JP2001085735A - Nitride compound semiconductor light emitting element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress adverse effect on the light emitting characteristics of an active layer due to grating distortion by regulating the composition change quantity of a barrier layer which is brought into contact with the active layer and affects it. SOLUTION: A low temperature buffer layer 12 formed of GaN and a Si dope GaN layer 13 as an n-type contact layer are sequentially laminated on a substrate 11. An InGaN layer 14 being an active layer and a Mg dope AlGaN layer 15 as a barrier layer are laminated and formed on it. Then, Al composition is continuously reduced so that it becomes 0.2 on an interface which is brought into contact with the InGaN layer 14 of the AlGaN layer 15 and to be 0.12 in an interface on a side opposite to a side which is brought into contact with the InGaN layer 14, and Mg doped GaN layer 16 as a p-type contact layer is formed thereon and an electrode 20 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor light emitting device using a group III-V nitride compound semiconductor and a method for manufacturing the same. Here, the group III-V nitride-based compound semiconductor refers to a semiconductor made of a group III-V compound containing at least nitrogen as a group V element. That is, I
It is a group III-V compound semiconductor that contains a group II element such as Al, Ga, and In and a group V element such as N, P, and As, and always contains N. For example, when written in a composition formula, it is as follows. Al _[a] Ga _[b] In _[c] N _[d] X _[1-d] (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, a + b + c = 1, 0 <D ≦ 1, X:
(Group V atoms such as P and As) Further, a semiconductor in which a part of each constituent atom is replaced with an impurity atom or the like is also included.

[0002]

2. Description of the Related Art Group III-V nitride compound semiconductors are:
Attention has been focused on light emitting elements in the wavelength range from ultraviolet to green, and use in semiconductor devices with high durability. In particular, in recent years, II
Since high-quality single-crystal thin film fabrication technology has been developed for group IV nitride compound semiconductors and the fabrication of single-crystal low-resistance p-type layers has become possible, the development of this semiconductor material has progressed rapidly. Practical use of light emitting diodes that emit light in the wavelength range from blue to green has been realized, and further development is expected.

[0003] In the future, efforts are being made from various aspects to improve the performance of light-emitting diodes that have been put into practical use and to realize semiconductor lasers and the like that are expected to be put into practical use. Making a double heterostructure is one of them. Here, InGaN is often used as the active layer due to wavelength issues, and AlGaN or GaN is often used as the barrier layer. For example, as a conventional technique, Japanese Patent Laid-Open No.
There is a structure disclosed in Japanese Patent Publication No.

In the second embodiment of this publication, InGaN? MQ
Al composition in W active layer and Si doping as n-side cladding layer
0.08 AlGaN layer (layer thickness 1μm) and p-side cladding layer
Between the Al-doped Mg layer and the AlGaN layer with an Al composition of 0.08 (layer thickness 1 μm), the Si-doped Al composition is 0.20 on the side in contact with the active layer and 0.08 on the side in contact with each cladding layer, respectively. And a laser diode having a structure having a Mg-doped AlGaN barrier layer (layer thickness 20 nm) is shown. (However, it is described as a stopper layer in the gazette.) In the sixth embodiment, a Si-doped and Mg-doped GaN guide layer is provided between each clad layer and the barrier layer from the structure of the second embodiment. In addition, the Al composition of the barrier layer is 0.1% on the side in contact with the active layer.
20, there is shown a laser diode having a structure that becomes zero on the side in contact with each guide layer.

The effect of the barrier layer is to confine carriers injected into the active layer.
Since the InGaN layer is thermally unstable compared to other nitride-based compound semiconductors, an effect of suppressing the deterioration of the crystallinity can be expected.

[0006] The reason is that, in the group III-V nitride compound semiconductors, GaN, AlN, and InN are typical materials, and InGaN and AlGaN are typical mixed crystals.
Among them, InGaN is often used as an active layer of a light emitting element. However, a group III-V nitride-based compound semiconductor containing In is difficult to produce a high-quality crystal under the same growth conditions as other group III-V nitride-based compound semiconductors. In many cases, the growth atmosphere gas, the raw material supply ratio, and the like are formed under growth conditions that are significantly different from the growth conditions of other group III-V nitride compound semiconductors. For this reason, when another mixed crystal layer is formed after the growth of the InGaN layer, the growth temperature and the like must be greatly changed, and the InGaN layer often deteriorates at this time.

In Japanese Patent Application Laid-Open No. Hei 10-145004, the most characteristic part is that the Al composition of AlGaN, which is a barrier layer (referred to as a stopper layer in the publication), gradually decreases as the Al composition moves away from the active layer. It is the part that is.
According to this publication, by adopting this structure,
This means that cracks are less likely to occur due to relaxation and absorption of stress on the stopper layer.

[0008]

The barrier layer must be formed close to the active layer, and the above effect can be greatly expected particularly when the barrier layer is in contact with the active layer. But II
In the group IV nitride compound semiconductor, when the composition changes, the lattice constant of the crystal greatly changes. Therefore, when creating a laminated structure, lattice distortion is inherent in each layer due to the difference in the mixed crystal ratio, and especially in the vicinity of the active layer, the state has a great effect on the light emission characteristics of the sample. . In this regard, there is a problem with the structure described in the related art. The above method is insufficient for fabricating a laminated structure while keeping the active layer in a good state.

For example, in the structure of the light emitting device disclosed in the above-mentioned publication, the change rate of the Al composition of the barrier layer is 0.006 / nm and 0.01 / nm, assuming that the change rate in the barrier layer is averagely changed. However, with such a value, the rate of change is too large, and an inappropriate distribution of lattice strain is inherently present in the vicinity of the active layer, and the light emission characteristics of the device deteriorate.

Therefore, according to the present invention, a laminated structure is produced while maintaining a good active layer, and an I
An object is to manufacture a II-V nitride compound semiconductor device.

[0011]

In order to solve the above-mentioned problems, the present invention regulates the composition change amount of the barrier layer which is in contact with the active layer and affects the light emission characteristics of the active layer due to lattice distortion. It is characterized by suppressing the adverse effects of.

In the present invention, the Al composition of the AlGaN layer as a barrier layer in contact with the InGaN active layer is set to be large on the side in contact with the active layer and small on the side opposite to the side in contact with the active layer;
It is characterized in that the above-mentioned problem is solved by setting the variation of the Al composition to 0.005 / nm or less. In particular, the above Al
The above problem is solved by setting the Al composition of the GaN barrier layer in contact with the active layer to 0.1 to 0.5.

In the present invention, the above-mentioned AlGa
The above problem is solved by setting the thickness of the N barrier layer to 10 to 100 [nm].

In the present invention, in particular, the above AlGa
When the N barrier layer is provided on the p-contact layer side of the active layer, a barrier layer having good electrical characteristics can be formed by adding an acceptor impurity.

In particular, by increasing the concentration distribution of the acceptor impurity on the side in contact with the active layer and increasing the impurity concentration on the side opposite to the side in contact with the active layer, electrical characteristics can be maintained while maintaining high luminous efficiency. A good barrier layer can be formed. The impurity concentration depends on the acceptor impurity.
When it is Mg, its impurity concentration is 1 × 10 ¹⁸ to 8 × 10 ¹⁹ [cm ⁻³ ] in a portion in contact with the active layer, and 1 × 10 ²⁰ to 5 × 10 ²⁰ [in a portion in contact with the opposite layer. cm ⁻³ ], a semiconductor element having good element characteristics can be obtained.

Further, in the present invention, the above Al
When the GaN barrier layer is provided on the n-contact layer side of the active layer, a barrier layer having good electrical characteristics can be formed by adding a donor impurity.

In particular, by increasing the concentration distribution of the donor-type impurity on the side in contact with the active layer and increasing the impurity concentration on the side opposite to the side in contact with the active layer, electrical characteristics can be maintained while maintaining high luminous efficiency. A good barrier layer can be formed. When the donor impurity is Si, the impurity concentration is 1 × 10 ¹⁶ to 6 × 10 ¹⁷ [cm ⁻³ ] at a portion in contact with the active layer, and is in contact with the opposite layer. In part, 8 × 10 ¹⁷ to 5 × 10 ¹⁸ [cm ^-3 ]
By doing so, a semiconductor element having good element characteristics can be obtained.

In the present invention, the growth temperature of the active layer is T1, the growth temperature of the barrier layer is T2, the growth temperature of the barrier layer on the side opposite to the side in contact with the active layer is T3, and the growth temperature T3
Is higher than T1, the barrier layer is grown at a growth temperature T2 of T1 or higher and T3 or lower to manufacture a semiconductor light emitting device. In particular, in order to solve the problem, the barrier layer is continuously grown while the temperature is raised from the growth temperature of the active layer to the growth temperature of the layer on the side opposite to the side in contact with the active layer of the barrier layer. Can be manufactured.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to a schematic sectional view showing the structure of a light emitting diode shown in FIG.

FIG. 1 shows a pn (double hetero) structure.
It is sectional drawing of a junction type light emitting diode. The structure is as shown below. For example, a low-temperature buffer layer 12 made of GaN, a Si-doped GaN layer 13 as an n-type contact layer, an InGaN layer 14 as an active layer, a barrier layer Mg-doped AlGaN layer 1
5, and a Mg-doped GaN layer 16 as a p-type contact layer.

Further, from the Mg-doped GaN layer 16 to the Si-doped GaN layer
13 are etched until the Si-doped GaN layer 13 is exposed on the surface, and an electrode 20 is formed on the Mg-doped GaN layer 16 and an electrode 21 is formed on the Si-doped GaN layer 13.

The InGaN layer 14, which is an active layer, can change the emission wavelength of the light emitting diode by changing the In composition, and can emit light from a wavelength in the ultraviolet region to a red wavelength. .

The Mg-doped AlGaN layer 15 which is a feature of the present invention
Functions as a barrier layer for carriers injected into the InGaN layer, which is an active layer, and further has a function of protecting the InGaN layer, which is a layer containing In, which is easily decomposed and deteriorated at high temperatures.

In view of the function as a barrier layer, this layer is expected to have a somewhat large band gap, that is, a high Al composition. Also, as a protective layer for the InGaN layer, it is considered that a higher Al composition has better thermal resistance, so a higher Al composition is preferable. Generally, preferably, the Al composition is 0.1 to 0.1.
5, most preferably 0.1 to 0.3. If the Al composition is lower than 0.1, it is not enough to function as a barrier layer,
On the other hand, when the Al composition is larger than 0.5, defects such as cracks are likely to occur.

However, Mg-doped GaN as a contact layer
In order to inject carriers from the layer 16 into the InGaN layer 14 as the active layer, it is preferable that the energy barrier by the Mg-doped AlGaN layer 15 is not so large, that is, the Al composition is small.

The Mg-doped AlGaN layer is difficult to form a low-resistance p-type conductive layer, and the tendency is particularly remarkable when the Al composition is high. Furthermore, an AlGaN layer having a high Al composition tends to have poor crystallinity. Therefore, if a film with a high Al composition is laminated thickly, the series resistance of the element increases,
There is also a problem that the injection of carriers into the active layer becomes worse.

Considering these facts, when the present invention is used, in the Mg-doped AlGaN layer 15, the contact layer on the opposite side from the InGaN layer 14, which is the active layer, to the contact layer on the opposite side.
By continuously decreasing the Al composition toward the g-doped GaN layer 16, compared to the case where the Al composition is kept constant,
It is possible to improve the carrier injection efficiency while having the original function of the N layer sufficiently.

Further, in the present invention, Mg-doped AlGaN
In the layer 15, when the Al composition is continuously changed, the rate of change with respect to the layer thickness is specified, thereby improving the element characteristics. This is because, when the Al composition is changed, the distribution of the intrinsic lattice strain in each minute region changes depending on the rate of change, and the state of the strain is changed to the active layer which is adjacent to the layer and easily affected. On the other hand, crystalline,
This is considered to have affected the light emission characteristics.

As the change rate α of the Al composition, the difference between the maximum value (the portion in contact with the active layer) and the minimum value (the portion on the side opposite to the active layer) of the Al composition is ΔAl, and the thickness of the layer is t. [Nm]
And is calculated by α = ΔAl / t. The change rate α and the change in the device characteristics are as shown in FIG. 3 when t = 20 [nm] and the Al composition maximum value (portion in contact with the active layer) is 0.1, 0.2, and 0.3. From this figure, it is understood that it is better to set α to be larger than 0 and equal to or smaller than 0.005. When α is 0.005 or more, the device characteristics deteriorate for the above-described reason. Also, when α is 0, that is, when the Al composition does not change, the device characteristics are worse than when α is larger than 0 and 0.005 or less for the above-described reason.

It is desirable that the maximum value of the Al composition be 0.1 to 0.5. If it is less than 0.1, the function as a barrier layer will not be sufficient, and if it is more than 0.5, the lattice distortion will be too large and cracks will easily occur, which will have a large adverse effect on device characteristics. More preferably, it is 0.1 to 0.3.

The layer thickness is desirably 10 to 100 [nm]. When the thickness is less than 10 [nm], the function of confining carriers as a barrier layer becomes insufficient. On the other hand, when the thickness is 100 [nm] or more, not only is the thickness too large, cracks are likely to occur, but also the efficiency of carrier injection into the active layer tends to deteriorate, which is not preferable.

From the above, in order to sufficiently obtain the original function of the AlGaN barrier layer, the Al composition is reduced in the direction away from the active layer side as in the present invention, and the Al composition is reduced. It is understood that it is important to define the rate of change and the layer thickness.

As for the addition of impurities to the barrier layer, donor impurities are added when the barrier layer is provided on the n-type contact layer side of the active layer, and acceptor impurities are added when the barrier layer is provided on the p-type contact layer side. However, it is desirable that the impurity concentration in the stacking direction be low on the side in contact with the active layer and high on the side away from the active layer. This is because, when an impurity is added at a high impurity concentration to a portion in contact with the active layer, the impurity is diffused in the stacking direction through threading dislocation near the active layer, and as a result, the diffusion of the acceptor impurity causes light emission efficiency and the like. This is due to the deterioration of the element characteristics.

For example, in the case of an acceptor impurity such as Mg, 1 × 10 ¹⁸ to 8 × 10 ¹⁹ [cm ⁻³ ],
1 × 10 ²⁰ to 5 × 10 ²⁰ [cm on the side opposite to the side in contact with the active layer
^-3 ]. On the other hand, in the case of a donor impurity such as Si, 1 × 10 ¹⁶ to 6 × 10
¹⁷ [cm ^-3 ], 8 × 10 ¹⁷ to 5 on the side opposite to the side in contact with the active layer
It is desirable to set to × 10 ¹⁸ [cm ⁻³ ].

Hereinafter, the present invention will be described with reference to specific embodiments.

(Embodiment 1) In this embodiment, a light emitting diode of a group III-V nitride compound semiconductor was manufactured by using the present invention. Using a MOCVD apparatus, the source gas was trimethylgallium, trimethylaluminum, trimethylindium as an organometallic compound containing a group III element, ammonia as a hydride containing a group V element, and bis as a p-type impurity as a source gas for impurities. Semiconductor layers were grown using cyclopentadienyl magnesium and silane as n-type impurities.

FIG. 1 shows a p having a DH structure manufactured in this embodiment.
1 shows a cross-sectional view of an n-junction light emitting diode. The structure is as shown above. FIG. 2 is a cross-sectional view of the semiconductor device illustrating a manufacturing process of the semiconductor device according to the present embodiment.

First, the cleaned sapphire substrate 11 is introduced into the MOCVD apparatus, and the substrate temperature is set to 1100 in an atmosphere of H ₂ gas.
Perform cleaning at ℃. Next, reduce the substrate temperature to 60
The temperature was set to 0 ° C., and trimethylgallium and ammonia were used as source gases and introduced into the reactor, and a GaN buffer layer 12 was grown on the sapphire substrate 11 by 30 [nm]. Then, the substrate temperature was set to 1050 ° C., and trimethylgallium, ammonia, and silane were used as source gases, and introduced into the reactor.
On the N buffer layer 12, a Si-doped GaN layer 13 was grown at 4 [μm]. Thereafter, the substrate temperature was set to 750 ° C., trimethylgallium, trimethylindium, and ammonia were introduced into the reactor as source gases, and an InGaN layer 14 having an In composition of 0.3 was formed on the Si-doped GaN layer 13 as an active layer by 2 [ nm].

Next, the substrate temperature was set at 1050 ° C., and trimethylgallium, trimethylaluminum, ammonia,
Biscyclopentadienyl magnesium is introduced into the reactor as a source gas, and the Al composition, which is a feature of the present invention, is continuously changed on the InGaN layer 14 as a barrier layer.
The Mg-doped AlGaN layer 15 was grown at 20 [nm]. The Al composition distribution was set as follows. InG of Mg-doped AlGaN layer 15
The Al composition was continuously reduced so that the Al composition was 0.2 at the interface in contact with the aN layer 14 and 0.12 at the interface opposite to the side in contact with the InGaN layer 14. At this time, the change rate of the Al composition is 0.004 / nm. The reason for changing the Al composition is as follows.
This is possible by changing the supply amounts of trimethylgallium and trimethylaluminum. Also,
In the Mg-doped AlGaN layer 15, the Mg impurity concentration is 2
It grew at a constant value of × 10 ²⁰ [cm ⁻³ ].

Further, the substrate temperature was set to 1050 ° C., and trimethylgallium, ammonia, and biscyclopentadienyl magnesium were introduced into the reactor as source gases,
On the Mg-doped AlGaN layer 15, the Mg-doped GaN layer 16 is 0.1 [μm]
grown.

Through the above steps, the gallium nitride-based III-V compound semiconductor multilayer structure shown in FIG. 2A can be manufactured.

Subsequently, the obtained semiconductor laminated structure is thermally annealed at 800 ° C. in, for example, an N ₂ atmosphere to obtain M
The resistance of the g-doped AlGaN layer 15 and the Mg-doped GaN layer 16 was reduced. Next, a photoresist film 22 is provided on the semiconductor surface of the semiconductor multilayer structure, and a part thereof is removed by photolithography. Then, etching is performed by RIE using the remaining photoresist film as a mask, and as shown in FIG. 2 (b), the Mg-doped GaN layer 16 is
The etching is performed until a part of the doped GaN layer 13 is exposed on the surface.

Thereafter, the photoresist film was peeled off, and FIG.
As shown in (c), a negative electrode is formed on the Si-doped GaN layer 13.
Ni as a positive electrode on the Ti / Al electrode layer 21 and the Mg-doped GaN layer 16
A metal film of the / Au electrode layer 20 is deposited to produce an electrode.

The light emitting diode chip can be obtained by dividing the thus obtained semiconductor laminated structure by dicing or the like.

When the characteristics of the light emitting diode chip obtained in the above steps were measured, an emission wavelength of 470 [nm] and an emission output of 1.7 [mW] could be obtained when the current was driven at 20 [mA].

Next, as a comparative example, the Al composition of the Mg-doped AlGaN layer 15 was made constant at 0.2 and 30
[Nm] Shows the case of lamination. Up to the growth of the InGaN layer 14, the same as in the previous embodiment, but with the Mg-doped AlGaN layer 15
Was grown at a constant Al composition of 0.2 nm. At this time, the change rate of the Al composition is 0 / nm. Thereafter, a semiconductor device was manufactured in the same manner as in the above-described embodiment.
When the characteristics of the light emitting diode chip obtained in this step were measured, the light emission wavelength was 47 when the current was driven at 20 mA.
0 [nm] and an emission output of 1.3 [mW] were obtained.

As another comparative example, Mg-doped AlGaN
The case where the Al composition of the layer 15 is greatly changed is shown. Si dope
Until the InGaN layer 14 is grown, the same as in the previous embodiment, except that the Al composition of the Mg-doped AlGaN layer 15 is 0.2 at the interface in contact with the InGaN layer 14, and 0.08 on the side opposite to the side in contact with the InGaN layer 14. , 30 [nm]. At this time, the change rate of the Al composition is 0.006 / nm. Thereafter, a semiconductor device was manufactured in the same manner as in the above-described embodiment. When the characteristics of the light emitting diode chip obtained in this step were measured, the emission wavelength was 470 [n] when the current was driven at 20 [mA].
m] and an emission output of 1.4 [mW].

As described above, by using the present invention, the characteristics of the light emitting element could be improved.

(Embodiment 2) In this embodiment, a group III-V nitride compound semiconductor light emitting diode was manufactured by using the present invention.

In this embodiment, the AlGaN barrier layer in contact with the active layer was manufactured by continuously changing the growth temperature. FIG. 4 shows a cross-sectional view of the light emitting diode manufactured in this embodiment. This laminated structure was manufactured as shown below.

First, a GaN buffer layer 12 having a thickness of 30 [nm], a Si-doped GaN layer 13 and an InG
Until the aN layer 14 was laminated, it was manufactured in the same manner as in the previous embodiment. Subsequently, the barrier layer 30 was manufactured by the following method.

While continuously changing the substrate temperature from 750 ° C. to 1050 ° C., trimethylgallium, trimethylaluminum, ammonia and biscyclopentadienylmagnesium were introduced into the reactor as source gases, and the
On the N layer 14, a Mg-doped AlGaN layer 30 having a continuously changing Al composition, which is a feature of the present invention, was grown to a thickness of 40 [nm]. At this time, the distribution of the Al composition is such that the InGaN layer of the Mg-doped AlGaN layer 15
The Al composition at the interface in contact with 14 was 0.18, and the Al composition at the interface opposite to the side in contact with the InGaN layer 14 was 0.16.
At this time, the change rate of the Al composition is 0.0005 / nm. Further, in the Mg-doped AlGaN layer 15, the Mg impurity concentration was grown at a constant value of 2 × 10 ²⁰ [cm ⁻³ ].

Thereafter, similarly to the first embodiment, Mg-doped GaN
Layer 16 was grown 0.1 [μm].

A semiconductor laminated structure was manufactured as described above, and thereafter, a Ni / Au electrode layer 20 and a Ti / Al electrode layer 21 were formed by the same process as in the previous embodiment, and a light emitting diode was manufactured.

When the characteristics of the light emitting diode chip thus obtained were measured, an emission wavelength of 470 [nm] and an emission output of 1.7 [mW] could be obtained when the current was driven at 20 [mA].

The result can be explained as follows.

The feature of this embodiment is that after growing the InGaN active layer, the Mg-doped AlGaN barrier layer is continuously grown when the substrate temperature is raised while growing the Mg-doped GaN layer as the p-type contact layer. Is to do. By this method
The Al composition of the Mg-doped AlGaN barrier layer can be changed. This is based on the trimethylaluminum
This is considered to be due to the difference in the reaction rate depending on the substrate temperature of trimethylgallium, which is a Ga raw material.

In the light emitting diode thus manufactured, the Al composition decreases from the active layer side to the contact layer side in the Mg-doped AlGaN barrier layer, and the change rate thereof is an appropriate value. The device characteristics are good.

Further, according to this method, after growing the InGaN active layer, the next Mg-doped AlGaN barrier layer is grown without exposing the unstable InGaN layer as a crystal to a high-temperature atmosphere. Can be suppressed. As a result, an element having good emission characteristics can be manufactured.

As described above, in the present embodiment, the Al composition of the AlGaN barrier layer was changed, and at the same time, the thermal degradation of the InGaN active layer could be suppressed, so that the device characteristics could be improved.

In this embodiment, the Al composition is changed by changing the substrate temperature. However, it is also possible to control the Al composition by combining the change in the substrate temperature with the change in the supply amounts of the Al raw material and the Ga raw material. , Of course it is possible.

In this embodiment, the AlGaN barrier layer 30 is continuously grown after the growth of the InGaN active layer 14 until the growth of the Mg-doped GaN layer 16. Alternatively, the AlGaN barrier layer may be grown by growing only in a certain temperature range.

(Embodiment 3) In this embodiment, a group III-V nitride compound semiconductor light emitting diode was manufactured by using the present invention.

In this embodiment, an AlGaN barrier layer in which the Al composition changes continuously is provided not only on the p-type conduction side but also on the n-type conduction side so as to be in contact with the active layer, thereby producing a light emitting diode. FIG. 5 shows a cross-sectional view of the light emitting diode manufactured in this embodiment. This laminated structure was manufactured as shown below.

First, a GaN buffer layer 12 was formed on the substrate 11 by 30 [nm], and a Si-doped GaN layer 13 as an n-type contact layer was formed in the same manner as in the first embodiment.

Next, subsequently, a barrier layer 40 was formed by the following method.

The substrate temperature was set to 1050 ° C., and trimethylgallium, trimethylaluminum, ammonia and silane were introduced into the reactor as source gases, and the Si-doped GaN layer 13 having an Al composition continuously changing was formed. AlGaN layer 40
Was grown to 20 [nm]. The Al composition distribution was set as follows. The Al composition was continuously increased so that the Al composition was 0.05 at the interface of the Si-doped AlGaN layer 40 in contact with the GaN layer 13 and 0.15 at the interface opposite to the side in contact with the GaN layer 13. At this time, the change rate of the Al composition is 0.005 / nm.

Further, the distribution of the Si impurity concentration in the Si-doped AlGaN layer 40 in the thickness direction is 1 × 10 3 at the interface in contact with the GaN layer 13.
¹⁸ [cm ⁻³ ], 5 × at the interface opposite to the side in contact with the GaN layer 13
It was continuously reduced to 10 ¹⁷ [cm ^-3 ].

Thereafter, as in the first embodiment, an InGaN active layer 14 was grown.

Mg-doped AlG formed on InGaN active layer 14
The aN layer 41 was continuously reduced so that the Al composition on the side in contact with the active layer was 0.15 and the Al composition on the side opposite to the side in contact with the active layer was 0.05. At this time, the change rate of the Al composition is 0.005 / nm
Becomes

The distribution of the Mg impurity concentration in the Mg-doped AlGaN layer 40 in the thickness direction is 5 × 10 5 at the interface in contact with the active layer.
¹⁹ [cm ^-3 ], 3 × 1 at the interface opposite to the side in contact with the active layer
It was continuously increased so as to be 0 ²⁰ [cm ^-3 ].

Thereafter, as in Embodiment 1, Mg
A doped GaN layer 16 was grown.

A semiconductor multilayer structure was manufactured as described above, and thereafter, a light emitting diode was manufactured through the same process as in the previous embodiment.

When the characteristics of the light emitting diode chip thus obtained were measured, a light emission wavelength of 470 [nm] and a light emission output of 1.6 [mW] could be obtained when the current was driven at 20 [mA].

The result can be explained as follows.

In this embodiment, an AlGaN barrier layer whose Al composition changes continuously is introduced not only into the barrier layer on the p-layer side of the active layer but also on the n-layer side. As a result, not only electrons but also holes are well confined, and it is considered that the device exhibited good characteristics.

Embodiment 4 In this embodiment, a group III-V nitride compound semiconductor laser diode was manufactured by using the present invention.

FIG. 6 shows a cross-sectional view of the manufactured laser diode.

The laminated structure includes a low-temperature buffer layer 52 of GaN, a Si-doped GaN layer 53 as an n-contact layer, an InGaN layer 54 as a crack prevention layer, an AlGaN layer 55 as an n-cladding layer, GaN layer 56 as a guide layer,
InGaN layer 57 as active layer, Al as barrier layer on p layer side
The GaN layer 58 includes a GaN layer 59 as a guide layer, an AlGaN layer 60 as a p-cladding layer, and a GaN layer 61 as a p-contact layer.

The laminated structure was manufactured as shown below.

First, up to the GaN layer 53 as the n-contact layer, the same method as in the first embodiment was used. Next, the substrate temperature was set to 800 ° C., trimethyl gallium, trimethyl indium, ammonia, and silane were used as source gases and introduced into the reactor, and a Si-doped InGaN layer 54 having an In composition of 0.07 was formed on the GaN layer 53. [Nm].

Thereafter, the substrate temperature was set to 1050 ° C., and trimethylgallium, trimethylaluminum, ammonia, and silane were introduced into the reactor as source gases, and the
On the GaN layer 54, a Si-doped AlGaN layer 55 having an Al composition of 0.10 is
[Μm], and trimethylgallium, ammonia, and silane were introduced into the reactor as source gases,
On the AlGaN layer 55, a Si-doped GaN layer 56 is grown to a thickness of 0.1 [μm].

Then, the substrate temperature was set again to 750 ° C., and trimethylgallium, trimethylindium, ammonia, and silane were introduced into the reactor as source gases, and a Si-doped InGaN having an In composition of 0.18 was formed on the GaN layer 56. Layer 2
[Nm] and In composition of 0.05% of Si-doped InGaN layer
The two layers were defined as one cycle, and the five layers were stacked to grow an InGaN active layer 57 having a multiple quantum well structure.

Next, while continuously changing the substrate temperature from 750 ° C. to 1050 ° C., trimethylgallium, trimethylaluminum, ammonia, and biscyclopentadienylmagnesium were introduced into the reactor as source gases to form an InGaN layer. 57, on which Mg whose Al composition is continuously changing
The doped AlGaN layer 58 was grown at 30 [nm]. At this time, Al
The composition distribution was such that the Al composition was 0.25 at the interface of the Mg-doped AlGaN layer 58 in contact with the InGaN layer 57, and 0.15 at the interface opposite to the side in contact with the InGaN layer 57. At this time,
The change rate of the Al composition is 0.0033 / nm.

Then, the substrate temperature was set at 1050 ° C., trimethylgallium, ammonia and biscyclopentadienylmagnesium were introduced as source gases into the reactor, and the Mg-doped GaN layer 59 was deposited on the AlGaN layer 58 by 0.1 μm. ], And trimethylgallium, trimethylaluminum, ammonia, and biscyclopentadienylmagnesium are introduced into the reactor as source gases, and a Mg-doped AlGaN layer 60 having an Al composition of 0.1 is formed on the GaN layer 59 by 0.45 mm. [Μm], and finally, trimethylgallium, ammonia and biscyclopentadienylmagnesium were introduced into the reactor as source gases, and a Mg-doped GaN layer was formed on the AlGaN layer 60.
61 grown 0.1 [μm].

The semiconductor laminated structure is manufactured as described above, and thereafter, the n-layer electrode 64 is manufactured using the same process as in the previous embodiment, and the p-layer electrode 63 is similarly formed by photolithography. An electrode stripe type laser diode was manufactured by using this to form a stripe-shaped electrode.

In this example, an electrode having a Pd / Au laminated structure was used as the p-layer electrode.

The characteristics of the laser diode chip thus obtained were measured.
When the laser was continuously oscillated at room temperature at [kA / cm ^-2 ] and an oscillation wavelength of 408 [nm], and was driven at a constant output of 2 [mW], the life was about 100 hours.

Embodiment 5 In this embodiment, a group III-V nitride-based compound semiconductor laser diode was manufactured by using the present invention.

FIG. 7 shows a cross-sectional view of the manufactured laser diode.

The feature of this structure is that GaN is used as the substrate. This GaN substrate 71 was produced as follows. FIG. 8 shows a schematic diagram of the manufacturing process.

First, a GaN layer 83 is grown on a sapphire substrate 81 by 2 [μm] via a GaN buffer layer 82 with a MOCVD apparatus as described in the previous embodiment.

Thereafter, the sample was taken out of the reactor, and the photolithography technique was used to form a GaN layer of <10-10
> Layer parallel to the direction, width 5 [μm], period 10 [μm], layer thickness 100
A [nm] stripe-shaped SiO ₂ layer 84 is formed.

Next, this wafer is introduced into an HVPE apparatus using Ga, HCl, and NH ₃ as raw materials. In this HVPE apparatus, a wafer is placed in a heated reactor, and GaCl and NH ₃ generated by reacting Ga and HCl in another heating area are introduced into the reactor, and a GaN film is formed on the wafer. It is a device that can grow.

Using this HVPE apparatus, a GaN layer 85 was grown at 300 [μm] at a substrate temperature of 1000 ° C.

Then, the wafer is taken out and the sapphire substrate is removed by polishing, so that the layer thickness is about 300 [μm].
A GaN substrate was produced.

In this step, the base layer
The GaN layer 93 was grown by the MOCVD apparatus.
This is because the controllability of crystal growth is good, but this underlayer may be grown by an HVPE apparatus. In this step, the Si
The GaN film is grown in two stages using an O ₂ mask, because this allows the dislocation density near the substrate surface to be reduced and a GaN substrate with good crystallinity to be obtained. However, even without such two-stage growth, for example, several hundred [μm] directly on sapphire by HVPE equipment
GaN layers may be grown.

Using the GaN substrate thus manufactured, a laser diode having a laminated structure shown in FIG. 7 was manufactured.

In this embodiment, since a GaN substrate was used, a laminated structure was formed without growing a GaN low-temperature buffer layer.

Further, the AlGaN layer 72 as a barrier layer is changed from the substrate temperature of 750 ° C.
The substrate was continuously grown while raising the substrate temperature to 1050 ° C., which is the substrate temperature of the guide layer 59 on the side. The structure was prepared such that the Al composition was 0.18 on the side in contact with the active layer, the Al composition was 0.14 on the side opposite to the side in contact with the active layer, and the layer thickness was 20 [nm]. At this time, the change rate of the Al composition is 0.002 / nm.

Further, an AlGaN layer 73 as an n-cladding layer is
2.5-nm-thick Si-doped GaN layer and 5-nm-thick Al
One cycle of two layers of AlGaN having a composition of 0.20 is defined as 10
Fabricated as a structure having a superlattice structure grown with zero period,
Similarly, the AlGaN layer 74 as the p-cladding layer has a thickness of 2.5 [n
m] Mg-doped GaN layer with a layer thickness of 5 nm and an Al composition of 0.20
A two-layer AlGaN layer was used as one cycle, and was fabricated as a structure having a superlattice structure in which the two layers were grown for 100 cycles.

Except for these, it was manufactured in the same manner as in the fourth embodiment.

As described above, a semiconductor multilayer structure is manufactured, and Ga
On the side opposite to the side on which the laminated structure of the N substrate is formed, an n-layer electrode 7 is provided.
A Ti / Al electrode was formed as No. 5, and a stripe-shaped Pd / Au electrode was similarly formed on the p-layer electrode 63 by photolithography to produce an electrode-stripe laser diode.

The characteristics of the laser diode chip thus obtained were measured.
When the laser was continuously oscillated at room temperature at [kA / cm ^-2 ] and an oscillation wavelength of 405 [nm], and was driven at a constant output of 2 [mW], the life was about 500 hours.

In the present embodiment, a GaN substrate is used. However, a further effect can be obtained.

The difference in thermal expansion coefficient between GaN and sapphire is large. For example, when a group III-V nitride compound semiconductor laminated structure is formed on a sapphire substrate, the wafer on which the structure is formed is large at room temperature. Warped,
A large crystal lattice strain is applied to each layer.

Therefore, the lattice distortion due to the warpage of the wafer, the change in the state of the lattice distortion due to cracks or dislocations caused by relaxing the warp, and the change in the crystal state such as the deterioration of the crystallinity itself are affected by the lattice distortion. On the other hand, the optical characteristics affect the active layer which is easily affected, so that the light emitting characteristics of the active layer are deteriorated, or the controllability and reproducibility of the characteristics are problematic.

However, in the case of a GaN substrate, such a problem does not occur because there is no warping as in the case of a sapphire substrate.

Further, since the group III-V nitride-based compound semiconductor layer formed on a GaN substrate has a lower threading dislocation density than a layer formed on a sapphire substrate, for example, impurities generated through threading dislocations are generated. Diffusion can be suppressed, and as a result, a long-life element can be manufactured.
In addition, since leakage current flowing through threading dislocations can be suppressed, there is an advantage that a light-emitting element having high reverse breakdown voltage can be manufactured.

In the first to fourth embodiments, examples using a sapphire substrate have been described. However, in the first to fourth embodiments, a GaN substrate is used, as shown in the fifth embodiment. It has been confirmed that the effects of the present invention can be further exhibited.

Regarding the plane orientation of the GaN substrate, preferably, the (0001) plane, (1-100) plane, (11-20) plane, and (1
The (-101) plane, the (11-22) plane, and the (01-12) plane, and it has been confirmed that the same effects as those of the present invention can be obtained even if the plane orientation deviates by ± 2 degrees.

[0112]

According to the present invention, III-V
The luminous efficiency of the group III nitride compound semiconductor light emitting device can be improved.

[Brief description of the drawings]

FIG. 1 shows an example of an I manufactured by using the present invention, which is described in Embodiment 1.
1 is a structural sectional view of a II-V nitride-based compound semiconductor device.

FIG. 2 illustrates an example of an I manufactured using the present invention, which is described in Embodiment 1.
It is a figure which shows the manufacturing process of a group II-V nitride compound semiconductor device.

FIG. 3 is a diagram showing a correlation between a change ratio of an Al composition in an AlGaN barrier layer and characteristics of a light emitting diode element.

FIG. 4 shows an example of an I manufactured by using the present invention described in Embodiment 2.
1 is a structural sectional view of a II-V nitride-based compound semiconductor device.

FIG. 5 illustrates an example of an I manufactured using the present invention, which is described in Embodiment 3.
1 is a structural sectional view of a II-V nitride-based compound semiconductor device.

FIG. 6 shows an example of an I manufactured by using the present invention, which is described in Embodiment 4.
1 is a structural sectional view of a II-V nitride-based compound semiconductor device.

FIG. 7 shows an example of an I fabricated using the present invention, which was described in Embodiment 5.
1 is a structural sectional view of a group II-V nitride compound semiconductor device.

FIG. 8 is a diagram illustrating a manufacturing process of a GaN substrate described in Embodiment 5.

[Explanation of symbols]

11 Substrate 12 GaN low-temperature buffer layer 13 Si-doped GaN layer 14 InGaN active layer 15 Mg-doped AlGaN barrier layer 16 Mg-doped GaN layer 20 Ni / Au positive electrode layer 21 Ti / Al negative electrode layer 22 Photoresist layer 30 Mg-doped AlGaN barrier Layer 40 Si-doped AlGaN barrier layer 41 Mg-doped AlGaN barrier layer 51 Substrate 52 GaN low temperature buffer layer 53 Si-doped GaN contact layer 54 Si-doped InGaN crack prevention layer 55 Si-doped AlGaN clad layer 56 Si-doped GaN guide layer 57 InGaN multiple quantum well Active layer 58 Mg-doped AlGaN barrier layer 59 Mg-doped GaN guide layer 60 Mg-doped AlGaN cladding layer 61 Mg-doped GaN contact layer 62 SiO ₂ insulating layer 63 Pd / Au positive electrode layer 64 Ti / Al negative electrode layer 71 GaN substrate 72 Mg Doped AlGaN barrier layer 73 Si-doped AlGaN cladding layer 74 Mg-doped AlGaN cladding layer 75 Ti / Al negative electrode layer 81 Sapphire substrate 82 GaN low temperature buffer layer 83 GaN underlayer 84 SiO ₂ mask 85 GaN layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuki Furukawa 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka Inside Sharp Corporation (72) Inventor Jun Ogawa 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka Sharp Incorporated F term (reference) 5F041 AA03 AA11 AA40 CA04 CA34 CA40 CA49 CA58 CA77 5F073 AA04 AA45 AA51 AA55 CA07 CB07 CB10 CB19 DA05 DA25 EA29

Claims (10)

[Claims] 1. A nitride-based compound semiconductor light emitting device having a double hetero structure manufactured using a group III-V nitride-based compound semiconductor, wherein In _{[x] is used} as an active layer _.
The semiconductor layer in contact with the Ga _[1 - _x] N (0 ≦ x ≦ 1) layer is Al
_[y] Ga _[1-y] N (0 ≦ y ≦ 1), and the Al composition at the portion of the semiconductor layer in contact with the active layer is y1, and the Al composition at the portion opposite to the side in contact with the active layer is Is y2, and when the thickness of the semiconductor layer is t [nm], 0.1 ≦ y1 ≦ 0.5 and 0 ≦ y
2. A nitride-based compound semiconductor light emitting device, wherein 2 <y1, 0 <(y1-y2) /t≦0.005. 2. The semiconductor layer having a thickness of 10 to 100.
2. The nitride-based compound semiconductor light-emitting device according to claim 1, wherein the thickness is [nm]. 3. The nitride-based compound semiconductor light emitting device according to claim 2, wherein an acceptor impurity is added to said semiconductor layer. 4. The nitride compound according to claim 3, wherein the impurity concentration of the acceptor impurity added to the semiconductor layer increases from a side in contact with the active layer to a side opposite to the active layer. Semiconductor light emitting device. 5. When the acceptor impurity added to the semiconductor layer is Mg, the concentration of the impurity is 1 × 10 ¹⁸ to 8 × 10 5 in a portion in contact with the active layer.
¹⁹ is a [cm ^-3], the portion in contact with the layer on the opposite side, 1 × 10 ²⁰ from 5 × 10 ²⁰ [cm ^-3] nitride-based compound according to claim 4, characterized in that the Semiconductor light emitting device. 6. The nitride-based compound semiconductor light emitting device according to claim 2, wherein a donor impurity is added to said semiconductor layer. 7. The nitride-based compound according to claim 6, wherein the impurity concentration of the donor impurity added to the semiconductor layer increases from a side in contact with the active layer to a side opposite to the active layer. Semiconductor light emitting device. 8. When the donor impurity added to the semiconductor layer is Si, the impurity concentration is 1 × 10 ¹⁶ to 6 × 10 ¹⁷ [cm] in a portion in contact with the active layer.
^-3 ], and at the portion in contact with the opposite layer, 8
The nitride-based compound semiconductor light-emitting device according to claim 7, wherein the size is from × 10 ¹⁷ to 5 × 10 ¹⁸ [cm ⁻³ ]. 9. A semiconductor light emitting device having a second semiconductor layer on a side of the semiconductor layer opposite to a side in contact with the active layer,
The substrate temperature (T3) during the growth of the second semiconductor layer is higher than the substrate temperature (T1) during the growth of the active layer, and the substrate temperature (T2) during the growth of the semiconductor layer is the same as the substrate temperature (T2).
The method for manufacturing a nitride-based compound semiconductor light-emitting device according to any one of claims 2, 3, 4, 5, 6, 7, and 8, wherein 1) or more and (T3) or less. 10. After the active layer is grown at a substrate temperature (T1), the semiconductor layer is continuously grown while the temperature is raised from the substrate temperature (T1) to the substrate temperature (T3). The method according to claim 9, wherein the second semiconductor layer is grown at a growth temperature (T3).