JP3518289B2 - Gallium nitride based compound semiconductor light emitting device - Google Patents

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, and more particularly, it improves the current injection into the entire p-type layer to increase the light emission efficiency. The present invention relates to a gallium nitride-based compound semiconductor light emitting device that can be maintained.

[0002]

2. Description of the Related Art GaN, AlGaN, InGaN and A
Gallium nitride-based compound semiconductors such as lGaInN are attracting attention as semiconductor materials for visible light emitting devices such as green and blue and high temperature operating electronic devices, and particularly in the field of optical devices such as blue and green light emitting diodes and laser diodes. Deployment is progressing.

In the manufacture of an optical device using this gallium nitride compound semiconductor, sapphire is exclusively used as a substrate for crystal growth because there is no substrate that is lattice-matched with the gallium nitride compound semiconductor. When using an insulating substrate such as sapphire, another G
Unlike a light-emitting element using a semiconductor substrate having conductivity such as aAs or InP, electrodes cannot be taken out from the substrate side. Therefore, the p-side and n-side electrodes provided in the semiconductor layer are substrates in which semiconductor layers are stacked. Will be formed on one surface side.

Generally, a gallium nitride-based compound semiconductor light-emitting device is prepared by stacking an n-type layer and a p-type layer on the surface of a substrate by a metal organic chemical vapor deposition method or a molecular beam epitaxy method, and then
A partial region of the p-type layer is removed by etching to expose the n-type layer, and an n-side electrode and a p-side electrode are formed on the exposed surface of the n-type layer and the surface of the p-type layer, respectively. Can be obtained as

In such a semiconductor light emitting device, n
It has already been widely known that it is possible to improve the light emission output by forming a stack of a p-type layer and a p-type layer into a double hetero structure including an n-type clad layer, an active layer and a p-type clad layer. Has been. Also, a structure is provided in which a p-type clad layer made of AlGaN doped with magnesium (Mg) as a p-type impurity is provided, and a p-type GaN contact layer doped with Mg is provided as a layer on which an electrode is to be formed. If so, good ohmic contact with the electrode can be obtained, the forward voltage of the device can be lowered, and the light emission efficiency can be improved. A semiconductor light emitting device having such a structure is disclosed in, for example, Japanese Patent Laid-Open No. 6-268259.

By the way, a p-type layer of a gallium nitride-based compound semiconductor generally has a higher electric resistance than an n-type layer, so that a current hardly flows. Therefore, if a pad electrode for wire bonding is formed as a p-side electrode on the surface of the p-type layer by a vapor deposition method or the like, the current injected from the pad electrode does not spread in the layer direction of the p-type layer, and this pad electrode is The current tends to flow only to the lower side of the formed region.
Therefore, the light emission in the light emitting portion is limited to the region below the pad electrode, and the light traveling toward the p-type layer side is blocked by the pad electrode, so that the light emission efficiency is reduced.

On the other hand, for example, Japanese Patent Laid-Open No. 6-31482.
As disclosed in Japanese Patent Laid-Open No. 2 (1994), in order to make it easier to inject current into the entire p-type layer, not only the pad electrode portion,
It is effective to form a conductive thin film on the upper surface of the p-type layer and use it as an electrode.

If an electrode made of a conductive thin film is formed as a light-transmitting film on almost the entire surface of the p-type layer to form a light-transmitting electrode,
A configuration is possible in which the upper surface of the p-type layer serves as an emission observation surface from the light emitting section. As the translucent electrode, Au and Ni that can obtain ohmic contact with the p-type layer are preferably used.

FIG. 2 is a cross-sectional view showing the structure of the above-mentioned conventional gallium nitride-based compound semiconductor light-emitting device, which is typical of what has been mainstream these days.

In FIG. 2 , the substrate 1 using sapphire
The buffer layer 2, the n-type gallium nitride-based compound semiconductor layer 3, the light emitting layer 4 made of InGaN, the p-type cladding layer 5 made of Mg-doped AlGaN, and the Mg-doped G
A p-type contact layer 7 made of aN is sequentially formed. An n-side electrode 10 is provided on the n-type gallium nitride compound semiconductor layer 3, and a translucent electrode 8 made of Au and Ni is formed on almost the entire upper surface of the p-type contact layer 7. Further, a p-side pad electrode 9 for bonding is formed on the upper surface of the transparent electrode 8.

[0011]

As the translucent electrode 8, Ni and Au are preferably used as described above,
Film thickness of 1 to 5 nm for Ni and 5 to 20 n for Au
It is generally formed to have a film thickness of m. That is, although a metal such as Ni or Au is formed as an extremely thin film in order to obtain translucency, the light transmittance of light emitted from the light emitting layer 4 is not 100%. For example, for light emission of blue wavelength, the transmittance is 40% to 7%.
It is about 0%. Therefore, when the translucent electrode is formed on almost the entire surface of the p-type layer as in the above-described conventional structure, when the light from the light emitting layer passes through the translucent electrode, the amount of light is attenuated and the luminous efficiency is lowered. I will end up.

On the other hand, in order to increase the transmittance, the transparent electrode 8
If the thickness is made thin, the adhesiveness with the p-type contact layer 7 and the ohmic property are deteriorated due to variations in the thickness of the translucent electrode 8 and the current may not be uniformly injected into the p-type layer. . Therefore, it is not preferable to make the translucent electrode 8 extremely thin, and as a result, it tends to be unavoidable that the translucent electrode 8 has a transmittance within the above range.

As described above, the light-transmitting electrode 8 formed on the upper surface of the p-type layer preferably has as large an area as possible from the viewpoint of injecting current into the entire p-type layer. Since increasing the transmittance of the electrode is limited as described above, light is attenuated by the translucent electrode, and the luminous efficiency cannot be maintained sufficiently high.

The problem to be solved in the present invention is to obtain a light emitting device having a structure capable of reducing the area of the transparent electrode and improving the light emission efficiency by improving the spread of the current in the p-type layer. Is to

[0015]

A gallium nitride-based compound semiconductor light-emitting device of the present invention is a light-emitting device having an n-type layer, a light-emitting layer and a p-type layer made of a gallium nitride-based compound semiconductor thin film on a substrate. , The p-type layer is a Mg-doped layer.
The first layer, which is the tact layer, and a lower concentration than this first layer
A second layer for the lower resistivity by doping with Mg, the second
Of Mg to a higher concentration than the layer of
A third layer, the second layer being between the first and third layers
It is characterized by being formed .

With this structure, the spread of the current in the p-type layer is improved, and as a result, the area of the transparent electrode formed on the upper surface of the p-type layer can be reduced. Therefore, it is possible to reduce the proportion of light passing through the translucent electrode and increase the proportion of light directly extracted from the p-type layer to maintain high luminous efficiency.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a semiconductor light-emitting device having an n-type layer made of a gallium nitride-based compound semiconductor thin film, a light-emitting layer, and a p-type layer.
-Type layer and the first layer is a contact layer doped with Mg, and a second layer was doped with Mg less <br/> resistivity lower concentration than the first layer, the second Higher concentration than Mg
Including a third layer doped with a high resistivity
The layer is formed between the first layer and the third layer ,
Since the p-type layer includes the second layer having a low resistivity, the second layer has an effect that the current easily flows in the layer direction and the current spread is improved.

Further , the p-type layer includes a third layer having a resistivity higher than that of the second layer, and the second layer is formed between the first layer and the third layer. Since the p-type layer includes a layer having a low resistivity between two layers having a high resistivity, it is easy for a current to flow in the layer direction in this layer and the action of improving the spread of the current can be achieved. Have.

Further, the second layer than the first layer is a p-type impurity Mg are lightly doped, when the first layer of the contact layer, ensuring the ohmic property between the metal electrode In order to do so, high resistance is obtained by doping Mg in a high concentration. Therefore, the resistivity can be lowered by doping Mg in the second layer to a lower concentration than in the first layer. Therefore, the current easily flows in the second layer in the layer direction, and the current spread is improved.

The invention according to claim 2 is the invention according to claim 1, characterized in that the second layer contains at least indium, and the p-type impurity is doped by containing indium. Therefore, the resistivity can be easily reduced, and thus, the current easily flows in this layer in the layer direction, and the current spread is improved.

The invention according to claim 3 is the same as claim 1 or
In the invention described in 2 , the resistivity of the second layer is 1 to 1
It is characterized in that it is in the range of 0 Ω · cm,
For example, by providing a p-type layer including a layer having a high resistivity of 10 to 100 Ω · cm with a layer having a resistivity as low as one digit or more,
This layer has the effect of making it easier for current to flow in the layer direction and improving current spreading.

Specific examples of embodiments of the present invention will be described below 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 an embodiment of the present invention. In FIG. 1, a buffer layer 2 made of AlN, an n-type gallium nitride compound semiconductor layer 3, a light emitting layer 4 made of undoped InGaN, and a p-type AlGaN are formed on the surface of an insulating substrate 1 using sapphire. The p-type clad layer 5, the p-type intermediate layer 6 made of p-type GaN, and the p-type contact layer 7 made of p-type GaN are formed by a conventionally known metal organic chemical vapor deposition method. A transparent electrode 8 is bonded to the upper surface of the p-type contact layer 7 by a vapor deposition method, and a p-side pad electrode 9 is also formed on the transparent electrode 8 by a vapor deposition method. Then, the p-type contact layer 7, the p-type intermediate layer 6, and the p-type
An n-side electrode 10 is similarly formed on the surface of the exposed portion of the n-type gallium nitride compound semiconductor layer 3 by etching by removing a part of the type cladding layer 5 by etching.

Here, the translucent electrode 8 is formed on almost the entire surface of the p-type contact layer 7 to promote the current injection into the entire p-type layer 20, thereby obtaining the total light emission from the light emitting layer 4. Is as described in the section of the prior art. The light extracted from the light-emitting layer 4 through the transparent electrode 8 has its light emission efficiency suppressed to a low level due to attenuation of the amount of light passing through the transparent electrode 8. It was the structure of.

On the other hand, in the present invention, as shown in FIG. 1, the p-type layer 20 has the p-type intermediate layer 6 between the p-type contact layer 7 and the p-type cladding layer 5. p-type intermediate layer 6
Is doped with Mg as a p-type impurity, and the resistivity of the p-type intermediate layer 6 is made lower than that of the p-type contact layer 7 by controlling the doping amount. That is, in the present embodiment, the p-type contact layer 7 is formed as the first layer of the p-type layer 20, and the p-type intermediate layer 6 is formed as the second layer.

As described above, by forming the p-type intermediate layer 6 having a resistivity lower than that of the p-type contact layer 7 and the p-type clad layer 5, the current injected from the p-type contact layer 7 becomes a p-type intermediate layer. In the layer 6, the current easily spreads in the layer direction, and the current spreading in the p-type layer 20 is improved. Therefore, even if the area where the translucent electrode 8 is formed is reduced, effective current injection into the entire light emitting layer 4 is not impaired. Therefore, of the light from the light emitting layer 4, the transparent electrode 8
The proportion of light passing through and being attenuated can be reduced, and the proportion of light directly extracted from the p-type contact layer 7 can be increased, so that the luminous efficiency can be improved.

The p-type contact layer 7 is composed of GaN and AlGa.
Although it can be formed using N, InGaN, or the like, it is particularly preferable to use InGaN, GaN, or the like having good ohmic properties. InGaN is AlGaN that does not contain In
Compared with GaN and GaN, the resistance tends to be low by doping with a p-type impurity, but when the InN composition is increased to improve the ohmic property, for example, the film thickness is increased to 0.1 μm. When formed, the crystallinity deteriorates,
On the contrary, the ohmic property and the surface flatness tend to deteriorate.
Therefore, it is difficult to obtain both ohmic property and sufficient current spread in this layer when the film thickness is increased. Further, by doping GaN with a high concentration of p-type impurities, the ohmic property with the transparent electrode 8 is improved, and the driving voltage of the light emitting element can be lowered.
This high concentration doping tends to increase the resistivity of the p-type contact layer 7. Although depending on the crystallinity of GaN, the Mg concentration of the p-type contact layer 7 that can obtain preferable ohmic properties is in the range of 8 × 10 ^{19 to} 5 × 10 ²⁰ / cm ³ , and the p-type contact layer 7 at this time has The resistivity is in the range of approximately 10 to 100 Ω · cm. For this reason,
If the Mg concentration is adjusted by giving priority to the ohmic property, it is not possible to obtain a resistivity low enough to obtain a sufficient current spread in the p-type layer 20.

The p-type clad layer 5 is made of GaN or AlG.
Although it can be formed using aN, AlInGaN, or the like, AlGaN or AlInGaN containing Al is generally used for the cladding layer in order to increase the band gap. The layer containing Al is Al even if it is doped with Mg.
The resistivity cannot be made sufficiently low as compared with the layer not containing. For example, in the case of Al _0.14 GaN _0.86 N, 5 × 1
0 ^{19 to} 2 × 10 ²⁰ / cm ³ , and the resistivity is in the range of about 20 to 150 Ω · cm at this time.

On the other hand, in the p-type intermediate layer 6, the p-type contact layer 7 and the p-type contact layer 7 are adjusted by adjusting the doping amount of the p-type impurity.
The resistivity can be made lower than that of the mold cladding layer 5. p
Although the preferable Mg concentration range of the type intermediate layer 6 depends on the crystallinity, for example, when GaN is used as the p-type intermediate layer 6, the Mg concentration is set to a range of 5 × 10 ¹⁸ to 8 × 10 ¹⁹ / cm ³ . The resistivity can be about 1.5 Ω · cm.

The resistivity of the p-type intermediate layer 6 is 1 to 10 Ω · cm.
It is desirable to set the range to. When the resistivity of the p-type intermediate layer 6 is as high as that of the p-type contact layer, the effect of current spreading tends to be reduced. Since the layer containing Al tends to have a higher resistivity than the layer not containing Al,
When AlGaN is used, it is desirable to appropriately adjust the Mg concentration so that the resistivity is smaller than that of the p-type contact layer 7 or the p-type cladding layer 5 from the relationship between the Mg concentration and the resistivity.

By the way, the smaller the value of the resistivity, the easier the current flows. Therefore, the resistivity is used as an index of the ease of current flow. A layer containing Al, such as AlGaN or AlInGaN, tends to have a higher resistivity than GaN even if it is doped with p-type impurities, and the relationship between the p-type impurity doping amount and the resistivity differs depending on the mixed crystal composition. For example, in the case of GaN, the resistivity decreases to about 1.5 Ω · cm when the Mg concentration is increased to about 2 × 10 ¹⁹ / cm ^3, but the resistivity increases when the Mg concentration is increased thereafter. . On the other hand, in the case of Al _0.08 Ga _0.92 N containing Al,
When the Mg concentration is increased to 1 × 10 ²⁰ / cm ³ , the resistivity decreases to about 6 Ω · cm, but when the Mg concentration is increased thereafter, the resistivity increases as in the case of GaN.
Further, even if the Mg concentration is the same, if Al is contained, the resistivity becomes higher than that when Al is not contained.

As described above, the resistivity of the p-type layer such as GaN or AlGaN greatly changes depending on the Mg concentration and the mixed crystal composition. That is, the easiness of current flow in the layer changes significantly.

On the other hand, when the resistivity is high, it tends to be difficult to stably measure the carrier concentration by the Hall effect measurement. Therefore, in the present invention, the light emitting element is characterized not by the Mg concentration or the carrier concentration but by the index of the easiness of current flow and by the resistivity which enables the measurement to be relatively stable and simple.

The p-type intermediate layer 6 may be a layer containing In. For example, when it is formed using In _0.05 Ga _0.95 N, GaN or AlG is formed by doping p-type impurities.
The resistivity can be lowered relatively easily as compared with aN. This is presumably because the band gap including In becomes smaller than that of GaN or AlGaN, and the ratio of the carrier concentration obtained with respect to the p-type impurities taken into the layer increases. For example, the Mg concentration is 2 × 10 ¹⁹ / cm ³
At that time, the resistivity of GaN was 1.5 Ω · cm, whereas the resistivity of In _0.05 Ga _0.95 N was 1 Ω · cm.

When the p-type cladding layer 5 is not formed, the p-type intermediate layer 6 can be used as the cladding layer. Further, the mixed crystal composition and the Mg concentration range of the p-type intermediate layer 6 are not limited to the above numerical ranges, and various modifications can be made as long as they are based on the technical idea of the present invention. Of course.

[0035]

The semiconductor light emitting device of the present invention will be described below based on its specific manufacturing method. The following example shows a method for growing a gallium nitride-based compound semiconductor by a metal organic chemical vapor deposition method.

(Example 1) This embodiment 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, 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 is performed to remove dirt and moisture such as organic substances attached to the surface of the substrate 1.

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

Next, after stopping only the carrier gas of TMA and raising the temperature to 1050 ° C., as the main carrier gas,
While flowing nitrogen gas at 9 liters / minute and hydrogen gas at 0.95 liters / minute, a carrier gas of trimethylgallium (hereinafter referred to as “TMG”) is newly added at 4 cc / minute,
SiH ₄ (monosilane) gas of 10 ppm as a Si source is flowed at 10 cc / min for growth for 60 minutes to grow an n-type gallium nitride compound semiconductor layer 3 made of Si-doped GaN to a thickness of 2 μm.

After the growth and formation of the n-type gallium nitride compound semiconductor layer 3, the carrier gas for TMG and the SiH ₄ gas are stopped, the substrate surface temperature is lowered to 750 ° C., and 10 liters of nitrogen gas is newly used as the main carrier gas. / Min, TMG
Carrier gas for 2 cc / min and carrier gas for trimethylindium (hereinafter referred to as "TMI") 200
The light emitting layer 4 made of undoped InGaN is grown to have a thickness of 3 nm while being grown for 30 seconds while flowing at cc / min.

After forming the light emitting layer 4, the carrier gas for TMI and the carrier gas for TMG are stopped, and the substrate surface temperature is set to 1
The temperature is increased to 050 ° C., nitrogen gas is 9 liters / minute, hydrogen gas is 0.90 liters / minute as new main carrier gas, carrier gas for TMG is 4 cc / minute, TMA.
Carrier gas for Cp ₂ Mg at 50 cc / min and carrier gas for Cp ₂ Mg at 4 cc / min for 4 minutes to grow,
A p-type cladding layer 5 made of Al _0.14 Ga _0.86 N doped with Mg is grown to a thickness of 0.1 μm. The resistivity of this p-type cladding layer 5 was 38 Ω · cm.

Subsequently, only the carrier gas for TMA was stopped, and at 1050 ° C., nitrogen gas of 9 liter / min and hydrogen gas of 0.98 liter / min were newly added as the main carrier gas, and the carrier gas for TMG was changed. 4 cc / min, Cp ₂
The carrier gas for Mg is allowed to flow for 20 minutes at a rate of 20 cc / min to grow the p-type intermediate layer 6 made of GaN doped with Mg to a thickness of 0.2 μm. The p-type intermediate layer 6 had a resistivity of 1.4 Ω · cm.

Then, at 1050 ° C., nitrogen gas is newly added as a main carrier gas at 9 liters / minute, hydrogen gas is newly added at 0.90 liters / minute, carrier gas for TMG is 4 cc / minute, and Cp ₂ Mg is used. Carrier gas of 100
The p-type contact layer 7 made of GaN doped with Mg is grown to a thickness of 0.1 μm by growing for 3 minutes while flowing at cc / min. The resistivity of this p-type contact layer 7 was 30 Ω · cm.

After the growth, the source gases TMG gas and Cp
_{2 After} stopping the Mg gas and the ammonia and cooling to room temperature while flowing the nitrogen gas and the hydrogen gas at the same flow rates, the wafer is taken out from the reaction tube.

Photolithography and reactive ion etching are applied to the pn junction including the quantum well structure composed of the n-type gallium nitride compound semiconductor layer 3, the light emitting layer 4 and the p-type layer 20 thus formed. P-type layer 20 using
A part of the light emitting layer 4 was etched to expose a part of the n-type gallium nitride based compound semiconductor thin film 3. And
An n-side electrode 10, which is an ohmic electrode, was formed on the exposed n-type gallium nitride compound semiconductor layer 3 by photolithography and vapor deposition. On the other hand, on the p-type contact layer 7, a translucent electrode 8 made of Ni and Au having an area occupying about 80% of the surface area of the p-type contact layer 7 was formed by bonding using photolithography and vapor deposition. The film thickness of Ni was 3 nm, and the film thickness of Au was 7 nm. Further, a p-side pad electrode 9 made of Au was formed on the transparent electrode 8 by photolithography and vapor deposition. As a result, the transparent electrode 8 with respect to the surface area of the p-type contact layer 7 is formed.
The ratio of the area occupied by is about 70%. The transmissivity of this translucent electrode was about 60%.

Thereafter, the back surface of the sapphire substrate 1 was polished to a thickness of about 100 μm, and scribed to separate it into chips. This chip was adhered to the stem with the electrode forming surface facing upward, and then the n-side electrode 10 and p of the chip were bonded.
Each of the side pad electrodes 9 was connected to the electrode on the stem with a wire, and then resin-molded to manufacture a light emitting diode. When this light emitting diode was driven with a forward current of 20 mA, the forward voltage was 3.6 V and the light emission output was 900
μW, and emitted blue-violet light with a wavelength of 430 nm. In addition, when the light emitting state of the chip was observed with a microscope before resin molding, it was found that light was emitted from almost the entire surface of the p-type contact layer 7 except the region where the p-side pad electrode 9 was formed. .

Example 2 A transparent electrode 8 having an area occupying about 70% of the surface area of the p-type contact layer 7 is formed on the p-type contact layer 7, and a p-side pad electrode 9 is formed thereon. As a result, the ratio of the area occupied by the transparent electrode 8 to the p-type contact layer 7 is about 40.
A light emitting diode was produced in the same manner as in Example 1 except that the percentage was changed. When this light emitting diode was driven with a forward current of 20 mA, the forward voltage was 3.6 V, the emission output was 1080 μW, and blue-violet emission with a wavelength of 430 nm was exhibited.

In this embodiment, although the area of the transparent electrode 8 is formed smaller than that of the first embodiment,
The luminescence output increased. It is considered that this is because the current spreads sufficiently in the p-type layer 20, the proportion of light passing through the transparent electrode 8 decreases, and the proportion of light directly extracted from the p-type contact layer 7 increases.

Here, a light emitting diode was manufactured as a comparative example in the same manner as in Example 2 except that the p-type intermediate layer 6 was not formed. When the manufactured light emitting diode was driven by a forward current of 20 mA, the forward voltage, wavelength and spectrum half-width were almost the same, but the light emission output was 720 μW, which was compared with the light emitting diode of Example 2. Then, a remarkable difference was recognized.

Example 3 A light emitting diode was produced in the same manner as in Example 2 except that the p-type intermediate layer 6 was formed by using Al _0.05 Ga _0.95 N instead of GaN. Specifically, the p-type intermediate layer 6 has 10
Nitrogen gas was newly added as the main carrier gas at 50 ° C.
L / min, hydrogen gas 0.90 l / min, T
Carrier gas for MG is 4 cc / min, carrier gas for TMA is 4 cc / min, carrier gas for Cp ₂ Mg is 5 cc / min.
Grow for 8 minutes while flowing at 0 cc / min to 0.2 μm
Grown to a thickness of. The resistivity of this layer was 9 Ω · cm. When this light emitting diode was driven with a forward current of 20 mA, the forward voltage was 3.8 V and the light emission output was 98.
It was 0 μW, and emitted blue-violet light with a wavelength of 430 nm.

(Example 4) (Al _0.05 Ga _0.95 ) _0.98 In instead of AlGaN
_A light emitting diode was produced in the same manner as in Example 3 except that the p-type intermediate layer 6 was formed using _0.02 N. Specifically, the p-type intermediate layer 6 has a new main carrier gas of nitrogen gas of 9 liters / minute, hydrogen gas of 0.90 liters / minute, and TMA carrier gas of 4 times at 1050 ° C.
cc / min, carrier gas for TMG 4 cc / min, TM
The carrier gas for I and the carrier gas for Cp ₂ Mg were allowed to grow at a flow rate of 10 cc / min and 70 cc / min, respectively, for 8 minutes to have a thickness of 0.2 μm. AlG of Example 3
By including In, the resistivity of this layer could be reduced to 4 Ω · cm as compared with the p-type intermediate layer 6 made of aN. When this light emitting diode was driven with a forward current of 20 mA, the forward voltage was 3.7 V, the emission output was 1030 μW, and blue-violet emission with a wavelength of 430 nm was exhibited.

Example 5 After growing the p-type cladding layer 5 made of AlGaN,
The p-type intermediate layer 6 made of GaN doped with Mg has a thickness of 0.3.
The light emitting diode was manufactured in the same manner as in Example 2 except that the p-type contact layer 7 made of In _0.05 Ga _0.95 N doped with Mg was grown to a thickness of 0.05 μm. Was produced. Specifically, the p-type intermediate layer 6 has a nitrogen gas of 9 l / min, a hydrogen gas of 0.98 l / min, and a carrier gas of 4 cc / min for TMG at 1050 ° C. Minutes,
The carrier gas for Cp ₂ Mg is grown at a flow rate of 20 cc / min for 9 minutes to grow to a thickness of 0.3 μm.
The resistivity of this layer was 1.4 Ω · cm. At 850 ° C., the p-type contact layer 7 has a nitrogen gas of 10 liter / min, a carrier gas of TMI of 12 cc / min, a carrier gas of TMG of 4 cc / min, and a Cp of Cp. ₂ Carrier gas for Mg 30cc /
Flowed for 1.5 minutes to grow In _0.05 Ga
_{A 0.95} N layer was formed with a thickness of 0.05 μm. The resistivity of this layer was 1.2 Ω · cm. When this light emitting diode was driven with a forward current of 20 mA, the forward voltage was 3.5 V, the light emission output was 1080 μW, and the wavelength was 430
It emitted blue-violet emission of nm.

[0053]

According to the present invention, in a light emitting device having an n-type layer made of a gallium nitride-based compound semiconductor thin film, a light-emitting layer and a p-type layer on a substrate, the p-type layer has a difference in resistivity. By adopting a three-layer structure or a three-layer structure, the spread of current in the p-type layer is improved, so that the area of the transparent electrode formed on the upper surface of the p-type layer can be reduced and the light can be transmitted. An excellent effect is obtained in which the ratio of light passing through the electrode is reduced and the ratio of light directly extracted from the p-type layer is increased to maintain high luminous efficiency.

[Brief description of drawings]

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

FIG. 2 shows a conventional gallium nitride-based compound semiconductor light emitting device.
Cross section showing structure

[Explanation of symbols]

1 substrate 2 buffer layers 3 n-type gallium nitride-based compound semiconductor layer 4 Light emitting layer 5 p-type clad layer 6 p-type intermediate layer (second layer) 7 p-type contact layer (first layer) 8 Translucent electrode 9 p-side pad electrode 10 n side electrode 20 p-type layer

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-8-97471 (JP, A) JP-A-8-32111 (JP, A) JP-A-6-9020 (JP, A) JP-A-8- 264831 (JP, A) JP-A-8-167735 (JP, A) JP-A-6-151966 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00

Claims (6)

(57) [Claims] 1. A semiconductor light emitting device having an n-type layer made of a gallium nitride-based compound semiconductor thin film, a light-emitting layer, and a p-type layer, wherein the p-type layer is a Mg-doped contact layer.
Of the first layer and Mg in a lower concentration than the first layer.
Second layer with low resistivity and higher than the second layer
A gallium nitride-based compound semiconductor, comprising a third layer having a high resistivity by doping with Mg in a concentration , wherein the second layer is formed between the first layer and the third layer Light emitting element. 2. The second layer contains at least indium.
The gallium nitride-based compound semiconductor light-emitting device according to claim 1, wherein the free it. 3. The resistivity of the second layer is 1 to 10 Ω · cm.
The gallium nitride-based compound semiconductor light-emitting device according to claim 1 or 2, characterized in that 4. The Mg concentration of the second layer is 5 × 10 ¹⁸ to
The gallium nitride-based compound semiconductor light emitting device according to any one of claims 1 to 3, wherein the gallium nitride-based compound semiconductor light emitting device has a range of 8 × 10 ¹⁹ / cm ³ . 5. A transparent electrode is formed on the first layer.
The gallium nitride-based compound semiconductor light emitting device according to any one of claims 1 to 4, wherein 6. The first layer is GaN and the second layer is
The gallium nitride-based compound semiconductor light emitting device according to any one of claims 1 to 5 , wherein GaN and the third layer are AlGaN .