JPH0964419A - Iii-v compound semiconductor and light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a III-V compound semiconductor having high luminance and light emitting performance and a light emitting element of a visible or ultraviolet region using the same. SOLUTION: A semiconductor element of a laminated structure that a light emitting layer 5 is sandwiched between two layers 4 and 6 having larger band gaps than that of the layer 5 and further the outside is sandwiched between an n-type layer 3 and a P-type layer 7 of III-V compound semiconductor represented by the general formula Inx Gay Alz N (where x+y+z=1, 0<=x<=1, 0<=y<=1, 0.002<=z<=0.10). This is laminated on a substrate 1 via a buffer layer 2 to form a light emitting element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Group 3-5 compound semiconductor and a light emitting device using the same in the visible or ultraviolet region.

[0002]

2. Description of the Related Art Conventionally, a blue light emitting diode (hereinafter referred to as L
Sometimes referred to as ED. ) As a general formula In _x Ga _y A
l _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y
What uses the 3-5 group compound semiconductor represented by <1 and 0 <z <1) is utilized. Since the compound semiconductor is a direct transition type, it has a high luminous efficiency, and can emit light in a wavelength range from yellow to violet and ultraviolet depending on the InN mixed crystal ratio (value of x). Is useful as

As a method of increasing the luminous efficiency of a light emitting element,
A so-called double hetero structure in which a light emitting layer is disposed between a p-type semiconductor layer and an n-type semiconductor layer and two layers having an energy gap larger than that of the light emitting layer are in contact with each other on both sides of the light emitting layer can be used. Widely known. The performance of the double heterostructure device is greatly affected by the electrical characteristics and crystal quality of the p-type and n-type layers. In particular, since the p-type compound semiconductor has a low activation rate of the p-type dopant, in order to obtain a high p-type carrier concentration of 10 ¹⁸ cm ⁻³ or more which is practically required for a light emitting device, 10 ¹⁹ cm ⁻³ is required. The p-type dopant must be doped to a high concentration, to a degree or higher. However, such high-concentration doping may cause deterioration of crystal quality. Also,
Group 2 elements such as Mg and Zn, which are p-type dopants generally used for the compound semiconductor, have a strong tendency to diffuse in the crystal, and the raw materials of these dopants have high reactivity with the growth device, so that they are bonded. It was difficult to form a steep doping profile at the interface. Due to these causes, there is a problem that it is difficult to manufacture a light emitting device having high luminous efficiency using the compound semiconductor.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a Group 3-5 compound semiconductor capable of enhancing the brightness and luminous efficiency of a light emitting device and a light emitting device using the same in the visible or ultraviolet region. It is in.

[0005]

In view of these problems, the present inventors have made various investigations on a light emitting device using a Group 3-5 compound semiconductor, and as a result, p-type 3-5 having a specific AlN mixed crystal ratio.
It has been found that the use of the group compound semiconductor layer improves the brightness and the luminous efficiency, and has reached the present invention.

That is, the present invention relates to [1] a p-type layer and n.
3-5 group for a light-emitting device including a layered structure having a layer of a type, a light-emitting layer being disposed between both layers, and two layers having a bandgap larger than that of the light-emitting layer being in contact with both sides of the light-emitting layer In a compound semiconductor, the p-type layer has the general formula In _x Ga
_y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0
≦ y ≦ 1, 0.0001 ≦ z ≦ 0.10) 3
The present invention relates to a 3-5 group compound semiconductor for a light emitting device, which is a -5 group compound semiconductor and is doped with a p-type dopant. Further, in the present invention, the [2] p-type layer is composed of a plurality of layers, and the layer closest to the n-type layer among the plurality of layers is represented by the general formula In _x Ga _y Al _z N (however,
x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0.000
The present invention relates to the 3-5 group compound semiconductor for a light emitting device according to [1], which is a 3-5 group compound semiconductor represented by 1 ≦ z ≦ 0.10). Furthermore, the present invention provides [3]
The present invention relates to a light emitting device using the 3-5 group compound semiconductor for a light emitting device according to the above [1] or [2]. Hereinafter, the present invention will be described in detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a method for producing a Group 3-5 compound semiconductor, a molecular beam epitaxy (hereinafter sometimes referred to as MBE) method, a metal organic chemical vapor deposition (hereinafter MOVPE) method.
It may be written. ) Method, hydride vapor phase epitaxy (hereinafter sometimes referred to as HVPE) method, and the like. Among them, the MOVPE method is a method of heating a substrate placed under normal pressure or reduced pressure, supplying an organometallic compound containing a Group 3 element and a raw material containing a Group 5 element in a vapor phase state, and heating the substrate. This is a method of causing a decomposition reaction to grow a compound semiconductor film. The MOVPE method is useful in that it can grow the uniform and high-quality Group 3-5 compound semiconductor over a large area.

3 for light emitting device of the present invention by MOVPE method
-The following raw materials are used to manufacture Group 5 compound semiconductors:
Can be. As a Group 3 raw material
Umm [(CH_Three)_ThreeGa, sometimes referred to as TMG
You. ], Triethylgallium [(C₂H_Five)_ThreeGa, less
Sometimes referred to as a lower TEG. General formula R such as₁R₂R_Three
Ga (where R₁, R₂, R_ThreeIs a lower alkyl group
You. ) Trialkylgallium represented by
Luminium [(CH_Three)_ThreeAl], triethylaluminium
Umm [(C₂H_Five)_ThreeAl, sometimes referred to as TEA below
You. ], Triisobutylaluminum [(i-C
_FourH₉) _ThreeAl] etc.₁R₂R_ThreeAl (here
R₁, R₂, R_ThreeIs the same as defined above. )
Trialkyl aluminum; trimethylamine ara
[[CH_Three)_ThreeN: AlH_Three]; Trimethylindiu
Mu [(CH_Three)_ThreeIn, sometimes referred to as TMI below
You. ], Triethylindium [(C₂H_Five)_ThreeIn]
General formula R such as₁R₂R_ThreeIn (where R₁, R₂, R_Three
Is the same as defined above. ) Trialkyl represented by
Examples include indium and the like. These can be used alone or as a mixture
Used.

Next, examples of the Group 5 raw materials include ammonia, hydrazine, methylhydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, t-butylamine, ethylenediamine and the like. These are used alone or in combination. Of these raw materials, ammonia and hydrazine do not contain carbon atoms in the molecule,
It is suitable because it has less carbon contamination in the semiconductor.

Examples of the p-type dopant used for the 3-5 group compound semiconductor include Mg, Cd, Zn, Hg, and Be. Among them, Mg is preferable because it is easy to form a low-resistance p-type compound semiconductor. As a raw material of the Mg dopant, biscyclopentadienyl magnesium, bismethylcyclopentadienyl magnesium, bisethylcyclopentadienyl magnesium, bis n-propylcyclopentadienyl magnesium, bis i-propylcyclopentadienyl magnesium, etc. Of the general formula (RC ₅
H _{4) 2} Mg (wherein R is suitably used for an organic metal compound is suitable vapor pressure represented by hydrogen or a number of 1 to 4 carbon atoms or less of a lower alkyl group.).

Si, Ge and O are used as the n-type dopant used in the Group 3-5 compound semiconductor. Among these, Si is preferable because it is easy to form a low-resistance n-type compound semiconductor and a high-purity starting material is obtained. As a raw material for the Si dopant, silane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used. Substrates for crystal growth include sapphire, ZnO, GaAs, Si, SiC,
Spinel _{(MgAl 2 O 4), NGO} (NdGaO 3)
Etc. are preferable, but particularly preferable because the sapphire substrate is transparent and a good crystal can be obtained in a large area.

FIG. 1 shows an example of a layered structure of a 3-5 group compound semiconductor for a light emitting device of the present invention. This will be described below with reference to FIG. The laminated structure of the group 3-5 compound semiconductor for a light emitting device of the present invention has an n-type layer 3 and a p-type layer 7, the light emitting layer 5 is disposed between both layers, and light is emitted on both sides of the light emitting layer. This is a so-called double hetero structure in which two layers having a band gap larger than that of the layers are in contact with each other. The double hetero structure is useful because it has the effect of confining the injected charges in the light emitting layer and can increase the light emission efficiency.

In the present invention, the p-type layer 7 has the general formula I
n _x Ga _y Al _z N (provided that, x + y + z = 1,0 ≦ x
≤1, 0 ≤ y ≤ 1, 0.0001 ≤ z ≤ 0.10), and is characterized by being doped with a p-type dopant. This allows
The brightness and light emission efficiency of the light emitting element can be improved. It is considered that this is because a steep doping profile at the junction interface can be obtained by adding AlN to the mixed crystal component and setting it to a specific low concentration. In general formula In _x Ga _y Al _z N (provided that, x + y + z = 1,0
≦ x ≦ 1, 0 ≦ y ≦ 1, 0.0001 ≦ z ≦ 0.10)
In the Group 3-5 compound semiconductor represented by
1 ≦ z ≦ 0.10 means that the AlN mixed crystal ratio is 0.0
It may be described as 1% or more and 10% or less. Similarly, the values of x and y may be expressed by the InN mixed crystal ratio and the GaN mixed crystal ratio, respectively.

The AlN mixed crystal ratio is preferably 0.05% or more and 5% or less, more preferably 0.1% or more and 3% or less. If the AlN mixed crystal ratio is less than 0.01%, the effect of the present invention cannot be sufficiently obtained. Also, the AlN mixed crystal ratio is 1
If it exceeds 0%, the band gap becomes large and it becomes difficult to obtain a p-type crystal having a high carrier concentration, which is not preferable. In the 3-5 group compound semiconductor for a light emitting device of the present invention, the buffer layer 2 is first grown in order to alleviate the lattice mismatch with the substrate 1, and then the n-type layer 3 is usually grown for ease of growth. However, it is preferable to grow the light emitting layer 5 above it and the p-type layer 7 above the light emitting layer. LED
As the basic structure of, the n-type layer 3, the light-emitting layer 5 and the p-type layer 7 are sufficient, but a non-doped layer or a low-concentration doped layer is provided between the light-emitting layer and the n-type layer and / or the p-type layer. In some cases, the luminous efficiency can be improved by setting it. In the case of FIG. 1, layers 4 and 6 correspond to this.

In the 3-5 group compound semiconductor for a light emitting device of the present invention, in order to efficiently confine charges in the light emitting layer, the band gaps of the two layers in contact with the light emitting layer are larger than the band gap of the light emitting layer. Specifically, it is preferable that it is larger by 0.1 eV or more. More preferably, it is 0.3 eV or more.

In FIG. 1, the p-type layer is one layer, but it may be a laminated structure composed of a plurality of layers having different dopant concentrations, Group III element composition ratios and the like. However, since the p-type layer doped with the p-type dopant containing AlN in the mixed crystal component in the present invention is considered to have a steep doping profile at the junction interface, it is the most n-type in the laminated structure. The effect of the present invention is remarkable when the layer is close to the layer. The layer thickness of the p-type layer doped with the p-type dopant in the present invention is preferably 30 Å or more and 5 μm or less. If the layer thickness is less than 30Å, the effect of the present invention is not remarkable and 5
If it is larger than μm, it takes a long time to grow and it is not practical. A more preferable range of layer thickness is 100 Å or more and 3 μm or less, and particularly preferably 200 Å or more and 1 μm or less.

Group 3-5 compound semiconductor for light emitting device of the present invention
The light emitting layer used for _xGa_yAl_zN
(However, x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1,
The group 3-5 compound semiconductor represented by 0 ≦ z ≦ 1) is useful.
is there. Those containing Al easily take in impurities such as oxygen
When used as a light-emitting layer, the luminous efficiency may decrease.
is there. In such a case, the light emitting layer contains Al.
Not general formula In_xGa_yN (however, x + y = 1, 0 ≦
x ≦ 1, 0 ≦ y ≦ 1) can be used.
preferable. The above general formula In not containing Al_xGa_yAt N
In the light-emitting layer composed of the 3-5 group compound semiconductor represented
However, if the InN mixed crystal ratio is 10% or more, the band gap
It is particularly useful for display applications because it can be made visible.
If the InN mixed crystal ratio is less than 10%, the band gap
Since it can be used in the ultraviolet region, it is especially suitable for ultraviolet light emitting device applications.
Useful.

The lattice constant of the compound semiconductor greatly changes depending on the composition. In particular, the lattice constant of InN is GaN or A
About 12% or more higher than 1N. For this reason,
Depending on the composition of each layer of the compound semiconductor, a large difference may occur in the lattice constant between layers. If there is a large lattice mismatch, defects may occur in the crystal, which causes deterioration of crystal quality. In order to suppress the occurrence of defects due to lattice mismatch, the layer thickness must be reduced according to the magnitude of strain due to lattice mismatch. The preferred thickness range depends on the amount of strain.

Ga _y Al _z N (where y + z = 1, 0
≦ y ≦ 1,0 ≦ z 3-5 group compound semiconductor represented by _{≦ 1) In x Ga y Al} z N ( provided that, x + y + z =
1, 0.1 ≤ x ≤ 1, 0 ≤ y <1, 0 ≤ z <1), when stacking the group 3-5 compound semiconductor, the preferable thickness of the layer containing In is 5 Å or more and 500 Å or less. And more preferably not less than 5Å and not more than 90Å. . When the thickness of the layer containing In is smaller than 5Å, the luminous efficiency becomes insufficient. On the other hand, if it is larger than 500 Å, defects will occur and the luminous efficiency will not be sufficient. A more preferable thickness range is 5Å or more and 90Å or less.

Further, by reducing the thickness of the light emitting layer,
Since the charges can be confined in the light emitting layer with high density,
The luminous efficiency can be improved. Therefore, even when the difference in lattice constant is smaller than that in the above example, the preferable thickness of the light emitting layer is 5Å or more and 500Å or less, and more preferably 5Å or more and 90Å or less. When the thickness of the light emitting layer is less than 5Å, the luminous efficiency becomes insufficient. Also 500Å
When it is larger, the luminous efficiency is not sufficient. The light emitting layer may be a layer composed of a plurality of layers functioning as a light emitting layer. A specific example in which a layer composed of a plurality of layers functions as a light emitting layer is a structure in which two or more light emitting layers are stacked with a layer having a larger band gap.

By doping the light emitting layer with impurities, it is possible to emit light at a wavelength different from the band gap of the light emitting layer. Since this is light emission from impurities, it is called impurity light emission. In the case of impurity emission, the emission wavelength is determined by the composition of the Group 3 element of the light emitting layer and the impurity element. in this case,
The InN mixed crystal ratio of the light emitting layer is preferably 5% or more. When the InN mixed crystal ratio is less than 5%, most of the emitted light is ultraviolet light, and sufficient brightness cannot be felt. In
The emission wavelength becomes longer as the N mixed crystal ratio is increased, and the emission wavelength can be adjusted from purple to blue and green. Impurities suitable for light emission are preferably Group 2 elements. Among the Group 2 elements, doping with Mg, Zn, and Cd is preferable because the luminous efficiency is high. Particularly, Zn is preferable. The concentration of these elements is preferably 10 ¹⁸ to 10 ²² cm ⁻³ . The light emitting layer may be simultaneously doped with Si or Ge together with these Group 2 elements. The preferred concentration range of Si and Ge is 10 ¹⁸
It is -10 ²² cm ^-3 .

In the case of impurity emission, the emission spectrum is generally
Becomes broader and the emission space increases as the injected charge increases.
The spectrum shifts or the peak of the band edge emission appears.
It has unfavorable emission characteristics such as
It is difficult to increase the light efficiency. Therefore, high color purity
Is required or the emission power is concentrated in a narrow wavelength range.
If necessary, or a device with high luminous efficiency is required
In such a case, it is advantageous to use interband emission. Ba
In order to realize a light-emitting element by emitting light between
The amount of impurities contained in must be kept low. Ingredient
Physically, each element of Si, Ge, Mg, Cd and Zn
For each, the concentration is 10¹⁹cm ^-3The following is preferred
More preferably 10¹⁸cm^-3It is the following.

In the case of band-to-band emission, the emission color is 3 of the emission layer.
Determined by the composition of group elements. When emitting light in the visible region, In
The N mixed crystal ratio is preferably 10% or more. InN mixed crystal ratio is 10
If it is less than%, the emitted light is mostly ultraviolet rays and sufficient brightness cannot be sensed. The emission wavelength becomes longer as the InN mixed crystal ratio increases, and the emission wavelength can be adjusted from purple to blue and green.

When the light emitting layer contains In, the thermal stability is not sufficient, and deterioration may occur during crystal growth or in the semiconductor process. In order to prevent the deterioration of the light emitting layer, the In _x Ga _y layer is formed on and in contact with the light emitting layer.
Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦
It is effective to form a protective layer made of a 3-5 group compound semiconductor represented by y ≦ 1, 0 ≦ z ≦ 1). In order to have a sufficient protective function, the InN mixed crystal ratio of the protective layer is 1
It is preferably 0% or less, and the AlN mixed crystal ratio is preferably 5% or more. More preferably, the InN mixed crystal ratio is 5% or less, and the AlN mixed crystal ratio is 10% or more.

The growth temperature of the protective layer is preferably the same as the growth temperature of the light emitting layer or lower than the growth temperature of the light emitting layer. However, in order to avoid the complexity of the growth operation, the growth temperature is the same as that of the light emitting layer. Is more preferable. A temperature higher than the growth temperature of the light emitting layer is not preferable because the protective function becomes insufficient. The conductivity of the protective layer is preferably p-type from the viewpoint of electrical characteristics. However, high-concentration doping of impurities may lower the crystallinity of the protective layer, which may lead to lower luminous efficiency. In such a case, it is necessary to keep the concentration of impurities contained in the protective layer low. The impurity concentration in the protective layer is preferably 10 ¹⁹ cm ^-3 or less, more preferably 10 ¹⁸ cm ^-3 or less, and particularly preferably 10 ¹⁷ cm ^-3 or less. The thickness of the protective layer is preferably 10 Å or more and 1 μm or less. If the thickness of the protective layer is less than 10Å, a sufficient protective effect cannot be obtained. On the other hand, if it is larger than 1 μm, the luminous efficiency is decreased, which is not preferable, and more preferably 50 Å
It is above 5000 Å.

[0026]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 A 3-5 group compound semiconductor having the structure shown in FIG. 1 was prepared by the MOVPE method, and a light emitting device was prepared therefrom. As the substrate, a sapphire C surface mirror-polished was used after organic cleaning. The growth was performed by a two-step growth method using a low temperature growth buffer layer. At a substrate temperature of 550 ° C., hydrogen is used as a carrier gas, and TMG and ammonia are supplied to form a Ga film having a film thickness of 500 Å.
The N buffer layer 2 was formed. Next, the substrate temperature is set to 110
The temperature was raised to 0 ° C., and TMG, ammonia, and silane gas were supplied onto the buffer layer 2 so that the Si-doped n-type carrier concentration was 1 × 10 ¹⁹ / cm ³ , and the film thickness was about 3 μm.
GaN layer 3 is grown, and TMG and ammonia are further supplied at the same temperature to form a non-doped GaN layer 4 1500
ÅI grew up.

Next, the substrate temperature is lowered to 785 ° C., the carrier gas is changed to nitrogen, and TEG, TMI, and ammonia are added at 0.04 sccm, 0.08 sccm, and 4 s, respectively.
Then, the In _0.3 Ga _0.7 N layer 5 as a light emitting layer was grown for 70 seconds. Furthermore, TEG, TEA at the same temperature
And ammonia are 0.032 sccm and 0.0, respectively.
Supplying 08sccm, 4slm, Ga as a protective layer
_{The 0.8} Al _0.2 N layer 6 was grown for 10 minutes.

However, sccm and slm are units of gas flow rate, and 1 sccm indicates that a weight of gas occupies a volume of 1 cc in a standard state per minute is flowing for 1 s.
lm is 1000 sccm. Regarding the thickness of these two layers, In _0.
Since the growth rates obtained from the thicknesses of the ₃ Ga _0.7 N layer and the Ga _0.8 Al _0.2 N layer are 43 Å / min and 30 Å / min, the layer thicknesses obtained from the above growth time are 50 Å and 300 respectively.
Can be calculated as Å.

After this, the temperature is raised to 1100 ° C. and TM
G, TEA, Cp ₂ Mg, and ammonia are supplied to supply M
Ga _1-x Al _x N doped with g was grown at 5000Å. The mixed crystal ratio (x) of AlN calculated from the supply ratio of TEA and TMG is 0.4%. 3-5 produced by the above
After the group compound semiconductor sample was taken out from the reaction furnace, it was annealed in nitrogen at 800 ° C. for 20 minutes. An electrode was formed on the thus obtained sample by a conventional method to obtain an LED. p
A Ni-Au alloy was used as an electrode, and Al was used as an n electrode. When a current was applied to this LED in the forward direction, clear blue light emission was exhibited. The efficiency at 20 mA was 2.2%.

Example 2 The mixed crystal ratio of AlN was set to 0.6% instead of 0.4%.
Ga doped with Mg _1-xAl_xExcept for growing N
Then, an LED was produced in the same manner as in Example 1. to this
A clear blue light emission was observed when a current was applied. 2
The luminous efficiency at 0 mA was 2.6%.

Comparative Example 1 A comparative LED was prepared in the same manner as in Example 1 except that a Mg-doped GaN layer containing no AlN was grown instead of the AlN mixed crystal ratio of 0.4%. Was produced. When a current was applied to this, blue light emission was observed,
The luminous efficiency at 20 mA was 1.5%. FIG. 2 shows the forward current dependence of the luminous efficiency of the light emitting devices of Example 2 and Comparative Example 1. It can be seen that the light emission efficiency of the sample manufactured in Example 2 is dramatically improved in the low current region.
This can be interpreted as the result of the steep rise of the p-type carrier concentration at the initial growth interface by using the p-layer including the AlN mixed crystal of the present invention.

[0032]

By using the p-type compound semiconductor layer having the AlN mixed crystal ratio within the specific range of the present invention, a light emitting device having improved brightness and luminous efficiency can be produced, which is extremely useful and has an industrial value. Is big.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a Group 3-5 compound semiconductor for a light emitting device according to Example 1 of the present invention.

FIG. 2 is a graph showing a relationship between current and light emission efficiency of the light emitting elements of Example 2 and Comparative Example 1.

[Explanation of symbols]

 1 ... Substrate 2 ... Buffer layer 3 ... N-type layer 4 ... Non-doped layer 5 ... Light-emitting layer 6 ... Non-doped layer (protective layer) 7 ... P-type layer

Claims (5)

[Claims] 1. A p-type layer and an n-type layer, a light emitting layer is disposed between both layers, and two layers having a band gap larger than that of the light emitting layer are in contact with each other on both sides of the light emitting layer. In a 3-5 group compound semiconductor for a light emitting device including a laminated structure, the p
Layer of the general formula In _x Ga _y Al _z N (where x +
y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0.0001 ≦
A compound semiconductor group 3-5 represented by z ≦ 0.10), and a compound semiconductor group 3-5 for a light emitting device, which is doped with a p-type dopant. 2. A p-type layer is composed of a plurality of layers, and a layer closest to the n-type layer among the plurality of layers is a general formula In _x Ga _y A
l _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y
≦ 1, 0.0001 ≦ z ≦ 0.10) 3-5
It is a group compound semiconductor, The group 3-5 compound semiconductor for light emitting elements of Claim 1 characterized by the above-mentioned. 3. The light emitting device according to claim 1, wherein the thickness of the light emitting layer is 5 Å or more and 500 Å or less.
-Group 5 compound semiconductor. 4. Si, Ge, Mg, Zn contained in the light emitting layer
The concentration of each element of Cd and Cd is 1 × 10 ¹⁹ cm ⁻³ or less, and the group 3-5 compound semiconductor for a light emitting device according to claim 1, 2 or 3. 5. A light emitting device comprising the group 3-5 compound semiconductor for a light emitting device according to claim 1, 2, 3 or 4.