JP3752739B2 - Light emitting element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses the general formula In _x Ga _y Al _z N (provided that, x + y + z = 1,0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦ 1) 3-5 group compound semiconductor represented by It is related with the light emitting element obtained.
[0002]
[Prior art]
As material for the light emitting element such as ultraviolet or blue light emitting diodes or ultraviolet or blue laser diode, the general formula In _x Ga _y Al _z N (provided that, x + y + z = 1,0 <x ≦ 1,0 ≦ y <1,0 A Group 3-5 compound semiconductor represented by ≦ z <1) is known. Hereinafter, x, y, and z in this general formula may be referred to as InN mixed crystal ratio, GaN mixed crystal ratio, and AlN mixed crystal ratio, respectively. Among these Group 3-5 compound semiconductors, those containing InN in a mixed crystal ratio of 10% or more are important for display applications because the emission wavelength in the visible region can be adjusted according to the InN mixed crystal ratio.
[0003]
The Group 3-5 compound semiconductor has been attempted to be deposited on various substrates such as sapphire, GaAs, ZnO, etc., but the lattice constant and chemical properties are greatly different from those of the compound semiconductor. Quality crystals are not obtained. Therefore, an attempt has been made to obtain an excellent crystal by first growing a GaN crystal having a lattice constant and chemical properties similar to those of the compound semiconductor, and then growing the compound semiconductor thereon. No. 55-3834).
[0004]
By the way, the lattice constant of the Group 3-5 compound semiconductor greatly depends on the InN mixed crystal ratio, and the lattice constant increases as the InN mixed crystal ratio increases. Therefore, when the Group 3-5 compound semiconductor having a large InN mixed crystal ratio is to be grown on a Group 3-5 compound semiconductor containing no In, such as GaN, the crystallinity is good only when the film thickness is sufficiently small. Can't get anything. However, it is known that when the film thickness is small, it is difficult to obtain a crystal having a lattice constant greatly different from that of the underlayer due to a so-called lattice constant pulling effect. That is, this indicates that it is difficult to form a thin film of the compound semiconductor having a high InN mixed crystal ratio on a semiconductor layer not containing In such as GaN. Therefore, it has been difficult to increase the emission wavelength of the light emitting element by increasing the InN mixed crystal ratio.
[0005]
On the other hand, as a method for obtaining a light emitting element having a long emission wavelength by using a light emitting layer having a low InN mixed crystal ratio, a light emitting element having a quantum well structure using the group 3-5 compound semiconductor emits a tensile stress. A method has been proposed in which the emission wavelength is substantially increased by adding to the layer (EP 0716457). However, in order to apply a tensile stress to a compound semiconductor having a larger lattice constant than the base layer, it is inevitable that many misfit dislocations occur at the bonding interface between the base layer and the light emitting layer. A decline was inevitable. Here, the misfit dislocation means a dislocation generated at the interface between the two layers due to the difference in lattice constant between the two layers.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a light-emitting element in which the occurrence of misfit dislocations at the interface of the light-emitting layer is suppressed.
Another object of the present invention is to provide a light-emitting element in which the occurrence of misfit dislocations at the interface of the light-emitting layer is suppressed and light emission with a longer wavelength can be easily obtained.
[Means for Solving the Problems]
[0007]
As a result of diligent study in view of such a situation, the inventors have made the misfit dislocation by making the lattice constant of the light emitting layer larger than the lattice constant of the base layer and bringing the light emitting layer into contact with the base layer with compressive strain. As a result, it was found that the emission wavelength is increased by making the AlN mixed crystal ratio of the underlayer within a specific range.
That is, the present invention provides an underlayer made of a Group 3-5 compound semiconductor represented by the general formula G _ab Al _c N ( where 0 <b <1, 0 <c <1 , b + c = 1), less formula than the underlying layer bandgap in _x Ga _y Al _z N (where, 0 <x ≦ 1,0 ≦ y <1,0 ≦ z <1, x + y + z = 1) 3-5 represented by A non-doped light emitting layer made of a group compound semiconductor layer, and a general formula G _{ab ′} Al _{c ′} N ( where 0 <b ′ <1, 0 <c ′ <1, b ′ And a non-doped protective layer made of a group 3-5 compound semiconductor represented by + c ′ = 1) is laminated in this order, and the thickness of the light emitting layer is 5 to 90 mm, and the lattice constant of the light emitting layer Is larger than the lattice constant of the underlayer and has a structure in which compressive stress is applied in the bonding direction to the light emitting layer. A light-emitting element is provided.
The present invention also provides a practically superior light-emitting device characterized in that, in the general formula G _ab Al _c N in the light-emitting device, c is 0.05 ≦ c <1.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described in detail.
The light emitting element in the present invention is a base layer represented by the general formula In _a Ga _b Al _c N (where a + b + c = 1, 0 ≦ a <1, 0 <b <1, 0 ≦ c <1), formula in _x Ga _y Al _z N (provided that, x + y + z = 1,0 <x ≦ 1,0 ≦ y <1,0 ≦ z <1) and the light-emitting layer represented by the general formula in _{a 'Ga b'} A protective layer represented by Al _{c ′} N (where 0 ≦ a ′ <1, 0 <b ′ ≦ 1, 0 ≦ c ′ <1, a ′ + b ′ + c ′ = 1) was sequentially stacked. It has a structure. The light emitting layer has a smaller band gap than the base layer and the protective layer, and the laminated structure of these three layers forms a so-called quantum well structure. Since the base layer and the protective layer have a function of injecting charges into the light emitting layer, these two layers may be referred to as charge injection layers hereinafter.
[0009]
One example of the structure of the Group 3-5 compound semiconductor of the present invention is shown in FIG. In the example shown in FIG. 1, a buffer layer 2, an n-type GaN layer 3, a base layer 4, a light emitting layer 5, a protective layer 6, and a p-type layer 7 are laminated on a substrate 1 in this order. An n-type layer 3 is provided with an n-electrode and a p-type layer 7 is provided with a p-electrode. A voltage is applied in the forward direction to inject current, and light emission is obtained from the light-emitting layer 5.
[0010]
Hereinafter, the underlayer, the light emitting layer, and the protective layer will be described.
The underlayer preferably has an AlN mixed crystal ratio of 0.05 or more and less than 1. When the AlN mixed crystal ratio is smaller than 0.05, the change in emission wavelength is small, so 0.05 or more is preferable. A more preferable mixed crystal ratio of AlN is 0.1 or more, and further preferably 0.15 or more. Further, if the AlN mixed crystal ratio exceeds 0.9, the drive voltage may increase, which is not preferable. Therefore, the AlN mixed crystal ratio is preferably 0.9 or less.
The film thickness of the underlayer is preferably 10 to 1 μm. When the thickness of the underlayer is less than 10 mm, the effect of the present invention is not remarkable, and when the thickness of the underlayer exceeds 1 μm, it takes time to grow the underlayer, which is not practical.
[0011]
The underlayer of the present invention may be doped with impurities as long as the crystallinity is not impaired. In particular, n-type doping is preferable because characteristics such as driving voltage and light emission efficiency of the light emitting element may be improved. A specific preferable range of the doping amount is a carrier concentration of 1 × 10 ¹⁶ cm ⁻³ or more and 1 × 10 ²² cm ⁻³ or less. More preferably, the carrier concentration range of the underlayer is 1 × 10 ¹⁷ cm ⁻³ or more and 1 × 10 ²¹ cm ⁻³ or less. When the carrier concentration is less than 1 × 10 ¹⁶ cm ⁻³ , the charge injection efficiency may not be sufficient, and when the carrier concentration is greater than 1 × 10 ²² cm ⁻³ , the crystallinity of the underlayer is lowered and light emission occurs. It may lead to a decrease in efficiency.
[0012]
One or more layers made of the n-type or non-doped compound semiconductor may be laminated between the base layer and the substrate. In particular, a structure in which a plurality of compound semiconductor thin films having different lattice constants are stacked is preferable because the crystallinity of a layer grown thereon may be improved.
[0013]
Next, the light emitting layer will be described.
Since the lattice constant of the Group 3-5 compound semiconductor in the present invention varies greatly depending on the mixed crystal ratio, when there is a large difference in the lattice constant between the light emitting layer and the charge injection layer of the Group 3-5 compound semiconductor, It is preferable to reduce the thickness of the light emitting layer according to the magnitude of distortion due to lattice mismatch.
A preferable range of the thickness of the light emitting layer depends on the magnitude of the strain. As a charge injection layer, a light emitting layer having an InN mixed crystal ratio of 10% or more is laminated on a layer represented by Ga _a Al _b N (where a + b = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1). In this case, the preferred thickness of the light emitting layer is 5 mm or more and 90 mm or less. In this case, if the thickness of the light emitting layer is less than 5 mm, the light emission efficiency is not sufficiently high, and if it is larger than 90 mm, defects are generated, and the light emission efficiency is also not sufficiently high.
[0014]
In addition, by reducing the thickness of the light emitting layer, charges can be confined in the light emitting layer with high density, so that the light emission efficiency can be improved. For this reason, even when the difference in lattice constant is smaller than that in the above example, the thickness of the light emitting layer is preferably the same as that in the above example.
In the case where the light emitting layer contains Al, impurities such as O are easily taken in, and the light emission efficiency may be lowered. In such a case, as the light emitting layer, a layer represented by the general formula In _x Ga _y N (where x + y = 1, 0 <x ≦ 1, 0 ≦ y <1) not including Al is used. be able to.
[0015]
The difference in band gap between the charge injection layer and the light emitting layer is preferably 0.1 eV or more, more preferably 0.3 ev or more. When the difference in band gap between the charge injection layer and the light emitting layer is smaller than 0.1 eV, the carriers are not sufficiently confined in the light emitting layer, and the light emission efficiency is lowered. However, if the band gap of the charge injection layer exceeds 5 eV, the voltage required for charge injection becomes high. Therefore, the band gap of the charge injection layer is preferably 5 eV or less.
In the present invention, the light emitting layer may be a single layer or a plurality of light emitting layers. As an example of such a structure, there is a stacked structure of (2n + 1) layers in which n light emitting layers and (n + 1) layer layers having a larger band gap than the light emitting layers are alternately stacked. Here, n is a positive integer, preferably 1 or more and 50 or less, more preferably 2 or more and 30 or less. When n exceeds 50, the light emission efficiency is lowered and it takes time to grow. Such a structure having a plurality of light emitting layers is particularly useful in the case of manufacturing a semiconductor laser that requires a strong light output.
[0016]
In the present invention, light can be emitted at a wavelength different from the band gap of the light emitting layer by doping the light emitting layer with impurities. Since this is light emission from impurities, it is called impurity light emission. In the case of impurity light 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%, the emitted light is almost ultraviolet rays, and a sufficient brightness cannot be felt. As the InN mixed crystal ratio increases, the emission wavelength becomes longer, and the emission wavelength can be adjusted from purple to blue and green.
[0017]
As an impurity suitable for impurity light emission, a group 2 element is preferable. Among group 2 elements, doping with Mg, Zn, and Cd is preferable because of high luminous efficiency. Zn is particularly 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. A preferable concentration range of Si and Ge is 10 ¹⁸ to 10 ²² cm ⁻³ .
[0018]
In the case of impurity emission, the emission spectrum generally becomes broad, and the emission spectrum may shift as the amount of injected charge increases. For this reason, when high color purity is required or when it is necessary to concentrate light emission power in a narrow wavelength range, it is advantageous to use band edge light emission. In order to realize a light emitting element using band edge light emission, the amount of impurities contained in the light emitting layer must be kept low. Specifically, the concentration of each element of Si, Ge, Mg, Cd and Zn is preferably 10 ¹⁹ cm ⁻³ or less. More preferably, it is 10 ¹⁸ cm ⁻³ or less.
[0019]
Next, the protective layer will be described.
In the Group 3-5 compound semiconductor, when the InN mixed crystal ratio of the light emitting layer is high, the thermal stability is not sufficient, and the semiconductor layer may deteriorate during crystal growth or in the semiconductor process. For the purpose of preventing such deterioration, a charge injection layer 6 having an InN mixed crystal ratio lower than that of the light emitting layer is laminated on the light emitting layer, and this layer has a function as a protective layer. be able to. In order for the protective layer to have a sufficient protective function, the InN mixed crystal ratio of the protective layer is preferably 10% or less, and the mixed crystal ratio of AlN 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.
[0020]
In order to give the protective layer a sufficient protective function, the thickness of the protective layer is preferably from 10 to 1 μm, and more preferably from 50 to 5,000. When the thickness of the protective layer is less than 10 mm, it is difficult to obtain a sufficient effect, and when it is more than 1 μm, the light emission efficiency is decreased, which is not preferable.
[0021]
The protective layer preferably has p-type conductivity from the viewpoint of current injection efficiency of the light emitting element. In order to give p-type conductivity to the protective layer, it is necessary to dope an acceptor impurity at a high concentration. Specific examples of acceptor-type impurities include group 2 elements. Among these, Mg and Zn are preferable, and Mg is more preferable. However, when the protective layer is doped with a high-concentration impurity, the crystallinity of the protective layer is lowered, and the characteristics of the light-emitting element are sometimes lowered. In such a case, it is necessary to reduce the impurity concentration. The range of the impurity concentration that does not lower the crystallinity is preferably 1 × 10 ¹⁹ cm ⁻³ or less, more preferably 1 × 10 ¹⁸ cm ⁻³ or less.
[0022]
In the laminated structure of the base layer, the light emitting layer, and the protective layer described above, in order to obtain a structure in which compressive stress is applied to the light emitting layer in the bonding direction, that is, a structure in which compressive stress is applied in a direction parallel to the bonding interface. For this purpose, the lattice constant of the light emitting layer may be made larger than the lattice constant of the base layer. For this purpose, for example, there is a method in which the InN mixed crystal ratio of the light emitting layer is made larger than the InN mixed crystal ratio of the underlayer.
However, even if the InN mixed crystal ratio of the light emitting layer is larger than the InN mixed crystal ratio of the base layer, misfit dislocations occur at the interface between the light emitting layer and the base layer depending on the method and conditions for growing these layers. In some cases, the light emitting layer is lattice-relaxed and a high crystalline light emitting layer cannot be obtained without applying compressive stress to the light emitting layer. In particular, after the light emitting layer is grown, when the protective layer is not formed and kept at a high temperature exceeding 1000 ° C. for a long time, or when the protective layer is grown at a high temperature exceeding 1000 ° C., the light emitting layer is thermally deteriorated. There is a case. In this respect, in the crystal growth of the protective layer, the growth temperature is preferably set to 1000 ° C. or lower.
[0023]
Next, the substrate used in the present invention will be described.
As the substrate for crystal growth of the Group 3-5 compound semiconductor in the present invention, sapphire, ZnO, GaAs, Si, SiC, NGO (NdGaO ₃ ), spinel (MgAl ₂ O ₄ ) and the like are used. In particular, sapphire is important because it is transparent and high-quality crystals with a large area can be obtained.
In the growth using these substrates, ZnO, SiC, GaN, AlN, GaAlN thin films, and their laminated films are grown as buffer layers on the substrate by a so-called two-stage growth method, so that highly crystalline GaN, AlN, A semiconductor such as GaAlN or InGaAlN can be grown, which is preferable.
[0024]
Next, the manufacturing method of the 3-5 group compound semiconductor in this invention is demonstrated.
Examples of the method for producing the Group 3-5 compound semiconductor include molecular beam epitaxy (hereinafter sometimes referred to as MBE) method, metal organic vapor phase epitaxy (hereinafter also referred to as MOVPE) method, and hydride vapor phase. Examples include a growth (hereinafter sometimes referred to as HVPE) method. When the MBE method is used, the nitrogen source is a gas source molecular beam epitaxy (hereinafter sometimes referred to as GSMBE) method, which is a method of supplying nitrogen gas, ammonia, and other nitrogen compounds in a gaseous state. Commonly used. In this case, the nitrogen raw material may be chemically inert and nitrogen atoms may not be easily taken into the crystal. In that case, the nitrogen uptake efficiency can be increased by exciting the nitrogen raw material with microwaves and supplying it in an activated state.
[0025]
Next, the manufacturing method by the MOVPE method of the 3-5 group compound semiconductor in this invention is demonstrated.
In the case of the MOVPE method, the following raw materials can be used.
That is, the Group 3 raw material may be described as trimethylgallium [(CH ₃ ) ₃ Ga, hereinafter TMG. ], Triethylgallium [(C ₂ H ₅ ) ₃ Ga, hereinafter sometimes referred to as TEG. ] Trialkylgallium represented by the general formula R ₁ R ₂ R ₃ Ga (where R ₁ , R ₂ and R ₃ represent lower alkyl groups); trimethylaluminum [(CH ₃ ) ₃ Al] , Triethylaluminum [(C ₂ H ₅ ) ₃ Al, hereinafter referred to as TEA. ], General formula R ₁ R ₂ R ₃ Al such as triisobutylaluminum [(i-C ₄ H ₉ ) ₃ Al] (wherein R ₁ , R ₂ and R ₃ are the same as defined above). Trimethylaluminum [(CH ₃ ) ₃ N: AlH ₃ ]; trimethylindium [(CH ₃ ) ₃ In, hereinafter sometimes referred to as TMI. ], General formula R ₁ R ₂ R ₃ In such as triethylindium [(C ₂ H ₅ ) ₃ In] (wherein R ₁ , R ₂ and R ₃ are as defined above). And trialkylindium. These may be used alone or in combination.
[0026]
Next, examples of the Group 5 raw material include ammonia, hydrazine, methyl hydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, t-butylamine, and ethylenediamine. These may be used alone or in combination. Among these raw materials, ammonia and hydrazine are preferable because they do not contain carbon atoms in their molecules and thus cause less carbon contamination in the semiconductor.
[0027]
Group 2 elements are important as p-type dopants for Group 3-5 compound semiconductors in the present invention. Specific examples include Mg, Zn, Cd, Hg, and Be. Among these, Mg that is easy to produce a low-resistance p-type is preferable.
Mg dopant materials include biscyclopentadienyl magnesium, bismethylcyclopentadienyl magnesium, bisethylcyclopentadienyl magnesium, bis-n-propylcyclopentadienyl magnesium, bis-i-propylcyclopentadienyl In order that the organometallic compound represented by the general formula (RC ₅ H ₄ ) ₂ Mg (eg, R represents hydrogen or a lower alkyl group having 1 to 4 carbon atoms) such as magnesium has an appropriate vapor pressure. Is preferred.
[0028]
As the n-type dopant of the Group 3-5 compound semiconductor, the Group 4 element and the Group 6 element are important. Specific examples include Si, Ge, and O. Among these, Si is preferable because it can easily produce a low-resistance n-type and can provide a material with high purity. As a raw material for the Si dopant, silane (SiH ₄ ), disilane (Si ₂ H ₆ ), monomethylsilane (CH ₃ SiH ₃ ), and the like are suitable.
[0029]
Examples of the growth apparatus based on the MOVPE method used for manufacturing the Group 3-5 compound semiconductor include a normal single-piece or multi-piece type. In the case of multiple wafers, it is preferable to grow under reduced pressure in order to ensure the uniformity of the epi film in the wafer surface. A preferable growth pressure range in the multi-sheet taking apparatus is 0.001 atm or more and 0.8 atm or less.
[0030]
As the carrier gas used in the production of the Group 3-5 compound semiconductor in the present invention, a gas such as hydrogen, nitrogen, argon, helium or the like can be used alone or in combination. However, when hydrogen is included in the carrier gas, sufficient crystallinity may not be obtained when a compound semiconductor having a high InN mixed crystal ratio is grown. In this case, it is necessary to reduce the hydrogen partial pressure in the carrier gas. A preferable partial pressure of hydrogen in the carrier gas is 0.1 atm or less.
[0031]
Among these carrier gases, hydrogen and helium are mentioned in that they have a large kinematic viscosity coefficient and hardly cause convection. However, helium is more expensive than other gases, and when hydrogen is used, the crystallinity of the compound semiconductor is not good as described above. Since nitrogen and argon are relatively inexpensive, they can be suitably used when a large amount of carrier gas is used.
[0032]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these.
Example 1
A Group 3-5 compound semiconductor having the structure of FIG. 2 was prepared by the MOVPE method.
A substrate 1 having a mirror-polished sapphire C surface was used after organic cleaning. As a growth method, a two-stage growth method using GaN as a low temperature growth buffer layer was used. GaN buffer layer 2 having a thickness of about 300 mm at 1/8 atm, 550 ° C., n-type layer 3 made of Si-doped GaN having a thickness of about 2.5 μm at 1050 ° C. Growing as a carrier gas.
[0033]
Next, the substrate temperature is 750 ° C., the carrier gas is nitrogen, carrier gas, TEG, TMI, silane and ammonia diluted to 1 ppm with nitrogen are respectively supplied at 4 slm, 0.04 sccm, 0.6 sccm, 5 sccm, 4 slm, An In _0.3 Ga _0.7 N layer 9 doped with Si was grown for 70 seconds. Hereinafter, this layer may be referred to as a strained layer.
Further, TEG, TEA, the above-mentioned silane and ammonia are supplied at 0.032 sccm, 0.008 sccm, 5 sccm and 4 slm, respectively, at the same temperature, and an underlayer 4 made of Si _0.8 doped Ga _0.8 Al _0.2 N is grown for 10 minutes. did.
However, slm and sccm are units of gas flow rate. 1 slm indicates that a gas having a weight that occupies a volume of 1 liter in a standard state flows per minute, and 1000 sccm corresponds to 1 slm.
It should be noted that the film thicknesses of the layer 9 and the layer 4 are obtained from the above growth time because the growth rates obtained from the thickness of the layer grown for a longer time under the same conditions are 43 Å / min and 30 Å / min, respectively. The resulting film thicknesses can be calculated as 50 mm and 300 mm, respectively.
[0034]
After the underlayer 4 was grown, the non-doped In _0.3 Ga _0.7 N light emitting layer 5 and the non-doped Ga _0.8 Al _0.2 N protective layer 6 were grown 300 μm by the same raw material supply amount as the strained layer and the underlayer.
After growing the protective layer 6, the growth pressure was set to 1 atm, the substrate temperature was set to 1100 ° C., and 5000 p-type layers 7 made of GaN doped with Mg were grown. The sample thus prepared was heat-treated at 800 ° C. for 20 minutes in nitrogen at 1 atm to make the Mg doped layer low resistance.
An electrode was formed on the sample thus obtained according to a conventional method to obtain a light emitting device. Ni-Au alloy was used as the p electrode, and Al was used as the n electrode. When a current of 20 mA was passed through the light emitting element in the forward direction, clear blue light emission was exhibited, and the central wavelength of the light emission peak was 4600 mm.
[0035]
Next, after the strained layer 9 was grown, a light emitting device was fabricated in the same manner as in the above example except that the Ga _0.7 Al _0.3 N layer 4 was grown instead of the Ga _0.8 Al _0.2 N layer 3. When this was evaluated in the same manner, the emission peak wavelength was 5050 mm, and the emission wavelength was longer than that in the above examples.
[0036]
Example 2
After growing up to the Ga _0.8 Al _0.2 N underlayer 4 in the same manner as in Example 1, the temperature was set to 785 ° C., the pressure was set to 1 atm, TMI and TEG were used, and the non-doped InGaN light emitting layer was formed using 50 A and TEA and TEG. A GaAlN protective layer 6 was grown by 300 mm. Further, the temperature was set to 1100 ° C., and a GaN layer 7 doped with Mg was grown in a thickness of 5000 mm in the same manner as in Example 1. A sample similar to the above sample was prepared except that the underlayer 4 was made of GaN.
When these samples were evaluated in the same manner as in Example 1, the center wavelength of the emission peak was 4800 mm when the base layer was Ga _0.8 Al _0.2 N, whereas it was 4600 mm when the base layer was GaN. there were.
[0037]
Example 3
Except that the pressure is 1 atm, the same as in Example 1, buffer layer 2 at 550 ° C., n-type GaN layer 3 (film thickness of about 3 μm) at 1100 ° C., n-type Ga _0.8 Al _0.2 N Underlayer 4 was grown at 800 ° C., InGaN active layer 5, Ga _0.8 Al _0.2 N protective layer 6, and Mg-doped GaN layer 7 was grown at 1100 ° C. A sample similar to the above example was prepared except that non-doped GaN was used as the base layer 4.
The sample thus obtained was evaluated in the same manner as in Example 1. As a result, when the underlayer was made of GaN, the emission wavelength was 4500 mm at 20 mA, whereas when the underlayer was Ga _0.8 Al _0.2 N, it was 4800 mm. Met.
[0038]
Example 3-2
A quantum well structure in which a non-doped GaN layer at 1100 ° C., a non-doped InGaN active layer at 800 ° C., and a non-doped GaAlN protective layer at this temperature was prepared in the same manner as in the above example, and a lattice image was observed with an electron microscope. The occurrence of misfit dislocations was not observed before and after the active layer. Since InGaN has a larger lattice constant than GaN, misfit dislocations do not occur before and after the quantum well structure, indicating that compressive stress is applied to the InGaN layer in the interface direction.
[0039]
Example 4
A sample was prepared in the same manner as in Example 3 except that 600 g of nGa _0.6 Al _0.4 N was grown as the underlayer 4 at 800 ° C. When this was evaluated in the same manner as in Example 1, clear green light emission was observed. The emission wavelength at 1 mA was 5200 nm.
[0040]
【The invention's effect】
According to the present invention, as a result of suppressing the occurrence of misfit dislocations at the interface of the light emitting layer, a high quality light emitting device can be obtained. Further, according to the present invention, light emission with a longer wavelength can be easily obtained. As a result, the emission wavelength can be easily controlled over a wide range, and the present invention has great industrial value.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating an example of a group 3-5 compound semiconductor used in a light-emitting element of the present invention.
2 is a schematic cross-sectional view showing a Group 3-5 compound semiconductor used in the light-emitting element of the present invention manufactured in Example 1. FIG.
[Explanation of symbols]
1. . . Substrate 2. . . 2. Buffer layer . . n-type layer 4. . . 4. Underlayer 5 . . Light emitting layer 6. . . Protective layer 7. . . p-type layer 8. . . 8. Non-doped GaN layer . . Strain layer

Claims (6)

A base layer made of a Group 3-5 compound semiconductor represented by a general formula Ga _b Al _c N (where 0 <b <1, 0 <c <1, b + c = 1), and a band gap of the base layer (wherein, 0 <x ≦ 1,0 ≦ y <1,0 ≦ z <1, x + y + z = 1) small general formula in _x Ga _y Al _z N consisting 3-5 group compound semiconductor layer represented by the non-doped And a light emitting layer having a band gap larger than that of the light emitting layer and represented by the general formula Ga _{b ′} Al _{c ′} N (where 0 <b ′ <1, 0 <c ′ <1, b ′ + c ′ = 1). And a non-doped protective layer made of a Group 3-5 compound semiconductor is laminated in this order, and the thickness of the light emitting layer is from 5 to 90 mm, and the lattice constant of the light emitting layer is greater than the lattice constant of the base layer A light-emitting element having a large structure in which compressive stress is applied to a light-emitting layer in a bonding direction. The light emitting device according to claim 1, wherein in the general formula Ga _b Al _c N, c is 0.05 ≦ c <1. The light emitting device according to claim 1, wherein the n-type carrier concentration in the underlayer is 1 × 10 ¹⁶ cm ⁻³ or more and 1 × 10 ²² cm ⁻³ or less. 4. The light-emitting element according to claim 1, wherein the concentration of each element of Si, Ge, Zn, Cd, and Mg contained in the light-emitting layer is 1 × 10 ¹⁹ cm ⁻³ or less. 5. The light-emitting element according to claim 1, wherein the concentration of Mg contained in the protective layer is 1 × 10 ¹⁹ cm ⁻³ or less.   The method for producing a light-emitting element according to claim 1, wherein the protective layer is grown at a temperature of 1000 ° C. or less.

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