JPH11233823A - Gallium nitride compound semiconductor light-emitting element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve emission brightness and emission output by doping a p-type impurity on an active layer, decreasing the concentration of the p-type impurity from a side in contact with a p-type layer to a side in contact with an n-type layer, and making specific at a side in contact with the n-type layer. SOLUTION: A buffer layer 2, an n-type layer 3, an active layer 4, a p-type clad layer 5, and a p-type contact layer 6 are laminated on a substrate 1 consisting of sapphire, a p-side electrode 7 is formed on the p-type contact layer 6, and an n-side electrode 8 is formed at the side of the n-type layer 3. Doping is made from a side in contact with the p-type clad layer 5 that is a p-type layer to that in contact with the n-type layer 3 in the active layer 4 so that Mg of a p-type impurity decreases. The concentration range of the p-type impurity is set to 1×10<16> cm<-3> or higher and 5×10<18> cm<-3> or less, thus forming a pn junction in the active layer and preventing the pn junction from being formed in the n-type layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride-based compound semiconductor light-emitting device used for an optical device such as a light-emitting diode or a laser diode, and in particular, can maintain a high luminous efficiency and greatly improve color purity. The present invention relates to a semiconductor light emitting device.

[0002]

2. Description of the Related Art Gallium nitride-based compound semiconductors have been widely used as semiconductor materials for visible light emitting devices and high-temperature operating electronic devices, and have been developed in the field of blue light emitting diodes.

The method of manufacturing a gallium nitride-based compound semiconductor is basically based on using an insulating sapphire as a substrate and growing a gallium nitride-based semiconductor thin film on the surface of the substrate by metal organic chemical vapor deposition. That is,
A more specific method of laminating a GaN-based compound semiconductor is as follows: a metal organic compound gas (trimethylgallium, trimethylaluminum, trimethylindium, ), And ammonia, hydrazine, or the like as a group V element source gas, and the temperature of the substrate is set to about 900 ° C. to 11 ° C.
Holding at a high temperature of 00 ° C., the n-type layer, the active layer and the p-type
In this method, a mold layer is grown, and these layers are laminated.

Although a light emitting device using a GaN-based compound semiconductor is useful as a device for emitting blue light as described above, it is somewhat delayed in terms of technical development as compared with a red or green light emitting device. Is seen. Such a delay in development is due to Ga
It is said that one of the reasons is that an appropriate material for the N-based compound semiconductor was not found, and it has been a conventional problem that the emission luminance and color purity are inferior to those of red and green light emitting elements.

For example, in order to improve the light emission luminance, a blue light emitting diode having a MIS structure in which a high-resistance i-type GaN-based compound semiconductor doped with a p-type impurity is laminated on an n-type GaN-based compound semiconductor. Is already known. However, even in the case of this MIS structure, both the light emission luminance and the light output tend to be insufficient, and there remains a difficulty in practical use as a light emitting element.

On the other hand, for example, Japanese Patent Application Laid-Open No. Hei 6-260680 discloses that a p-type impurity Zn and an n-type impurity S
There has been proposed a GaN-based compound semiconductor light emitting device using an n-type InGaN layer doped with i as an active layer as an active layer.
According to this publication, it is considered that blue emission intensity is increased due to an increase in the number of donor-acceptor pair emission, and the emission efficiency and emission intensity are significantly improved as compared with a MIS structure light-emitting element. I got it.

Further, Japanese Patent Application Laid-Open No. Hei 8-46240 discloses that
There is disclosed a light-emitting element in which a p-type light-emitting layer is formed by doping an acceptor impurity which is a p-type impurity and a donor impurity which is an n-type impurity. According to this publication, a high concentration of holes can be imparted to the light emitting layer, and the amount of electrons that can be injected deep into the light emitting layer can be increased. It is said that the number of light-emitting elements can be increased, and thereby the emission luminance can be improved.

Further, Japanese Patent Application Laid-Open No. 9-186362 discloses that a light emitting layer is doped with a donor impurity and an acceptor impurity, and output light is emitted between a donor impurity level and a valence band or between a conduction band and an acceptor level. A light-emitting element has been proposed in which light is emitted by an electronic transition between potential bands or between a conduction band and a valence band.

Although the light emitting devices described in these publications are different from each other in terms of p-type or n-type conductivity, each of them has p-type impurities and n-type impurities in an active layer serving as a light-emitting layer. It is the same in that they are doped at the same time. It is already known that the light emission intensity is significantly improved as compared with the conventional MIS structure type light emitting element.

[0010]

With the improvement of the light emission luminance, the light emitting element described in the above-mentioned publication can be used, for example, in the field of full color display for outdoor use. However, in the case of outdoor displays, in particular, daylight tends to interfere with the emission of light from the element, and therefore, in order to enhance visibility and display clear images, an even higher emission luminance is required than conventional ones. That is the current situation.

In addition, all of the light-emitting elements disclosed in each of the publications are, for example, DA-pair emission of a so-called donor-acceptor in which a p-type impurity as an acceptor impurity and a donor impurity emit light in a pair, and so on. It utilizes light emission related to the position.

However, the light emission related to the impurity level is:
Generally, it has a tendency to show a broad spectrum, and further has a property such that the peak wavelength shifts to a shorter wavelength side as the operating current increases. The former property, which tends to have a broad spectrum, affects the color purity of the emission characteristics, and, for example, narrows the color reproduction range when used in a full-color display. Further, if the peak wavelength shifts to the shorter wavelength side, the color reproduction range is similarly reduced when applied to a full color display.

As described above, the GaN-based compound semiconductor light emitting device utilizing the light emission related to the impurity level has insufficient light emission characteristics in view of the light emission characteristics. There are problems such as insufficient color purity and poor color purity.

The problem to be solved in the present invention is to obtain a light-emitting element having a high luminous luminance and luminous output and improved color purity so that it can be more suitably applied to a full-color display or the like.

[0015]

Means for Solving the Problems The present inventors have attempted to improve the color intensity of light emission while improving the light emission intensity.
The p-type impurity and the n-type impurity to be doped into the active layer were studied diligently. As a result, the p-type impurity is made to have a specific concentration distribution and a specific concentration range, and the p-type impurity is contained in the active layer.
By forming an n-junction, it has been found that not only the emission intensity but also the color purity are greatly improved. Further, if the distribution and range of the concentration of the p-type impurity are under the specified conditions, even if the active layer is doped with a small amount of the n-type impurity, the effect is small and may be negligible. understood.

That is, the present invention provides a gallium nitride-based compound semiconductor light emitting device in which an n-type layer made of a gallium nitride-based compound semiconductor, an active layer and a p-type layer are stacked on a substrate by metal organic chemical vapor deposition. And in the manufacturing method thereof, the active layer is doped with a p-type impurity such that the concentration decreases from the side in contact with the p-type layer to the side in contact with the n-type layer, so that the emission luminance and the color purity are improved. It was possible to improve.

According to such a light emitting device or a method of manufacturing the same, a pn junction can be formed in the active layer, so that luminous efficiency can be improved. Also, the p-type impurity has a conduction band of −
Since light emission between acceptor levels is not so doped as to be dominant, light emission using electron transition between the conduction band and the valence band can be used instead of light emission involving the acceptor level. An element is obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is directed to a gallium nitride-based compound semiconductor light emitting device in which an n-type layer made of a gallium nitride-based compound semiconductor, an active layer and a p-type layer are stacked on a substrate. Forming a pn junction in the active layer, wherein the active layer is doped with a p-type impurity such that the concentration tends to decrease from the side in contact with the p-type layer to the side in contact with the n-type layer. As a result, the injection of electrons and holes into the active layer can be performed more efficiently, which has the effect of improving the emission intensity.

According to a second aspect of the present invention, the p-type impurity is doped in a concentration range of 1 × 10 ¹⁶ cm ⁻³ to 5 × 10 ¹⁸ cm ⁻³ on the side in contact with the n-type layer. The gallium nitride-based compound semiconductor light-emitting device according to claim 1, wherein a pn junction can be easily formed in the active layer, and the light-emitting intensity and color purity can be appropriately increased.

According to a third aspect of the present invention, in the semiconductor device according to the first aspect, the p-type impurity is 1 × 1 on the side of the active layer that contacts the p-type layer.
3. The gallium nitride-based compound semiconductor light emitting device according to claim 2, which is doped in a concentration range of 0 ¹⁸ cm ^-3 or more and 5 × 10 ²⁰ cm ^-3 or less, wherein a pn junction can be easily formed in the active layer. It has an effect that the emission intensity and the color purity can be appropriately increased.

Incidentally, in the inventions of claims 2 and 3,
In addition to making it easier to form a pn junction in the active layer, by lowering the concentration of the p-type impurity on the side in contact with the n-type layer to a specific range, even if the p-type impurity is doped, this region can be formed. It can be n-type. By increasing the concentration of the p-type impurity on the side in contact with the p-type layer to a specific range, this region can be made p-type. Thus, a pn junction can be reliably formed in the active layer. Further, in such a concentration range of the p-type impurity, light emission due to electronic transition between the conduction band and the acceptor level is slight, and light emission due to transition between the conduction band and the valence band can be used.

According to a fourth aspect of the present invention, the active layer comprises:
4. The method according to claim _{1, wherein said material comprises} In _x Ga ₁ -xN (0 <x <1).
The gallium nitride-based compound semiconductor light-emitting device according to any one of the above, which has an effect of suppressing a decrease in crystallinity of the active layer because the active layer does not contain Al.

According to a fifth aspect of the present invention, there is provided the gallium nitride-based compound semiconductor light emitting device according to any one of the first to fourth aspects, wherein the p-type impurity is Mg. Since it is difficult to form a deep impurity level in the GaN-based compound semiconductor as compared with the type impurity, an effect is obtained in that an active layer in which light emission related to the acceptor level does not easily occur can be obtained.

According to a sixth aspect of the present invention, an n-type layer made of a gallium nitride-based compound semiconductor, an active layer, and a p-type layer are sequentially laminated on a substrate by metal organic chemical vapor deposition. In the method for manufacturing a gallium nitride-based compound semiconductor light emitting device, the active layer is doped with a p-type impurity such that the concentration decreases from the side in contact with the p-type layer to the n-type layer, and the pn junction Can be formed in the active layer.

The invention according to claim 7 is the gallium nitride-based compound semiconductor according to claim 6, wherein the p-type impurity is doped by diffusion of the p-type impurity contained in the p-type layer from the p-type layer. This is a method for manufacturing a light-emitting element, and has an effect of obtaining an active layer having a gradient concentration in which the concentration decreases from the side in contact with the p-type layer to the n-type layer.

The invention according to claim 8 is the method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to claim 7, wherein the p-type impurity is Mg.
Since a deep impurity level is less likely to be formed in the gallium nitride-based compound semiconductor than a type impurity, an active layer in which light emission related to the acceptor level hardly occurs is obtained.

Hereinafter, a specific example of the embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing the structure of a gallium nitride-based compound semiconductor light emitting device according to one embodiment of the present invention.

In FIG. 1, a substrate 1 made of sapphire
An n-type layer 3, an active layer 4, and a p-type cladding layer 5 are formed on the buffer layer 2 in this order from the bottom.
And a p-type contact layer 6 are laminated by metal organic chemical vapor deposition. Then, a p-side electrode 7 is formed on the p-type contact layer 6, and a part of the p-type cladding layer 5 and the active layer 4 is removed by etching to expose an n-side electrode 8 on the surface of the n-type layer 3. To form The material of the n-side electrode 8 can be a metal such as aluminum (Al) or titanium (Ti). Each of the p-side and n-side electrodes 7 and 8 is obtained by a metal evaporation method. Can be

As the buffer layer 2, GaN or GaAl
N, AlN, AlInN, or the like can be used. The active layer 4 is made of InGaN and doped with Mg as a p-type impurity in a predetermined concentration range.

As the p-type cladding layer 5, AlGaN, GaN, AlGaInN or the like can be used. GaN or InGaN can be used for the p-type contact layer 6. Then, the p-type cladding layer 5 and p
The p-type impurity doped into the p-type contact layer 6 is M
g is used.

Here, in the present invention, the active layer 4 is doped with Mg as an impurity. The doping of Mg is performed by diffusion from the p-type layer.

In this case, Mg is other p-type material such as Zn.
Since a deep impurity level is less likely to be formed in a GaN-based compound semiconductor than a p-type impurity, a deep p-type impurity level is not formed in the obtained light emitting device. Therefore, the active layer 4 in which light emission involving the acceptor level is unlikely to occur can be obtained. Further, by doping Mg by diffusion from the p-type layer, it is easier to suppress the doping of Mg into the entire active layer at a high concentration as compared with doping Mg into the active layer 4 directly. A gradient concentration in which the concentration of Mg decreases from the side in contact with the p-type layer to the side in contact with the n-type layer 3 can be easily formed.

Normally, the active layer 4 made of a gallium nitride-based compound semiconductor tends to show an n-type conductivity when undoped, and the concentration distribution of the p-type impurity as described above is formed in the active layer 4. Thus, the p-type layer on the high-concentration p-type layer side can have a p-type conductivity, and the n-type layer on the low-concentration n-type layer side can have an n-type conductivity type.

The active layer 4 is made of InGaN.
1 is not included. If Al is contained, the crystallinity tends to decrease, so that the crystallinity of the active layer 4 itself decreases.

Therefore, by forming the active layer 4 from an InGaN compound semiconductor containing no Al, the crystallinity can be kept high and the light emission characteristics do not deteriorate.

The present inventors have conducted intensive studies on a gallium nitride-based compound semiconductor light emitting device in order to maintain high emission luminance and emission luminance while improving color purity. As a result, a significant improvement can be achieved by using light emission due to electronic transition between the conduction band and the valence band, instead of using light emission involving impurity levels as described in the section of the prior art. This was obtained by knowledge.

That is, if the active layer 4 is doped with a p-type impurity at such a concentration that an acceptor level is not formed, light emission involving the acceptor level formed by the p-type impurity is used. Without this, light emission due to electronic transition between the conduction band and the valence band can be obtained. And p
It has been found that when the concentration of the type impurity, ie, Mg, is in the range of 1 × 10 ¹⁶ cm ⁻³ or more and 5 × 10 ²⁰ cm ⁻³ or less, improvements in both luminous efficiency and color purity can be obtained.

[0038] In the concentration range of 1 × 10 ¹⁶ cm ^-3 or less of Mg, it does not utilize luminescence D-A impurity level pair emission or the like is involved, the conduction band - electron transition between valence band It can be seen from the fact that a light emission wavelength similar to that at the time of undoping in which light emission is obtained is obtained. The concentration of Mg in the active layer is 5 × 10 ²⁰
When it is higher than cm ^-3 , light emission related to the acceptor level can be observed.

As described above, when doping is performed by specifying the concentration range of Mg, light emission due to the electron transition between the conduction band and the valence band can be obtained. With such light emission,
The emission spectrum tends to be sharper than the emission in which the impurity potential is involved, and even if the operating current increases, the peak wavelength hardly shifts to the short wavelength side, so that the color purity is improved.

Further, in the structure in which the active layer 4 is doped so that the concentration of Mg decreases from the side in contact with the p-type layer to the side in contact with the n-type layer 3, the pn junction is formed in the active layer 4
It can be formed inside. By providing a pn junction in the active layer 4 itself, a light emitting element with high luminous efficiency can be obtained. If the concentration of the p-type impurity, ie, Mg, on the side in contact with the n-type layer 3 is reduced, the pn junction becomes n-type.
Formation in the mold layer 3 is prevented. Further, when the concentration of Mg on the side in contact with the p-type layer is high, the efficiency of current injection into the active layer 4 can be increased, so that the luminous efficiency is further improved.

Here, the concentration range of Mg which is a p-type impurity to be doped into the active layer 4 is 1 × 10 ¹⁶ cm ^{−3 as described above.}
If the above is 5 × 10 ²⁰ cm ⁻³ or less, both luminous efficiency and color purity can be improved.

However, even in this concentration range, when the concentration of Mg on the side in contact with the n-type layer 3 is higher than 1 × 10 ¹⁸ cm ⁻³ , the entire active layer 4 tends to be p-type, It was found that the emission intensity was reduced. If the concentration of Mg is lower than 1 × 10 ¹⁶ cm ⁻³ , the pn junction is biased toward the p-type layer, or the entire active layer 4 becomes n-type, and the active layer 4 has a high resistance. It was also recognized that the emission intensity similarly decreased.

Further, the Mg concentration on the side in contact with the p-type layer is 5
When it was larger than × 10 ²⁰ cm ⁻³ , light emission related to the acceptor level was observed, and it was found that the color purity tended to decrease. Then, M on the side in contact with the p-type layer
If the concentration of g is less than 1 × 10 ¹⁸ cm ⁻³ , it becomes difficult to make this region a p-type, and a pn junction cannot be formed in the active layer 4, and the emission intensity tends to decrease. understood.

Here, in order to obtain the effect of improving both emission intensity and color purity, it is desirable that the active layer is not doped with n-type impurities. However, if the concentration of the p-type impurity, that is, Mg, doped in the p-type layer is the condition described above, the effect is negligible even if a small amount of the n-type impurity is doped. The formation of a joint is likewise possible. This is because, even when, for example, Si is doped at about 1 × 10 ¹⁷ cm ⁻³ as an n-type impurity, the p-type conduction type is maintained on the side of the active layer in contact with the p-type layer, and even on the side in contact with the n-type layer. This is because the n-type conductivity is maintained. Thus p
By maintaining the respective conductivity types of n-type and n-type, a pn junction can still be formed in the active layer, and no light emission related to the acceptor level is observed. That is, as long as the p-type conductivity is maintained on the side of the active layer that is in contact with the p-type layer, the effect of improving both emission intensity and color purity can be obtained even if n-type impurities are doped. it is obvious.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a semiconductor light emitting device of the present invention will be described based on a specific manufacturing method.

This embodiment shows a method for growing a gallium nitride-based compound semiconductor using a metal organic chemical vapor deposition method, which will be described with reference to FIG.

First, a sapphire substrate 1 having a mirror-finished surface is placed on a substrate holder in a reaction tube, and then the surface temperature of the substrate 1 is maintained at 1100 ° C. for 10 minutes, and the substrate is heated while flowing hydrogen gas. As a result, cleaning for removing dirt and moisture, such as organic substances, attached to the surface of the substrate 1 is performed.

Next, the surface temperature of the substrate 1 was lowered to 600 ° C., nitrogen gas as a main carrier gas was 10 liter / minute, ammonia was 5 liter / minute, and trimethyl aluminum (hereinafter referred to as “TMA”). The buffer layer 2 made of AIN is grown to a thickness of 25 nm while flowing a carrier gas for TMA containing 20 cc / min.

Next, after stopping only the carrier gas of TMA and raising the temperature to 1050 ° C.,
While flowing nitrogen gas at 9 L / min and hydrogen gas at 0.95 L / min, a new carrier gas for trimethylgallium (hereinafter referred to as “TMG”) was added at 4 cc / min.
10% of SiH ₄ (monosilane) as a Si source
Growing for 60 minutes while flowing gas at 10 cc / min,
An n-type layer 3 made of GaN doped with Si is grown to a thickness of 2 μm.

After growing and forming the n-type layer 3, the carrier gas for TMG and the SiH ₄ gas are stopped, and the substrate surface temperature is reduced to 75%.
The temperature was lowered to 0 ° C., and nitrogen gas was newly added as a main carrier gas at 10 L / min.
c / min, while flowing a carrier gas for trimethylindium (hereinafter referred to as “TMI”) at 200 cc / min.
The active layer 4 made of InGaN is grown for 1 second for 1 second.
Grow at a thickness of 0 nm.

After forming the active layer 4, the carrier gas for TMI and the carrier gas for TMG are stopped, and the substrate surface temperature is reduced to 1 °.
The temperature was increased to 050 ° C., and 9 liters / minute of nitrogen gas, 0.90 liter / minute of hydrogen gas, 4 cc / minute of carrier gas for TMG, 6 cc / minute of carrier gas for TMA were newly added as main carrier gases. While flowing a carrier gas for biscyclopentadienyl magnesium (hereinafter referred to as “Cp ₂ Mg”) as a Mg source at a flow rate of 60 cc / min.
Then, the p-type cladding layer 5 made of Mg-doped AlGaN is grown to a thickness of 0.1 μm.

After growing and forming the p-type cladding layer 5, the TM
Carrier gas for A, carrier gas for TMG, and C
Stop the carrier gas for p ₂ Mg and set the substrate temperature to 105
The Mg doped in the p-type cladding layer 5 is diffused into the active layer 4 by keeping the temperature at 0 ° C. for 10 minutes.

Subsequently, at 1050 ° C., 9 L / min of nitrogen gas, 0.90 L / min of hydrogen gas and 4 mg of TMG carrier gas were newly used as main carrier gases.
GaN doped with Mg and grown for 3 minutes while flowing at a carrier gas of 100 cc / min for Cp ₂ Mg.
Is grown to a thickness of 0.1 μm.

After the growth, the carrier gas for TMG, the carrier gas for Cp ₂ Mg, and ammonia, which are the source gases, are stopped, and the wafer is cooled to room temperature while flowing nitrogen gas and hydrogen gas at the same flow rate. Remove from

With respect to the laminated structure made of the gallium nitride-based compound semiconductor including the pn junction thus formed,
After depositing a SiO ₂ film on the surface by a CVD method, the film is patterned into a predetermined shape by photolithography to form an etching mask. And
The p-type contact layer 6 is formed by reactive ion etching.
And a part of the p-type cladding layer 5 and the active layer 4 is about 0.25 μm
To expose the surface of the n-type layer 3. Then, an n-side electrode 8 made of Al is formed by vapor deposition on the surface of the n-type layer 3 exposed by photolithography and vapor deposition. Further, a p-side electrode 7 made of Ni and Au is formed on the surface of the p-type contact layer 6 in the same manner.

Thereafter, the back surface of the sapphire substrate 1 is polished to a thickness of about 100 μm, and separated into chips by scribing. In this way, p
A light-emitting element having an n-junction is obtained. In the active layer 4 of this light emitting device, the Mg concentration ranges from 1 × 10 ¹⁹ cm ⁻³ on the side in contact with the p-type cladding layer 5 to 2% on the side in contact with the n-type layer 3.
The gradient distribution was reduced to × 10 ¹⁷ cm ^-3 .

After the light emitting element is bonded to the stem with the electrode forming surface facing upward, the n-side electrode 8 and the p-side electrode 7 of the chip are connected to the respective electrodes on the stem with wires, and then resin-molded to emit light. A diode was fabricated. When this light emitting diode was driven with a forward current of 20 mA,
It emits blue light with a wavelength of 450 nm and has a spectral half width of 1
8 nm, and the light emission output was 1100 μW.

On the other hand, as a comparative example, in the step of growing the active layer 4 and the p-type clad layer 5 of the above embodiment, a nitrogen gas was newly added as a main carrier gas at 750 ° C. at a rate of 10 l / min. 2c carrier gas
c / min, the carrier gas for trimethylindium is 20
N-type InGa doped with Si and Zn is grown for 100 seconds while flowing 0 cc / min, 10 cc / min of a SiH ₄ gas, and 10 cc / min of a diethyl zinc gas as a Zn source.
An active layer 4 made of N is grown to a thickness of 10 nm. Thereafter, the carrier gas for TMI, the carrier gas for TMG, the SiH ₄ gas and the diethyl zinc gas are stopped, and the substrate surface temperature is increased to 1050 ° C. A light emitting device was manufactured in the same manner as in the example except that the mold clad layer 5 was grown. When this light-emitting diode was driven with a forward current of 20 mA, it emitted blue light with a wavelength of 450 nm. However, the spectral half-value width was 31 nm, which was larger than that of the example, the color purity was reduced, and the light emission output was 710 μW. Met.

In this embodiment, in order to diffuse the p-type impurity contained in the p-type layer from the p-type layer into the active layer 4, the substrate temperature is kept constant after growing the p-type cladding layer 5. A method of holding and diffusing Mg contained in the p-type cladding layer 5 into the active layer 4 was adopted. Alternatively, in order to diffuse Mg into active layer 4, after growing p-type contact layer 6, Mg contained in p-type cladding layer 5 is maintained while the substrate temperature is kept constant.
, A method of growing a p-type layer and then diffusing it in a relatively short time by increasing the substrate temperature, and a method of growing a p-type layer and then diffusing it in a relatively long time by lowering the substrate temperature. Can also be adopted. Since the diffusion of the p-type impurity into the active layer 4 depends on the concentration of the p-type impurity contained in the p-type layer, the retention time for the diffusion, the retention temperature, and the like, the p-type impurity doped into the active layer 4 is doped. It is desirable to appropriately change and adjust these so that the density of the above becomes the above-mentioned range.

[0060]

According to the first aspect of the present invention, since a pn junction can be formed in the active layer, a light-emitting element having high luminous efficiency can be obtained. Since the junction is prevented from being formed in the n-type layer and the p-type impurity concentration on the side in contact with the p-type layer is increased to increase the efficiency of current injection into the active layer, the luminous efficiency is further improved. Therefore, it can be used for a full-color display for outdoor equipment without any trouble.

According to the second and third aspects of the present invention, p
By optimizing the value of the mold impurity concentration, it is possible to obtain a light emitting device with further improved light emission output and color purity.

According to the fourth aspect of the present invention, since the active layer does not contain Al, a decrease in the crystallinity of the active layer is suppressed, and more stable light emission can be maintained.

According to the fifth aspect of the present invention, by forming Mg as the p-type impurity, a deep p-type impurity level can be prevented from being formed, and a light-emitting element which does not easily emit light related to the acceptor level can be obtained. be able to.

According to the sixth aspect of the present invention, since a pn junction can be formed in the active layer, a light emitting device having high luminous efficiency can be manufactured.

According to the seventh aspect of the present invention, the gradient concentration whose concentration decreases from the side contacting the p-type layer to the side contacting the n-type layer can be simply reduced as compared with the case where the p-type impurity is directly doped into the active layer. Can be built.

According to the eighth aspect of the present invention, it is possible to manufacture a light emitting element that does not easily emit light related to the acceptor level, and it is possible to obtain a light emitting element that does not easily emit light related to the acceptor level.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a gallium nitride-based compound semiconductor light emitting device according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 buffer layer 3 n-type layer 4 active layer 5 p-type cladding layer 6 p-type contact layer 7 p-side electrode 8 n-side electrode

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[Procedure amendment]

[Submission date] May 13, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is directed to a gallium nitride-based compound semiconductor light emitting device in which an n-type layer made of a gallium nitride-based compound semiconductor, an active layer and a p-type layer are stacked on a substrate. , A p-type impurity is doped into the active layer.
Is-loop reduces over the side in contact with the concentration of the p-type impurity into the p-type layer on the side in contact with the n-type layer, the n
5 × 1 at 1 × 10 ¹⁶ cm ⁻³ or more on the side in contact with the mold layer
0 ¹⁸ cm ⁻³ or less , and since a pn junction can be formed in the active layer, the injection of electrons and holes into the active layer is performed more efficiently, and the emission intensity and color purity are reduced. Suitable
Has the effect of Ru can be positively increased.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

According to a second aspect of the present invention, a substrate is provided on a substrate.
N-type layer made of gallium arsenide compound semiconductor, active layer, and p
Gallium nitride-based compound semiconductor light-emitting device with stacked layer
In the method, the active layer is doped with a p-type impurity.
Is, from the side in contact with the concentration of the p-type impurity before Symbol p-type layer
Decreasing toward the side in contact with the n-type layer,
5 × 10 ²⁰ c at 1 × 10 ¹⁸ cm ^-3 or more on the contact side
m ⁻³ or less , and since a pn junction can be formed in the active layer, injection of electrons and holes into the active layer is better.
It is performed more efficiently, and has an effect that emission intensity and color purity can be appropriately increased.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

The invention according to claim 3 is the invention according to claim 1.
Of the p-type impurity in the active layer in the invention
The concentration is 1 × 10 ¹⁸ cm ⁻³ on the side in contact with the p-type layer.
As described above, the range is set to 5 × 10 ²⁰ cm ⁻³ or less.
Since a pn junction can be formed in the active layer, electrons
In addition, holes are more efficiently injected, and the emission intensity and the color purity can be appropriately increased.

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[Correction contents]

According to the first, second and third aspects of the present invention, in addition to making it easy to form a pn junction in the active layer, the concentration of the p-type impurity on the side in contact with the n-type layer is set within a specific range. By lowering this range, even if a p-type impurity is doped, this region can be made n-type. By increasing the concentration of the p-type impurity on the side in contact with the p-type layer to a specific range, this region can be made p-type. Thus, a pn junction can be reliably formed in the active layer. Further, in such a concentration range of the p-type impurity, light emission due to electronic transition between the conduction band and the acceptor level is slight, and light emission due to transition between the conduction band and the valence band can be used.

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[Correction contents]

According to a fourth aspect of the present invention, an n-type layer made of a gallium nitride-based compound semiconductor, an active layer, and a p-type layer are sequentially laminated on a substrate by metal organic chemical vapor deposition. the method of manufacturing a gallium nitride-based compound semiconductor light-emitting device, the p-type impurity doped as tends to reduce the concentration from the side in contact with the p-type layer to the active layer over the side in contact with the n-type layer, wherein The concentration of the p-type impurity is
5 × at 1 × 10 ¹⁶ cm ⁻³ or more on the side in contact with the n-type layer
10 ¹⁸ cm ^-3 or less, on the side in contact with the p-type layer
1 × 10 ¹⁸ cm ^-3 or more and 5 × 10 ²⁰ cm ^-3 or less
The pn junction can be formed in the active layer, and the concentration can be increased from the side in contact with the p-type layer to the side in contact with the n-type layer.
Degrees has the effect that the active layer is Ru obtained inclined concentration decreases.

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[Correction contents]

[0060]

As described above, the gallium nitride system of the present invention is
According to the compound semiconductor light emitting device, the pn junction is formed in the active layer by lowering the p-type impurity concentration on the side in contact with the n-type layer.
Formation can also because it increases the efficiency of current injection into the active layer by increasing the p-type impurity concentration of the side in contact with the p-type layer, high emission efficiency gallium nitride-based compound semiconductor onset
An optical element is obtained. Therefore, it can be used for a full-color display for outdoor equipment without any trouble. Sa
Furthermore, to optimize the value of the p-type impurity concentration in the active layer
Nitridation with even higher emission output and color purity
A gallium compound semiconductor light emitting device is obtained.

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[Correction contents]

As described above, the gallium nitride based compound of the present invention
According to the manufacturing method of the semiconductor light emitting device, the n-type layer is in contact with the n-type layer.
The pn junction by lowering the p-type impurity concentration on the
P-type impurity which can be formed in the conductive layer and is in contact with the p-type layer.
The current injection efficiency into the active layer is increased by increasing the
Gallium nitride based compound with high luminous efficiency
A semiconductor light emitting device can be manufactured. Therefore,
Can be used without difficulty for full-color displays for outdoor equipment
can do. Furthermore, the p-type impurity concentration in the active layer
By optimizing the value of
Gallium nitride-based compound semiconductor light-emitting device with further improvement
Can be manufactured.

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Claims (8)

[Claims] 1. A gallium nitride-based compound semiconductor light emitting device in which an n-type layer made of a gallium nitride-based compound semiconductor, an active layer, and a p-type layer are stacked on a substrate. A gallium nitride-based compound semiconductor light-emitting device, characterized in that a concentration of the gallium nitride-based compound semiconductor light-emitting element decreases from the side in contact with the layer to the side in contact with the n-type layer. 2. The method according to claim 1, wherein the p-type impurity is doped in a concentration range of 1 × 10 ¹⁶ cm ⁻³ to 5 × 10 ¹⁸ cm ⁻³ on the side in contact with the n-type layer. Item 3. A gallium nitride-based compound semiconductor light emitting device according to item 1. 3. The semiconductor device according to claim 1, wherein the p-type impurity is not less than 1 × 10 ¹⁸ cm ^{-3 and not} more than 5 × 10 ¹⁸ cm ⁻³ on the side of the active layer that contacts the p-type layer.
3. The gallium nitride-based compound semiconductor light emitting device according to claim 2, wherein the gallium nitride-based compound semiconductor light emitting device is doped in a concentration range of ²⁰ cm ^-3 or less. 4. The active layer is composed of In _x Ga ₁ -xN (0 <x <
4. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the light emitting device comprises: 5. The gallium nitride based compound semiconductor light emitting device according to claim 1, wherein said p-type impurity is Mg. 6. A method according to claim 1, wherein said metalorganic vapor phase epitaxy method comprises:
In the method for manufacturing a gallium nitride-based compound semiconductor light emitting device in which an n-type layer made of a gallium nitride-based compound semiconductor, an active layer, and a p-type layer are sequentially stacked, the active layer is in contact with the p-type layer. A method for manufacturing a gallium nitride-based compound semiconductor light emitting device, comprising doping a p-type impurity as the concentration tends to decrease from the side to the n-type layer. 7. The gallium nitride-based compound semiconductor light emitting device according to claim 6, wherein the p-type impurity is doped by diffusion of the p-type impurity contained in the p-type layer from the p-type layer. Manufacturing method. 8. The method according to claim 7, wherein the p-type impurity is Mg.