first group III nitride semiconductor layer 17 provided on the major surface 13 a of the semiconductor region 13. The first group III nitride semiconductor layer 17 can be, for example, AlN, InN, a gallium nitride based semiconductor, or the like. The gallium nitride based semiconductor can be, for example, GaN, InGaN, AlGaN, InAlGaN, InAlN, or the like.

  Alternatively, the group III nitride semiconductor region 15 can include, for example, a first group III nitride semiconductor layer 17 and a second group III nitride semiconductor layer 19. The first group III nitride semiconductor layer 17 and the second group III nitride semiconductor layer 19 are provided on the main surface 13a of the semiconductor region 13, and are arranged in the direction of the normal Ax of the main surface 13a in this embodiment. The Alternatively, the group III nitride semiconductor region 15 can include, for example, a first group III nitride semiconductor layer 17, a second group III nitride semiconductor layer 19, and a third group III nitride semiconductor layer 21. The first group III nitride semiconductor layer 17, the second group III nitride semiconductor layer 19, and the third group III nitride semiconductor layer 21 are provided on the main surface 13 a of the semiconductor region 13. They are arranged in the direction of the normal Ax of the surface 13a. The third group III nitride semiconductor layer 21 is provided between the first group III nitride semiconductor layer 17 and the second group III nitride semiconductor layer 19. In the present embodiment, the third group III nitride semiconductor layer 21 forms a junction J1 with the first group III nitride semiconductor layer 17, and the junction J1 can be, for example, a heterojunction or a homojunction. The third group III nitride semiconductor layer 21 forms a junction J2 with the second group III nitride semiconductor layer 19, and the junction J2 can be a heterojunction or a homojunction, for example.

  The group III nitride semiconductor of the first group III nitride semiconductor layer 17 contains a first metal element. The first group III nitride semiconductor layer 17 includes at least one of a transition metal and a rare earth metal as the first metal element.

  According to the magnetic semiconductor element 11, the first group III nitride semiconductor layer 17 of the magnetic semiconductor element is provided on the semipolar surface or the nonpolar surface. The first group III nitride semiconductor layer 17 provided on the semipolar plane and the nonpolar plane is excellent in incorporating a transition metal and a rare earth metal into a crystal of a magnetic metal, and contains a magnetic metal. Excellent crystallinity at the time.

  The magnetic semiconductor element 11 may include an electrode 23 that is in contact with the upper surface 15 a of the group III nitride semiconductor region 15. In addition, the magnetic semiconductor element 11 can include an electrode 25 that is in contact with the back surface 13 a of the semiconductor region 13.

  In the magnetic semiconductor element 11, the transition metal is at least one of Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Mn, Y, Zr, Nb, Mo, Ag, and Cd. it can. The rare earth element can be at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The first group III nitride semiconductor layer 17 on the semipolar plane and the nonpolar plane is excellent in incorporating these metals into the crystal, and also excellent in crystallinity when containing a magnetic metal. Such first group III nitride semiconductor layer 17 has ferromagnetism at room temperature. According to this magnetic semiconductor element, it is possible to realize a magnetic device such as a magnetic sensor or a magnetic memory that operates at room temperature or higher and has high sensitivity and low power consumption. The Curie temperature of the first group III nitride semiconductor layer 17 is, for example, 300 Kelvin or higher, and the first group III nitride semiconductor layer 17 exhibits ferromagnetism at room temperature. Preferably, the Curie temperature of the first group III nitride semiconductor layer 17 is 600 Kelvin or higher, and the magnetic semiconductor element 11 exhibits stable ferromagnetism at room temperature.

  Preferably, when the first group III nitride semiconductor layer 17 includes V, Cr, Mn, Nd, Eu, Gd, Dy, Er as the first metal element, the first group on the semipolar plane and the nonpolar plane The group III nitride semiconductor layer 17 is excellent in the incorporation of these metals into crystals, and is also excellent in crystallinity when a magnetic metal is added.

  The metal element content of the first group III nitride semiconductor layer 17 may be 3% or more. According to this magnetic semiconductor element 11, the properties resulting from the metal elements contained in the first group III nitride semiconductor layer 17 appear relatively clearly. The metal element content of the first group III nitride semiconductor layer 17 may be 10% or more. According to the magnetic semiconductor element 11, a magnetic device such as a magnetic sensor or a magnetic memory that operates at room temperature or higher and has high sensitivity and low power consumption can be realized.

  The first group III nitride semiconductor layer 17 can have either p-type conductivity or n-type conductivity. In order to provide either p-type conductivity or n-type conductivity, a dopant is added to the group III nitride semiconductor separately from the magnetic metal. Depending on the addition of the dopant, the carrier concentration can be changed, whereby the ferromagnetic properties can be adjusted. Silicon, germanium, or the like can be used as the n-type dopant, and magnesium, zinc, or the like can be used as the p-type dopant.

  As shown in FIG. 1, the group III nitride semiconductor region 15 may include a first group III nitride semiconductor layer 17 and a second group III nitride semiconductor layer 19. The second group III nitride semiconductor layer 19 can be, for example, AlN, InN, a gallium nitride based semiconductor, or the like. The gallium nitride based semiconductor can be, for example, GaN, InGaN, AlGaN, InAlGaN, InAlN, or the like. The first group III nitride semiconductor layer 17 and the second group III nitride semiconductor layer 19 form a junction JJ. This junction can be heterozygous or homozygous.

  The group III nitride semiconductor of the second group III nitride semiconductor layer 19 contains a second metal element, and the second group III nitride semiconductor layer has at least one of a transition metal and a rare earth metal as the second metal element. Can be provided. As the transition metal and rare earth metal, the elements described above can be applied. Further, the second group III nitride semiconductor layer 19 on the semipolar plane and the nonpolar plane is excellent in the incorporation of these metals into crystals, and also excellent in crystallinity when containing a magnetic metal. . Such a second group III nitride semiconductor layer 19 has ferromagnetism at room temperature. According to this magnetic semiconductor element, it is possible to realize a magnetic device such as a magnetic sensor or a magnetic memory that operates at room temperature or higher and has high sensitivity and low power consumption. The Curie temperature of the second group III nitride semiconductor layer 19 is, for example, 300 Kelvin (K) or more, and the second group III nitride semiconductor layer 19 exhibits ferromagnetism at room temperature. Preferably, the Curie temperature of the second group III nitride semiconductor layer 19 is 600 Kelvin or higher, and the second group III nitride semiconductor layer 19 exhibits stable ferromagnetism at room temperature. Further, when the content of the metal element in the second group III nitride semiconductor layer 19 is 3% or more, the properties resulting from the metal element contained in the second group III nitride semiconductor layer 19 are relatively clear. Appears. In addition, when the content of the metal element in the second group III nitride semiconductor layer 19 is 10% or more, a magnetic device such as a magnetic sensor or a magnetic memory that operates at room temperature or higher and that operates at room temperature or higher is realized. it can.

  When the second group III nitride semiconductor layer 19 includes a transition metal and / or a rare earth metal, the second group III nitride semiconductor layer exhibits ferromagnetism. The coercivity of the second group III nitride semiconductor layer 19 is preferably different from the coercivity of the first group III nitride semiconductor layer 17. In order to generate films having different holding powers, for example, the metal element content can be changed between two layers. By using a plurality of group III nitride semiconductor layers having different coercive forces in the magnetic semiconductor element 11, a magnetic device using the tunnel magnetoresistive effect (TMR) such as a magnetic memory (MRAM) can be realized. By using a group III nitride semiconductor, the difference in coercive force can be made to be 50% or more, for example.

  Similar to the first group III nitride semiconductor layer 17, the second group III nitride semiconductor layer 19 can have conductivity from either p-type conductivity or n-type conductivity. A dopant is added to the group III nitride semiconductor for providing either p-type conductivity or n-type conductivity. Depending on the addition of the dopant, the carrier concentration can be changed, whereby the ferromagnetic properties can be adjusted.

  The combination of the material of the first group III nitride semiconductor layer 17 and the material of the second group III nitride semiconductor layer 19 can be GaGdN, GaGdN, etc. with different amounts of Gd added. Such a two-layer magnetic semiconductor element is applied to a giant magnetoresistive (GMR) element.

  The magnetic semiconductor element 11 can further include a third group III nitride semiconductor layer 21. The third group III nitride semiconductor layer 21 is provided between the first group III nitride semiconductor layer 17 and the second group III nitride semiconductor layer 19. The third group III nitride semiconductor layer 21 does not have magnetism. The magnetic semiconductor element having such a structure can provide a magnetic sensor and a magnetic memory.

  In one embodiment, the third group III nitride semiconductor layer 21 forms a junction J1 with the first group III nitride semiconductor layer 17, and the third group III nitride semiconductor layer 21 is a second group III nitride. The physical semiconductor layer 19 and the junction J2 are formed. The third group III nitride semiconductor layer 21 is preferably composed of a nonmagnetic layer that is not magnetic. For example, the third group III nitride semiconductor layer 21 does not exhibit ferromagnetism in the operating temperature range of the device. It may be formed as follows. In the growth of the group III nitride semiconductor layer, the third group III nitride semiconductor layer 21 is preferably grown so as not to intentionally add the magnetic metal. The third group III nitride semiconductor layer 21 is preferably made of a material that provides a barrier to the carriers of the first group III nitride semiconductor layer 17 and the second group III nitride semiconductor layer 19. Alternatively, the resistivity of the third group III nitride semiconductor layer 21 is preferably higher than the resistivity of the first group III nitride semiconductor layer 17 and the resistivity of the second group III nitride semiconductor layer 19.

  The combination of the material of the first group III nitride semiconductor layer 17, the material of the second group III nitride semiconductor layer 19, and the material of the third group III nitride semiconductor layer 21 is GaGdN, GaGdN, AlGaN, or the like. Can be.

  In the magnetic semiconductor element 11, the semiconductor region 13 can include a group III nitride semiconductor substrate, and includes, for example, a GaN substrate. According to the magnetic semiconductor element 11, a magnetic device including a group III nitride semiconductor layer having excellent crystallinity can be provided. The semiconductor region 13 can include a silicon substrate and a group III nitride semiconductor layer provided on the silicon substrate. According to the magnetic semiconductor element 11, the substrate cost can be reduced, and it can be integrated on the Si substrate together with the existing semiconductor device such as the Si-MOSFET.

  The magnetic semiconductor element 11 having the structure as described above can provide a magnetic sensor including a group III nitride semiconductor layer having an excellent ability to take in metal elements such as transition metals and rare earth metals. Alternatively, the magnetic semiconductor element 11 can provide a magnetic memory including a group III nitride semiconductor layer excellent in the ability to take in metal elements such as transition metals and rare earth metals.

  When the main surface 13a of the semiconductor region 13 includes a semipolar surface, a group III nitride semiconductor layer excellent in metal element uptake and crystallinity can be produced. Further, when the main surface 13a of the semiconductor region 13 includes a nonpolar surface, a group III nitride semiconductor layer having excellent metal element uptake ability and excellent crystallinity can be produced. In addition, a group III nitride semiconductor layer having a cubic crystal structure can be produced.

  When the group III nitride semiconductor layers 15 and 21 include a transition metal as the first metal element, the amount of the metal element added can be increased. Further, when the group III nitride semiconductor layers 15 and 21 are provided with a rare earth metal as the first metal element, strong magnetic properties can be exhibited even with a small addition amount of the metal element. Further, when the group III nitride semiconductor layers 15 and 21 include both a transition metal and a rare earth metal as the first metal element, they can exhibit stronger magnetism.

Example 1
A method of growing a magnetic semiconductor film will be described with reference to FIG. In step S101, a GaN substrate is prepared. The plane orientations of the prepared GaN substrates are as follows: c-plane, {20-21} plane, m-plane, a-plane, {11-22} plane, and {10-11} plane. In step S102, the GaN substrate is placed in a growth furnace. Using this growth furnace, a GaGdN film is grown on the GaN substrate in step S103. In the step of growing the semiconductor layer, as shown in FIG. 3, a group III source material of a group III constituent element, a nitrogen source material of a group V constituent element, and a source material G0 of a metal element are supplied to the growth reactor 10. As the growth method, for example, a molecular beam epitaxy (MBE) method is used. As the gallium raw material, nitrogen raw material, and gadolinium (Gd) raw material, Ga metal, nitrogen RF plasma, and Gd metal are used, respectively. During MBE growth, the substrate temperature is 700 degrees Celsius. The thickness of the GaGdN film is 200 nm. Specifically, the epitaxial film structure shown in FIG. 3 is produced.

By adjusting the flux in the MBE method, the following three types of Gd content GaGdN films are grown on the GaN {20-21} plane. The magnetization of these GaGdN films is measured and the Curie temperature is evaluated.
GaGdN film (Gd composition, unit atom%), Curie temperature.
GaGdN film (Gd composition 10%), 400K.
GaGdN film (Gd composition 15%), 500K.
GaGdN film (Gd composition 20%), 600K.
The Gd composition is estimated by X-ray diffraction (XRD), Rutherford backscattering (RBS), energy dispersive X-ray spectroscopy (EDX), or the like.
Note that a GaGdN film can also be grown by metal organic vapor phase epitaxy, and for example, tricyclopentadienyl gadolinium ((Cp) ₃ Gd) can be used as a Gd raw material. Instead of gadolinium (Gd), dysprosium (Dy), manganese (Mn), chromium (Cr), vanadium (V), neodymium (Nd), europium (Eu), erbium (Er), etc. are also used to grow GaN-based semiconductors. Applicable. In this embodiment, a GaN substrate is used as the growth substrate, but a silicon substrate can be used as the growth substrate instead of the GaN substrate.

(Example 2)
A method of manufacturing a magnetic semiconductor element will be described with reference to FIG. A magnetic sensor element is produced. In step S201, a GaN substrate is prepared. An epitaxial film for the magnetic sensor element is grown on the GaN substrate. The plane orientations of the prepared GaN substrates are as follows: c-plane, {20-21} plane, m-plane, a-plane, {11-22} plane, and {10-11} plane. In step S202, the GaN substrate is placed in a growth furnace. Using this growth furnace, in step S203, a GaGdN film is grown on the GaN substrate. As the growth method, for example, a molecular beam epitaxy (MBE) method is used. Specifically, the epitaxial film structure shown in FIG. 5 is produced. During MBE growth, the substrate temperature is 700 degrees Celsius. The flux in the MBE method is adjusted, and a GaGdN film is grown on the GaN {20-21} plane to produce an epitaxial substrate. The thickness of the GaGdN film is 500 nm. The Gd composition of the GaGdN film is 20%. The carrier concentration of the GaGdN film is 1 × 10 ¹⁸ cm ⁻³ .

  In step S204, a Schottky electrode is formed on the epitaxial surface of the epitaxial substrate. This Schottky electrode is made of Ni and has an electrode size of 0.2 mmφ. A pad electrode (for example, Au) is formed on the Schottky electrode. In step S205, an ohmic electrode is formed on the back surface of the epitaxial substrate GaN substrate. The ohmic electrode is made of Ti / Al / Ti / Au. As shown in FIG. 5, a magnetic sensor having a Schottky barrier diode structure is manufactured.

As shown in FIG. 6, a voltmeter, an ammeter, and a variable power source are connected to this magnetic sensor, and the current-voltage characteristics of the Schottky barrier diode of the magnetic sensor are applied while applying an external field H at 25 degrees Celsius. Measure. As shown in FIG. 7, the resistance change of the n-GaGdN layer is measured by applying a magnetic field. The characteristics S1 and S2 of the n-GaGdN layer correspond to the applied external magnetic field 0 Oersted and 20 Oersted, respectively. In accordance with the application of the magnetic field, the forward characteristics of the magnetic sensor having the Schottky barrier diode structure change. This characteristic indicates that a normally-off magnetic sensor can be realized. That is, it is possible to realize a sensor in which current does not flow when a magnetic field is zero and current flows when a magnetic field is applied. The minimum detectable magnetic field of this magnetic sensor is 1 × 10 ⁻² oersted (1E-2Oe) or less. In addition, since the Curie temperature of the GaGdN film is high, this magnetic sensor exhibits sensitivity close to room temperature (25 degrees Celsius) even at a temperature of 200 degrees Celsius or higher. For example, when an applied voltage indicated by an arrow in FIG. 7 is applied to the magnetic sensor element, a change in external magnetic field and application can be detected as a change in electrical resistance. In this embodiment, a GaN substrate is used as the growth substrate, but a silicon substrate can be used as the growth substrate instead of the GaN substrate.

Example 3
A method of manufacturing a tunnel magnetoresistive element will be described with reference to FIG. In step S301, a GaN substrate is prepared. An epitaxial film for the tunnel magnetoresistive element is grown on the GaN substrate. The plane orientations of the prepared GaN substrates are as follows: c-plane, {20-21} plane, m-plane, a-plane, {11-22} plane, and {10-11} plane.
In step S302, the GaN substrate is placed in a growth furnace. Using this growth furnace, a GaGdN film is grown on the GaN substrate. As the growth method, for example, a molecular beam epitaxy (MBE) method is used. Specifically, the epitaxial film structure shown in FIG. 9 is produced. During MBE growth, the substrate temperature is 700 degrees Celsius. By adjusting the flux in the MBE method, in step S303, an n-type Ga _1-X Gd _X N film, a p-type Al _Z Ga _1-Z N film, and an n-type Ga _{1-Y are formed} on the GaN {20-21} plane. Gd _Y N films are grown in order to produce an epitaxial substrate. In step S304, growing the n-type _{Ga 1-X} Gd X N film GaN {20-21} on the surface. In step S305, to grow a p-type _{Al Z Ga 1-Z} N layer on the n-type _{Ga 1-X} Gd X N film. In step S306, growing the n-type _{Ga 1-Y} Gd Y N film on the p-type _{Al Z Ga 1-Z} N layer. In this laminated structure, n-type _{Ga 1-X} Gd X N film forms a heterojunction with the p-type _{Al Z Ga 1-Z} N layer, n-type _{Ga 1-Y} Gd Y N layer is p-type _Al Z Ga _{1 -ZN} Heterojunction is formed in the NN film. In this embodiment, X = 0.20 (20%), Y = 0.10, Z = 0.20. n-type _{Ga 1-X} Gd X N film and n-type _{Ga 1-Y} Gd Y N layer is Si-doped, p-type _{Al Z Ga 1-Z} N layer is Mg doped. The thickness of the n-type _{Ga 1-X} Gd X N film is 100 nm, the thickness of the n-type _{Ga 1-Y} Gd Y N film is 100 nm. The thickness of the p-type _{Al Z Ga 1-Z} N layer is 20 nm. dopant concentration of the n-type _{Ga 1-X} Gd X N film is 1 × ¹⁰ 18 ^{cm -3.} The dopant concentration of the n-type Ga _1-Y Gd _Y N film is 1 × 10 ¹⁸ cm ⁻³ . The dopant concentration of the p-type Al _Z Ga _1-Z N film is 1 × 10 ¹⁹ cm ⁻³ .

In step S307, an electrode is formed on the epitaxial substrate. In step S308, the ohmic electrode on the epitaxial surface of the epitaxial substrate (n-type _{Ga 1-Y} Gd Y N surface of the film). The ohmic electrode is made of Ti / Al / Ti / Au and has an electrode size of 0.2 mmφ. A pad electrode (for example, Au) is formed on the ohmic electrode. In step S309, an ohmic electrode is formed on the back surface of the epitaxial substrate GaN substrate. The ohmic electrode is made of Ti / Al / Ti / Au. As shown in FIG. 9, a magnetic sensor having a TMR structure is manufactured.

As in the second embodiment, a voltmeter, an ammeter, and a variable power source are connected to this magnetic sensor, and the current-voltage characteristics of the TMR element of the magnetic sensor are measured at 25 degrees Celsius. The resistance change of the TMR element layer can be measured by applying a magnetic field. Since the resistance of the TMR layer changes according to application of a magnetic field, magnetic sensing becomes possible. The minimum detectable magnetic field of this magnetic sensor is 1 × 10 ⁻⁶ oersted (1E-6Oe) or less. In addition, since the Curie temperature of the GaGdN film is high, this magnetic sensor exhibits a sensitivity close to room temperature even at a temperature of 200 degrees Celsius or higher. In this embodiment, a GaN substrate is used as the growth substrate, but a silicon substrate can be used as the growth substrate instead of the GaN substrate.

Example 4
A method of manufacturing a tunnel magnetoresistive (TMR) element will be described with reference to FIG. In step S401, a magnetic memory using a tunnel magnetoresistive element is manufactured. A GaN substrate is prepared. An epitaxial film for the tunnel magnetoresistive element is grown on the GaN substrate. The plane orientations of the prepared GaN substrates are as follows: c-plane, {20-21} plane, m-plane, a-plane, {11-22} plane, and {10-11} plane. In step S402, the GaN substrate is placed in a growth furnace. Using this growth furnace, a GaGdN film is grown on the GaN substrate. As the growth method, for example, a molecular beam epitaxy (MBE) method is used. Specifically, the epitaxial film structure shown in FIG. During MBE growth, the substrate temperature is 700 degrees Celsius. By adjusting the flux in the MBE method, in step S403, the n-type Ga _1-X Gd _X N film, the p-type Al _Z Ga _1-Z N film, and the n-type Ga _{1-Y are formed} on the GaN {20-21} plane. Gd _Y N films are grown in order to produce an epitaxial substrate. In this laminated structure, n-type _{Ga 1-X} Gd X N film forms a heterojunction with the p-type _{Al Z Ga 1-Z} N layer, n-type _{Ga 1-Y} Gd Y N layer is p-type _Al Z Ga _{1 -ZN} Heterojunction is formed in the NN film. In this embodiment, X = 0.20 (20%), Y = 0.10, Z = 0.20. n-type _{Ga 1-X} Gd X N film and n-type _{Ga 1-Y} Gd Y N layer is Si-doped, p-type _{Al Z Ga 1-Z} N layer is Mg doped. The thickness of the n-type _{Ga 1-X} Gd X N film is 100 nm, and the n-type _{Ga 1-Y} Gd Y N thickness of the film is 100 nm. The thickness of the p-type _{Al Z Ga 1-Z} N layer is 20 nm. dopant concentration of the n-type _{Ga 1-X} Gd X N film is 1 × ¹⁰ 18 ^{cm -3.} The dopant concentration of the n-type Ga _1-Y Gd _Y N film is 1 × 10 ¹⁸ cm ⁻³ . The dopant concentration of the p-type Al _Z Ga _1-Z N film is 1 × 10 ¹⁹ cm ⁻³ .

In step S404, an electrode is formed on the epitaxial substrate. Epi surface of the epitaxial substrate (n-type _{Ga 1-Y} Gd Y N surface of the film) forming an ohmic electrode. The ohmic electrode is made of Ti / Al / Ti / Au and has an electrode size of 0.2 mmφ. A pad electrode (for example, Au) is formed on the ohmic electrode. An ohmic electrode is formed on the back surface of the GaN substrate of the epitaxial substrate. The ohmic electrode is made of Ti / Al / Ti / Au. As shown in FIG. 11A, a magnetic memory having a TMR structure is manufactured.

  In this magnetic memory, it can be confirmed that the parallel / anti-parallel of the spin (SPIN) of the TMR layer is changed by applying a magnetic field from the outside as shown in FIGS. 11 (b) and 11 (c). Therefore, information of “0” and “1” can be stored. Memory operation is possible in this magnetic memory.

  Further, in this magnetic memory, it can be confirmed that the spin parallel / anti-parallel of the TMR layer is changed by the current injection from the outside, and therefore information of “0” and “1” can be stored. Memory operation is possible in this magnetic memory. Further, in this magnetic memory, it can be confirmed that the spin parallel / anti-parallel of the TMR layer is changed by applying an external voltage, and therefore, information of “0” and “1” can be stored. Memory operation is possible in this magnetic memory.

  The power consumption in these storage operations is very small, and the power consumption of the magnetic memory element of this embodiment is estimated to be 1/100 or less of the current power consumption of DRAM when compared on a bit-by-bit basis.

  The present invention is not limited to the specific configuration disclosed in the present embodiment.

  As described above, according to the present embodiment, it is possible to eliminate the problems associated with the stability of the ferromagnetism and the Curie temperature, and to provide a magnetic semiconductor element using a group III nitride magnetic semiconductor. In addition, according to the present embodiment, it is possible to provide a method of manufacturing a magnetic semiconductor element that can eliminate the problems related to the stability of the ferromagnetism and the Curie temperature. Furthermore, according to the present embodiment, it is possible to provide a method for growing a magnetic semiconductor film that can eliminate the problems related to the stability of ferromagnetic and the Curie temperature.

DESCRIPTION OF SYMBOLS 11 ... Magnetic semiconductor element, 13 ... Semiconductor region, 15 ... III nitride semiconductor region, 13a ... Main surface, 19 ... 2nd group III nitride semiconductor layer, 21 ... 3rd group III nitride semiconductor layer, 23 ... Electrode, 25 ... Electrode, J0 ... Joining, J1 ... Joining, J2 ... Joining.

Claims (20)

A magnetic semiconductor element,
A semiconductor region having a main surface made of a hexagonal group III nitride semiconductor;
A first group III nitride semiconductor layer provided on the main surface of the semiconductor region;
With
The group III nitride semiconductor of the first group III nitride semiconductor layer contains a first metal element, and the first group III nitride semiconductor layer includes a transition metal and a rare earth metal as the first metal element. With at least one,
The magnetic semiconductor element, wherein the main surface includes at least one of a semipolar surface and a nonpolar surface. The transition metal is at least one of Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Mn, Y, Zr, Nb, Mo, Ag, and Cd.
The said rare earth metal is at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Magnetic semiconductor element.   3. The magnetic semiconductor element according to claim 1, wherein the first group III nitride semiconductor layer includes V, Cr, Mn, Nd, Eu, Gd, Dy, and Er as the first metal element. .   4. The magnetic semiconductor element according to claim 1, wherein the first group III nitride semiconductor layer has ferromagnetism at room temperature. 5.   5. The magnetic semiconductor element according to claim 1, wherein a Curie temperature of the first group III nitride semiconductor layer is 300 Kelvin or higher.   The said main surface is equipped with the group III nitride semiconductor crystal surface which inclines at an angle of 5 degree | times or more with respect to c surface of the said semiconductor region, The Claim 1 characterized by the above-mentioned. Magnetic semiconductor element.   7. The magnetic semiconductor element according to claim 1, wherein a content of the metal element in the first group III nitride semiconductor layer is 3% or more. A second group III nitride semiconductor layer provided on the semiconductor region;
The group III nitride semiconductor of the second group III nitride semiconductor layer contains a second metal element, and the second group III nitride semiconductor layer includes a transition metal and a rare earth metal as the second metal element. With at least one,
The second group III nitride semiconductor layer has ferromagnetism, and the coercivity of the second group III nitride semiconductor layer is different from the coercivity of the first group III nitride semiconductor layer. The magnetic semiconductor element as described in any one of Claims 1-7. A third group III nitride semiconductor layer provided between the first group III nitride semiconductor layer and the second group III nitride semiconductor layer;
The magnetic semiconductor element according to claim 8, wherein the third group III nitride semiconductor layer does not have magnetism. The first group III nitride semiconductor layer is different from the material of the third group III nitride semiconductor layer,
The magnetic semiconductor element according to claim 9, wherein the second group III nitride semiconductor layer is different from a material of the third group III nitride semiconductor layer.   11. The magnetic semiconductor element according to claim 1, wherein the first group III nitride semiconductor layer has either p-type conductivity or n-type conductivity.   The magnetic semiconductor element according to claim 1, wherein the semiconductor region includes a GaN substrate.   The magnetic semiconductor element according to any one of claims 1 to 11, wherein the semiconductor region includes a silicon substrate and a group III nitride semiconductor layer provided on the silicon substrate.   The magnetic semiconductor element according to claim 1, wherein the magnetic semiconductor element includes a magnetic sensor.   The magnetic semiconductor element according to claim 1, wherein the magnetic semiconductor element includes a magnetic memory.   The magnetic semiconductor element according to claim 1, wherein the main surface includes a semipolar surface.   The magnetic semiconductor element according to claim 1, wherein the main surface includes a nonpolar surface. A method for producing a magnetic semiconductor element, comprising:
Preparing a substrate having a main surface made of a hexagonal group III nitride semiconductor;
Growing a first group III nitride semiconductor layer on the main surface of the substrate in a growth furnace;
With
The group III nitride semiconductor of the first group III nitride semiconductor layer contains a first metal element, and the first group III nitride semiconductor layer includes a transition metal and a rare earth metal as the first metal element. With at least one,
In the step of growing the semiconductor layer, a Group III material of a Group III constituent element, a nitrogen source of a Group V constituent element, and a source of a first metal element of the first Group III nitride semiconductor layer are supplied to the growth furnace And
The method for producing a magnetic semiconductor element, wherein the main surface includes one of a semipolar surface and a nonpolar surface.   The method for producing a magnetic semiconductor element according to claim 18, wherein the main surface includes a semipolar surface.   The method for producing a magnetic semiconductor element according to claim 18, wherein the main surface includes a nonpolar surface.

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