JP2011082528A - Semiconductor light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for growing a crystal of group III nitride, capable of doping impurities of a transition metal, and the like, to the crystal of group III nitride at a desired concentration in a controllable manner, the crystal of group III nitride, a device of the crystal of group III nitride and a light-emitting device. <P>SOLUTION: In the method, a mixed melt 103 is formed with an alkaline metal, a substance containing at least group III metal, and a dopant metal inside a reaction chamber 113, and a crystal of group III nitride doped with the dopant metal is grown by using the mixed melt 103 and a substance containing at least nitrogen. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a group III nitride crystal growth method, a group III nitride crystal, a group III nitride semiconductor device, and a light emitting device.

  Conventionally, group III nitride crystals are used in light emitting devices in the ultraviolet to green wavelength band, high frequency electronic devices, and the like. By the way, in recent years, a proposal has been made to derive new physical properties by doping a group III nitride (GaN, AlN, InN, BN and mixed crystals thereof) with a transition metal.

  For example, Patent Document 1 proposes realizing a magnetic semiconductor by doping a group III nitride with a transition metal.

  Further, Patent Document 2, Patent Document 3, and Patent Document 4 propose that a transition metal is doped into a group III nitride and used as a light emitting region to increase the light emission wavelength.

  In any of these conventional techniques, the transition metal is doped by MBE (molecular beam epitaxy) or MOCVD (metal organic chemical vapor deposition). However, when the transition metal is doped by the MBE method or the MOCVD method, there is a problem that the doping amount cannot be increased sufficiently or the controllability is difficult.

  On the other hand, for example, Patent Document 1 proposes to increase the doping amount of the transition metal by doping an element other than the transition metal (Si, O, Mg, Be, C, etc.) simultaneously with the transition metal. ing. However, in this case, in addition to the desired physical properties that are originally desired, control of electrical conduction is required. In Patent Document 1, the MBE apparatus shown in FIG. 4 is used to dope a transition metal such as V, Cr, Mn, etc., and the MBE apparatus must maintain an ultra-high vacuum, resulting in high cost. Connected. Also, the MOCVD apparatus uses expensive parts such as a raw material supply system, a reaction system, and an exhaust system, so that the apparatus cost increases.

  The present invention relates to a group III nitride crystal growth method, a group III nitride crystal, and a group III, which are capable of doping a group III nitride crystal with a desired concentration of impurities such as transition metals at a desired concentration. An object is to provide a nitride semiconductor device. Another object of the present invention is to provide a group III nitride crystal growth method that can be doped with impurities such as transition metals at a lower cost than MOCVD and MBE methods.

  In order to achieve the above object, according to the first aspect of the present invention, in the reaction vessel, an alkali metal, a substance containing at least a group III metal, and a dopant metal form a mixed melt, and the mixed melt and at least nitrogen It is characterized in that a group III nitride crystal doped with a dopant metal is grown from a substance containing.

  The invention described in claim 2 is the group III nitride crystal growth method described in claim 1, characterized in that the dopant metal is a transition metal.

  The invention described in claim 3 is a group III nitride crystal doped with a dopant metal, which is grown using the group III nitride crystal growth method described in claim 1 or claim 2.

  The invention according to claim 4 is the group III nitride crystal according to claim 3, wherein the group III nitride crystal has magnetism.

  The invention described in claim 5 is a group III nitride semiconductor device characterized in that the group III nitride crystal described in claim 3 is used as a light emitting region.

  According to a sixth aspect of the present invention, in the group III nitride semiconductor device according to the fifth aspect, a light emitting device having a semiconductor multilayer structure is formed on the group III nitride crystal according to the third aspect, and the light emission A light emitting device characterized in that the group III nitride crystal is emitted by irradiating the group III nitride crystal with light emitted from the device and exciting the group III nitride crystal. is there.

  Further, the invention according to claim 7 is the light emitting device according to claim 6, wherein the light emission from the group III nitride crystal is light emission due to an inner shell transition of a transition metal doped in the group III nitride crystal. It is a light emitting device characterized by being.

  According to the first and second aspects of the invention, in the reaction vessel, the alkali metal, the substance containing at least a group III metal, and the dopant metal form a mixed melt, and the mixed melt and at least nitrogen are included. Since the group III nitride crystal doped with the dopant metal is grown from the material, the group III nitride doped with the dopant metal as a high-quality impurity can be grown with good controllability, and the crystal A growth method can be realized at low cost. That is, in the present invention, the dopant to the group III nitride crystal can be easily maintained while maintaining a high quality crystal without performing special doping like the MBE method or MOCVD method described in the prior art. Metal doping is possible.

  Further, according to the invention described in claim 3 or claim 4, the group III nitride doped with a dopant metal is grown using the group III nitride crystal growth method according to claim 1 or claim 2. Because it is a crystal, it is possible to realize a high-quality group III nitride crystal doped with a transition metal, etc., and as a result, to display new physical properties such as light emission at a wavelength that cannot be achieved with magnetism or a group III nitride crystal alone. Is possible.

  Further, according to the invention of claim 5, claim 6 and claim 7, since the group III nitride crystal of claim 3 is a group III nitride semiconductor device used as a light emitting region, group III Light emission at a wavelength that cannot be realized by using a nitride crystal alone is possible.

  Further, according to the inventions of claims 6 and 7, since the light emitting device having the semiconductor laminated structure laminated on the high-quality group III nitride crystal according to claim 3 is used as the excitation light source, The light emitting device itself has high luminous efficiency and high reliability. As a result, it is possible to realize a light emitting device with high output and long life. Furthermore, the intensity of light emission from the group III nitride crystal can be adjusted by the thickness of the group III nitride crystal according to claim 3 and the doping amount of the dopant metal.

It is a figure which shows an example of the group III nitride crystal growth apparatus which concerns on this invention. It is a figure which shows an example of the group III nitride semiconductor device which concerns on this invention. It is a figure which shows the other example of the group III nitride crystal growth apparatus which concerns on this invention. It is a figure for demonstrating a prior art. It is a figure which shows an example of the group III nitride semiconductor device which concerns on this invention. It is a figure which shows an example of the group III nitride semiconductor device which concerns on this invention.

  Hereinafter, the best mode for carrying out the present invention will be described.

  Until now, the inventors of the present application have realized a high-quality group III nitride crystal by reacting a mixed melt composed of an alkali metal and a group III metal with a group V raw material containing nitrogen. Yes. This method is called a flux method.

  The inventor of the present application pays attention to this flux method, and by using this flux method, a transition metal or other metal (dopant metal) that becomes an impurity is doped into a group III nitride crystal to develop a new physical property. .

(First form)
According to a first aspect of the present invention, in a reaction vessel, a substance containing an alkali metal, at least a group III metal, and a dopant metal form a mixed melt, and the dopant is formed from the mixed melt and a substance containing at least nitrogen. It is characterized by growing a group III nitride crystal doped with metal.

  Here, in the present invention, the group III metal is Ga, Al, In or the like. In the present invention, Li, Na, K, etc. can be used as the alkali metal. The substance containing nitrogen is a compound containing nitrogen as a constituent element, such as nitrogen gas, sodium azide, or ammonia.

  That is, in the present invention, nitrogen is dissolved from a substance containing at least nitrogen in a mixed melt composed of an alkali metal and a substance containing at least a group III metal. At this time, since the dopant metal is mixed in the mixed melt, the group III nitride doped with the dopant metal can be crystal-grown.

(Second form)
The second aspect of the present invention is characterized in that the dopant metal is a transition metal in the group III nitride crystal growth method of the first aspect described above.

  Here, the transition metal is an element of 3A group, 4A group, 5A group, 6A group, 7A group, 8 group or 1B group in the periodic table. As described in the above prior art, it is difficult to dope these elements into group III nitrides with good controllability. On the other hand, in the present invention, nitrogen is dissolved from a substance containing at least nitrogen in a state where a transition metal is added to a mixed melt composed of an alkali metal and a substance containing at least a group III metal, A group III nitride doped with a transition metal with good controllability can be crystal-grown.

(Third form)
A third aspect of the present invention is a group III nitride crystal doped with a dopant metal, which is grown using the group III nitride crystal growth method of the first or second aspect.

(4th form)
A fourth aspect of the present invention is a group III nitride crystal characterized in that the group III nitride crystal has magnetism in the group III nitride crystal of the third aspect.

  Here, magnetism means paramagnetic and ferromagnetic, and the doped group III nitride crystal has paramagnetic and ferromagnetic properties.

(5th form)
A fifth aspect of the present invention is a group III nitride semiconductor device, wherein the group III nitride crystal of the third aspect is used as a light emitting region.

(Sixth form)
According to a sixth aspect of the present invention, in the Group III nitride device of the fifth aspect, a light emitting device having a semiconductor multilayer structure is formed on the Group III nitride crystal of the third aspect. Is emitted to the group III nitride crystal to excite the group III nitride crystal so that the group III nitride crystal emits light.

(7th form)
According to a seventh aspect of the present invention, in the Group III nitride device according to the sixth aspect, light emission from the Group III nitride crystal is caused by an inner shell transition of a transition metal doped in the Group III nitride crystal. The light emitting device is characterized in that it emits light.

  Example 1 corresponds to the first to fourth embodiments. FIG. 1 is a diagram for explaining a first embodiment of the present invention. That is, FIG. 1 shows a group III nitridation doped with a transition metal from a mixed melt and a substance containing at least nitrogen, in which the alkali metal, the substance containing at least a group III metal, and the transition metal form a mixed melt. It is a figure which shows the crystal growth apparatus which grows a physical crystal.

  Referring to FIG. 1, there is a second reaction vessel 113 inside the first reaction vessel 101, and in the meantime (inside the first reaction vessel 101 and outside the second reaction vessel 113) III A heating device 106 is provided to control the group nitride to a temperature at which crystal growth is possible. Further, a mixed melt holding container 102 is installed inside the second reaction vessel 113, and Ga and alkali metals as substances containing at least a group III metal are contained in the mixed melt holding container 102. A mixed melt 103 composed of Na and manganese (Mn) as a transition metal is accommodated. Further, a lid 109 is provided on the mixed melt holding container 102, and there is a slight gap between the mixed melt holding container 102 and the lid 109 to allow gas to enter and exit.

  A thermocouple 112 for detecting the temperature of the mixed melt holding container 102 is installed in the second reaction container 113. The thermocouple 112 is connected to the heating device 106 so that temperature feedback control is possible.

  In Example 1, nitrogen gas is used as the substance containing at least nitrogen. Nitrogen gas is supplied from the nitrogen gas container 107 installed outside the first reaction container 101 to the space 108 in the first reaction container 101 and the second reaction container 113 through the gas supply pipe 104. Be able to. In order to adjust the pressure of the nitrogen gas, a pressure adjustment valve 105 is provided. Further, a pressure sensor 111 that detects the pressure of nitrogen gas in the reaction vessels 101 and 113 is provided. At this time, the pressure sensor 111 is fed back to the pressure adjustment valve 105 so that the pressure in the first reaction vessel 101 and the pressure in the second reaction vessel 113 are substantially the same pressure and a predetermined pressure. It has become such a thing.

  Here, the constituent metal in the mixed melt 103 has a melt composition in which Ga is 15 mmol, Na is 30 mmol, and Mn is 1 mmol. In contrast, the nitrogen pressure in the reaction vessel 101 is set to 5 MPa, and the temperature of the mixed melt holding vessel 102 is set to 850 ° C. By maintaining these temperatures and pressures in this state, the GaN crystal 110 doped with Mn grows.

  That is, since it is a group III nitride crystal grown by dissolving nitrogen in the mixed melt 103, it is possible to grow a high-quality and large-sized GaN crystal. Further, Mn is doped, and this GaN crystal exhibits magnetism.

  Example 2 corresponds to the first to third modes. In Example 2, Mn of Example 1 is replaced with europium (Eu).

  That is, in Example 2, in the crystal growth apparatus of FIG. 1, 15 mmol of Ga, 30 mmol of Na, and 2 mmol of Eu are mixed as the mixed melt 103, the nitrogen pressure in the reaction vessel 101 is 5 MPa, and the mixed melt is mixed. The temperature of the liquid holding container 102 is set to 800 ° C. By maintaining these temperatures and pressures in this state, the GaN crystal 110 doped with Eu can be grown.

  A normal high-quality GaN crystal shows the strongest emission characteristic at a wavelength near 365 nm, but a GaN crystal doped with Eu shows an emission characteristic having a peak at a wavelength of about 620 nm. Thus, the Eu-doped GaN crystal of Example 2 is characterized by high quality and a light emission wavelength different from that of GaN alone.

  In Examples 1 and 2 described above, Mn and Eu are used as doping metals, respectively, but in the present invention, other metal materials such as transition metals can be used as doping metals.

  Example 3 corresponds to the fifth mode. FIG. 2 is a diagram for explaining a third embodiment of the present invention. That is, FIG. 2 is a diagram (perspective view) showing a light emitting diode as an example of the group III nitride semiconductor device of the present invention.

  Referring to FIG. 2, an n-type AlGaN cladding layer 202, an Eu-doped GaN active layer 203, a p-type AlGaN cladding layer 204, and a p-type GaN contact layer 205 are sequentially stacked on an n-type GaN substrate 201. Yes. Further, an n-side ohmic electrode Al / Ti 207 is formed below the n-type GaN substrate 201, and a p-side ohmic electrode Au / Ni 206 is formed above the p-type GaN contact layer 205.

  In the light emitting diode of FIG. 2, the active layer 203 emits light by injecting current from the p-side ohmic electrode Au / Ni 206 and the n-side ohmic electrode Al / Ti 207. At this time, the light emission wavelength shows a light emission characteristic having a peak wavelength near 620 nm.

  Since the light emitting region of this light emitting diode is formed of Eu-doped GaN crystal grown by dissolving nitrogen in a mixed melt of Na and Ga, it has few defects and is of high quality. Therefore, there are few non-light-emitting recombination centers and highly efficient light emission characteristics are exhibited. For this reason, the lifetime of the device is also long.

  Example 4 corresponds to the first to third and fifth embodiments. FIG. 3 is a diagram for explaining a fourth embodiment of the present invention. In FIG. 3, the same parts as those in FIG.

  In Example 4, first, an MO-CVD method, an MBE method, or the like is performed on an n-type GaN substrate grown by a group III nitride crystal growth method (flux method) devised by the inventors of the present application. The n-type AlGaN cladding layer 202 is crystal-grown. At this time, since the GaN substrate 201 is a crystal grown by a flux method, it is a high-quality crystal with a low defect density. Therefore, the n-type AlGaN cladding layer 202 is also of high quality with few defects.

  Next, as shown in FIG. 3, the substrate 310 on which the n-type AlGaN cladding layer 202 is grown on the n-type GaN substrate 201 as described above is placed in the mixed melt 103. In FIG. 3, the substrate 310 is installed on the bottom surface of the mixed melt holding container 102. At this time, Eu is added to the mixed melt 103 in addition to Ga and Na. The melt composition is 15 mmol Ga, 30 mmol Na, and 2 mmol Eu as in Example 2.

  In this state, by setting the nitrogen pressure in the reaction vessel 101 to 5 MPa and the temperature of the mixed melt holding vessel 102 to 800 ° C., the GaN crystal layer 203 doped with Eu grows on the substrate 310.

  Thereafter, the p-type AlGaN cladding layer 204 and the p-type GaN contact layer 205 are sequentially stacked by MO-CVD method, MBE method, or the like. Finally, an n-side ohmic electrode Al / Ti 207 is formed below the n-type GaN substrate 201, and a p-side ohmic electrode Au / Ni 206 is formed above the p-type GaN contact layer 205 to produce a device structure. be able to.

  Thus, by using the flux method for forming the active layer, it is possible to grow a high-quality and highly controllable doped GaN crystal.

  Example 5 corresponds to the sixth embodiment. FIG. 5 is a diagram for explaining a fifth embodiment of the present invention. That is, FIG. 5 is a diagram (sectional view) showing a white light emitting diode as an example of the group III nitride semiconductor device of the present invention.

  Referring to FIG. 5, an n-type GaN layer 302, an n-type AlGaN cladding layer 303, an InGaN active layer 304, a p-type AlGaN cladding layer 305, and a p-type GaN contact layer 306 are sequentially stacked on the GaN substrate 301. Yes. This laminated structure is crystal-grown by the MOCVD method. A part of the laminated structure is scraped from the p-type GaN contact layer 306 to the surface of the n-type GaN layer 302, and the n-type GaN layer 302 is exposed. An n-side ohmic electrode Al / Ti 308 is formed on the exposed n-type GaN layer 302 surface, and a p-side ohmic electrode Au / Ni 307 is formed on the p-type GaN contact layer 306.

  In the light-emitting diode of FIG. 5, the active layer 304 emits light by injecting current from the p-side ohmic electrode Au / Ni 307 and the n-side ohmic electrode Al / Ti 308. At this time, the emission wavelength shows a blue emission characteristic having a peak wavelength in the vicinity of 460 nm.

  The GaN substrate 301 on which the stacked structure of the light emitting diode is formed is a Li-doped GaN crystal grown by adding Li to a mixed melt of Na and Ga and dissolving nitrogen.

  The Li-doped GaN crystal has yellow emission characteristics due to light emission from the energy level caused by Li.

  In the light emitting diode of Example 5, when light is injected into the electrodes 307 and 308, blue light emission occurs, and this light enters the GaN substrate 301, the GaN substrate 301 is excited, and the GaN substrate 301 becomes yellow. Emits light. Then, since blue and yellow light is emitted from the substrate side, the extracted light becomes white light due to a complementary color relationship.

  Since the GaN substrate 301 is a crystal grown by a flux method, it is a high-quality crystal with a low defect density. For this reason, the light emitting diode laminated structure formed thereon has few non-light emitting recombination centers and exhibits highly efficient light emission characteristics. For this reason, the lifetime of the device is also long. Therefore, the white light emitting diode of Example 5 has high efficiency and long life.

  In addition, although Li was used as a dopant metal in the present Example 5, other metals, such as Cd and Mg, can be used as a dopant metal.

  Example 6 corresponds to the seventh embodiment. FIG. 6 is a diagram for explaining a sixth embodiment of the present invention. That is, FIG. 6 is a diagram (cross-sectional view) showing a red light emitting diode as an example of the group III nitride semiconductor device of the present invention.

  Referring to FIG. 6, an n-type GaN layer 402, an n-type AlGaN cladding layer 403, an InGaN active layer 404, a p-type AlGaN cladding layer 405, and a p-type GaN contact layer 406 are sequentially stacked on the GaN substrate 401. Yes. This laminated structure is crystal-grown by the MOCVD method. Also, a part of the laminated structure is scraped from the p-type GaN contact layer 406 to the surface of the n-type GaN layer 402, and the n-type GaN layer 402 is exposed. An n-side ohmic electrode Al / Ti 408 is formed on the exposed n-type GaN layer 402 surface, and a p-side ohmic electrode Au / Ni 407 is formed on the p-type GaN contact layer 406.

  In the light emitting diode of FIG. 6, the active layer 404 emits light by injecting current from the p-side ohmic electrode Au / Ni 407 and the n-side ohmic electrode Al / Ti 408. At this time, the emission wavelength exhibits ultraviolet emission characteristics having a peak wavelength near 375 nm.

  The GaN substrate 401 on which the laminated structure of the light emitting diode is formed is an Eu-doped GaN crystal grown by adding Eu to a mixed melt of Na and Ga and dissolving nitrogen.

  The Eu-doped GaN crystal has a red light emission characteristic due to light emission caused by the ionic core transition of Eu.

  In the light emitting diode of Example 6, ultraviolet light is emitted by injecting current into the electrodes 407 and 408, and this light is incident on the GaN substrate 401, and Eu in the GaN substrate 401 is excited, and the inner shell transition. Occurs and emits red light.

  Further, since the GaN substrate 401 is a crystal grown by a flux method, it is a high-quality crystal with a low defect density. For this reason, the light emitting diode laminated structure formed thereon has few non-light emitting recombination centers and exhibits highly efficient light emission characteristics. For this reason, the lifetime of the device is also long. Therefore, the white light emitting diode of this example has high efficiency and long life.

  In Example 6, Eu is used as the dopant metal. However, substances such as Er, Tb, and other rare earth metals that can emit light by inner-shell transition can be used as the dopant metal.

  The present invention can be used for a light emitting device (LD, LED), a group III nitride magnetic device, an electronic device, and the like in an ultraviolet to infrared wavelength region.

DESCRIPTION OF SYMBOLS 101 1st reaction container 102 Mixed melt holding container 103 Mixed melt 104 Gas supply pipe 105 Nitrogen pressure regulating valve 106 Heating device 107 Nitrogen gas container 108 Space in reaction container 109 Lid of mixed melt holding container 110 GaN crystal 111 Pressure sensor 112 Thermocouple 113 Second reaction vessel 201 n-type GaN substrate 202, 303, 403 n-type AlGaN cladding layer 203 Eu-doped GaN active layer 204, 305, 405 p-type AlGaN cladding layer 205, 306, 406 p Type GaN contact layer 206,307,407 p-side ohmic electrode Au / Ni
207, 308, 408 n-side ohmic electrode Al / Ti
301 Li-doped GaN substrate 302, 402 n-type GaN layer 304 InGaN active layer 310 substrate 401 Eu-doped GaN substrate 404 InGaN active layer

JP 2002-260922 A JP 10-27923 A JP 2002-368267 A JP 2002-543595 A

Claims (7)

  In a reaction vessel, a substance containing an alkali metal, at least a group III metal, and a dopant metal form a mixed melt, and a group III nitride doped with the dopant metal from the mixed melt and a substance containing at least nitrogen A method for growing a group III nitride crystal, comprising growing a crystal.   2. The group III nitride crystal growth method according to claim 1, wherein the dopant metal is a transition metal.   A group III nitride crystal doped with a dopant metal, which is grown using the group III nitride crystal growth method according to claim 1 or 2.   The group III nitride crystal according to claim 3, wherein the group III nitride crystal has magnetism.   A group III nitride semiconductor device, wherein the group III nitride crystal according to claim 3 is used as a light emitting region.   The group III nitride semiconductor device according to claim 5, wherein a light emitting device having a semiconductor multilayer structure is formed on the group III nitride crystal according to claim 3, and light emitted from the light emitting device is emitted from the group III nitride A light emitting device characterized in that a group III nitride crystal is made to emit light by irradiating a physical crystal and exciting the group III nitride crystal.   7. The light emitting device according to claim 6, wherein the light emission from the group III nitride crystal is light emission by an inner shell transition of a transition metal doped in the group III nitride crystal.

Images