JP2005191589A - Light-emitting element and group iii-v compound semiconductor therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a group III-V compound semiconductor capable of realizing a light-emitting element having high luminous efficacy, and to provide the light emitting element. <P>SOLUTION: The group III-V compound semiconductor has a laminated structure having an n-type layer 4 expressed by a general expression In<SB>x</SB>Ga<SB>y</SB>Al<SB>z</SB>N (in this case, x+y+z=1, 0≤x≤1, 0≤y≤1, and 0≤z≤1), a luminous layer 5, and a p-type layer 7 in this order on a substrate 1. The group III-V compound semiconductor for the light-emitting element has an underlayer 3 of which carrier concentration is lower than that of the n-type layer and n-type dopant concentration is lower than that of the n-type layer between the n-type layer and the substrate. The light-emitting element uses the semiconductor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a group 3-5 compound semiconductor represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1), and The present invention relates to a light emitting element using the same.

As a material of a light emitting element such as an ultraviolet or blue light emitting diode or an ultraviolet or blue laser diode, the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 A group 3-5 compound semiconductor represented by ≦ z ≦ 1) is known. In particular, those containing 10% or more of InN as a mixed crystal ratio are particularly important for display applications because the emission wavelength in the visible region can be adjusted according to the In concentration.

In the case of manufacturing a light-emitting element using the Group 3-5 compound semiconductor, it is necessary to form an n-type layer and a p-type layer doped with impurities that act as a charge injection layer for driving at a low voltage. However, when doping is performed to obtain a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ or more that provides good charge injection characteristics, the crystal quality of the n-type layer is significantly reduced. In general, when the crystallinity of the lower layer of the light emitting layer is low, it is difficult to obtain a light emitting layer with high crystallinity, and the light emission efficiency is lowered. As a method for preventing a decrease in light emission efficiency due to the decrease in crystallinity, application of a layer structure in which the carrier concentration is gradually reduced as the light emitting layer is approached has been reported (Japanese Patent Laid-Open Nos. 6-151965 and 7). -15041). However, in such a structure, since a layer having a low carrier concentration is formed between the n-type charge injection layer and the p-type charge injection layer, ideal current-voltage characteristics cannot be obtained, and a light-emitting element is manufactured. It was a problem.

  The objective of this invention is providing the 3-5 group compound semiconductor and light emitting element which can implement | achieve the light emitting element of high luminous efficiency.

  As a result of diligent examination in view of such a situation, the inventors of the present invention formed a high carrier concentration and high quality semiconductor crystal by laminating a high carrier concentration layer above a low carrier concentration layer grown at a high temperature. It has been found that it can be realized and has led to the present invention.

That is, the present invention provides an n-type represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1) on the substrate. A group 3-5 compound semiconductor having a laminated structure having a layer, a light emitting layer, and a p-type layer in this order, and having a lower carrier concentration than the n-type layer and n-type layer between the n-type layer and the substrate The present invention relates to a Group 3-5 compound semiconductor for a light emitting device having an underlayer having a lower n-type dopant concentration.

Furthermore, the present invention relates to a substrate, _a buffer layer represented by the general formula Ga _a Al _b N (where a + b = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1) and grown at a temperature of 1000 ° C. or lower. formula in _c Ga _d Al _e N (provided that, c + d + e = 1,0 ≦ c <1,0 ≦ d ≦ 1,0 ≦ e ≦ 1) becomes grown in represented at temperatures above 1000 ° C. 3-5 Group 3-5 represented by a base layer made of a group compound semiconductor, represented by a general formula In _f Ga _g Al _h N (where f + g + h = 1, 0 ≦ f <1, 0 ≦ g ≦ 1, 0 ≦ h ≦ 1) An n-type layer made of a compound semiconductor and doped in an n-type, with a general formula In _i Ga _j Al _k N (where i + j + k = 1, 0 ≦ i ≦ 1, 0 ≦ j ≦ 1, 0 ≦ k ≦ 1) emitting layer composed of group III-V compound semiconductor represented, and the general formula In _m Ga _n Al _o n (provided that, m + n + o = 1,0 ≦ <1, 0 ≦ n ≦ 1, 0 ≦ o <1) A p-type layer doped with a p-type compound composed of a Group 3-5 compound semiconductor is in contact with this order or via another layer A group 3-5 compound semiconductor having a stacked structure in which the underlayer has a lower carrier concentration than the n-type layer and a lower n-type dopant concentration than the n-type layer. The present invention relates to a compound semiconductor and a light-emitting element using the semiconductor.

Next, the present invention will be described in detail.
The compound semiconductor of the present invention is represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1) on the substrate. A group 3-5 compound semiconductor having a stacked structure having a type layer, a light emitting layer, and a p-type layer in this order, and having a lower carrier concentration than the n-type layer and n-type between the n-type layer and the substrate It is a 3-5 group compound semiconductor for light emitting elements which has a base layer whose n type dopant concentration is lower than a layer.

Examples of such a Group 3-5 compound semiconductor include a substrate, a general formula Ga _a Al _b N (where a + b = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1) and is grown at a temperature of 1000 ° C. or lower. buffer layer formed by the general formula in _c Ga _d Al _e N (provided that, c + d + e = 1,0 ≦ c <1,0 ≦ d ≦ 1,0 ≦ e ≦ 1) in the represented growth at temperatures above 1000 ° C. An underlayer made of a Group 3-5 compound semiconductor, represented by the general formula In _f Ga _g Al _h N (where f + g + h = 1, 0 ≦ f <1, 0 ≦ g ≦ 1, 0 ≦ h ≦ 1). An n-type layer made of a Group 3-5 compound semiconductor and doped with an n-type, general formula In _i Ga _j Al _k N (where i + j + k = 1, 0 ≦ i ≦ 1, 0 ≦ j ≦ 1, 0 ≦ k ≦ 1) light emitting layer composed of group III-V compound semiconductor represented by, and the general formula in _m Ga _n Al _o n (provided that m + n + o = 1,0 ≦ m <1,0 ≦ n ≦ 1,0 ≦ o <1
A p-type layer doped with a p-type composed of a group 3-5 compound semiconductor represented by a group 3-5 compound semiconductor composed of a laminated structure arranged in contact with each other or via another layer Thus, there can be mentioned a Group 3-5 compound semiconductor for a light emitting device in which the carrier concentration of the underlayer is lower than that of the n-type layer and the n-type dopant concentration is lower than that of the n-type layer.

  Further, for example, after the buffer layer is grown, an n-type layer with a high carrier concentration is grown, an underlayer is further grown, and an n-type layer with a high carrier concentration is grown again.

  In the Group 3-5 compound semiconductor of the present invention, the preferred thickness of the light emitting layer is 5 to 500 mm, and the more preferable thickness range is 5 to 90 mm. When the thickness of the light emitting layer is smaller than 5 mm, the light emission efficiency is not sufficient. On the other hand, if it is larger than 500 mm, defects are generated and the luminous efficiency is not sufficient. Further, 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.

In order to obtain good current injection characteristics in such a Group 3-5 compound semiconductor, the carrier concentration of the n-type layer is preferably 5 × 10 ¹⁷ cm ⁻³ or more. More preferably, it is 1 × 10 ¹⁸ cm ⁻³ or more.

The carrier concentration of the underlayer is preferably 1 × 10 ¹⁷ cm ⁻³ or less, more preferably 5 × 10 ¹⁶ cm ⁻³ or less. In particular, it is possible not to dope.

  The growth temperature of the underlayer is preferably higher than 1000 ° C and not higher than 1200 ° C, more preferably not lower than 1020 ° C and not higher than 1150 ° C. When the growth temperature is 1000 ° C. or lower or higher than 1200 ° C., the resulting crystallinity is poor, the crystallinity of the layer stacked thereon is lowered, and when the compound semiconductor is used as a light emitting element, the light emitting efficiency is sufficient. Not.

  The thickness of the underlayer is preferably 100 mm or more and 10 μm or less. More preferably, it is 1000 to 5 μm. When the thickness is less than 100 mm, the effect of improving the crystallinity of the layer laminated thereon cannot be obtained sufficiently. On the other hand, if the thickness is larger than 10 μm, cracks occur in the crystal due to strain. Therefore, when the compound semiconductor is used as a light emitting element, the light emission efficiency is not sufficient.

The light emitting device of the present invention is formed using the group 3-5 compound semiconductor for light emitting devices of the present invention.
Specifically, the light-emitting element of the present invention is represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). A compound semiconductor stacked structure, in which a light-emitting layer forms a so-called quantum well structure in which two layers having a larger band gap are in contact with each other, and the quantum well structure further includes an n-type layer and a p-type layer. What is sandwiched between. Hereinafter, the layer in contact with the light emitting layer may be referred to as a barrier layer. The barrier layer itself may be doped n-type or p-type.

  The quantum well structure is particularly important because it can confine charges in the light emitting layer and increase the recombination probability in this layer. In order to effectively confine the charge, the band gap of the two layers in contact with both sides of the light emitting layer is preferably larger than the light emitting layer by 0.1 eV or more. More preferably, it is 0.3 eV or more.

By the way, the light emission mechanism of a light emitting element can be divided roughly into two. One is a mechanism in which injected electrons and holes are recombined via a level formed by impurities in the band gap, and is generally called impurity emission. The other is that the injected electrons and holes are recombined without going through the level due to impurities, and in this case, light emission at a wavelength substantially corresponding to the band gap can be obtained. This is called band edge emission.
Here, in the compound semiconductor represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1), the value of x is indicated. InN mixed crystal ratio may be x. Similarly, the values of y and z may be described in terms of GaN mixed crystal ratio and AlN mixed crystal ratio, respectively.

  In the case of impurity emission, the emission wavelength is determined by the composition of the Group 3 element in the light emitting layer and the impurity element. In this case, the InN mixed crystal ratio in 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 light, and 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.

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. In particular, 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. A preferable concentration range of Si and Ge is 10 ¹⁸ to 10 ²² cm ⁻³ .

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.

  In the case of band edge emission, the emission color is determined by the composition of the Group 3 element in the emission layer. When light is emitted in the visible part, the InN mixed crystal ratio is preferably 10% or more. When the InN mixed crystal ratio is less than 10%, the emitted light is almost ultraviolet light, and 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 to green.

When 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, the light emitting layer is represented by the general formula In _{i ′} Ga _{j ′} N (where i ′ + j ′ = 1, 0 <i ′ ≦ 1, 0 ≦ j ′ <1) not including Al. Can be used.

The layer below the light emitting layer not containing Al is a group 3-5 compound semiconductor represented by the general formula Ga _u Al _v N (where u + v = 1, 0 ≦ u ≦ 1, 0 ≦ v ≦ 1). It is preferable that it is a layer which consists of. Since a mixed crystal containing In has a low decomposition temperature, growth is usually performed at a temperature of 850 ° C. or lower. On the other hand, Ga _u Al _v N (where u + v = 1, 0 ≦ u ≦ 1, 0 ≦ v ≦ 1) has a high decomposition temperature and can grow at a high temperature of 1000 ° C. or higher, so that the quality of the obtained crystal is good. . Therefore, Ga _u Al _v N (where u + v = 1, 0 ≦ u ≦ 1, 0 ≦ v ≦ 1) is preferable as the layer below the light emitting layer not containing Al.

Since the lattice constant of the Group 3-5 compound semiconductor varies greatly depending on the mixed crystal ratio, there may be a large difference in the lattice constant between layers. In that case, the thickness of the layer must be reduced in accordance with the magnitude of strain due to lattice mismatch. The preferred thickness range depends on the magnitude of strain. When a light emitting layer made of a Group 3-5 compound semiconductor having an InN mixed crystal ratio of 10% or more is stacked on the Ga _u Al _v N, the preferred thickness of the light emitting layer is 5 mm or more and 500 mm or less. When the thickness of the light emitting layer is smaller than 5 mm, the light emission efficiency is not sufficient. On the other hand, if it is larger than 500 mm, defects are generated and the luminous efficiency is not sufficient. A more preferable thickness range is 5 to 90 mm.

  Further, 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 small, the thickness of the light emitting layer is preferably the same as in the above example.

Examples of the substrate for heteroepitaxial crystal growth of the Group 3-5 compound semiconductor of the present invention include sapphire, ZnO, GaAs, Si, SiC, NGO (NdGaO ₃ ), spinel (MgAl ₂ O ₄ ) and the like. It is preferable because it is transparent and high quality crystals with a large area can be obtained.

When the group 3-5 compound semiconductor is grown on a substrate such as sapphire or Si, it is represented by the general formula Al _a Ga _b N (where a + b = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1). Good quality crystals can be obtained by growing through the buffer layer. Such a buffer layer is preferably grown at a temperature of 500 ° C. or higher and 1000 ° C. or lower.

In the compound semiconductor of the present invention, without impairing the object of the present invention, a low impurity concentration between the n-type layer and the light-emitting layer, the general formula Ga _p Al _q N (provided that, p + q = 1,0 ≦ p ≦ It is also possible to stack an intermediate layer made of a Group 3-5 compound semiconductor represented by 1, 0 ≦ q ≦ 1).

  In that case, the thickness of the intermediate layer is preferably 1 μm or less, and more preferably 5000 mm or less. When the thickness is larger than 1 μm, the electrical characteristics are deteriorated, which is not preferable.

In the compound semiconductor of the present invention, in order to increase thermal stability, the general formula In _r Ga _s Al _t N (where r + s + t = 1, 0 ≦ r ≦ 0.1, 0 ≦ s ≦ 1, a protective layer made of a Group 3-5 compound semiconductor represented by 0.05 ≦ t ≦ 1) can be laminated. In order to provide the protective layer with 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.

  In order to provide the protective layer with a sufficient protective function, the thickness is preferably 10 to 1 μm. If the thickness of the protective layer is less than 10 mm, a sufficient effect cannot be obtained. On the other hand, if it is larger than 1 μm, the luminous efficiency is decreased, which is not preferable. More preferably, it is 50 to 5000 inches.

  The crystal quality of the Group 3-5 compound semiconductor can be evaluated by measuring a rocking curve of a diffraction peak in X-ray diffraction. Here, the rocking curve is an X-ray diffraction intensity distribution curve obtained by applying a monochromatic X-ray to a crystal from a certain direction and rotating the crystal in the vicinity of a target diffraction peak. A high-quality single crystal with uniform crystal orientation can provide a sharp spectrum with a narrow half-width of the rocking curve.

  The crystal quality can also be evaluated by etching pits generated during etching. The group 3-5 compound semiconductor is etched by being immersed in phosphoric acid (a mixture of sulfuric acid and phosphoric acid) heated to 200 ° C. or higher. If crystal defects such as dislocations are present in the crystal, the etching rate increases at that portion, so that a hole is formed during etching. This hole is called an etching pit. That is, if the number of etching pits generated during etching is small, it can be said that the crystal is high quality with few defects.

An example of the structure of a light-emitting element using the semiconductor of the present invention is shown in FIG.
In this example of the structure of the light emitting element, a buffer layer 2 and a base layer 3 are formed in this order on a substrate 1. Further, layers 4 and 6 having a band gap larger than that of the light emitting layer 5 are formed on both sides of the light emitting layer 5, and formed into a layer 4 having n-type conductivity and a layer 7 having p-type conductivity. When a voltage is applied from the electrode, a current flows and the layer 5 emits light.

  Although FIG. 1 shows an example in which a single quantum well layer is a light emitting layer, the layer functioning as the light emitting layer may be a layer composed of a plurality of layers. Specifically, an example in which a layer composed of a plurality of layers functions as a light emitting layer includes a structure in which two or more light emitting layers are stacked with a layer having a larger band gap.

  As a method for producing a Group 3-5 compound semiconductor according to the present invention, a metal organic vapor phase epitaxy (hereinafter sometimes referred to as MOVPE) method, a molecular beam epitaxy (hereinafter sometimes referred to as MBE) method, Examples thereof include a hydride vapor phase epitaxy (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.

In the case of the MOVPE method, the following raw materials can be used.
That is, as a Group 3 material, trimethylgallium [(CH ₃ ) ₃ Ga, hereinafter referred to as “TMG” may be used. ], Triethylgallium [(C ₂ H ₅ ) ₃ Ga, hereinafter referred to as “TEG”. ] Trialkylgallium represented by the general formula R ¹ R ² R ³ Ga (where R ¹ , R ² , R ³ are lower alkyl groups); trimethylaluminum [(CH ₃ ) ₃ Al] Triethylaluminum [(C ₂ H ₅ ) ₃ Al, hereinafter sometimes referred to as “TEA”. ], And a general formula R ¹ R ² R ³ Al such as triisobutylaluminum [(i-C ₄ H ₉ ) ₃ Al] (where R ¹ , R ² and R ³ represent lower alkyl groups). Trialkylaluminum; trimethylamine allane [(CH ₃ ) ₃ N: AlH ₃ ]; trimethylindium [(CH ₃ ) ₃ In, hereinafter sometimes referred to as “TMI”. ], Triethylindium [(C ₂ H ₅ ) ₃ In] and other general formulas R ¹ R ² R ³ In (where R ¹ , R ² and R ³ represent lower alkyl groups). Examples include alkyl indium. These may be used alone or in combination.

  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.

The n-type dopant of the Group 3-5 compound semiconductor is preferably a Group 4 element or a Group 6 element. Specific examples include Si, Ge, O, S, and Se. Among these, Si that can easily produce a low-resistance n-type and that has a high raw material purity is preferable. As a raw material for the Si dopant, silane (SiH ₄ ), disilane (Si ₂ H ₆ ), and the like are suitable.

  The p-type dopant of the Group 3-5 compound semiconductor is preferably a Group 2 element. Specific examples include Mg, Zn, Cd, Hg, and Be. Among these, Mg, which is easy to produce a low-resistance p-type, is preferable.

Examples of Mg dopant materials include biscyclopentadienyl magnesium, bismethylcyclopentadienyl magnesium, bisethylcyclopentadienyl magnesium, bis-n-propylcyclopentadienyl magnesium, and bis-i-propylcyclopentadienyl. An organometallic compound represented by a general formula (RC ₅ H ₄ ) ₂ Mg such as magnesium (wherein R represents a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms) has an appropriate vapor pressure. Therefore, it is suitable.

  Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.

Example 1
The group 3-5 compound semiconductor was produced by the MOVPE method. The substrate was used after organically cleaning a mirror-polished sapphire having a C-plane substrate surface. In the growth, 500 GaN of TMG and ammonia is formed at 550 ° C. as a buffer layer, and then non-doped GaN is grown at 1100 ° C. with a thickness of 1.5 μm using TMG and ammonia. Using SiH ₄ ), GaN doped with Si was formed at a thickness of 3 μm at 1100 ° C. When the rocking curve of the (0002) plane by X-ray diffraction of the sample thus obtained was measured, the half-value width was 5.6 minutes. This half-value width is almost the same value as that of the non-doped sample, and it can be seen that the crystallinity is not lowered by the Si doping.

Comparative Example 1
The growth was performed in the same manner as in Example 1 except that the non-doped layer was not grown after the buffer layer was grown. Similarly, when the rocking curve of the (0002) plane was measured by X-ray diffraction, the half width was 8.0 minutes. There was a decrease in crystallinity.

Example 2
After forming a 500-nm GaN buffer layer as in Example 1, non-doped GaN was grown to a thickness of 3.0 μm at 1100 ° C. using TMG and ammonia, and then silane (SiH ₄ ) was used as a dopant. A GaN film doped with Si at 1100 ° C. was formed to a thickness of 1 μm. The sample thus obtained was soaked in 240 ° C. phosphoric acid (sulfuric acid: phosphoric acid = 4: 1) for 5 minutes. As a result, the number of etching pits generated was 3 or less per 1 mm ² .

Comparative Example 2
After growing a 500 GaN buffer layer in the same manner as in Example 1, GaN directly doped with Si was grown to a thickness of 3.0 μm. When the sample thus obtained was immersed in phosphoric acid at 240 ° C. for 5 minutes in the same manner as in Example 2, the generated etching pits were about 1200 per mm ² .

Example 3
As in Example 1, a 500-inch GaN buffer layer was grown, then directly doped Si-doped GaN was grown to a thickness of 3.0 μm, then non-doped GaN was grown to 1 μm, and further Si-doped GaN was 1. Growing with a thickness of 0 μm. When the sample thus obtained was immersed in phosphoric acid at 240 ° C. for 5 minutes in the same manner as in Example 2, the number of etching pits generated was 3 or less per 1 mm ² .

Example 4
As in Example 1, after growing a Si-doped GaN layer on the non-doped GaN layer, and further growing a non-doped GaN layer having a thickness of 1500 mm, the carrier gas was changed from hydrogen to nitrogen, and TEG, TMI, and TEA were used. In _0.3 Ga _0.7 N was grown for 70 seconds and Ga _0.8 Al _0.2 N was grown for 10 minutes. The growth rate of In _0.3 Ga _0.7 N obtained from the thickness of the layer grown for a longer time under the same conditions is about 33 Å / min, and the growth rate of Ga _0.8 Al _0.2 N is about 25 Å / min. The thicknesses were about 40 mm and about 250 mm, respectively. Next, the temperature was raised to 1100 ° C., and 5000 mg of GaN doped with Mg using TMG, ammonia, and biscyclopentadienylmagnesium (Cp ₂ Mg) as a dopant was grown. After completion of the growth, the substrate was taken out and heat-treated at 800 ° C. for 20 minutes in nitrogen.

  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 with a peak wavelength of 460 nm was exhibited, and the luminance was 1050 mcd.

Sectional drawing which shows one example of the light emitting element of this invention

Explanation of symbols

1. . . Substrate 2. . . 2. Buffer layer . . Underlayer 4. . . n-type layer 5. . . Light emitting layer 6. . . Protective layer 7. . . p-type layer

Claims (9)

An n-type layer represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1), a light emitting layer, and A Group 3-5 compound semiconductor having a p-type layer in this order, which has a lower carrier concentration than the n-type layer and an n-type dopant concentration between the n-type layer and the substrate. A group 3-5 compound semiconductor for a light-emitting element, comprising a low underlayer.   The group 3-5 compound semiconductor for a light emitting device according to claim 1, wherein the underlayer is non-doped.   The group 3-5 compound semiconductor for light emitting elements according to claim 1 or 2, further comprising a buffer layer between the substrate and the underlayer. Substrate, the general formula Ga _a Al _b N (provided that, a + b = 1,0 ≦ a ≦ 1,0 ≦ b ≦ 1) buffer layer represented made grown at 1000 ° C. or less of the temperature, the general formula an In _c Ga _d It is represented by Al _e N (where c + d + e = 1, 0 ≦ c <1, 0 ≦ d ≦ 1, 0 ≦ e ≦ 1) and is made of a Group 3-5 compound semiconductor grown at a temperature exceeding 1000 ° C. formations, the general formula in _f Ga _g Al _h n (provided that, f + g + h = 1,0 ≦ f <1,0 ≦ g ≦ 1,0 ≦ h ≦ 1) n -type consisting of group III-V compound semiconductor represented by n-type layer formed by doped, general formula in _i Ga _j Al _k n (provided that, i + j + k = 1,0 ≦ i ≦ 1,0 ≦ j ≦ 1,0 ≦ k ≦ 1) 3-5 represented by emitting layer comprising a group compound semiconductor, and the general formula In _m Ga _n Al _o n (provided that, m + n + o = 1,0 ≦ m <1,0 ≦ n ≦ 1 A p-type layer doped with a p-type composed of a group 3-5 compound semiconductor represented by 0 ≦ o <1) is formed in a laminated structure in which the p-type layers are arranged in contact with each other or through another layer. A Group 5-5 compound semiconductor for a light-emitting device, wherein the Group 5 compound semiconductor has a lower carrier concentration than the n-type layer and a lower n-type dopant concentration than the n-type layer. An intermediate represented by the general formula Ga _p Al _q N (p + q = 1, 0 ≦ p ≦ 1, 0 ≦ q ≦ 1) between the n-type layer and the light-emitting layer and having an impurity concentration lower than that of the n-type layer. The group 3-5 compound semiconductor for light emitting elements according to any one of claims 1 to 4, further comprising a layer. 6. The carrier concentration of the n-type layer is 5 × 10 ¹⁷ cm ⁻³ or more, and the carrier concentration of the underlayer is 1 × 10 ¹⁷ cm ⁻³ or less. 3-5 group compound semiconductor for light emitting elements.   The thickness of a light emitting layer is 5 to 500 mm, The group 3-5 compound semiconductor for light emitting elements in any one of Claims 1-6 characterized by the above-mentioned. 8. The light emitting device according to claim 1, wherein the concentration of each element of Si, Ge, Mg, Zn and Cd contained in the light emitting layer is 1 × 10 ¹⁹ cm ⁻³ or less. For Group 3-5 compound semiconductor. A light emitting device comprising the group 3-5 compound semiconductor for a light emitting device according to claim 1.

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