JP2003115606A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize reduction in cost of a semiconductor light emitting element which assures lower power consumption and operation voltage. SOLUTION: A buffer layer 12 of the composite layer structure, in which a plurality of layers of a first layer 12a formed of Alx Ga1-x N including Si as the n-type impurity and a second layer 12b formed of a GaN or Aly Ga1-y N including Si as the n-type impurity are alternately formed, is provided on a substrate 11 formed of silicon of low resistance. On the buffer layer 12, an n-type semiconductor region 13 formed of gallium nitride, an active layer 14 formed of indium gallium nitride, and a p-type semiconductor region 15 formed of gallium nitride are sequentially formed. An anode electrode 17 is provided on the p-type semiconductor region 15, and a cathode electrode 18 is provided on the substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device using a gallium nitride compound semiconductor.

[0002]

2. Description of the Related Art GaN (Gallium Nitride), GaAlN
Semiconductor light emitting devices such as blue light emitting diodes using gallium nitride-based compound semiconductors such as (gallium aluminum nitride), InGaN (indium gallium nitride), and InGaAlN (indium gallium aluminum nitride) are known. A typical conventional light emitting device is an insulating substrate made of sapphire, and is formed on one main surface (upper surface) of this insulating substrate, for example, Japanese Patent Laid-Open No. 4-29.
Ga _x Al _1-x N (provided that x
Is a numerical value in the range of 0 <x ≦ 1. ), A gallium nitride-based compound semiconductor (for example, Ga) formed on the buffer layer by epitaxial growth.
N), an n-type semiconductor region, an active layer made of a gallium nitride-based compound semiconductor (for example, InGaN) formed on the n-type semiconductor region by an epitaxial growth method, and an epitaxial layer formed on the active layer. It has a p-type semiconductor region. The cathode electrode is connected to the n-type semiconductor region, and the anode electrode is connected to the p-type semiconductor region.

[0003]

By the way, as is well known, a light emitting device is manufactured by cutting a wafer in which a large number of devices are formed by dicing, scribing, cleavage or the like. At this time, since the insulating substrate made of sapphire has high hardness, it was difficult to perform this dicing favorably and with good productivity. Further, since sapphire is expensive, the cost of the light emitting device is high. Further, since the substrate made of sapphire is an insulator, the cathode electrode cannot be formed on the substrate. For this reason, it is necessary to expose a part of the n-type semiconductor region and connect the cathode electrode thereto, and the area of the semiconductor substrate, that is, the chip area, becomes relatively large, and the cost of the light emitting element becomes high accordingly. became. Further, in the conventional light emitting device using the sapphire substrate, current flows not only in the vertical direction of the n-type semiconductor region but also in the horizontal direction, that is, the direction along the main surface of the sapphire substrate. Since the thickness of the portion of the n-type semiconductor region in which the horizontal current flows is as thin as about 4 to 5 μm, the resistance of the horizontal current path of the n-type semiconductor region becomes considerably large, and the power consumption and the operating voltage increase. Invited. Further, it is necessary to remove the active layer and the p-type semiconductor region by etching in order to expose the connection portion of the cathode electrode of the n-type semiconductor region. It had to be formed to be a little thick. Therefore, the time required for the epitaxial growth of the n-type semiconductor region is long and the productivity is low. Further, a light emitting device using a conductive substrate made of silicon carbide (SiC) instead of the sapphire substrate is known. In this light emitting device, the cathode electrode can be formed on the lower surface of the conductive substrate. Therefore, as compared with the light emitting device using the sapphire substrate, the light emitting device using the SiC substrate has advantages that the chip area can be reduced and the wafer can be easily separated by cleavage. However, since SiC is much more expensive than sapphire, it is difficult to reduce the cost of the light emitting element. Further, it is difficult to bring the n-type semiconductor region into low resistance contact on the SiC substrate, and the power consumption and operating voltage of this light emitting device are relatively high as in the light emitting device using the sapphire substrate.

Therefore, an object of the present invention is to provide a semiconductor light emitting device capable of improving productivity and performance and reducing cost.

[0005]

The present invention for solving the above problems and achieving the above objects is a semiconductor light emitting device having a gallium nitride-based compound semiconductor, which comprises silicon or a silicon compound containing impurities. It is composed of a substrate having a low resistivity and Al _x Ga _1-x N (where x is a numerical value satisfying 0 <x ≦ 1) arranged on one main surface of the substrate. A first layer containing silicon as an impurity and GaN or Al _y Ga _1-y N (where y is y <x
And 0 <y <1. ) Consisting of a second
On a surface of the semiconductor region, and a semiconductor region including a plurality of gallium nitride-based compound layers disposed on the buffer layer to obtain a light emitting function. The present invention relates to a semiconductor light emitting device including a first electrode arranged on the first main surface and a second electrode arranged on the other main surface of the substrate. Each of the plurality of gallium nitride-based compound semiconductor layers in the semiconductor region may be, for example, a GaN (gallium nitride) layer or GaAlN.
It is a (gallium aluminum nitride) layer, an InGaN (indium gallium nitride) layer, or an InGaAlN (indium gallium aluminum nitride) layer. The chemical formulas of materials of the second layer Al _y Ga _1-y N (where, y
Is a numerical value satisfying y <x and 0 ≦ y <1. ).

It is preferable that the second layer contains silicon as an n-type impurity.
Further, as described in claim 3, the semiconductor region includes a first semiconductor region of a first conductivity type formed of a gallium nitride-based compound, which is disposed on the buffer layer, and the semiconductor region on the first semiconductor region. And a second semiconductor region made of a gallium nitride-based compound disposed on the active layer and having a second conductivity type opposite to the first conductivity type. It is desirable to have it. The semiconductor region may include an active layer made of GaInN arranged on the buffer layer, a gallium nitride-based compound in contact with the active layer, and a p-type impurity. And a second semiconductor region which is exposed. Further, as set forth in claim 5, the buffer layer comprises:
It is preferable that the plurality of first layers and the plurality of second layers are provided, and the first layers and the second layers are alternately stacked.

[0007]

The invention of each claim has the following effects. (1) Substrate is relatively inexpensive silicon or silicon compound
Since it is a product, it can reduce the cost of the light emitting element.
Wear. (2) Al_x Ga_1-x A first layer of N and GaN or
Is Al_yGa_1-yConsisting of a composite layer with a second layer consisting of N
The buffer layer is a gallium nitride-based compound formed on this
Contributes to the improvement of crystallinity and flatness. Therefore, it is cheap
Despite the use of a substrate, it has good emission characteristics,
A light emitting element having light efficiency can be provided. (3) The buffer layer is Al_x Ga_1-x First consisting of N
Layer and GaN or Al_yGa_1-yDouble layer with N
Since it is a laminated layer, the thermal expansion coefficient of this buffer layer is
And the thermal expansion coefficient of the substrate made of this compound and GaN
A value intermediate between the thermal expansion coefficient of the semiconductor region composed of compounds
Due to the difference in coefficient of thermal expansion between the substrate and the semiconductor region
Generation of distortion can be suppressed. (4) The first and second electrodes are arranged so as to face each other.
And silicon as an impurity in the first layer.
Power consumption by reducing the resistance value of the current path
Also, the operating voltage can be reduced. Also, the claims
According to the second aspect of the invention, the resistance value of the second layer is lowered to reduce the power consumption.
Also, the operating voltage can be reduced. Also, the claims
According to the third aspect of the invention, it is possible to provide an element having good light emission characteristics.
According to the invention of claim 4, G is formed on the upper surface of the buffer layer.
It has a structure in which an active layer made of aInN is directly formed.
Then, the active layer is formed by interposing a thick AlGaN cladding layer.
The tensile stress applied to the active layer is
Will be alleviated. Therefore, the crystallinity of the active layer becomes good,
The light emitting characteristics of the light emitting element can be further improved. Also bill
According to the invention of Item 5, the difference in lattice constant from silicon is compared.
Small Al_x Ga_1-x The first layer of N is on the substrate
Disposed and this is GaN or Al _yGa_1-yConsists of N
Since it is also placed between the second layers, the flatness of the buffer layer
The flatness is improved and the crystallinity of the semiconductor region is also improved.

[0008]

First Embodiment Next, a gallium nitride-based compound blue light emitting diode as a semiconductor light emitting device according to the first embodiment will be described with reference to FIGS. 1 and 2.

The blue light emitting diode according to the embodiment of the present invention shown in FIGS. 1 and 2 has a semiconductor region 10 composed of a plurality of gallium nitride-based compound layers for obtaining a light emitting function and a crystal plane orientation of a main surface (111). ), A substrate 11 made of a silicon semiconductor, and a buffer layer 12. The semiconductor region 10 having a light emitting function is made of GaN.
N as a first semiconductor region made of (gallium nitride)
-Shaped semiconductor region 13, light emitting layer or active layer 14 made of p-type InGaN (indium gallium nitride), and second
And a p-type semiconductor region 15 made of GaN (gallium nitride) as the semiconductor region. An anode electrode 17 serving as a first electrode is provided on one main surface (upper surface) of a base 16 formed of a laminated body of a substrate 11, a buffer layer 12, and a semiconductor region 10 having a light emitting function, that is, a surface of a p-type semiconductor region 15. The cathode electrode 1 serving as the second electrode is disposed on the other main surface (lower surface) of the base body 16, that is, the other main surface of the substrate 11.
8 are arranged. The buffer layer 12, the n-type semiconductor region 13, the active layer 14, and the p-type semiconductor region 15 are the substrate 1
1 was epitaxially grown on the No. 1 in order with the respective crystal orientations aligned.

The substrate 11 is made of silicon single crystal containing conductivity determining impurities. The impurity concentration of the substrate 11 is 5
× 10 ¹⁸ a cm ^-3 ~5 × 10 ¹⁹ cm ^-3 or so, the resistivity of the substrate 11 is 0.0001Ω · cm~0.01Ω ·
It is about cm. The substrate 11 of this embodiment is As (arsenic).
Of n-type silicon introduced therein. The substrate 11 having a relatively low resistivity functions as a current path between the anode electrode 17 and the cathode electrode 18. The substrate 11 has a relatively large thickness of about 350 μm, and the p-type semiconductor region 1
5, the active layer 14 and the n-type semiconductor region 13 function as a support for the semiconductor region 10 having a light emitting function and the buffer layer 12.

The buffer layer 12 arranged so as to cover the entire one main surface of the substrate 11 includes a plurality of first layers 12a.
And a plurality of second layers 12b are alternately laminated. 1 and 2, for convenience of illustration, the buffer layer 12 is shown as two first layers 12a and two second layers 12b.
1st layer 12a and 10 2nd layers 12b. The first layer 12a contains Si (silicon) as an n-type conductivity determining impurity and has the chemical formula Al _x Ga _1-x N, where x is an arbitrary value satisfying 0 <x ≦ 1. It is made of a material that can That is, the first layer 12a is made of AlN (aluminum nitride) or AlGaN.
(Aluminum gallium nitride). In the embodiment of FIGS. 1 and 2, AlN (aluminum nitride) corresponding to the material in which x in the above formula is set to 1 is the first layer 12a.
Is used for. Although AlN of the first layer 12a has an insulating property, in the embodiment, since Si (silicon) as an n-type conductivity determining impurity is contained, the electric resistance is relatively small. Material the second layer 12b are GaN (gallium nitride), or where the formula _{Al y Ga 1-y N,} y can that can be represented by y <x and 0 <y <Any numerical value satisfying 1, Is an extremely thin film of n-type semiconductor. When an n-type semiconductor made of Al _y Ga _1-y N is used as the second layer 12b, y is set to 0 <y <0.8 in order to suppress an increase in electric resistance of the second layer 12b. It is desirable to set it to a satisfactory value, that is, larger than 0 and smaller than 0.8. In this embodiment, the second layer 12b is made of GaN so that the electric resistance becomes small. The thickness of the first layer 12a of the buffer layer 12 is preferably 0.5 nm to 10 nm, that is, 5 to 100 angstroms.
The thickness is more preferably 1 nm to 8 nm. First layer 1
If the thickness of 2a is less than 0.5 nm, the buffer layer 12
The flatness of the semiconductor region 10 formed on the upper surface of the substrate cannot be kept good. When the thickness of the first layer 12a exceeds 10 nm, the quantum mechanical tunnel effect cannot be obtained well, and the electrical resistance of the buffer layer 12 increases. Second
The thickness of the layer 12b is preferably 0.5 nm to 300 n.
m, that is, 5 to 3000 angstroms, and more preferably 10 nm to 300 nm. When the thickness of the second layer 12b is less than 0.5 nm, that is, less than 5 angstroms, the one first layer 1 formed on the second layer 12b.
The electrical connection between 1a and the other first layer 11a formed under the second layer 12b is not achieved well, and the electrical resistance of the buffer layer 12 increases. When the thickness of the second layer 12b exceeds 300 nm, that is, 3000 angstroms, the flatness of the n-type semiconductor region 13 cannot be maintained well. If the thickness of the second layer is 10 nm or more,
The resistance and voltage between the first and second electrodes during the operation of the light emitting element are relatively small. That is, if the thickness of the second layer is less than 10 nm, discrete energy levels are generated in the valence band and the conduction band of the second layer, which contributes to the conduction of carriers in the second layer. The energy level that appears is increased apparently. As a result, the energy band discontinuity between the substrate and the second layer becomes relatively large, and the resistance and voltage between the first and second electrodes during the operation of the light emitting element become relatively large. On the other hand, when the thickness of the second layer is 10 nm or more, generation of discrete energy levels in the valence band and the conduction band of the second layer is suppressed, and the conduction of carriers in the second layer is suppressed. The increase in energy levels involved is suppressed. As a result, deterioration of the energy band discontinuity between the substrate and the second layer is suppressed, and the resistance and voltage between the first and second electrodes during operation of the light emitting element are reduced. In the embodiment of FIGS. 1 and 2, the first layer 12a has a thickness of 5 nm or 50 angstroms and the second layer 12b has a thickness of 30 nm or 300 angstroms. Thickness is 350nm, ie 3
It is 500 angstroms.

Next, the first layer 12a is AIN and the second layer is
A method for manufacturing a semiconductor light emitting device in which GaN is used will be described.
It The buffer layer 12 of one embodiment shown in FIGS. 1 and 2.
Is a well-known MOCVD (Metal Organic Chemical Vapor
por Deposition) that is, by metalorganic chemical vapor deposition
The first layer 12a made of AlN and the second layer made of GaN.
Formed by repeatedly stacking layers 12b of
It That is, the silicon single crystal substrate 11 is used for the MOCVD apparatus.
Place it in the reaction chamber and first perform thermal annealing.
Then, the oxide film on the surface is removed. Next, in the reaction chamber, TMA
(Trimethylaluminum) gas and NH ₃ (Ammoni
A) Gas and SiH_Four Supply (silane) gas for about 24 seconds
The thickness of about 5 nm, that is, about 50 nm, on one main surface of the substrate 11.
Form a first layer 12a of a Ngstrom AlN layer
To achieve. In this embodiment, the heating temperature of the substrate 11 is 1120 ° C.
After that, the flow rate of TMA gas, that is, the supply amount of Al is about 6
3 μmol / min, NH₃Gas flow rate, NH₃ Companion
Supply amount about 0.14 mol / min, SiH_Four Gas flow rate
That is, the supply amount of Si was set to about 21 nmol / min. This
Here, SiH_FourThe gas is an n-type impurity in the first layer 12a.
For introducing Si as Then, the group
Supplying TMA gas with heating temperature of plate 11 at 1120 ° C
After stopping, TMG (trimethylgallium) in the reaction chamber
Gas and NH₃ (Ammonia) gas and SiH_Four (Silane)
The gas is supplied for about 85 seconds to form a gas on one main surface of the substrate 11.
Formed on the upper surface of the first layer 12a made of AlN,
N-type G with a thickness of about 30 nm or 300 Å
A second layer 12b made of aN is formed. In this example
Is about 63 μmo of the flow rate of TMG gas, that is, the supply amount of Ga.
l / min, NH₃ Gas flow rate, NH₃ Supply of about
0.14 mol / min, SiH_Four Gas flow rate, ie Si
Was supplied at about 21 nmol / min. Where S
iH_FourThe gas is used as an n-type impurity in the second layer 12b.
It is for introducing Si. In this embodiment, the above
A first layer 12a of AlN and a second layer of GaN
The formation of the layer 12b of AlN is repeated 10 times,
1 layer 12a and second layer 12b made of GaN alternate
Then, the buffer layer 12 having 20 layers is formed. Of course A
The first layer 12a made of 1N and the second layer made of GaN
12b can be changed to any number such as 50 layers
Wear.

Next, a well-known MO is formed on the upper surface of the buffer layer 12.
The n-type semiconductor region 13, the active layer 14, and the p-type semiconductor region 15 are sequentially formed by the CVD method. That is, the substrate 11 having the buffer layer 12 formed on the upper surface is MOCVD
The buffer layer 12 is placed in the reaction chamber of the apparatus, and trimethylgallium gas, that is, TMG gas, NH ₃ (ammonia) gas, and SiH ₄ (silane) gas are first supplied into the reaction chamber.
An n-type semiconductor region 13 is formed on the upper surface of the. Here, the silane gas is used as S as an n-type impurity in the n-type semiconductor region 13.
It is for introducing i. In this embodiment, after heating the substrate 11 on which the buffer layer 12 is formed to 1040 ° C., the flow rate of TMG gas, that is, the supply amount of Ga is about 4.3.
μmol / min, the flow rate of NH ₃ gas, that is, the supply amount of NH ₃ is about 53.6 mmol / min, the flow rate of silane gas, that is, S
The amount of i supplied was about 1.5 nmol / min. Further, in this embodiment, the thickness of the n-type semiconductor region 13 is set to about 0.2 μm.
And In the case of the conventional general light emitting diode, since the thickness of the n-type semiconductor region is about 4.0 to 5.0 μm,
In comparison with this, the n-type semiconductor region 13 of this embodiment in FIG. 1 is formed to be considerably thin. In addition, the n-type semiconductor region 13
Has an impurity concentration of about 3 × 10 ¹⁸ cm ⁻³ , which is sufficiently lower than the impurity concentration of the substrate 11. According to the present embodiment, since the buffer layer 12 is interposed, the n-type semiconductor layer 13 can be formed at a relatively high temperature such as 1040 ° C.

Then, the heating temperature of the substrate 11 is set to 800 ° C., TMG gas and ammonia gas are added to the reaction chamber, and trimethylindium gas (hereinafter, referred to as TMI gas) and biscyclopentaenyl magnesium gas (hereinafter, referred to as C).
It is called p ₂ Mg gas. ) Is supplied to the n-type semiconductor region 13
P-type InGaN (Indium gallium nitride) on top of
The active layer 14 of is formed. Here, Cp ₂ Mg gas is used as Mg as an impurity of p-type conductivity in the active layer 14.
It is for introducing (magnesium). In this embodiment, the TMG gas flow rate is about 1.1 μmol / min,
The NH ₃ gas flow rate is about 67 mmol / min, the TMI gas flow rate, that is, the In supply rate is about 4.5 μmol / min, G
The flow rate of p2 Mg gas, that is, the supply amount of Mg is about 12 nmol /
It was set to min. The thickness of the active layer 14 is about 2 nm, that is, 20 Å. The impurity concentration of the active layer 14 is about 3 × 10 ¹⁷ cm ⁻³ .

Subsequently, the heating temperature of the substrate 11 is set to 1040 ° C.
And TMG gas, ammonia gas and Cp in the reaction chamber.
₂ Mg gas is supplied to p-type GaN on the upper surface of the active layer 14.
A p-type semiconductor region 15 made of (gallium nitride) is formed. In this embodiment, the flow rate of TMG gas at this time is about 4.
3 μmol / min, flow rate of ammonia gas is about 53.6
μmol / min, Cp ₂ Mg gas flow rate about 0.12μ
It was set to mol / min. The thickness of the p-type semiconductor region 15 is about 0.2 μm. The impurity concentration of the p-type semiconductor region 15 is about 3 × 10 ¹⁸ cm ⁻³ .

According to the MOCVD growth method described above, it is possible to form the buffer layer 12 in which the crystal orientation of the substrate 11 made of silicon single crystal is favorably inherited. Moreover, the crystal orientations of the n-type semiconductor region 13, the active layer 14, and the p-type semiconductor region 15 can be aligned with the crystal orientation of the buffer layer 12.

The anode electrode 17 as the first electrode is
For example, nickel and gold are formed by adhering to the upper surface of the semiconductor substrate 16, that is, the upper surface of the p-type semiconductor region 15 by a well-known vacuum deposition method or the like, and brought into low resistance contact with the surface of the p-type semiconductor region 15. The anode electrode 17 has a circular plane shape as shown in FIG.
Is located almost in the center of the upper surface of. A region 19 of the upper surface of the semiconductor substrate 16 where the anode electrode 17 is not formed functions as a light extraction region.

The cathode electrode 18 as the second electrode is
For example, titanium and aluminum are formed on the entire lower surface of the substrate 11 by the well-known vacuum deposition method or the like, without being formed in the n-type semiconductor region 13.

When the blue light emitting diode shown in FIG. 1 is attached to an external device, for example, the cathode electrode 18 is fixed to an external electrode such as a circuit board with solder or a conductive adhesive, and the anode electrode 17 is formed by a well-known wire bonding method. A wire is electrically connected to the external electrode.

According to the blue light emitting diode of this embodiment,
The following effects are obtained. (1) Since the substrate 11 made of silicon, which is significantly lower in cost than sapphire and has good workability, can be used, the material cost and the production cost can be reduced. Therefore, the cost of the GaN-based light emitting diode can be reduced. (2) First layer 1 formed on one main surface of the substrate 11
The buffer layer 12 made of a composite layer of 2a and the second layer 12b contributes to improvement of crystallinity and flatness of the semiconductor region 10. That is, the buffer layer 12 can favorably take over the crystal orientation of the substrate 11 made of silicon. As a result, on the main surface of the buffer layer 12, the n-type semiconductor region 13,
The GaN-based semiconductor region 10 including the active layer 14 and the p-type semiconductor region 15 can be favorably formed with the crystal orientations aligned. Therefore, the characteristics of the GaN-based semiconductor region 10 are improved and the emission characteristics are also improved. (3) When the semiconductor region 10 is formed via the buffer layer 12 formed by stacking a plurality of first layers 12a and second layers 12b, the semiconductor region 10 has improved flatness. That is, if a buffer layer composed of only a GaN semiconductor layer is formed on one main surface of the substrate 11 made of silicon, the difference in lattice constant between silicon and GaN is large,
A GaN-based semiconductor region having excellent flatness cannot be formed on the upper surface of this buffer layer. Further, if the buffer layer 12 is formed relatively thick only with the first layer 12a,
The resistance of the buffer layer increases. Further, if the buffer layer 12 is formed relatively thin with only the first layer 12a,
Not enough buffer function can be obtained. On the other hand, in the present embodiment, between the substrate 11 and the GaN-based semiconductor region 10, the first layer 12a made of AlN and the second layer 12b made of GaN have a relatively small lattice constant difference from silicon. Since the buffer layer 12 composed of the composite layer is interposed, GaN
The flatness of the system semiconductor region 10 is improved. As a result, Ga
The light emission characteristics of the N-based semiconductor region 10 are improved. (4) Since the anode electrode 17 and the cathode electrode 18 are arranged opposite to each other and the first layer 12a is doped with silicon, the anode electrode 17 and the cathode electrode 18 are
The resistance value and voltage between and can be lowered, and the power consumption of the light emitting diode can be reduced. (5) Since each of the plurality of first layers 12a included in the buffer layer 12 is set to have a thickness that causes a quantum mechanical tunnel effect, an increase in the resistance of the buffer layer 12 can be suppressed. . (6) It is possible to suppress the occurrence of strain due to the difference in thermal expansion coefficient between the substrate 11 and the GaN-based semiconductor region 10. That is, since the coefficient of thermal expansion of silicon and the coefficient of thermal expansion of GaN are significantly different, if the both are directly laminated, distortion due to the difference in coefficient of thermal expansion is likely to occur. However, the first layer 1 of this embodiment
Buffer layer 1 comprising a composite layer of 2a and second layer 12b
The coefficient of thermal expansion of 2 has an intermediate value between the coefficient of thermal expansion of the substrate 11 and the coefficient of thermal expansion of the GaN-based semiconductor region 10. Therefore, the buffer layer 12 can suppress the occurrence of strain due to the difference in thermal expansion coefficient between the substrate 11 and the GaN semiconductor region 10. (7) Since the second layer 12b has a relatively large thickness of 30 nm, the energy band of the substrate 11 and the second layer 12 are
The discontinuity with the energy band of b is improved, and the resistance value and voltage between the anode electrode 19 and the cathode electrode 18 during operation are reduced. (8) The cathode electrode 18 can be formed more easily than the conventional light emitting device using the sapphire substrate. That is, in the case of a light emitting device using a conventional sapphire substrate, parts of those corresponding to the p-type semiconductor region 15 and the active layer 14 of FIGS. 1 and 2 are removed to expose a part of the n-type semiconductor region 13. Then, it becomes necessary to connect the cathode electrode to the exposed n-type semiconductor region 13. Therefore, the conventional light emitting device has a drawback that the cathode electrode is difficult to form, and that the area of the n-type semiconductor region is large because the cathode electrode is formed. The light emitting device of FIGS. 1 and 2 does not have the above drawbacks. (9) Since the crystal orientation of the main surface 11a of the silicon substrate 11 is the (111) just plane, the number of steps in the semiconductor region 10 is reduced and the luminous efficiency is increased.

[0021]

Second Embodiment Next, a semiconductor device according to a second embodiment will be described with reference to FIG. However, in FIG. 3, parts that are substantially the same as those in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted.

In the semiconductor device shown in FIG. 3, a transistor 20 as another semiconductor element is provided on the silicon substrate 11 of the light emitting diode shown in FIG. Transistor 2
0 consists of a collector region C, a base region B and an emitter region E formed in a P-type semiconductor region 21 for element isolation. In this way, by combining the light emitting diode and the transistor, it is possible to reduce the size and cost of the circuit device including them.

[0023]

[Modification] The present invention is not limited to the above-described embodiment, and the following modifications are possible. (1) The substrate 11 can be made of polycrystalline silicon other than single crystal silicon or a silicon compound such as SiC. (2) The conductivity type of each layer of the semiconductor substrate 16 can be reversed from that of the embodiment. (3) Each of the n-type semiconductor region 13, the active layer 14, and the p-type semiconductor region 15 can be formed by combining a plurality of semiconductor regions. The active layer 1 made of GaInN is formed on the buffer layer 12 by omitting the n-type semiconductor region 13.
4 can be contacted directly. As a result, the tensile stress applied to the active layer 14 is relaxed as compared with the case where the active layer 14 is formed with a thick AlGaN cladding layer interposed. Therefore, the crystallinity of the active layer 14 is improved, and the light emitting characteristics of the light emitting element are further improved. (4) A P ^{+ type} semiconductor region for ohmic contact can be provided under the anode electrode 17. (5) The anode electrode 17 can be a transparent electrode. (6) The number of the second layers 12b of the buffer layer 12 is increased by one more than that of the first layers 12a so that the substrate 11 and the first layers 12a are formed.
A second layer 12b can be placed between and. (7) The first layer 12a and the second layer 12b may contain impurities as long as they do not hinder these functions.

[Brief description of drawings]

FIG. 1 is a central longitudinal sectional view showing a light emitting diode according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the light emitting diode of FIG.

FIG. 3 is a sectional view showing a semiconductor device according to a second embodiment of the present invention.

[Explanation of symbols]

10 GaN-based semiconductor region 11 Substrate made of silicon single crystal 12 buffer layers 12a first layer 12b second layer 13 n-type semiconductor region 14 Active layer 15 p-type semiconductor region 16 base 18 Anode electrode 19 Cathode electrode

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuji Mochi             Sanke, 3-6 Kitano, Niiza City, Saitama Prefecture             N Denki Co., Ltd. (72) Inventor Takashi Egawa             Gokisho-cho (Showa-ku, Nagoya, Aichi Prefecture)             Shi) Inside Nagoya Institute of Technology (72) Inventor Hiroyasu Ishikawa             Gokisho-cho (Showa-ku, Nagoya, Aichi Prefecture)             Shi) Inside Nagoya Institute of Technology (72) Inventor Takashi Jimbo             Gokisho-cho (Showa-ku, Nagoya, Aichi Prefecture)             Shi) Inside Nagoya Institute of Technology F-term (reference) 5F041 AA24 CA40 CA46 CA57 CA65

Claims (5)

[Claims] 1. A semiconductor light-emitting device having a gallium nitride-based compound semiconductor, comprising a substrate made of silicon or a silicon compound containing impurities and having a low resistivity, and a substrate on one main surface of the substrate. Placed, Al _x Ga _1-x N
(Where x is a numerical value satisfying 0 <x ≦ 1) and GaN and the first layer containing silicon as an impurity.
Or Al _y Ga _1-y N (where y is y <x and 0 <y <1
Is a numerical value that satisfies. A buffer layer consisting of a composite layer with a second layer consisting of a), a semiconductor region containing a plurality of gallium nitride-based compound layers arranged on the buffer layer to obtain a light emitting function, A semiconductor light emitting device comprising: a first electrode arranged on a surface of a semiconductor region; and a second electrode arranged on the other main surface of the substrate. 2. The semiconductor light emitting device according to claim 1, wherein the second layer contains silicon as an n-type impurity. 3. The semiconductor region includes a first semiconductor region of a first conductivity type formed of a gallium nitride-based compound, which is disposed on the buffer layer, and an active region disposed on the first semiconductor region. A layer, and a second semiconductor region comprising a gallium nitride-based compound disposed on the active layer and having a second conductivity type opposite to the first conductivity type. The semiconductor light emitting device according to claim 1 or 2, which is characterized. 4. The semiconductor region comprises an active layer of GaInN in contact with the buffer layer, a gallium nitride based compound disposed on the active layer, and contains p-type impurities. The semiconductor light emitting device according to claim 1, further comprising a second semiconductor region. 5. The buffer layer comprises a plurality of first layers made of Al _x Ga _1-x N and containing silicon as an impurity, and a plurality of second layers made of a GaN layer or Al _y Ga _1-y N. Layer, and the first layer and the second layer) are alternately laminated.
Further, 4 is the semiconductor light emitting device described.