JP4304497B2 - Semiconductor element - Google Patents

Description

The present invention relates to a semiconductor element which is implemented as a like ultraviolet or blue light emitting diodes and semiconductor lasers, and more particularly to forming a buffer layer on a substrate, the crystal quality gallium nitride-based compound semiconductor layer thereon It relates to the method of growing.

  In recent years, a semiconductor element having a gallium nitride compound semiconductor layer capable of obtaining blue light has attracted attention. Conventionally, the gallium nitride compound semiconductor layer has been crystal-grown on a substrate by vapor deposition or vapor deposition. However, since it is difficult to obtain a single crystal of gallium nitride, a heterogeneous substrate such as sapphire is used as the substrate. In this case, since the lattice constants of the substrate and the gallium nitride compound semiconductor layer are different, lattice defects and stress are generated in the grown gallium nitride compound semiconductor layer. In order to alleviate these problems, a layer called a buffer layer is provided on the substrate. As the structure and growth method of this buffer layer, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4 are known.

Patent Document 1 relates to a structure of a buffer layer formed on a sapphire substrate and a crystal growth method, and Al _x1 Ga _1-x1 N (0.5 ≦ x1 ≦ 1) is used as the buffer layer. It is formed on a sapphire substrate with a thickness of 0.2 μm or less under a temperature condition lower than the growth temperature of the substrate, and a polycrystalline formed by low temperature is partially raised as a single crystal by raising the temperature. A light emitting element is formed on the sapphire substrate by growing a gallium nitride compound semiconductor doped with Si or Mg on the crystal.

  Patent Documents 3 and 4 are patents relating to a crystal growth method of a gallium nitride compound light-emitting element on a sapphire substrate, in which a buffer layer is formed between the n-type gallium nitride layer and the sapphire substrate. The buffer layer is made of AlN, and crystal growth is performed at a temperature between 400 to 600 ° C. or 500 ° C. or less, and the thickness is made 100 to 1000 mm.

In the semiconductor light emitting devices according to these conventional examples, an n-type gallium nitride compound semiconductor layer containing n-type dopants including Si is stacked as a contact layer on a sapphire as a supporting substrate, and a buffer layer is further formed thereon. A light emitting layer having a light emitting junction layer (active layer), a p-type gallium nitride compound semiconductor layer containing a p-type dopant such as Mg, and a contact layer are sequentially stacked thereon. In the light emitting layer, an n-type clad layer and a p-type clad layer made of a group III nitride semiconductor are arranged on the lower and upper sides, and a light emitting junction is formed at the boundary between them. In the light emitting layer, holes and electrons are combined in the light emitting bonding layer, and light having a wavelength determined by the band gap energy of the light emitting layer is emitted.
Japanese Patent No. 3257498 Japanese Patent No. 3257344 Japanese Patent No. 3140751 Japanese Patent No. 3026087

  In the above-described prior art, GaN is used as the buffer layer in Patent Documents 1 and 2, and AlN is used in Patent Documents 3 and 4, both of which are grown at a low temperature so that the crystal is lateral (plane). It is intended to suppress the lattice defects by growing in the direction and joining the defective portions. However, in the case of such a buffer layer of only GaN or AlN, a thick film thickness of about 100 nm is required in order to stack an epi layer on the buffer layer. Therefore, it takes time to form a film, and when the film thickness increases, the residual stress of the buffer layer itself affects, and the lattice defect occurs in the thickness direction of the semiconductor element. There is a problem that light emission shift due to the piezo effect occurs and the light emission efficiency is lowered.

An object of the present invention is to provide a semiconductor element capable of improving the crystallinity of the grown gallium nitride-based semiconductor layer on a substrate.

The semiconductor device of the present invention, on a substrate, a semiconductor element formed by stacking a gallium nitride-based compound semiconductor layer through the buffer layer, the buffer layer, Ri formed by laminating the aluminum nitride and gallium nitride alternately In the case where the thermal expansion coefficient of the substrate is smaller than that of aluminum nitride, the total film thickness of each of the aluminum nitride and gallium nitride is aluminum nitride> gallium nitride, and the thermal expansion coefficient of the substrate is higher than that of aluminum nitride. wherein the relationship and to Rukoto aluminum nitride <gallium nitride is greater.

According to the arrangement, be realized as such an ultraviolet or blue light-emitting diode or a semiconductor laser, a sapphire _{(Al 2 O 3), Si} , on a substrate such as SiC, a buffer layer for relaxing the difference in lattice constant In the semiconductor element formed by stacking gallium nitride compound semiconductor layers such as Al _x Ga _1-x N (0 ≦ x <1), the buffer layer is made of aluminum nitride (AlN) and gallium nitride (GaN). Are alternately stacked.

  Therefore, cracks due to lattice defects caused by stacking can be prevented in the aluminum nitride layer and the lattice defects can be prevented from extending further, and the threading transition in which the lattice defects extend in the thickness direction of the semiconductor element is reduced. The high quality gallium nitride compound semiconductor layer can be crystal-grown. Accordingly, in the case of a semiconductor light emitting device, it is possible to suppress the occurrence of non-emissive coupling that does not contribute to light emission in the lattice defects and the loss of input current due to the non-emissive coupling. In the case of a light-emitting element, it is possible to manufacture a semiconductor light-emitting element that has high emission efficiency and no shift in emission peak wavelength. Moreover, even if the buffer layer is thin, the intended purpose can be achieved and the film formation time can be shortened.

Furthermore , focusing on the fact that the thermal expansion coefficient of gallium nitride is larger than the thermal expansion coefficient of aluminum nitride among aluminum nitride and gallium nitride constituting the buffer layer, the film thickness of the aluminum nitride and gallium nitride is When the thermal expansion coefficient of the substrate is smaller than that of aluminum nitride, the relation of aluminum nitride> gallium nitride is satisfied, and the proportion of the aluminum nitride layer having a smaller thermal expansion coefficient is increased, and the thermal expansion coefficient of the substrate is larger than that of aluminum nitride. as a relation of the aluminum nitride <gallium nitride in, that the proportion of the thermal expansion coefficient is large gallium nitride layer, it is possible to further relax the stress between the substrate and the gallium nitride compound semiconductor layer, the stress High quality gallium nitride compound semiconductor layer without influence can be crystal-grown and light emitting device In this case, it can be high luminous efficiency, to realize a semiconductor light emitting element is no shift in the emission peak wavelength. In addition, the said film thickness should just have the said relationship for the sum total of the film thickness by each material, when the pair layer of the said aluminum nitride and gallium nitride is laminated | stacked two or more layers.

  Furthermore, in the semiconductor device of the present invention, the buffer layer includes two or more pair layers of the aluminum nitride and the gallium nitride.

  According to the above configuration, the threading transition can be further reduced in the buffer layer, and a high-quality gallium nitride compound semiconductor layer can be crystal-grown. A semiconductor light emitting element having no shift of the emission peak wavelength can be realized.

  The semiconductor device of the present invention is a semiconductor light emitting device, and the gallium nitride compound semiconductor layer is formed by sequentially laminating an n-type gallium nitride compound semiconductor layer, a light emitting layer, and a p-type gallium nitride compound semiconductor layer. Thus, an aluminum nitride layer having a thickness larger than that of the buffer layer is provided between the buffer layer and the n-type gallium nitride compound semiconductor layer.

  According to the above configuration, the threading transition can be further reduced in the aluminum nitride layer having a thickness larger than that of the buffer layer, and thus a semiconductor light emitting device with higher luminous efficiency can be realized.

Furthermore, in the semiconductor element of the present invention, the buffer layer is characterized in that the total film thickness of the aluminum nitride layer and the gallium nitride layer constituting the buffer layer is in the range of 0.31 to 10 nm.

  According to the above configuration, the aluminum nitride layer and the gallium nitride layer constituting the buffer layer are already effective when the thickness of the monomolecular film is 0.31 nm. On the other hand, even if the thickness exceeds 10 nm, there is no difference in effect, and the buffer layer itself may crack due to internal stress as described above. And This can reduce threading transition as described above.

In the semiconductor element of the present invention, the n-type contact layer is Al _x1 Ga _1-x1 N (0 ≦ x1 ≦ 1), the clad layer is Al _X2 Ga _1-x2 N (0 <x2 ≦ 1), and the light emitting layer is Al _x3 In _y Ga _1-x3-y N (0 <x3 ≦ 1, 0 ≦ y ≦ 1), p-type layer is Al _x4 Ga _1-x4 N (0 <x4 ≦ 1) .

  According to said structure, the highly efficient ultraviolet light emitting element which can change light emission wavelength by the ratio of Al and In, ie, x3: y, can be obtained.

  As described above, the semiconductor device of the present invention is realized as an ultraviolet or blue light emitting diode or a semiconductor laser, and a gallium nitride-based compound semiconductor layer is interposed on the substrate via a buffer layer for reducing the difference in lattice constant. The buffer layer is formed by alternately laminating aluminum nitride (AlN) and gallium nitride (GaN).

  Therefore, cracks due to lattice defects caused by stacking can be prevented from occurring in the aluminum nitride layer, and the lattice defects can be prevented from extending further, and a threading transition in which the lattice defects extend in the thickness direction of the semiconductor element can be prevented. The reduced high-quality gallium nitride compound semiconductor layer can be crystal-grown. As a result, in the case of a semiconductor light emitting device, it is possible to suppress non-luminous coupling that does not contribute to light emission and to prevent the input current from being lost due to the non-luminous coupling. Therefore, it is possible to manufacture a semiconductor light emitting device with high luminous efficiency and no shift in emission peak wavelength. Moreover, even if the buffer layer is thin, the intended purpose can be achieved and the film formation time can be shortened.

Furthermore, focusing on the fact that the thermal expansion coefficient of gallium nitride is larger than the thermal expansion coefficient of aluminum nitride among aluminum nitride and gallium nitride constituting the buffer layer, the total film of each of the aluminum nitride and gallium nitride When the thermal expansion coefficient of the substrate is smaller than that of aluminum nitride, the relationship of aluminum nitride> gallium nitride is set, and the proportion of the aluminum nitride layer having the smaller thermal expansion coefficient is increased so that the thermal expansion coefficient of the substrate is higher than that of aluminum nitride. Is large, the relationship between aluminum nitride and gallium nitride is satisfied. By increasing the proportion of the gallium nitride layer having a large thermal expansion coefficient, the stress between the substrate and the gallium nitride compound semiconductor layer can be further relaxed. It is possible to grow a high-quality gallium nitride compound semiconductor layer that is not affected by stress. , In the case of a light-emitting element has high luminous efficiency can be realized a semiconductor light emitting element is no shift in the emission peak wavelength.

[Embodiment 1]
FIG. 1 is a cross-sectional view schematically showing the structure of a semiconductor light emitting device 10 according to the first embodiment of the present invention. The semiconductor light-emitting element 10 includes a buffer layer 2 according to the present invention when a gallium nitride compound semiconductor layer is stacked on a sapphire substrate 1. It should be noted that the buffer layer 2 is composed of a plurality of pair layers in which aluminum nitride (AlN) and gallium nitride (GaN) are alternately stacked.

On the sapphire substrate 1 used as a support substrate, the buffer layer 2 having a thickness of 1 nm in total is formed by vapor deposition of the AlN and GaN, and an n-type dopant having a thickness of 2.2 μm is formed thereon. An n-type gallium nitride compound semiconductor layer 3 made of Al _0.5 Ga _0.5 N containing Si is vapor-phase grown, and further a light-emitting layer 4 made of Al _0.6 Ga _0.4 N and p-type electric conduction And a p-type gallium nitride compound semiconductor layer 5 made of Al _0.6 Ga _0.4 N having a thickness of 0.1 μm containing a dopant Mg indicating vapor phase growth.

Below, the growth method of this semiconductor light-emitting device 10 is shown. Gases used for growth are H ₂ and N ₂ as carrier gases, and ammonia (NH ₃ ), trimethyl gallium (Ga (CH ₃ ), hereinafter abbreviated as TMG), trimethyl aluminum (Al (CH ₃ ) ₃ , hereinafter abbreviated as TMA), silane (SiH ₄ ), and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ).

First, the sapphire substrate 1 is washed with an organic and acid solution. Then, while flowing H ₂ gas at 2 (L / min), the temperature is raised to 1100 ° C. by heater heating or induction heating, and the sapphire substrate 1 is vapor-phase etched. Next, the temperature was lowered to 800 ° C., and while flowing H ₂ gas at 20 (L / min), NH ₃ gas of 10 (L / min) and 1.8 × 10 ⁻⁵ (mol / min) TMA, and then 10 (L / min) of NH ₃ gas and 1.1 × 10 ⁻⁵ (mol / min) of TMG were alternately supplied thereafter, for a total of 1 nm each. Thickness. As a result, the buffer layer 2 on which a pair layer in which AlN is first formed, then GaN, and then AlN and GaN are alternately formed is grown on the sapphire substrate 1.

Thus, when the substrate processing is completed, the semiconductor layer is formed, the temperature is raised to 1000 ° C., and H ₂ gas is supplied at 20 (L / min), while 10 (L / min) NH ₃ gas and 1.8 An n-type having a thickness of 2.2 μm while alternately introducing SiO ₄ by alternately supplying × 10 ⁻⁵ (mol / min) TMA and 1.1 × 10 ⁻⁵ (mol / min) TMG Al _0.5 Ga _0.5 N containing Si as a dopant is crystal-grown on the buffer layer 2 as the n-type gallium nitride compound semiconductor layer 3. While maintaining the temperature at 1000 ° C. and flowing H ₂ gas at 20 (L / min), 10 (L / min) NH ₃ gas, 1.8 × 10 ⁻⁵ (mol / min) TMA and 1 .Alternatively, 1 × 10 ⁻⁵ (mol / min) TMG was supplied alternately, and while introducing SiH ₄ , Al _0.6 Ga _0.4 N having a thickness of 3 nm was used as the light emitting layer 4, and the n A crystal is grown on the type gallium nitride compound semiconductor layer 3.

Further, while maintaining the temperature at 1000 ° C. and flowing H ₂ gas at 20 (L / min), 10 (L / min) NH ₃ gas, 1.8 × 10 ⁻⁵ (mol / min) TMA and 1 .1 × 10 ⁻⁵ (mol / min) TMG alternately supplied to introduce p-type having a thickness of 0.1 μm while introducing cyclopentadienylmagnesium (Mg (C ₅ H ₅ ) ₂ ) The gallium nitride compound semiconductor layer 5 is crystal-grown on the light emitting layer 4. In the present embodiment, although the growth substrate showed an example of a sapphire substrate 1, as a substrate material other than sapphire may be such as SiC and ZrB _2.

As described above, when the gallium nitride compound semiconductor layer (Al _x Ga _1-x N (0 ≦ x <1)) is stacked on the sapphire substrate 1 via the buffer layer 2, the buffer layer 2 is made of AlN. By making a pair layer formed by alternately laminating GaN, cracks due to lattice defects caused by lamination can be suppressed in the AlN layer, and the lattice defects can be prevented from extending further. High quality gallium nitride compound semiconductor layers 3 to 5 with reduced threading transition extending in the thickness direction of the semiconductor element can be crystal-grown. As a result, non-radiative bonds that do not contribute to light emission occur in the lattice defects, and it is possible to suppress the loss of the input current due to the non-luminescent bonds, high luminous efficiency, and shift of the emission peak wavelength. This makes it possible to manufacture a semiconductor light emitting device that emits light in the ultraviolet region. Moreover, even if the buffer layer 2 is thin, the intended purpose can be achieved and the film formation time can be shortened.

  Further, the buffer layer 2 includes two or more pairs of AlN and GaN, thereby further reducing the threading transition and crystal growth of high-quality gallium nitride compound semiconductor layers 3 to 5. Therefore, it is possible to realize a semiconductor light emitting device with higher luminous efficiency and no shift in emission peak wavelength.

  Furthermore, in the above-described example, in the buffer layer 2, the total film thickness of each of the AlN layer and the GaN layer is equally formed by 1 nm. However, when other types of substrates are used, GaN When the thermal expansion coefficient of the substrate is smaller than that of AlN, the film thickness is assumed to have a relationship of AlN> GaN, and the AlN layer having a small thermal expansion coefficient. When the thermal expansion coefficient of the substrate is larger than that of AlN, the ratio of the GaN layer having a large thermal expansion coefficient may be increased by setting the film thickness as AlN <GaN. As a result, the stress between the substrate and the gallium nitride compound semiconductor layer can be further relaxed, and a high-quality gallium nitride compound semiconductor layer without the influence of stress can be crystal-grown, and the luminous efficiency is high. A semiconductor light emitting element having no shift of the emission peak wavelength can be realized.

  In addition, according to the above crystal growth method, the crystal growth of the gallium nitride compound semiconductor layers 3 to 5 can be performed at a temperature lower than that of the conventional method. Therefore, the stress applied to the grown gallium nitride compound semiconductor layers 3 to 5 is reduced. The generation of cracks and the like can be suppressed during the vapor phase growth. As a result, wavelength peak shift can be prevented, and a highly efficient semiconductor light emitting device can be realized. In the above description, although the growth temperature is 1000 ° C. with high reproducibility, the growth can be performed in the range of 600 to 1200 ° C. In particular, the minimum temperature can be lowered from about 800 ° C. to about 600 ° C.

  Furthermore, in the buffer layer 2, although the total thickness of the AlN layer and the GaN layer constituting the buffer layer 2 is 1 nm in total, it may be in the range of 0.31 to 10 nm. That is, the minimum value of 0.31 nm is the thickness of the monomolecular film of the AlN layer, and even a monomolecular film can exert the effect. On the other hand, if the thickness exceeds 10 nm, there is no difference in effect, and the buffer layer itself may crack due to internal stress as described above. Therefore, the maximum value is 10 nm, which has a short film formation time.

The n-type gallium nitride compound semiconductor layer 3 includes an n-type contact layer made of Al _x1 Ga _1-x1 N (0 ≦ x1 ≦ 1) and a clad made of Al _X2 Ga _1-x2 N (0 <x2 ≦ 1). The light emitting layer 4 is made of Al _x3 In _y Ga _1-x3-y N (0 <x3 ≦ 1, 0 ≦ y ≦ 1), and the p-type gallium nitride compound semiconductor layer 5 is made of Al _x4 Ga. _By forming with _1-x4 N (0 <x4 ≦ 1), it is possible to obtain a highly efficient ultraviolet light-emitting element capable of changing the emission wavelength depending on the ratio of Al to In, that is, x3: y.

Furthermore, in producing the gallium nitride compound semiconductor layers 3 to 5, TMA, TMG, and NH ₃ are alternately supplied and grown, so that a parasitic reaction between the group III and group V in the reaction gas occurs. Thus, an AlGaN layer having a high Al composition ratio can be grown, and a semiconductor light emitting device that emits light in the ultraviolet region with high light emission efficiency and no shift in light emission peak wavelength can be manufactured. This point will be described in detail below.

That is, in the semiconductor light emitting device, in order to emit light in the ultraviolet region having a wavelength shorter than that of blue, it is necessary to increase the Al composition ratio in the GaN layer. However, the conventional growth method uses a reaction gas in which the TMA, TMG, and NH ₃ are mixed. For this reason, a parasitic reaction between group III and group V in the reaction gas occurs, and it is difficult to grow an AlGaN layer having a high Al composition ratio. Specifically, (CH ₃ ) 6 Al ₂ +2 (NH ₃ ) → 2 (CH ₃ ) ₃ Al: NH ₃ , AlN is precipitated, and the proportion of Al taken into the AlGaN layer on the substrate decreases. . Therefore, in the present invention, the gallium nitride compound semiconductor layers 3 to 5 are grown by alternately supplying TMA, TMG, and NH ₃ as described above, so that the group III and group V in the reaction gas can be obtained. The occurrence of parasitic reactions is suppressed.

[Embodiment 2]
FIG. 2 is a cross-sectional view schematically showing the structure of the semiconductor light emitting device 20 according to the second embodiment of the present invention. The semiconductor light emitting element 20 is similar to the semiconductor light emitting element 10 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted that in this semiconductor light emitting device 20, an AlN layer 6 having a thickness greater than that of the buffer layer 2 is provided between the buffer layer 2 and the n-type gallium nitride compound semiconductor layer 3a. is there.

Also in this semiconductor light emitting device 20, the sapphire substrate 1 is used as a support substrate, and the buffer layer 2 is formed on the sapphire substrate 1 by a pair layer of AlN and GaN each having a total thickness of 1 nm. Is vapor-grown, and the AlN layer 6 having a thickness of 1.5 μm is vapor-grown on the n-type gallium nitride made of Al _0.84 Ga _0.16 N containing an n-type dopant. The compound semiconductor layer 3a is vapor-phase grown, and the light-emitting layer 4a composed of an Al _0.6 Ga _0.4 N layer and an Al _0.8 Ga _0.2 N layer is further vapor-grown, and the p-type gallium nitride is further grown. The compound semiconductor layer 5 is vapor-phase grown.

Below, the growth method of this semiconductor light-emitting device 20 is shown. The gases used for the growth are H ₂ and N ₂ as carrier gases, and NH ₃ , TMG, TMA, SiH ₄ , and Mg (C ₅ H ₅ ) ₂ as growth gases, as in the semiconductor light emitting device 10. is there.

First, the sapphire substrate 1 is washed with an organic and acid solution. Then, while flowing H ₂ gas at 2 (L / min), the temperature is raised to 1100 ° C. by heater heating or induction heating, and the sapphire substrate 1 is vapor-phase etched. Next, the temperature was lowered to 800 ° C., and 10 (L / min) NH ₃ gas and 1.8 × 10 ⁻⁵ (mol / min) TMA were flowed while flowing H ₂ gas at 20 (L / min). And 10N (L / min) of NH ₃ gas and 1.1 × 10 ⁻⁵ (mol / min) of TMG are alternately supplied to form a total thickness of 1 nm each from AlN and GaN. The buffer layer 2 on which the pair layers formed are stacked is crystal-grown on the sapphire substrate 1. The above process is the same as that of the semiconductor light emitting device 10.

Subsequently, the flow proceeds to create a semiconductor layer, the temperature was raised to 1000 ° C., while the _{H 2} gas flow 20 (L / min), and NH ₃ gas 10 (L / min), 2.1 × ^{10 -5} (Mol / min) TMG is alternately supplied to crystallize the AlN6 having a thickness of 1.5 μm on the buffer layer 2.

Further, while maintaining the temperature at 1000 ° C. and flowing H ₂ gas at 20 (L / min), 10 (L / min) NH ₃ gas, 1.8 × 10 ⁻⁵ (mol / min) TMA and 1 Al _0.84 Ga _0.16 containing Si as an n-type dopant having a thickness of 0.1 μm while alternately supplying 1 × 10 ⁻⁵ (mol / min) TMG and introducing SiH ₄ N is crystal-grown on the AlN layer 6 as the n-type gallium nitride compound semiconductor layer 3a. Further, while maintaining the temperature at 1000 ° C. and flowing H ₂ gas at 20 (L / min), 10 (L / min) NH ₃ gas, 1.8 × 10 ⁻⁵ (mol / min) TMA and 1 0.1 × 10 ⁻⁵ (mol / min) alternately supplied with TMG, while introducing SiH ₄ , Al _0.6 Ga _0.4 N layer and Al _0.8 Ga _{0 having} a thickness of 3 nm _.2 Crystal growth of the light emitting layer 4a composed of the N layer on the n-type gallium nitride compound semiconductor layer 3a.

Further, while maintaining the temperature at 1000 ° C. and flowing H ₂ gas at 20 (L / min), 10 (L / min) NH ₃ gas, 1.8 × 10 ⁻⁵ (mol / min) TMA and 1 The p-type gallium nitride compound semiconductor layer 5 having a thickness of 0.1 μm is introduced while alternately supplying 1 × 10 ⁻⁵ (mol / min) TMG and introducing Mg (C ₅ H ₅ ) _2. Crystals are grown on the light emitting layer 4.

FIG. 3 shows a TEM observation image of the semiconductor light emitting element 20 produced as described above. On the other hand, FIG. 4 shows a TEM observation image of a comparative example according to the prior art in which the AlN layer 6 is not formed. FIG. 5 is a cross-sectional view schematically showing the structure of the semiconductor light emitting device 30 of the comparative example. In the same manner as the semiconductor light emitting device 10 shown in FIG. 1, this semiconductor light emitting device 30 has a 50 μm buffer layer 32 made of AlN on a sapphire substrate 31 and Al _0.5 Ga containing Si as a 1.0 μm n-type dopant. _Al 0.6 containing _0.5 n-type gallium nitride compound semiconductor layer ₃₃ made of _n, Al 0.6 _{Ga 0.4} emitting layer 34 consisting of n and p-type dopant Mg showing the electrical conductivity of _{Ga 0.4} n A p-type gallium nitride compound semiconductor layer 35 is sequentially stacked.

A method for producing the semiconductor light emitting device 30 of the comparative example is as follows. First, the sapphire substrate 31 is washed with an organic and acid solution. Then, the temperature is raised to 1100 ° C. while flowing H ₂ gas at 2 (L / min), and the sapphire substrate 31 is vapor-phase etched. Next, the temperature was lowered to 800 ° C., and 10 (L / min) NH ₃ gas and 1.8 × 10 ⁻⁵ (mol / min) TMA were flowed while flowing H ₂ gas at 20 (L / min). And an AlN buffer layer 32 having a thickness of 50 nm is grown on the sapphire substrate 31.

Thus, when the substrate processing is completed, the semiconductor layer is formed, the temperature is raised to 1000 ° C., and H ₂ gas is supplied at 20 (L / min), while 10 (L / min) NH ₃ gas and 1.8 × ^{10 -5} to supply alternately and TMG of TMA and 1.1 × ^{10 -5} (molar / min) (mol / min), while introducing SiH _4, n-type having a thickness of 1.0μm Al _0.5 Ga _0.5 N containing Si as a dopant is crystal-grown on the buffer layer 32 as the n-type gallium nitride compound semiconductor layer 33. While maintaining the temperature at 1000 ° C. and flowing H ₂ gas at 20 (L / min), 10 (L / min) NH ₃ gas, 1.8 × 10 ⁻⁵ (mol / min) TMA and 1 .Alternatively supplying 1 × 10 ⁻⁵ (mol / min) TMG and introducing SiH ₄ , Al _0.6 Ga _0.4 N having a thickness of 0.1 μm was used as the light emitting layer 34. Crystals are grown on the n-type gallium nitride compound semiconductor layer 33.

Further, while maintaining the temperature at 1000 ° C. and flowing H ₂ gas at 20 (L / min), 10 (L / min) NH ₃ gas, 1.8 × 10 ⁻⁵ (mol / min) TMA and 1 .1 × 10 ⁻⁵ (mol / min) TMG alternately supplied to introduce p-type having a thickness of 0.1 μm while introducing cyclopentadienylmagnesium (Mg (C ₅ H ₅ ) ₂ ) The gallium nitride compound semiconductor layer 35 is grown on the light emitting layer 34.

As is clear from comparison between FIGS. 3 and 4, the threading transition from the sapphire substrate 1 to the light emitting layer 4a occurs in the buffer layer 2 composed of an AlN layer and a GaN layer grown on the sapphire substrate 1 in a vapor phase. The convergence of the transition is observed, and the convergence of the transition can be confirmed in the same manner in the AlN layer 6 formed thereon. Note that the penetration transition density on the surface of the light emitting layer 4a composed of the Al _0.6 Ga _0.4 N layer and the Al _0.8 Ga _0.2 N layer in the present embodiment is 10 ⁷ / cm ² , and PL The emission spectrum of (Photoluminescence) has a peak at 240 nm as shown in FIG.

  In this way, the threading transition can be further reduced in the AlN layer 6 having a thickness greater than that of the buffer layer 2, so that a semiconductor light emitting device with higher luminous efficiency can be realized.

It is sectional drawing which shows typically the structure of the semiconductor light-emitting device concerning the 1st Embodiment of this invention. It is sectional drawing which shows typically the structure of the semiconductor light-emitting device which concerns on the 2nd Embodiment of this invention. It is a photograph figure which shows the TEM observation image of the semiconductor light-emitting device shown in FIG. It is a photograph figure which shows the TEM observation image of the semiconductor light-emitting device by a prior art. It is sectional drawing which shows typically the structure of the semiconductor light-emitting device by the prior art shown in FIG. It is a graph which shows the emission spectrum of the semiconductor light-emitting device shown in FIG.

DESCRIPTION OF SYMBOLS 1 Sapphire substrate 2 Buffer layer 3, 3a N type gallium nitride compound semiconductor layer 4, 4a Light emitting layer 5 P type gallium nitride compound semiconductor layer 6 AlN layer 10, 20 Semiconductor light emitting element

Claims (5)

In a semiconductor element formed by laminating a gallium nitride compound semiconductor layer on a substrate via a buffer layer,
The buffer layer, Ri formed by laminating the aluminum nitride and gallium nitride are alternately and respectively the total thickness of said aluminum nitride and gallium nitride, when the thermal expansion coefficient of the substrate than the aluminum nitride is smaller the relationship between the aluminum nitride> gallium nitride, the semiconductor device characterized relationships and to Rukoto aluminum nitride <gallium nitride when the thermal expansion coefficient of the substrate than the aluminum nitride is large. The buffer layer, according to claim 1 Symbol mounting the semiconductor device characterized in that it comprises a pair layers between the aluminum nitride and gallium nitride two or more layers. In the semiconductor light emitting device, the gallium nitride compound semiconductor layer is formed by sequentially stacking an n-type gallium nitride compound semiconductor layer, a light emitting layer, and a p-type gallium nitride compound semiconductor layer,
3. The semiconductor element according to claim 1, wherein an aluminum nitride layer having a thickness larger than that of the buffer layer is provided between the buffer layer and the n-type gallium nitride compound semiconductor layer. The buffer layer, the total thickness of the aluminum nitride layer and the gallium nitride layer constituting the, semiconductor according to any one of claims 1 to 3, characterized in that in the range of 0.31~10nm voxels child. The n-type contact layer is Al _x1 Ga _1-x1 N (0 ≦ x1 ≦ 1), the clad layer is Al _X2 Ga _1-x2 N (0 <x2 ≦ 1), and the light emitting layer is Al _x3 In _y Ga _{1-x3- y N (0 <x3 ≦ 1,0} ≦ y ≦ 1), p -type layer semiconductor voxels according to claim 3, characterized in that the _{Al x4 Ga 1-x4 N (} 0 <x4 ≦ 1) Child.