JP2000196144A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element having a low working voltage. SOLUTION: A semiconductor laser element 100 comprises a low temperature buffer layer 2, an n-GaN layer 3, an n-clad layer 4, an n-optical guide layer 5, an n-MQW light emitting layer 6, a p-AlGaN layer 7, a p-optical guide layer 8, a p-clad layer 9 and a p-contact layer 10 formed sequentially on a sapphire substrate 1. Partial region from the p-contact layer 10 to the n-clad layer 4 is etched and an n-electrode 21 is formed on the exposed n-clad layer 4. A p-electrode 20 is formed on the p-contact layer 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a group III-V nitride semiconductor such as BN (boron nitride), GaN (gallium nitride), AlN (aluminum nitride) or InN (indium nitride) or a mixed crystal thereof. (Hereinafter, referred to as a nitride-based semiconductor).

[0002]

2. Description of the Related Art In recent years, GaN-based semiconductor light-emitting devices have been put into practical use as semiconductor light-emitting devices such as light-emitting diodes and semiconductor laser devices that emit blue or violet light. When manufacturing a GaN-based semiconductor light-emitting device, sapphire (Al
_A semiconductor layer is epitaxially grown on an insulating substrate such as ₂ O ₃ ).

FIG. 7 is a sectional view showing the structure of a GaN-based semiconductor laser device. FIG. 8 is a schematic energy band structure diagram of a main part of the semiconductor laser device shown in FIG.

As shown in FIG. 7, a semiconductor laser device has a buffer layer 2 made of undoped GaN, an n-GaN layer 3 and an n-A
n-cladding layer 4 made of lGaN, n-GaN light guide layer 5, n-MQW (multiple quantum well) light emitting layer 6, p-A
lGaN layer 7, p-GaN light guide layer 8, p-AlGa
A p-cladding layer 9 made of N and a p-contact layer 10 made of p-GaN are sequentially formed.

As shown in FIG. 8, the n-MQW light emitting layer 6
Has a multiple quantum well structure in which n-InGaN quantum barrier layers 6a and n-InGaN quantum well layers 6b are alternately stacked.

The sapphire substrate 1 is an insulating substrate having no conductivity. For this reason, usually, the p-contact layer 10
Is removed by etching, and the exposed n-GaN layer 3 is brought into ohmic contact with the n-electrode 51. On the other hand, the p-electrode 52 is brought into ohmic contact with the p-contact layer 10.

In such a semiconductor laser device, n
The electrons injected from the electrode 51 into the n-GaN layer 3 flow in the n-GaN layer 3 and then flow in a direction perpendicular to the sapphire substrate 1 as shown by an arrow 70 in the figure.
N-MQW via the cladding layer 4 and the n-light guide layer 5
It is injected into the light emitting layer 6. On the other hand, holes are indicated by arrows 80 in the figure.
As shown by p, the p-contact layer 10 from the p-electrode 52,
p-cladding layer 9, p-light guide layer 8, and p-AlG
It is injected into the n-MQW light emitting layer 6 through the aN layer 7 in order. Thus, electrons and holes are recombined in the n-MQW light emitting layer 6, and the semiconductor laser device emits light.

[0008]

As shown in FIG. 8, n
GaN layer 3 and n-cladding layer 4 have different band gaps, and n-cladding layer 4 containing Al
Has a larger band gap. Therefore, in the electron flow 71, a large energy barrier exists between the n-GaN layer 3 and the n-cladding layer 4. Since the height H of the barrier is at least several hundred meV, the flow of electrons 71 is obstructed. In order for electrons to cross such a barrier, a high voltage must be applied.

Usually, since the n-GaN layer 3 is deeply etched to form the n-electrode 51, the electrons are n-MQW
The path when flowing in the direction perpendicular to the light emitting layer 6 is long, and n
-The series resistance from the GaN layer 3 to the n-MQW light emitting layer 6 increases.

As a result, the operating voltage of the semiconductor laser device is increased, the power consumption is increased, and the life of the device is shortened.

An object of the present invention is to provide a semiconductor light emitting device having a low operating voltage.

[0012]

A semiconductor light emitting device according to the present invention comprises a nitride semiconductor containing at least one of boron, gallium, aluminum and indium, and has a first conductivity type cladding layer and a light emitting device. A first semiconductor layer including layers in order, and a first semiconductor layer formed on the first semiconductor layer, the nitride semiconductor including at least one of boron, gallium, aluminum and indium, and including a second conductivity type cladding layer. And two semiconductor layers,
Part of the first semiconductor layer is exposed, and an ohmic electrode is formed on the exposed part of the region.

In the semiconductor light emitting device according to the present invention, carriers injected from the ohmic electrode flow toward the light emitting layer in the first semiconductor layer on which the ohmic electrode is formed.

In this case, since there is no energy barrier in the path from the ohmic electrode to the light emitting layer, carriers can flow to the light emitting layer without crossing the energy barrier. Further, since the distance between the ohmic electrode and the light emitting layer is short, the series resistance from the ohmic electrode to the light emitting layer is reduced. As a result, the operating voltage of the semiconductor light emitting device decreases.

Further, since the applied voltage can be reduced, the power consumption is reduced and the life of the semiconductor light emitting element is prolonged.

[0016] A part of the first conductive type clad layer of the first semiconductor layer may be exposed, and an ohmic electrode may be formed on the exposed part of the first conductive type clad layer.

In this case, the carriers injected from the ohmic electrode flow in the first conductivity type cladding layer, and further flow vertically in the first semiconductor layer toward the light emitting layer.

As described above, since the carriers are injected into the first conductivity type cladding layer having a large energy band gap, the energy barrier does not exceed the energy barrier existing between the first conductivity type cladding layer and the layer adjacent thereto. It flows to the light emitting layer. Further, since the distance between the first conductivity type cladding layer and the light emitting layer is short, the series resistance from the ohmic electrode to the light emitting layer is reduced. From the above, the operating voltage of the semiconductor light emitting device becomes lower.

Since the first conductivity type cladding layer is doped with the first conductivity type impurity to reduce the resistance, an ohmic electrode can be easily formed.

Also, a part of the light emitting layer of the first semiconductor layer may be exposed, and an ohmic electrode may be formed on the part of the exposed light emitting layer.

In this case, since the carriers are directly injected from the ohmic electrode into the light emitting layer, the series resistance from the ohmic electrode to the light emitting layer is reduced. In addition, the carrier does not need to cross the energy barrier existing between the first conductivity type cladding layer and the layer adjacent thereto. From the above, the operating voltage of the semiconductor light emitting device becomes lower.

Further, the first semiconductor layer further includes a light guide layer between the first conductivity type cladding layer and the light emitting layer,
A part of the light guide layer of the semiconductor layer may be exposed, and an ohmic electrode may be formed on the part of the exposed light guide layer.

In this case, carriers are injected from the ohmic electrode into the light emitting layer through the light guide layer.

As described above, the carriers are injected into the light guide layer on the first conductivity type cladding layer, and therefore, the carriers do not exceed the energy barrier existing between the first conductivity type cladding layer and the layer adjacent thereto. It flows to the light emitting layer. Further, since the light guide layer is in contact with the light emitting layer, the series resistance from the ohmic electrode to the light emitting layer is reduced. From the above, the operating voltage of the semiconductor light emitting device becomes lower.

The first conductivity type cladding layer is an n-type cladding layer, the second conductivity type cladding layer is a p-type cladding layer,
A partial region of the n-type cladding layer may be exposed, and an ohmic electrode may be formed in the exposed partial region of the n-type cladding layer.

In this case, the electrons injected from the ohmic electrode flow in the n-type cladding layer, and further flow in the first semiconductor layer in the vertical direction toward the light emitting layer.

As described above, since electrons are injected into the n-type cladding layer having a large energy band gap, the electrons flow to the light-emitting layer without exceeding the energy barrier existing between the n-type cladding layer and the layer adjacent thereto. . Further, since the distance between the n-type cladding layer and the light emitting layer is short, the series resistance from the ohmic electrode to the light emitting layer is reduced. From the above, the operating voltage of the semiconductor light emitting device becomes lower.

Further, since the n-type cladding layer is doped with an n-type impurity to reduce the resistance, an ohmic electrode can be easily formed.

Further, the first conductivity type cladding layer is an n-type cladding layer, the second conductivity type cladding layer is a p-type cladding layer, the light emitting layer is doped with an n-type impurity, and a partial region of the light emitting layer is formed. May be exposed, and an ohmic electrode may be formed in a part of the exposed light emitting layer.

In this case, since the electrons are directly injected into the light emitting layer from the ohmic electrode, the series resistance from the ohmic electrode to the light emitting layer is reduced. Also, electrons need not cross the energy barrier existing between the n-type cladding layer and the layer adjacent thereto. From the above, the operating voltage of the semiconductor light emitting device becomes lower.

Since the light emitting layer is doped with an n-type impurity to reduce the resistance, an ohmic electrode can be easily formed.

Further, the first conductivity type cladding layer is an n-type cladding layer, the second conductivity type cladding layer is a p-type cladding layer, and the first semiconductor layer is formed between the n-type cladding layer and the light emitting layer. May further include an n-type light guide layer, a part of the n-type light guide layer of the first semiconductor layer may be exposed, and an ohmic electrode may be formed on a part of the exposed n-type light guide layer.

In this case, electrons move from the ohmic electrode to n
It is injected into the light emitting layer through the mold light guide layer.

As described above, electrons are emitted from the n-type cladding layer on the n-type cladding layer.
Since it is injected into the type light guide layer, it flows to the light emitting layer without crossing the energy barrier existing between the n-type clad layer and the layer adjacent thereto. Further, since the n-type light guide layer is in contact with the light emitting layer, the series resistance from the ohmic electrode to the light emitting layer is reduced. From the above, the operating voltage of the semiconductor light emitting device becomes lower.

Since the n-type light guide layer is doped and has low resistance, an ohmic electrode can be easily formed.

The first conductivity type cladding layer is a p-type cladding layer, the second conductivity type cladding layer is an n-type cladding layer,
A partial region of the p-type clad layer may be exposed, and an ohmic electrode may be formed in the exposed partial region of the p-type clad layer.

In this case, the holes injected from the ohmic electrode flow in the p-type cladding layer, and further flow in the first semiconductor layer in the vertical direction toward the light emitting layer.

As described above, since the holes are injected into the p-type cladding layer having a large energy band gap, the holes can reach the light-emitting layer without exceeding the energy barrier existing between the p-type cladding layer and the layer adjacent thereto. Flows. Further, since the distance between the p-type cladding layer and the light emitting layer is short, the series resistance from the ohmic electrode to the light emitting layer is reduced. From the above, the operating voltage of the semiconductor light emitting device becomes lower.

Since the p-type cladding layer is doped with a p-type impurity to reduce the resistance, an ohmic electrode can be easily formed.

Further, the first conductivity type cladding layer is a p-type cladding layer, the second conductivity type cladding layer is an n-type cladding layer, and the first semiconductor layer is between the p-type cladding layer and the light emitting layer. Further includes a p-type light guide layer, and the p-type light guide layer
A partial region of the mold light guide layer may be exposed, and an ohmic electrode may be formed in a partial region of the exposed p-type cladding layer.

In this case, holes are generated from the ohmic electrode by p
It is injected into the light emitting layer through the mold light guide layer.

As described above, the holes are formed on the p-type cladding layer by the p-type cladding layer.
Since it is injected into the mold light guide layer, it flows to the light emitting layer without crossing the energy barrier existing between the p-type clad layer and the layer adjacent thereto. Further, since the p-type light guide layer is in contact with the light emitting layer, the series resistance from the ohmic electrode to the light emitting layer is reduced. From the above, the operating voltage of the semiconductor light emitting device becomes lower.

Since the p-type light guide layer is doped and has a low resistance, an ohmic electrode can be easily formed.

[0044]

FIG. 1 is a sectional view of a GaN-based semiconductor laser device according to a first embodiment of the present invention.

In the semiconductor laser device 100 shown in FIG. 1, the MO (MO) is placed on the c (0001) plane of the sapphire substrate 1.
Undoped GaN low-temperature buffer layer 2, n-GaN layer 3, n-A by CVD (metal organic chemical vapor deposition)
n-cladding layer 4 made of lGaN, n-light guide layer 5 made of n-GaN, n-MQW light emitting layer 6, p-AlG
aN layer 7, p-light guide layer 8 made of p-GaN, p-
P-cladding layer 9 made of AlGaN and p-GaN
Are formed in order.

Part of the region from the p-contact layer 10 to the n-cladding layer 4 is etched,
Is exposed. The n-electrode 21 is in ohmic contact with the exposed n-clad layer 4. On the other hand, the p-electrode 20 is in ohmic contact with the p-contact layer 10.

Note that Si is used as the n-type dopant, and Mg is used as the p-type dopant.

In a semiconductor light emitting device using another compound semiconductor material such as GaAs, bending of the energy band due to the piezo effect does not occur. Therefore, an undoped light emitting layer and an undoped light guide layer are used to prevent the threshold current from being lowered due to the scattering of electrons. Therefore, in a semiconductor light emitting device using another compound semiconductor material such as GaAs, it is difficult to make an electrode in ohmic contact with the light guide layer or the light emitting layer.

On the other hand, in the GaN-based semiconductor laser device 100, the light guide layer 5 and the n-MQW light-emitting layer 6 are made of n in order to prevent a decrease in the light emission intensity caused by bending of the energy band due to the piezo effect. The light guide layer 8 is doped with p-type. The doping of the light emitting layer or the light guide layer is as follows.
This is unique to nitride-based semiconductor light emitting devices.

The energy band structure in each of the layers 3 to 6 is as shown in FIG.

In FIG. 1, electrons injected from the n-electrode 21 into the n-cladding layer 4 flow in the n-cladding layer 4 as shown by an arrow 11 in the figure, and further toward the n-MQW light emitting layer 6. Accordingly, the gas flows along a direction perpendicular to the sapphire substrate 1. On the other hand, as shown by the arrow 12, holes are generated from the p-electrode 21 to the p-contact layer 10, the p-cladding layer 9,
Through the light guide layer 8 and the p-AlGaN layer 7 in order,
The light reaches the n-MQW light emitting layer 6. Thus, n-M
Electrons and holes are recombined in the QW light emitting layer 6, and the semiconductor laser device 100 emits light.

AlGaN has the property of easily becoming n-type, and the n-cladding layer 4 made of n-AlGaN
-Has a high electron concentration comparable to that of the GaN layer 3; Therefore, the resistance when the n-electrode 21 is in contact with the n-clad layer 4 to form a current path in the n-clad layer 4 is smaller than the resistance when the n-electrode 21 is in contact with the n-GaN layer 3. It does not increase in comparison.

N-cladding layer 4 made of n-AlGaN
When the n-electrode 21 is brought into contact with AlGaN, the contact resistance between the n-cladding layer 4 and the n-electrode 21 tends to increase because AlGaN has a large band gap. However, the n-electrode 21
Are many of the materials that can form an ohmic electrode compared to the material that forms the p-electrode 20. Therefore, it is possible to easily obtain ohmic contact with n-cladding layer 4 made of n-AlGaN, and to select a material having low contact resistance.

In the semiconductor laser device 100, electrons are directly injected from the n-electrode 21 into the n-cladding layer 4.
For this reason, electrons are transferred to the n-GaN layer 3 and the n-GaN layer 3 as shown in FIG.
-It is not necessary to cross the barrier between the cladding layer 4.

The n-cladding layer 4 is usually made of n-M
It is located within 1 μm below the QW light emitting layer 6 and has n-Ga
It is closer to the n-MQW light emitting layer 6 than the N layer 3. Therefore,
When the n-electrode 21 is brought into contact with the n-cladding layer 4,
The current path in the direction perpendicular to the sapphire substrate 1 is shorter than when the n-electrode 21 is in contact with the n-GaN layer 3. Thereby, the series resistance from the n-electrode 21 to the n-MQW light emitting layer 6 decreases.

As a result, the operating voltage of the semiconductor laser device 100 decreases. As described above, since the operating voltage of the semiconductor laser device 100 is reduced, the applied voltage can be reduced, and energy saving is achieved. Further, by reducing the applied voltage, deterioration of the semiconductor laser device 100 is suppressed, and the device life is prolonged.

Further, at the time of manufacturing the semiconductor laser device 100, since the p-contact layer 10 to the n-cladding layer 4 are etched, the p-contact layer 10
-The etching amount is smaller than when etching up to the GaN layer 3. Therefore, the time required for manufacturing the semiconductor laser device 100 can be reduced.

The n-cladding layer 4 of the semiconductor laser device 100 is made of n-type doped AlGaN, but may be an undoped cladding layer made of undoped AlGaN. Also, n-
If it is possible to sufficiently confine light in the cladding layer 4, the n-cladding layer 4 may be formed directly on the buffer layer 2. However, in order to grow the n-cladding layer 4 made of AlGaN having a large band gap, it is preferable to form a single crystal layer of GaN or the like (in this case, the n-GaN layer 3) as a base.

FIG. 2 is a sectional view of a GaN-based semiconductor laser device according to a second embodiment of the present invention.

The semiconductor laser device shown in FIG. 2 has the same configuration as the semiconductor laser device 100 shown in FIG. 1 except for the following points.

In the semiconductor laser device 101, the n-electrode 22 is in contact with the n-GaN layer 3 and the n-cladding layer 4. In this case, the n-cladding layer 4
Injected into the n-MQW through the path shown by the arrow 11 in FIG.
It flows toward the light emitting layer 6. On the other hand, n-
The electrons injected into the GaN layer 3 move in the n-GaN layer 3 through the course shown by the arrow 13 in the figure, and move toward the n-MQW light emitting layer 6 along a direction perpendicular to the sapphire substrate 1. Flowing.

As described above, in the semiconductor laser device 101, the electrons injected into the n-cladding layer 4 are
Since the current flows along the path indicated by the arrow 13 in addition to the path indicated by 1, the operating voltage is further reduced.

FIG. 3 is a sectional view of a GaN-based semiconductor laser device according to a third embodiment of the present invention. Note that FIG.
Has the same configuration as the semiconductor laser device 100 of FIG. 1 except for the following points.

In the semiconductor laser device 102, the n-electrode 23 is in ohmic contact with the n-light guide layer 5.
In this case, the electrons injected from the n-electrode 23 into the n-light guide layer 5 flow in the n-light guide layer 5, and furthermore, the n-MQ
It flows toward the W light emitting layer 6 in a direction perpendicular to the sapphire substrate 1.

As described above, in the semiconductor laser device 102, electrons do not need to cross the barrier between the n-GaN layer 3 and the n-cladding layer 4. Further, the n-light guide layer 5
Is closer to the n-MQW light emitting layer 6 than the n-GaN layer 3, the current path in the direction perpendicular to the sapphire substrate 1 is shortened, and the series resistance from the n electrode 23 to the n-MQW light emitting layer 6 is reduced. .

As described above in the semiconductor laser device 100 of FIG. 1, the n-light guide layer 5 of the semiconductor laser device 102 is doped with n-type to reduce the resistance, and has an electron concentration of 10 ¹⁸ / cm ^3. And high. For this reason, the n-electrode 23 can be brought into ohmic contact with the n-light guide layer 5.

The band gap of the n-light guide layer 5 made of n-GaN is smaller than that of the n-cladding layer 4 made of n-AlGaN. Therefore, when the n-electrode 23 is brought into contact with the n-light guide layer 5, the contact resistance does not increase.

From the above points, the semiconductor laser element 102
As in the case of the semiconductor laser device 100, the operating voltage becomes lower.

FIG. 4 is a sectional view of a GaN-based semiconductor laser device according to a fourth embodiment of the present invention. FIG.
Has the same configuration as the semiconductor laser device 100 of FIG. 1 except for the following points.

In the semiconductor laser device 103, the n-electrode 24 is in ohmic contact with the n-MQW light emitting layer 6.

In this case, the electrons injected from the n-electrode 24 into the n-MQW light-emitting layer 6 flow in the n-MQW light-emitting layer 6 and recombine with the holes flowing from the p-electrode 20 side.

As described above, in the semiconductor laser device 103, electrons do not need to cross the barrier between the n-GaN layer 3 and the n-cladding layer 4. Further, since the current path is short, the series resistance from the n-electrode 24 to the n-MQW light emitting layer 6 becomes small.

The n-MQW light emitting layer 6 comprises the n-light guide layer 5
Similarly to the above, the resistance is reduced by doping, and the electron concentration is high. Therefore, the n-electrode 24 can be brought into ohmic contact with the n-MQW light emitting layer 6.

The band gap of the n-MQW light emitting layer 6 made of InGaN is smaller than that of the n clad layer 4 made of AlGaN. Therefore, when the n-electrode 24 is brought into contact with the n-MQW light emitting layer 6, the contact resistance does not increase.

As for electrons and holes, electrons have significantly smaller effective mass and larger momentum. Therefore, the electrons are n-
It easily overflows from the MQW light emitting layer 6 to the p-AlGaN layer 7 side. On the other hand, holes have a large effective mass and a small momentum as compared with electrons. Therefore, holes hardly overflow from the n-MQW light emitting layer 6 to the n-light guide layer 5 side. Therefore, recombination of electrons and holes occurs in the n-MQW light emitting layer 6 near the p-AlGaN layer 7.
Therefore, there is no effect on light emission due to the contact of the n-electrode 25 with the n-MQW light-emitting layer 6.

From the above points, the semiconductor laser device 103
As in the case of the semiconductor laser device 100, the operating voltage becomes lower.

FIG. 5 is a sectional view of a BN-based semiconductor laser device according to a fifth embodiment of the present invention. The semiconductor laser device 200 shown in FIG.
0, but each layer 32 to 35, 37 to 4
0 is the material of each of the layers 2 to 5, 7 to
Different from 10 materials.

In the semiconductor laser device 200 shown in FIG.
MOCV on the c (0001) plane of the sapphire substrate 31
The low-temperature buffer layer 32 made of undoped BAlGaN, the n-BAlGaN layer 33, the n-BAlG
n-cladding layer 34 made of aN, n-light guide layer 35 made of n-BAlGaN, n-MQW light emitting layer 36, p
-BAlGaN layer 37, p- made of p-BAlGaN
A light guide layer 38, a p-cladding layer 39 made of p-BAlGaN, and a p-contact layer 40 made of p-BAlGaN are formed in this order.

Part of the region from the p-contact layer 40 to the n-cladding layer 34 is etched, and the n-electrode 41 is in ohmic contact with the exposed n-cladding layer 34.
On the other hand, the p-electrode 42 is in ohmic contact with the p-contact layer 40. The energy band structure of each of the layers 33 to 36 is the same as the energy band structure shown in FIG.

Such a BN semiconductor laser device 200
In this case, the operating voltage is reduced as in the GaN-based semiconductor laser device 100 shown in FIG.

FIG. 6 is a sectional view of a BN semiconductor laser device according to a sixth embodiment of the present invention.

The semiconductor laser device 201 has the same configuration as the semiconductor laser device 200 shown in FIG. 5, except for the following points.

In the semiconductor laser element 201, the n-electrode 43 is in ohmic contact with the n-light guide layer 35.

In such a semiconductor laser device 201 as well, the operating voltage is reduced as in the case of the semiconductor laser device 200 of FIG.

In the first to sixth embodiments, the semiconductor laser device having the n-type semiconductor layer formed on the sapphire substrate has been described. However, the semiconductor light emitting device according to the present invention is not limited to the sapphire substrate. The present invention is also applicable to a semiconductor laser device in which a p-type semiconductor layer is formed. In this case, for example, the semiconductor laser devices 100 to 1 shown in FIGS.
In 03, 200 and 201, the n-type and p-type are reversed. However, in this case, since light is emitted in a portion near the p-light guide layer in the n-MQW light-emitting layer, the p-electrode is p-type.
It is preferable to make ohmic contact with the cladding layer or the p-light guide layer.

[0086]

EXAMPLES For each of the semiconductor laser devices shown in the following Examples 1 to 4 and Comparative Example, the operating voltage and light output when a driving current of 300 mA was passed were measured.

Manufacturing of the semiconductor laser devices shown in Examples 1 to 4 and Comparative Example was the same except that a step of forming an electrode contact region in a predetermined semiconductor layer by etching was performed as follows.

An undoped Ga is deposited on the c (0001) plane of the sapphire substrate 1 sufficiently cleaned by MOCVD.
Low-temperature buffer layer 2 made of N and having a thickness of 20 nm, thickness of 4 μm
m-n-GaN layer 3, n-Al _0.1 Ga _0.9 N 700 nm thick n-cladding layer 4, 200 nm thick n-GaN n-light guide layer 5, n-InGaN
The n-MQW light-emitting layer 6 was sequentially grown.

The n-MQW light emitting layer 6 has a thickness of 15 n.
m, three n-In _0.13 GaN _0.87 quantum well layers 6b;
Four n-In _0.03 GaN _0.97 quantum barrier layers 6a each having a thickness of 20 nm are alternately stacked.

On the n-MQW light emitting layer 6,
0-nm p-AlGaN layer 7, 200-nm-thick p-light guide layer 8 made of p-GaN, p-Al _0.1 Ga _0.9
A 700 nm thick p-cladding layer 9 and p
-P-contact layer 1 made of GaN and having a thickness of 100 nm
0 were grown sequentially.

In the growth of each of the semiconductor layers 9 to 10, the substrate temperature during the growth of the low-temperature buffer layer 2 is about 600 ° C.
The substrate temperature during the growth of the n-MQW light emitting layer 6 and the p-AlGaN layer 7 is set to about 800 ° C., and the remaining layers 3 to 5
The substrate temperature during growth of 8 to 10 was set to about 1080 ° C. In addition, Si was used as an n-type dopant, and Mg was used as a p-type dopant.

Subsequently, the layers 2 to 10 grown on the sapphire substrate 1 are placed in a nitrogen atmosphere at 600 ° C.
The p-type dopant was activated.

Next, a photoresist is formed except for a part of the region on the p-contact layer 10 and the p-contact layer 1 is formed.
On top of that, Ni was vapor-deposited on the photoresist and the photoresist was removed. In this manner, a predetermined region on the p-contact layer 10 was covered with Ni having a thickness of 500 nm. Further, in the region not covered with Ni, the region from the p-contact layer 10 to the predetermined semiconductor layer was etched by a reactive ion etching method using chlorine ions, thereby exposing the predetermined semiconductor layer. Thus, an n-electrode contact region was formed in a predetermined semiconductor layer.

When manufacturing the semiconductor laser devices of Examples 1 to 4 and Comparative Example, the semiconductor layers exposed by etching are different from each other, and the details will be described later.

On the predetermined semiconductor layer exposed as described above, Ti having a thickness of 100 nm, Al having a thickness of 200 nm, and Au having a thickness of 500 nm are sequentially vapor-deposited.
23 and 51 were formed.

Further, p electrodes 20 and 52 were formed on p-contact layer 10. When forming the p-electrodes 20 and 52, first, a width 1
A photoresist having a stripe shape of 0 μm and a length of 700 μm was formed. Next, the p-contact layer 10
On top of 300 nm thick Pt and 400 nm thick Au
After vapor deposition, the photoresist is removed. Thus, the striped p-electrodes 20 and 52 were formed.

Finally, the sapphire substrate 1 and the semiconductor layers 2 to 10 are cleaved along a plane parallel to the short sides of the p-electrodes 20 and 52, that is, the c (0001) plane of the sapphire substrate 1, to have a width of 10 μm and a length of 500 μm. Was fabricated.

Example 1 In Example 1, the semiconductor laser device 100 of FIG. 1 in which the n-electrode 21 was in contact with the n-clad layer 4 was used.

In manufacturing such a semiconductor laser device 100, the p-contact layer 10 to the n-cladding layer 4
The n-cladding layer 4 was exposed by etching up to 2 μm.

Example 2 In Example 2, the semiconductor laser device 101 of FIG. 2 in which the n-electrode 22 was in contact with the n-cladding layer 4 and the n-GaN layer 3 was used.

In manufacturing such a semiconductor laser device 101, the p-contact layer 10 to the n-cladding layer 4
The n-cladding layer 4 was exposed to expose the n-cladding layer 4 and a predetermined region of the exposed n-cladding layer 4 was further etched to expose the n-GaN layer 3.

Example 3 In Example 3, the semiconductor laser device 102 of FIG. 3 in which the n-electrode 23 was in contact with the n-light guide layer 5 was used.

In manufacturing such a semiconductor laser device 102, the p-contact layer 10 is replaced by the n-light guide layer 5.
Then, the n-light guide layer 5 was exposed.

Example 4 In Example 4, the semiconductor laser device 103 of FIG. 4 in which the n-electrode 24 was in contact with the n-MQW light emitting layer 6 was used.

In manufacturing such a semiconductor laser device 103, 1.1 μm from the p-contact layer 10 to the n-MQW light emitting layer 6 was etched to expose the n-MQW light emitting layer 6.

Comparative Example In the comparative example, the semiconductor laser device of FIG. 7 in which the n-electrode 51 was in contact with the n-GaN layer 3 was used.

In the manufacture of such a semiconductor laser device, three layers from the p-contact layer 10 to the n-GaN layer 3 are formed.
μm was etched to expose the n-GaN layer 3.

Table 1 shows the measurement results of Examples 1 to 4 and Comparative Example.

[0109]

[Table 1]

As shown in Table 1, the semiconductor laser devices 100 to 103 of Examples 1 to 4 have a lower operating voltage and a higher light output than the semiconductor laser devices of Comparative Examples. Therefore, the luminous efficiency of the semiconductor laser devices 100 to 103 increases. In particular, when the n-electrode 21 is brought into contact with the n-cladding layer 4, the luminous efficiency is significantly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a GaN-based semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a GaN-based semiconductor laser device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a GaN-based semiconductor laser device according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a GaN-based semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a BN semiconductor laser device according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a BN semiconductor laser device according to a sixth embodiment of the present invention.

FIG. 7 is a cross-sectional view of a conventional GaN-based semiconductor laser device.

FIG. 8 is an energy band structure diagram of a main part in the GaN-based semiconductor laser device of FIGS.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sapphire substrate 2 Low temperature buffer layer 3 n-GaN layer 4 n-cladding layer 5 n-light guide layer 6 n-MQW light emitting layer 7 p-AlGaN layer 8 p-light guide layer 9 p-cladding layer 10 p-contact layer 20, 52 p electrode 21 to 24, 41, 43, 51 n electrode 100 to 103, 200, 201 semiconductor laser element

Claims (9)

[Claims] A first semiconductor layer made of a nitride-based semiconductor containing at least one of boron, gallium, aluminum and indium, the first semiconductor layer including a first conductivity type cladding layer and a light emitting layer in order; and the first semiconductor layer. Formed on boron, gallium,
A second semiconductor layer comprising a nitride-based semiconductor containing at least one of aluminum and indium and including a cladding layer of a second conductivity type, wherein a partial region of the first semiconductor layer is exposed, and A semiconductor light emitting device wherein an ohmic electrode is formed in a partial region. 2. The method according to claim 1, wherein a part of the first conductive type clad layer of the first semiconductor layer is exposed, and the ohmic electrode is formed on the exposed part of the first conductive type clad layer. The semiconductor light emitting device according to claim 1, wherein: 3. The device according to claim 1, wherein a part of the light emitting layer of the first semiconductor layer is exposed, and the ohmic electrode is formed in a part of the exposed light emitting layer. Semiconductor light emitting device. 4. The first semiconductor layer further includes a light guide layer between the first conductivity type cladding layer and the light emitting layer, and a partial region of the light guide layer of the first semiconductor layer is formed. 2. The semiconductor light emitting device according to claim 1, wherein the ohmic electrode is formed in an exposed part of the exposed light guide layer. 5. The cladding layer of the first conductivity type is an n-type cladding layer, the cladding layer of the second conductivity type is a p-type cladding layer, and a part of the n-type cladding layer is exposed. 3. The semiconductor light emitting device according to claim 1, wherein the ohmic electrode is formed in a partial region of the n-type clad layer. 6. The cladding layer of the first conductivity type is an n-type cladding layer, the cladding layer of the second conductivity type is a p-type cladding layer, the light emitting layer is doped with an n-type impurity, 4. The semiconductor light emitting device according to claim 1, wherein a part of the light emitting layer is exposed, and the ohmic electrode is formed in a part of the exposed light emitting layer. 7. The cladding layer of the first conductivity type is an n-type cladding layer, the cladding layer of the second conductivity type is a p-type cladding layer, and the first semiconductor layer is the same as the n-type cladding layer. Further comprising an n-type light guide layer between the light-emitting layer and a part of the n-type light guide layer of the first semiconductor layer; 5. The semiconductor light emitting device according to claim 1, wherein an ohmic electrode is formed. 8. The cladding layer of the first conductivity type is a p-type cladding layer, the cladding layer of the second conductivity type is an n-type cladding layer, and a partial region of the p-type cladding layer is exposed. 3. The semiconductor light emitting device according to claim 1, wherein said ohmic electrode is formed in a partial region of said p-type cladding layer. 9. The cladding layer of the first conductivity type is a p-type cladding layer, the cladding layer of the second conductivity type is an n-type cladding layer, and the first semiconductor layer is light-emitting with the p-type cladding layer. A p-type light guide layer between the first semiconductor layer and a part of the p-type light guide layer in the first semiconductor layer; 5. The semiconductor light emitting device according to claim 1, wherein an electrode is formed.