JP4633251B2 - Group III nitride semiconductor light-emitting diode and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for forming a group III nitride semiconductor light emitting diode having a pn junction type double heterojunction structure using a silicon single crystal as a substrate.
[0002]
[Prior art]
Traditional electrically insulating sapphire (α-Al₂O_Three) Group III nitride semiconductors using silicon (Si) single crystal as substrate instead of single crystal substrate (see Mat. Res. Soc. Symp. Proc., Vol. 468 (1977), P.481-P.486) A technique for forming a light emitting diode (LED) is disclosed (see Electron. Lett., Vol. 33 No. 23 (1997) P. 1986-1987). If a silicon single crystal exhibiting conductivity and cleavage is used as a substrate, a group III nitride semiconductor light emitting diode can be constructed conveniently by a simple device fabrication process (Appl. Phys. Lett., Vol. 72 No .4 (1998), pages 415-417).
[0003]
In group III nitride semiconductor light emitting diodes, aluminum nitride, gallium, indium (Al_αGa_βIn_{1- α - β}A light emitting part of a pn junction type double hetero (DH) junction structure made of a group III nitride semiconductor crystal layer such as N: 0 ≦ α, β, α + β ≦ 1) is formed. The light emitting portion having a DH junction structure refers to a portion responsible for light emission in a structure in which a light emitting layer is sandwiched between p-type and n-type clad layers. Both the light emitting layer and the clad layer can be made of an aluminum nitride / gallium layer. In that case, the forbidden band width of the cladding layer is made larger than the forbidden band width of the light emitting layer by making the aluminum mixed crystal ratio (α) of the cladding layer higher than the aluminum mixed crystal ratio of the light emitting layer. A confinement effect of injected electrons is provided. In addition, a light emitting layer for emitting short wavelength visible light in a blue band or a green band is made of gallium nitride / indium (Ga_βIn_{1- β}N: 0 ≦ β ≦ 1) is exclusively (see Japanese Patent Publication No. 55-3834).
[0004]
However, when a silicon single crystal is used as the substrate, the forbidden band width of the silicon single crystal is about 1.1 eV (Akira Teramoto, “Introduction to Semiconductor Devices” (March 30, 1995, first edition published by Baifukan Co., Ltd. 28) The transition energy corresponding to the light emission in the blue band is less than half, so that the short wavelength light emitted from the light emitting part is absorbed by the silicon single crystal used as the substrate. That is, the group III nitride semiconductor light-emitting diode formed on the silicon substrate has a problem that it is difficult to obtain an LED having high emission intensity due to absorption of light emitted by the substrate.
[0005]
[Problems to be solved by the invention]
The present invention relates to a group III nitride semiconductor light emitting diode using a silicon single crystal as a substrate, and light from the light emitting part is absorbed by the silicon substrate, so that the group III nitride semiconductor light emitting diode having high intensity light emission is provided. The purpose of the present invention is to provide a short-wavelength group III nitride semiconductor light-emitting diode having high emission intensity using an inexpensive and high-quality silicon substrate. To do.
[0006]
[Means for Solving the Problems]
  In order to solve the above problems, the light-emitting diode of the present invention has a general formula Al laminated on a silicon single crystal substrate._aGa_bIn_1-abN_cM_1-c(Where 0 ≦ a, b, a + b ≦ 1, M represents a group V element other than nitrogen, and 0 <c ≦ 1), which is composed of a group III nitride layer represented by a pn junction type A group III nitride semiconductor light-emitting diode having a light emitting portion having a double hetero (DH) junction structure, wherein a boron phosphide (BP) crystal layer and phosphorous phosphide are provided between the silicon single crystal substrate and the light emitting portion. Gallium (GaN_1-XP_X: 0 ≦ X ≦ 1) provided with a reflective layer having a multilayer structure in which crystal layers are alternately stackedThe phosphorus composition ratio of the gallium nitride phosphide crystal layer is 2 atomic% or more and 4 atomic% or less.A group III nitride semiconductor light emitting diode was obtained. With this structure, the light emitted from the light emitting portion to the substrate side is not absorbed by the substrate, but can be reflected to the light extraction side and effectively extracted to the visual field side. A group nitride semiconductor light emitting diode can be obtained.At the same time, lattice matching with the boron phosphide crystal which is the other crystal layer constituting the multilayer laminated structure is obtained, and a good crystalline multilayer laminated structure is obtained..
[0007]
  In the present invention, the carrier concentration of the boron phosphide crystal layer and the gallium nitride phosphide crystal layer constituting the multilayer laminated structure is 1 × 10¹⁷cm^-3That's 5x10¹⁹cm^-3The following is preferable. With such a carrier concentration, since the conductivity is high, an operating current can flow in the vertical direction of the light emitting diode through the multilayer structure and the silicon substrate, and the structure of the light emitting diode can be simplified and provided at low cost. Have advantages.
[0008]
In the present invention, the number of cycles of the multilayer laminated structure is 2 or more, preferably 7 or more.
This is because when the number of periods is 2 or more, the reflectance increases rapidly, and when it is 7 or more, a reflectance of almost 100% is obtained in the visible light region.
[0009]
In the present invention, the {111} crystal plane is preferably used as the plane orientation of the silicon single crystal substrate surface.
This is because Si atoms are densely arranged on the {111} crystal plane, so that intrusion of impurity atoms is prevented and a flat surface can be easily obtained.
Further, a buffer layer may be interposed between the silicon single crystal substrate and the multilayer stacked structure.
This is because the buffer layer prevents the propagation of crystal defects in the silicon single crystal substrate, so that it is easy to obtain a high-quality multilayer structure having excellent crystallinity.
[0010]
In the present invention, a metal organic chemical vapor deposition method can be used to form the multilayer laminated structure. This is because according to the metal organic chemical vapor deposition method, the composition of the crystal phase to be laminated can be easily adjusted, and a high-quality multilayer laminated structure can be easily obtained.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The group III nitride semiconductor light-emitting diode of the present invention uses a silicon single crystal that has a high-quality crystal and is available at a relatively low cost as a substrate. There is no particular restriction on the crystal plane orientation of the silicon single crystal used as the substrate, but in general {111} or {100} single crystal can be used. The {111} crystal plane has denser Si atoms than the {100} crystal plane. Therefore, the effect of suppressing thermal diffusion of boron (B) and phosphorus (P), which are constituent elements of the boron phosphide layer constituting the multilayer laminated structure of the present invention, into the inside of the substrate is exhibited. That is, it is advantageous in preventing non-planarization of the silicon substrate surface due to diffusion and penetration of boron and phosphorus.
[0012]
On the surface of the silicon single crystal substrate, a boron phosphide (BP) crystal layer and a gallium nitride phosphide (GaN) that constitute the reflective layer_1-XP_X: 0.ltoreq.X.ltoreq.1) A multilayer laminated structure composed of crystal layers is formed. The multilayer stack structure can be deposited directly on the silicon substrate, or alternatively via a buffer layer.
The material constituting the buffer layer is generally gallium nitride phosphide (GaN) lattice-matched to a silicon single crystal (lattice constant = 5.4309３０)._0.02P_0.98, Lattice constant = 5.431Å), gallium arsenide nitride (GaN)_0.19As_0.81, Lattice constant = 5.431Å), gallium borohydride (B_0.02Ga_0.98P, lattice constant = 5.431Å) (see JP-A-11-266006), or gallium boron arsenide (B_0.25Ga_0.75As, lattice constant = 5.431 Å (see Japanese Patent Application Laid-Open No. 11-260720) or the like can be used. Indium phosphide (B) containing indium (In) as a constituent element_0.33In_0.67P, lattice constant = 5.431Å) or indium boron arsenide or the like (B_0.40In_0.60As, lattice constant = 5.431Å) can also be used. Further, cubic indium phosphide (InN_0.49P_0.51, Lattice constant = 5.431Å) or indium arsenide nitride (InN_0.58As_0.42Lattice constant = 5.431Å) can also be used. Use of the buffer layer has an advantage that it is possible to prevent the propagation of crystal defects in the silicon substrate and to prevent the diffusion of impurities.
[0013]
Further, the buffer layer can be made of a material having a lattice constant different from that of the silicon single crystal. For example, when the buffer layer is composed of boron phosphide (BP, lattice constant = 4.538 cm), the buffer layer (low temperature buffer layer) grown at a relatively low temperature is almost amorphous, and a silicon single crystal and a multilayer laminated structure There is an advantage that a multilayer laminated structure having excellent crystallinity can be obtained by relaxing a lattice mismatch with the body. For example, a boron phosphide low-temperature buffer layer formed at a relatively low temperature of 250 ° C. or more and 500 ° C. or less is approximately 16% of lattice mismatch between a silicon single crystal and a boron phosphide crystal or a gallium nitride phosphide crystal (“Japan (See Journal of Crystal Growth Society, Vol. 24, No. 2 (1997), p. 150), which has the effect of producing a high-quality multilayered structure with a low density of crystal defects such as misfit dislocations (USA) (See Patent No. 6,069,021).
[0014]
When a multi-layer structure is formed by laminating a large number of semiconductor layers having different refractive indexes at specific intervals, a function of reflecting light of a specific wavelength is generated according to Bragg's law. This is the so-called Bragg reflector (DBR).
In the present invention, the boron phosphide (BP) crystal layer having a difference in refractive index of 0.5 or more and the gallium nitride phosphide (GaN) are used as the semiconductor layers having different refractive indexes._1-XP_X) Utilize the crystal layer.
In order to make the difference in refractive index from the BP crystal layer (refractive index = 3.1) 0.5 or more, GaN_1-XP_XThe phosphorus mixed crystal ratio x of the crystal layer may be a value in the range of x = 0 (GaN, refractive index = 2.0) to x = 1 (GaP, refractive index = 2.1). GaN_1-XP_XThe phosphorus mixed crystal ratio x of the crystal layer is preferably in the range of x = 0.02 to x = 0.04 in consideration of lattice matching with the BP crystal layer as will be described later.
The thickness (nm) of each layer to be stacked is set to λ / 4N with respect to the emission wavelength λ (nm). Here, N is the optical refractive index of the semiconductor material constituting each layer. A multilayer laminated structure having such a thickness is laminated to form a thickness of 0.2 to 3 μm as a whole.
[0015]
In the multilayer laminated structure, the bottom layer closest to the silicon single crystal substrate side is BP or GaN._1-XP_XAny one of (0 ≦ X ≦ 1) can be used. In addition, the outermost layer of the multilayer structure is BP or GaN._1-XP_XAny of these can be used. The lowermost layer and the outermost layer are not necessarily made of the same material. What is important is the BP crystal layer and GaN._1-XP_XThe crystal layer is alternately laminated to form a multilayer laminated structure to constitute a so-called Bragg reflection layer (see “Introduction to Semiconductor Devices”, page 28).
1 BP crystal layer and 1 GaN layer_1-XP_XAssuming that the multilayer unit structure composed of the crystal layers is one period, it is desirable that the multilayer laminated structure is composed of at least two periods. BP and GaN_1-XP_XA semiconductor multilayer reflector with a wide reflection bandwidth from the periodic laminated structure consisting of (for reflectors, co-authored by Iga and Koyama, “Surface Emitting Laser”, September 25, 1990, published by OM Corp.) 1st printing, 1st printing, pp. 118-119) is obtained.
[0016]
For example, GaN with a BP and phosphorus composition ratio of 3%_0.97P_0.03FIG. 1 shows a theoretical calculation value of the reflectance for blue light having a wavelength of 450 nm with respect to the number of periods of a multilayer laminated structure composed of The refractive index of BP is 3.1 and GaN_0.97P_0.03It is set to 2.0. BP and GaN_0.97P_0.03The layer thickness of each constituent layer is 36 nm and 56 nm, respectively. The reflectance increases rapidly when the number of periods exceeds 2. If the number of periods is 7 or more, a reflectance of about 99.8% can be obtained.
[0017]
The layer thickness (nm) of each constituent layer of the multilayer laminated structure having the function as a Bragg reflection layer is λ / (4 × N) (where N is the wavelength of the light to be reflected is λ (nm)). Refractive index). For example, when the refractive index of boron phosphide is 3.1 and the refractive index of gallium nitride phosphide is 2.0, a multilayer laminated structure that can reflect red light with a wavelength (λ) of 600 nm with high efficiency is BP layer having a layer thickness of about 48 nm and GaN layer having a thickness of 75 nm_0.97P_0.03What is necessary is just to comprise from the periodic laminated structure with a layer. FIG. 2 shows a BP layer having a thickness of about 48 nm and a GaN layer having a thickness of 75 nm, respectively._0.97P_0.03The reflectance of the multilayer laminated structure which laminated | stacked the layer 10 cycles alternately is shown. The target of reflection is blue light having a center wavelength of 460 nm to red light having a center wavelength of 700 nm. BP layer and GaN_1-XP_XIn a multilayer laminated structure composed of layers, a reflectivity close to 100% can be obtained with a small number of periods of about 10 cycles by changing the layer thickness of the multilayer laminated structure constituting layer according to the wavelength to be reflected. available.
[0018]
In the present invention, the constituent layers of the periodic multilayer laminated structure are made of a conductive BP crystal layer and GaN._1-XP_XIt consists of a crystal layer. In particular, the carrier concentration is 1 × 10¹⁷cm^-3That's 5x10¹⁹cm^-3It is preferably composed of the following n-type or p-type conductive layer. If a multilayer laminated structure is composed of conductive constituent layers, the LED drive current can be passed from the top of the structure toward the silicon single crystal substrate, so one electrode can be formed on the surface of the silicon substrate. This is advantageous in terms of manufacturing. Carrier concentration is 1 × 10¹⁷cm^-3If the ratio is less than 1, it is difficult to form a constituent layer having a sufficiently low resistance to pass a driving current. Carrier concentration is 5 × 10¹⁹cm^-3Since the crystallinity of the layer to which the carrier impurity is added at a higher concentration is deteriorated as it exceeds the range, it becomes difficult to obtain a multilayer laminated structure having sufficiently stable reflection performance. The p-type carrier concentration can be adjusted by appropriately controlling the doping amount of zinc (Zn), magnesium (Mg) or the like during film formation. The n-type carrier concentration is adjusted by appropriately controlling the doping amount of n-type impurities such as silicon (Si) and selenium (Se).
[0019]
The conductive types of the constituent layers constituting the periodic laminated structure are the same. When constituent layers having opposite conductivity types are joined, a pn junction is formed inside the multilayer structure. For this reason, electricity supply to the silicon single crystal substrate of the LED driving current is obstructed, which is not preferable. Also, the conductivity type of the multilayer structure constituting layer is unified to the conductivity type of a silicon single crystal as a substrate. If the conductivity types of the silicon substrate and the multilayer laminated structure conflict, a pn junction is formed at the junction interface between the silicon substrate and the multilayer laminated structure. For this reason, there arises a disadvantage that the LED drive current is not sufficiently supplied to the silicon substrate. Each conductive layer having the same conductivity type as that of the silicon single crystal substrate can be formed by means such as a halogen vapor deposition method, a hydride vapor deposition method, or a metal organic chemical vapor deposition (MOCVD) method. .
[0020]
In the present invention, GaN constituting a multilayer laminated structure together with a BP crystal layer_1-XP_XGaN with a phosphorus composition ratio of 2% to 4% for the crystal layer_1-XP_XIt is preferable to comprise a crystal layer (0.02 ≦ X ≦ 0.04). According to Vegard's law, cubic GaN with a phosphorus composition ratio ranging from 2% to 4%_1-XP_XThe lattice constant of the crystal layer is in the range of 4.548 to 4.529. On the other hand, the lattice constant of zinc blende BP is 4.538 （(see “Introduction to Semiconductor Devices” on page 28 above). Therefore, if the phosphorus composition ratio is limited to the above range, GaN substantially lattice-matched with the BP crystal layer._1-XP_XA crystalline layer is obtained. GaN with a phosphorus composition ratio of 3% (0.03)_0.97P_0.03Has a lattice constant of 4.538 、 and lattice matches with BP. Therefore, GaN with a BP crystal layer and phosphorus composition ratio in the range of 3% ± 1%_1-XP_XThe lattice mismatch with the crystal layer (0.02 ≦ X ≦ 0.04) is within about ± 0.2%, and there is an advantage that a high-quality multilayer laminated structure can be formed because of good lattice matching.
At this time, GaN_1-XP_XSince the refractive index of the crystal layer is about 2.1, and the difference in refractive index of 0.5 or more with the BP crystal layer is kept sufficiently, it is possible to constitute a multilayer laminated structure having excellent reflectivity. it can.
As a result, a group III nitride semiconductor light-emitting diode excellent in electrical characteristics with a constant forward voltage (Vf) can be obtained.
[0021]
On the multi-layer structure, the general formula Al_aGa_bIn_1-abN_cM_1-c The light emitting part of the pn junction type double heterojunction structure which consists of a group III nitride layer represented by is formed. Here, 0 ≦ a, b, a + b ≦ 1, M represents a group V element other than nitrogen (N) such as phosphorus (P), arsenic (As), antimony (Sb), and 0 <c ≦ 1. Therefore, the double heterojunction structure forming the light emitting part in the present invention is
The group III element includes at least one element of Al, Ga, and In, and the group V element includes nitrogen (N) as an essential element.
[0022]
A light emitting part having a DH junction structure is a light emitting part having a structure in which a light emitting layer is sandwiched between p-type and n-type cladding layers. Al in either the light emitting layer or the cladding layer_aGa_bIn_1-abN_cM_1-c It only needs to contain a layer. Al in the light emitting layer_aGa_bIn_1-abN_cM_1-cIf the layer is used, a blue light-emitting diode of a short wavelength system can be obtained.
[0023]
  The forbidden band width of the cladding layer is made larger than the forbidden band width of the light emitting layer so as to enhance the confinement effect of electrons injected into the light emitting layer. Further, the thickness of the light emitting layer is usually 5 to 30 nm, and the thickness of the cladding layer is formed to be 100 to 800 nm, which is thicker than that.
[0024]
The ohmic electrodes for applying a drive current are formed on the top and bottom of the laminated body laminated as described above to obtain a light emitting diode. Al_aGa_bIn_1-abN_cM_1-c As an electrode material forming an ohmic junction with the layer, aluminum (Al) can be used for an n-type electrode, and gold (Au) can be used for a p-type electrode. As the material of the ohmic electrode formed on the silicon substrate, aluminum (Al) can be used for the n-type electrode, and aluminum-antimony (Al-Sb) alloy can be used for the p-type electrode. Since the overall LED resistance is low, the drive current can be passed through the substrate.
[0025]
[Action]
The present invention relates to a BP crystal layer and GaN._1-XP_XA periodic multilayer structure composed of crystal layers is used as a so-called Bragg reflection structure that reflects light emitted from a light emitting portion.
[0026]
In the present invention, the BP crystal layer and GaN_1-XP_XThe carrier concentration of the conductive periodic multi-layer laminated structure composed of the crystal layer is limited to a specific range so that the LED driving current can be passed through the silicon substrate.
[0027]
Furthermore, in the present invention, GaN with a phosphorus composition ratio limited to a specific range_1-XP_XBy using the crystal layer, BP crystal layer and GaN_1-XP_XLattice matching with the crystal layer was maintained, so that excellent crystallinity of the periodic multilayer structure was ensured.
[0028]
【Example】
Example 1
The present invention takes as an example the case of forming a group III nitride semiconductor light emitting diode by providing a multilayer laminated structure, which is a Bragg reflection layer made of boron phosphide and gallium phosphide mixed crystal, on a silicon single crystal substrate. Will be described in detail.
FIG. 3 shows a schematic cross-sectional view of the light emitting diode 10 according to this example.
[0029]
For the silicon substrate 101, boron-doped p-type silicon single crystal (111) was used. A low temperature buffer layer 102 made of boron phosphide was deposited on the silicon substrate 101. The low-temperature buffer layer 102 is made of triethylboron ((C₂H_Five)_ThreeB) / phosphine (PH_Three) / Hydrogen (H₂) It was deposited at 350 ° C. by atmospheric pressure MOCVD using a reaction gas. The layer thickness of the low temperature buffer layer 102 was about 10 nm. On the surface of the low temperature buffer layer 102, a p-type BP layer doped with zinc (Zn) was deposited at 1000 ° C. using the MOCVD method as the high temperature buffer layer 103. Dimethyl zinc ((C₂H_Five)₂Zn) was used. The carrier concentration of the high-temperature buffer layer 103 is about 7 × 10¹⁸cm^-3It was. The layer thickness was 500 nm.
[0030]
On the high-temperature buffer layer 103, as the first constituent layer 104-1 constituting the multilayer laminated structure 104 serving as a Bragg reflective layer, zinc-doped p-type phosphide nitride having a phosphorus (P) composition ratio of 0.03 Gallium (GaN_0.97P_0.03) Layers were laminated. GaN_0.97P_0.03The layer consists of trimethylgallium ((CH_Three)_ThreeGa) / phosphine (PH_Three ) / Ammonia (NH_Three) / Hydrogen (H₂) It was grown at 1000 ° C. by an atmospheric pressure MOCVD method using a reaction gas. Carrier concentration is about 8 × 10¹⁷cm^-3The layer thickness was about 59 nm. On the first constituent layer 104-1, a zinc-doped p-type BP layer having a thickness of about 38 nm was stacked as the second constituent layer 104-2. In the same manner, a total of 8 units of the lamination units composed of the first and second constituent layers 104-1 and 104-2 were repeated and laminated. From this, the bottom layer on the silicon substrate 101 side is GaN_0.97P_0.03As a layer, a multilayer laminated structure 104 having a period number of 8 with BP as the outermost layer was formed.
[0031]
The internal structure of the multilayer laminated structure 104 was observed using a normal cross-sectional TEM method. Crystal defects such as misfit dislocations were observed in the low temperature buffer layer 102. Since the dislocation propagating inside the multilayer structure 104 is small and the low-temperature buffer layer 102 mitigates the misfit with the silicon single crystal substrate 101, it was interpreted as containing defects. Due to the action of the low-temperature buffer layer 102, good crystals with a low crystal defect density were obtained in the constituent layers 104-1 and 104-2 of the multilayer laminated structure 104.
[0032]
On the surface of the multilayer laminated structure 104, a lower clad layer 105 is formed by (CH_Three)_ThreeGa / PH_Three/ NH_Three/ H₂Lamination was performed at 1000 ° C. by an atmospheric pressure MOCVD method using a reaction gas of the system. The lower cladding layer 105 is a zinc-doped p-type GaN lattice-matched to the BP layer that forms the outermost layer of the multilayer stacked structure 104._0.97P_0.03Composed of layers. The carrier concentration of the lower clad layer 105 is about 8 × 10.¹⁷cm^-3The layer thickness was 800 nm.
[0033]
On the lower cladding layer 105, a silicon-doped n-type gallium nitride indium (Ga_0.90In_0.10A light emitting layer 106 made of N) was laminated. The light-emitting layer 106 includes trimethylgallium ((CH_Three)_ThreeGa) / trimethylindium ((CH_Three)_ThreeIn) / phosphine (PH_Three) / Ammonia (NH_Three) / Hydrogen (H₂) It was grown at 890 ° C. by an atmospheric pressure MOCVD method using a reaction gas of the system. The average indium composition ratio of the light emitting layer 106 was 0.10. The layer thickness was about 30 nm. Carrier concentration is about 3 × 10¹⁸cm^-3It was.
[0034]
Ga_0.90In_0.10On the light emitting layer 106 made of N, a silicon-doped n-type aluminum nitride / gallium mixed crystal (Al_γGa_{1- γ}N) layers were laminated. The Al composition ratio (γ) was monotonously decreased from 0.2 to 0 (zero) in the increasing direction of the layer thickness to give a gradient to the aluminum composition. The layer thickness was 200 nm.
[0035]
P-type GaN above_0.97P_0.03Lower cladding layer 105, n-type Ga_0.90In_0.10N light emitting layer 106 and n-type Al_γGa_{1- γ}A light emitting portion 108 having a pn junction type double heterojunction structure was formed from three layers of the upper clad layer 107 made of an N layer.
[0036]
A p-type ohmic electrode 109 made of aluminum-antimony (Al—Sb) was formed on the back surface of the p-type silicon single crystal substrate 101. A circular n-type ohmic electrode 110 made of aluminum was formed on the surface of the upper cladding layer 107. The diameter of the n-type ohmic electrode 110 was about 130 μm. Thereafter, the silicon single crystal substrate 101 was cut in the [110] direction by using the cleavage property, and cut into chips having a side of about 300 μm to obtain the light emitting diode 10.
[0037]
An LED driving current was passed between the p-type and n-type ohmic electrodes 109 to 110. The current-voltage (IV) characteristics showed normal rectification characteristics due to the good pn junction characteristics of the light emitting unit 108. The forward voltage (Vf) obtained from the IV characteristics was about 3.0 V (forward current = 20 mA). The reverse voltage was about 15 V (reverse current = 10 μA). When an operating current of 20 mA was applied in the forward direction, blue light having an emission center wavelength of about 470 nm was emitted. The half width of the emission spectrum was about 18 nm. The light emission intensity in a chip state measured using a general integrating sphere was about 14 μW, and a group III nitride semiconductor light emitting device having a high light emission intensity was obtained.
[0038]
(Example 2)
Next, as a second embodiment of the present invention, only a low-temperature buffer layer is deposited on an n-type silicon substrate, and a multi-layer laminated structure serving as a Bragg reflection layer is deposited thereon to form a group III nitride semiconductor light emitting unit. An example is shown.
FIG. 4 shows a schematic sectional view of a light emitting diode according to a second embodiment of the present invention.
[0039]
On the (111) plane of the phosphorus-doped n-type silicon single crystal substrate 201, a low-temperature buffer layer 202 made of BP is formed by diborane (B₂H₆) / Phosphine (PH_Three) / Hydrogen (H₂) Lamination was performed at 430 ° C. by a low pressure MOCVD method using a reaction gas. V / III ratio, that is, supply ratio of group V source gas to group III source gas (= PH_Three / B₂H₆ ) Was set to about 120. The pressure of the reaction system during growth is about 3 × 10^Four Pa and disilane (Si₂H₆) -Hydrogen (H₂ ) A mixed gas was used. The layer thickness of the low temperature buffer layer 202 was about 17 nm.
[0040]
The internal structure of the low-temperature buffer layer 202 was observed by a cross-sectional TEM method. When the low-temperature buffer layer 202 was formed (as-grown state), the upper region from the bonding surface with the silicon single crystal substrate 201 to approximately 2 nm was mainly composed of BP single crystal. For this reason, no separation was observed between the low-temperature buffer layer 202 and the silicon single crystal substrate 201, and good adhesion was maintained. The upper part of the low-temperature buffer layer 202 is mainly composed of a BP amorphous material.
[0041]
On the low-temperature buffer layer 202, a silicon-doped n-type BP crystal layer was formed as the first layer 204-1 of the multilayer stacked structure 204 serving as a Bragg reflection layer. This BP crystal layer utilizes the above-described reduced pressure MOCVD method, and the pressure of the reaction system is about 3 × 10.^Four It was set at Pa and formed at 980 ° C. According to the analysis by X-ray diffraction, it was confirmed that this BP crystal layer was a BP crystal layer mainly composed of cubic crystals. The layer thickness is about 41 nm and the carrier concentration is about 1 × 10¹⁸cm^-3Met.
[0042]
After the film formation of the first layer 204-1 is completed, most of the amorphous body in the low-temperature buffer layer 202 is single crystal starting from the single crystal layer existing in the boundary region with the silicon single crystal substrate 201. It was recognized that In addition, since the low-temperature buffer layer 202 is provided on the surface of the silicon single crystal substrate 201, the BP crystal layer is a continuous film that does not peel off from the silicon single crystal substrate 201 and the first layer 204-1.
[0043]
On the first layer 204-1, a silicon-doped n-type gallium phosphide nitride (GaN) is formed as the second constituent layer 204-2._0.97P_0.03) Layers were laminated. 3% of the phosphorus composition ratio of the gallium nitride phosphide layer is lattice matched to BP. The second constituent layer 204-2 is disilane (Si) as a silicon dopant.₂H₆) -Hydrogen (H₂) About 3 × 10 using mixed gas^Four A film was formed at 980 ° C. under a pressure of Pa. Layer thickness is about 64 nm, carrier concentration is about 9 × 10¹⁷cm^-3Met.
[0044]
The multilayer unit composed of the first and second constituent layers 204-1 and 204-2 as described above was repeatedly laminated for 10 periods to constitute a multilayer laminated structure 204 serving as a Bragg reflective layer. In the multilayer structure 204, the lowermost layer on the silicon substrate 201 side is a BP layer, and the outermost layer is GaN._0.97P_0.03The total layer thickness was about 1050 nm.
[0045]
On the multilayer structure 204, a silicon-doped n-type GaN is formed as the lower cladding layer 205._0.97P_0.03A layer was formed. The lower cladding layer 205 is formed of (CH_Three)_ThreeGa / PH_Three / NH_Three/ H₂It laminated | stacked at 980 degreeC by the pressure reduction MOCVD method using a system reaction gas. Layer thickness is about 800 nm, carrier concentration is about 2 × 10¹⁸cm^-3Met. The carrier concentration was adjusted by controlling the amount of disilane added to the MOCVD reaction system.
[0046]
On the lower cladding layer 205, (CH_Three)_ThreeGa / PH_Three / NH_Three/ H₂The light emitting layer 206 was laminated at 980 ° C. by a low pressure MOCVD method using a system reaction gas as a raw material. The light emitting layer 206 is a silicon-doped n-type Ga._0.82In_0.18It consisted of N layers. The layer thickness is about 10 nm and the carrier concentration is about 2 × 10.¹⁸cm^-3It was. The carrier concentration was adjusted by controlling the amount of disilane added to the MOCVD reaction system.
[0047]
On the light emitting layer 206, zinc-doped p-type GaN._0.97P_0.03An upper clad layer 207 composed of layers was laminated. The upper cladding layer 207 is made of (CH_Three)_ThreeGa / PH_Three / NH_Three/ H₂Lamination was performed at 980 ° C. by a low pressure MOCVD method using a system reaction gas as a raw material. The upper cladding layer 207 has a thickness of about 100 nm and a carrier concentration of about 8 × 10.¹⁷cm^-3Met. The carrier concentration was adjusted by controlling the amount of disilane added to the MOCVD reaction system.
[0048]
N-type GaN above_0.97P_0.03Lower cladding layer 205, n-type Ga_0.82In_0.18N light emitting layer 206 and p-type GaN_0.97P_0.03The light-emitting portion 208 having a pn junction type double heterojunction structure is formed from the upper clad layer 207 made of layers.
[0049]
An n-type ohmic electrode 209 made of an aluminum (Al) alloy was formed on the back surface of the n-type silicon single crystal substrate 201. A circular p-type ohmic electrode 210 made of gold (Au) was formed on the surface of the upper cladding layer 207. The diameter of the p-type ohmic electrode 210 was about 110 μm. After that, the silicon single crystal substrate 201 was cut into a chip having a side of about 350 μm in the [110] direction by using the cleavage property, and the light emitting diode 20 was obtained.
[0050]
An LED driving current was passed between the p-type and n-type ohmic electrodes 209-210. The current-voltage (IV) characteristics showed normal rectification characteristics due to the good pn junction characteristics of the light emitting portion 208. The forward voltage (Vf) obtained from the IV characteristics was about 3.2 V (forward current = 20 mA). The reverse voltage was about 15 V (reverse current = 10 μA). When an operating current of 20 mA was applied in the forward direction, blue-green light having an emission center wavelength of about 510 nm was emitted. The half width of the emission spectrum was about 22 nm. The emission intensity in a chip state measured using a general integrating sphere was about 18 μW, and a group III nitride semiconductor light-emitting device having a high emission intensity was obtained.
[0051]
【The invention's effect】
According to the present invention, the reflective layer having the semiconductor multilayer structure in which the boron phosphide crystal layers and the gallium nitride phosphide crystal layers are alternately stacked is provided between the silicon single crystal substrate and the light emitting portion. Since the light emitted from the light emitting part can be reflected and extracted in the light extraction direction, a group III nitride semiconductor light emitting diode with high emission intensity can be provided.
[0052]
Further, according to the present invention, the carrier concentration of the boron phosphide crystal layer and the gallium nitride phosphide crystal layer constituting the multilayer laminated structure reflection layer is set to 1 × 10¹⁷cm^-3That's 5x10¹⁹cm^-3In the following cases, it is possible to form a thin layer with excellent conductivity, which is particularly excellent in crystallinity, and it is possible to pass the LED drive current in the vertical direction of the laminated structure. It can be used to provide a group III nitride semiconductor light emitting diode with high emission intensity.
[0053]
Furthermore, according to the present invention, when the phosphorus composition ratio of the gallium nitride phosphide crystal layer constituting the multilayer laminated structure reflective layer is 2% or more and 4% or less, the boron phosphide crystal layer constituting the reflective layer Since good lattice matching can be maintained, a reflective layer with few crystal defects and excellent crystallinity can be formed, and there is an effect that a group III nitride semiconductor light-emitting diode with much higher emission intensity can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing the dependence of reflectance on the number of lamination periods.
FIG. 2 is a diagram showing the wavelength dependence of the reflectance of a reflective layer.
3 is a schematic cross-sectional view of a light-emitting diode described in Example 1. FIG.
4 is a schematic cross-sectional view of a light-emitting diode described in Example 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10,20 ... Light emitting diode 101, 201 ... Silicon single crystal substrate, 102, 202 ... Low temperature buffer layer, 103 ... High temperature buffer layer, 104, 204 ... Multilayer laminated structure, 105, 205 ... Lower cladding layer, 106, 206 ... Light emitting layer, 107, 207 ... Upper cladding layer, 108, 208 ... Light emitting portion, 109, 209 ... P-type ohmic electrode, 110, 210 ... N-type ohmic electrodes,

Claims (7)

A general formula Al _a Ga _b In _1-ab N _c M _1-c stacked on a silicon single crystal substrate (where 0 ≦ a, b, a + b ≦ 1, M is a group V other than nitrogen) A group III nitride semiconductor light-emitting element including a light emitting portion of a pn junction type double heterojunction structure, which is composed of a group III nitride layer represented by 0 <c ≦ 1) A reflective layer having a multilayer structure in which a boron phosphide crystal layer and a gallium nitride phosphide crystal layer are alternately laminated between the silicon single crystal substrate and the light emitting portion; and the gallium nitride phosphide crystal layer III-nitride semiconductor light emitting diode you wherein the phosphorus composition ratio of is 4 atomic% or less 2 atomic% or more. The carrier concentration of the boron phosphide crystal layer and the gallium nitride phosphide crystal layer constituting the multilayer stacked structure is 1 × 10 ¹⁷ atom cm ⁻³ or more and 5 × 10 ¹⁹ atom cm ⁻³ or less. Item 3. A group III nitride semiconductor light-emitting diode according to item 1. 3. The group III nitride semiconductor light-emitting diode according to claim 1, wherein the number of cycles of the multilayer stacked structure is 2 or more. 4. The group III nitride semiconductor light-emitting diode according to claim 3 , wherein the number of cycles of the multilayer stacked structure is 7 or more. The group III nitride semiconductor light-emitting diode according to any one of claims 1 to 4 , wherein the surface of the silicon single crystal substrate is a {111} crystal plane. The group III nitride semiconductor light-emitting diode according to any one of claims 1 to 5 , wherein a buffer layer is interposed between the silicon single crystal substrate and the multilayer stacked structure. The method of manufacturing a group III nitride semiconductor light emitting diode according to any one of claims 1 to 6, characterized in that to form the multi-layer laminate structure in metal organic chemical vapor deposition.

Images