JP3447920B2 - Gallium nitride based compound semiconductor laser and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using a gallium nitride-based compound semiconductor material, and more particularly to a gallium nitride-based compound semiconductor laser used for light emission of a short wavelength and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, GaN has been used as a material for short wavelength light emitting diodes and semiconductor lasers in the blue to ultraviolet range.
Gallium nitride-based compound semiconductors, such as, are drawing attention. Above all, a blue semiconductor laser using this material system is expected to be applied as a light source for high-density information processing because of its short oscillation wavelength.

In order to oscillate a semiconductor laser with a low threshold current, it is necessary to efficiently inject carriers into the active layer and confine light. In order to efficiently inject carriers into the active layer, a double heterojunction having a pn junction and a current constriction structure are important. Further, in order to efficiently confine light, it is important to form an optical waveguide having a large refractive index difference.

However, for gallium nitride-based compound semiconductor lasers, only formation of an optical waveguide by mesa or a surface emission type has been proposed, and other structures and manufacturing methods have not been reported. Further, in such a conventional semiconductor laser, carrier injection and light confinement are not always sufficient, and in the mesa type optical waveguide, the contact area on the p side is small, resulting in high element resistance. In other compound semiconductor materials, it is possible to embed both sides of the mesa with current blocking layers to efficiently inject carriers and confine light, but in gallium nitride-based compound semiconductor materials, such a configuration is applied as it is. I can't do it either.

This is considered to be due to the following reason. That is, the gallium nitride-based compound semiconductor material has difficulty in crystal growth, and it is difficult to obtain good crystal quality. For this reason, it is difficult to form the desired surface by etching to form the desired surface. Furthermore, it is extremely difficult to re-grow the gallium nitride-based compound semiconductor material in a stepped portion after the mesa etching, and as described above, it is difficult to form a desired mesa by exposing a desired surface by mesa etching. Makes embedding on both sides of the mesa increasingly difficult.

[0006]

As described above, in the conventional semiconductor laser using the gallium nitride-based compound semiconductor material, carrier injection and light confinement are not always sufficient, and the threshold value cannot be lowered. . Further, in the mesa type optical waveguide, there is a problem that the contact area on the side opposite to the substrate (generally the p-side) is small, resulting in high element resistance.

The present invention has been made in view of the above circumstances, and an object thereof is to favorably inject carriers and confine light in a double hetero structure portion using a gallium nitride compound semiconductor material. A gallium nitride-based compound semiconductor laser that can be used as a light source of a short wavelength that oscillates at a low threshold and a method for manufacturing the same.

[0008]

[Means for Solving the Problems]

(Structure) In order to solve the above problems, the present invention employs the following structures. The present invention provides a gallium nitride-based compound semiconductor materials _{(In x Ga y Al z B} 1-xyz N:
0 ≦ x, y, z, x + y + z ≦ 1), and a gallium nitride-based compound semiconductor laser having a double heterostructure part in which an active layer is sandwiched by clad layers having different conductivity types,
The double heterostructure portion is formed on the substrate via a buffer layer made of a gallium nitride-based compound semiconductor material,
In addition, it is characterized in that it is formed in a mesa type, and both sides of this mesa type structure are filled with a current blocking layer.

The preferred embodiments of the present invention are as follows. (1) The current blocking layer is made of gallium nitride-based compound semiconductor material. (2) The current blocking layer made of gallium nitride compound semiconductor material should be a high resistance layer. (3) The current blocking layer made of a gallium nitride-based compound semiconductor material should be one in which a plurality of layers are stacked and a pn reverse junction is used. (4) The current blocking layer should consist of an insulating film such as an oxide film. (5) The active layer should have a multiple quantum well structure. (6) Both sides of the mesa-type active layer are partially removed, and a mass transport layer made of a gallium nitride-based compound semiconductor is formed on the removed portion. (7) The current blocking layer is formed on the surface where at least the layer containing Al is exposed. (8) The position of the mesa structure formed in the double hetero structure portion is located closer to the electrode than the center of the mesa structure for forming the substrate-side electrode. (9) The width of the mesa structure formed in the double hetero structure portion is 1 of the width of the mesa structure for forming the electrode on the substrate side.
/ 50 or less. (10) The distance between the mesa structure formed in the double hetero structure and the end of the mesa structure for forming the electrode on the substrate side is 3 times the width of the mesa structure formed in the double hetero structure. More than 20 times and less than 20 times. (11) The effective refractive index of the mesa structure formed in the double hetero structure portion is smaller than the effective refractive index of the current blocking layer. (12) The double hetero structure portion is formed in a mesa type except for a part of the cladding layer on the substrate side, the cladding layer is a layer containing Al, and the current blocking layer is a layer not containing Al. (13) The element main part including the double hetero structure part and the current block layer is formed on the first conductivity type contact layer formed on the insulating substrate, and the second conductivity type contact layer is formed on the double hetero structure part. Formed, part of the element main part is the first
The conductive type contact layer is removed until it is exposed, the first electrode is formed on the exposed first conductive type contact layer, and the second electrode is formed on the second conductive type contact layer. (14) The mesa-type double hetero structure portion is formed so as to be biased toward the first electrode side closer to the substrate than the center of the element main portion. (15) The current blocking layer is made of a gallium nitride-based compound semiconductor material, and the active layer portion has at least In _a Ga _b Al _c.
A well layer made of B _1-abc N (0 ≦ a, b, c, a + b + c ≦ 1) and In _e Ga _f Al _g B _1-efg N (0 ≦
e, f, g, a barrier layer composed of e + f + g ≦ 1) and a single quantum well or multiple quantum wells. (16) The refractive index of the current blocking layer is larger than the equivalent refractive index of the double hetero structure section.

According to the present invention, in the method of manufacturing a semiconductor laser having the above structure, a step of forming a buffer layer made of a gallium nitride compound semiconductor material on a substrate, and a step of making a gallium nitride compound semiconductor material on the buffer layer. ,
A step of forming a double heterostructure part in which an active layer is sandwiched by clad layers having different conductivity types, a step of selectively etching the double heterostructure part in a mesa shape to form a mesa structure, and leaving it in a gas phase at a high temperature. Then, by re-evaporating the crystal, a part of both sides of the active layer of the mesa structure is partially removed, and the crystal is grown by leaving it in a vapor phase at a high temperature.
The method further comprises the steps of forming a mass transport layer made of a gallium nitride-based compound semiconductor material on at least the removed portions on both sides of the active layer, and growing a current blocking layer on both sides of the mesa structure. To do. Furthermore, in order to selectively etch the double heterostructure,
A mask pattern is formed by using a three-layer resist of resist / intermediate layer / resist.

(Function) According to the present invention, the double heterostructure made of gallium nitride compound semiconductor material is not directly formed on the substrate such as sapphire, but is made of the gallium nitride compound semiconductor material on the substrate. By forming the buffer layer and forming the double hetero structure portion on the buffer layer, crystal growth for the double hetero structure portion can be relatively easily performed, and the quality of each crystal layer is improved. You can Therefore, the mesa structure having a desired shape can be formed by exposing a desired surface by etching for forming a mesa. Therefore, it becomes easy to re-grow the gallium nitride-based compound semiconductor material in a stepped portion after the mesa etching, and the side portion of the mesa structure can be filled with the current blocking layer.

By embedding both sides of the mesa structure with the current block layer, carriers can be efficiently injected into the active layer, and if the refractive index of the current block layer is made smaller than that of the active layer. The light can be confined in the active layer, and the oscillation threshold can be reduced. In particular, when the active layer has a multiple quantum well structure, the oscillation threshold can be further reduced. Furthermore, by embedding both sides of the mesa structure with the current blocking layer, it is possible to form the contact layer not only on the mesa structure but also on the current blocking layer, and thereby widen the contact of the p-side electrode. Therefore, it is possible to drive at a low voltage by reducing the contact resistance between the electrode and the semiconductor layer.

Further, by forming the current blocking layer on the surface where the layer containing at least Al is exposed, the reactive current flowing through the regrowth interface is reduced and the low threshold current,
It is possible to realize low operating voltage and high reliability devices.

Further, by arranging the position of the mesa structure formed in the double hetero structure portion closer to the electrode than the center of the mesa structure portion for forming the electrode, the current path is shortened and the operating voltage is reduced. Can be reduced. However, the distance between the mesa structure formed in the double hetero structure and the end of the mesa structure for forming the electrode is 3 times or more the width of the mesa formed in the double hetero structure, It is desirable to be within 20 times. This is because when the mesa structure formed in the double hetero structure portion is close to the electrode forming mesa, the reactive current path flowing on the side surface becomes longer than the current flowing through the mesa portion, which causes an increase in operating voltage. Because.

Further, the width of the mesa structure formed in the double hetero structure portion is set to 1/50 or less of the width of the mesa structure for forming the substrate side electrode, so that the double hetero structure portion is formed. Giving an appropriate strain to the mesa type structure,
The threshold current can be reduced.

Further, by making the effective refractive index of the mesa structure formed in the double hetero structure portion smaller than that of the current blocking layer, the width of the mesa structure formed in the double hetero structure portion is reduced. Even if the width is not extremely narrowed, a light guiding effect is generated, and it is possible to realize a stable element having a small transverse difference and stable fundamental transverse mode oscillation.

Further, both sides of the mesa-type active layer are removed by re-evaporation of the crystal by leaving it in the vapor phase at high temperature, and a mass transport layer is formed in this portion by growing the crystal by leaving it in the vapor phase at high temperature. Therefore, the crystallinity between the current block layer embedded in the side surface of the mesa structure and the mesa interface is improved. Therefore, the leak current on the side surface of the mesa is reduced and the current is effectively injected into the active layer, so that it is possible to realize a high-power short-wavelength semiconductor laser that oscillates at a lower threshold value.

Further, by using the three-layer resist for forming the mesa structure of the double hetero structure portion, a mask having vertical sidewalls can be formed, whereby the mesa structure of the double hetero structure portion can be formed. It is possible to control the width accurately.

[0019]

DETAILED DESCRIPTION OF THE INVENTION The details of the present invention will be described below with reference to the illustrated embodiments. (First Embodiment) FIG. 1 is a sectional view showing the device structure of a gallium nitride-based compound semiconductor laser according to the first embodiment of the present invention.

An n-type GaN contact layer 103 is formed on a sapphire substrate 101 with a GaN buffer layer 102 interposed therebetween. N-type AlG is formed on the contact layer 103.
aN clad layer 104, n-type GaN guide layer 105, multiple quantum well structure (MQW) active layer 106, p-type GaN
A mesa structure having a guide layer 107 and a p-type AlGaN cladding layer 108 is formed, and a high-resistance GaN current blocking layer 110 having a smaller refractive index than the active layer 106 is buried and formed on both sides of the mesa structure. Where M
The QW active layer 106 is made of In having a In content of 5% as a barrier layer.
GaN and InGaN with an In composition of 15% are used for the well layer. Then, the mesa structure and the current blocking layer 11
On 0, a p-type GaN contact layer 109 is formed.

The current block layer 110 is not formed on the entire surface of the contact layer 103, but is formed so that a part of the contact layer 103 is exposed. The n-side electrode 11 is formed on the exposed portion of the contact layer 103.
1 is formed. Further, a p-side electrode 112 is formed on the p-type GaN contact layer 109.

The mesa structure has a stripe shape in the front and back direction of the paper, and the stripe width is 0.5 to 3 μm.
The length in the stripe direction was 500 μm. The length of the mesa structure and the current blocking layer in the direction orthogonal to the stripe is 200 μm, and the length of the exposed portion of the n-type GaN contact layer 103 in the direction orthogonal to the stripe is 200 μm.
And

As a manufacturing process, a well-known metal organic chemical vapor deposition method (MOCVD method) is used to grow a GaN buffer layer 102 having a thickness of 50 nm on a sapphire substrate 101, and an n-type GaN layer having a thickness of 4 μm. A contact layer 103, an n-type AlGaN cladding layer 104 having a thickness of 1 μm, a thickness of 0.
5 μm n-type GaN guide layer 105, 0.3 μm-thick MQW active layer 106, 0.5 μm-thick p-type GaN guide layer 107, 1 μm-thick p-type AlGaN cladding layer 1
Up to 08 are sequentially grown and formed.

Next, the above-mentioned laminated film is selectively etched in a mesa shape until the n-type GaN contact layer 103 is exposed to form a mesa structure. As an etching method, SiO ₂ is used as a mask material, a dry etching method using chlorine gas or the like, or NaO heated to about 300 ° C. is used.
It is desirable to use wet etching by immersing in H solution. Here, the surface of the GaN layer 103, which is the base of the mesa structure, is the (0001) plane, and the side surface of the mesa is the (11′00) plane or the (112′0) plane. However, x'means the inversion symbol of x.

With respect to the mesa structure thus formed, the mesa portion is protected and the high resistance GaN block layer 110 is formed.
Grow selectively. The high resistance GaN layer 110 can be formed by adding zinc. p-type Al
After adjusting the GaN clad layer 108 and the high-resistance GaN layer 110 to be substantially in the same plane, the thickness is 0.3 μm.
The p-type GaN contact layer 109 is grown. The contact layer 109 is heavily doped with impurities (about 1 × 10 ¹⁹ cm ⁻³ ) to spread the current in the lateral direction.

Here, when growing the p-type GaN contact layer 109, since the wafer is once taken out from the growth apparatus, an oxide film is formed on the original crystal region, and the crystal quality of the regrowth layer is improved. It's not good. Therefore,
It is desirable to form the p-type contact layer 109 after lightly vapor-phase etching the surface with hydrogen before regrowth. Through such a step, it is possible to avoid the formation of an insulating layer at the interface between the original crystal region and the regrown layer.

Further, the regrown layer (p-type contact layer 10
It is also possible to form a low temperature buffer layer at about 550 ° C. immediately before forming 9). By doing so, three-dimensional growth of the regrown layer in the initial growth mode can be suppressed, and a flat two-dimensional grown crystal can be obtained from the initial stage.

Needless to say, the same effects can be obtained when the high resistance GaN block layer 110 is formed by the above-mentioned two steps. The embedded structure thus formed is etched by a dry etching method using SiO ₂ or the like as a mask until a part of the n-type GaN layer 103 is exposed. Then, the electrodes are formed by a known vacuum deposition method. The electrode material is n
As the n-side electrode for the p-type GaN contact layer 103, a Ti / Au laminated film 111 and a p-type GaN contact layer 10 are used.
As the p-side electrode for 9, the Ni / Au laminated film 112 is used. It is desirable to perform heat treatment at 700 ° C. for 5 minutes in order to make the electrode ohmic.

As described above, according to this embodiment, the GaN buffer layer 102 for relaxing the lattice mismatch is formed on the sapphire substrate 101, and the laminated structure including the double hetero structure portion is formed thereon. Therefore, the crystal growth for the double hetero structure can be easily performed, and the quality of each crystal layer can be improved. Therefore, by etching for the mesa shape, a desired surface can be formed and a mesa having a desired shape can be formed. Therefore, it is relatively easy to re-grow the gallium nitride-based compound semiconductor material in the place where there is a step after the mesa etching, and the mesa side portion can be well filled with the gallium nitride-based compound semiconductor.

Usually, many interface states are formed on the side surface of the crystal just etched. Such an interface state becomes a source of leak current (reactive current), and reduces the efficiency of current injection. Therefore, the action of the interface state on the side surface of the mesa must be suppressed. As one means for suppressing the effect of such an interface state, there is a method of forming the block layer after protecting the side surface of the mesa with an oxide film such as SiO ₂ . As another means, after the mesa structure is formed, the side surface of the mesa may be lightly etched with hydrogen or the like, and then the block layer may be formed. The former can suppress the effect of the interface level by passivating the interface level with an oxide film or the like, and the latter by removing the disorder of the crystal surface which is the source of the interface level.

In addition, since both sides of the mesa structure are filled with the GaN current blocking layer 110, the active layer 10 is formed.
Carrier can be efficiently injected into the active layer 10 and GaN is used as the current blocking layer 110.
Since the refractive index is smaller than that of 6, light can be confined in the active layer 106, and the oscillation threshold value can be reduced. In particular, since the active layer 106 has a multiple quantum well structure, it is possible to further reduce the oscillation threshold.

Further, by embedding both sides of the mesa structure in the current blocking layer 110, the p-type GaN contact layer 109 can be formed not only on the mesa structure but also on the current blocking layer 110. Side electrode 11
The second contact can be widened, and low voltage driving is possible by reducing the contact resistance between the electrode and the semiconductor layer.

(Modification of the First Embodiment) In the first embodiment, the active layer 106 is an MQ having an InGaN barrier layer with an In composition of 5% and an InGaN well layer with an In composition of 15%.
Although the W structure is used, a single InGaN or single quantum well structure may be used. The MQW is advantageous in the following points. That is, in the layer closer to the substrate than the active layer, the substrate and the G
Lattice defects are likely to occur due to the difference in lattice constant from the aN-based layer, but when the active layer is MQW, lattice relaxation occurs and the impurity activation rate of the p-type layer formed above the active layer is increased. be able to. Further, the barrier layer and the well layer is not limited to InGaN, GaN-based compound semiconductor materials _{In x Ga y Al z B 1} -xyz N (0 ≦
If x, y, z, x + y + z ≦ 1), it can be used.

In the first embodiment, the current blocking layer 11
As a manufacturing method of the high resistance layer as 0, Z at the time of crystal growth is used.
Although the addition of n has been shown as an example, it is also possible to increase the resistance by inactivating impurities by ion implantation of hydrogen or the like. Further, the etching mask and the growth mask in the manufacturing process are not necessarily limited to SiO ₂ and may be Si ₃ N ₄ or the like. The substrate is not limited to sapphire, but spinel, oxides such as ZnO and S
It is also possible to use semiconductors such as iC, GaAs, GaN, ZnSe and Si, and insulators such as MgF ₂ .

The current blocking layer 110 is not limited to Zn-doped high-resistance GaN, but may be AlN, InN, or the like.
Alternatively, a mixed crystal of these and GaN, or an insulating film such as SiO ₂ may be used. Further, as shown in FIG.
The type GaN layer 121 and the n-type GaN layer 122 may be laminated and the pn reverse junction between them may be used.

The peripheral structure of the burying layer is not limited to simple burying and may be a structure as shown in FIG. 2 (b). In FIG. 2B, the p-type GaN contact layer 10
9 is also formed on the side surface of the mesa structure, and the active layer 106 of Zn added to the current block layer (high resistance layer) 110 is formed.
To spread to. In this case, the current confinement can be performed by utilizing the difference in the built-in potential.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
3 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to the embodiment of FIG. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

This embodiment is different from the first embodiment in that the cladding layer 104, the guide layer 105 and the active layer 10 are different.
In the mesa structure composed of 6, the guide layer 107 and the clad layer 108, a part of the clad layer 104 on the substrate side is left. In this case, high-resistance GaN containing no Al
The current blocking layer 110 is to be embedded and grown on the n-type AlGaN cladding layer 104 containing Al.

With such a structure, the same effects as those of the first embodiment can be obtained, and the following effects can be obtained. That is, the high-resistance GaN current blocking layer 110 is not in contact with the n-type GaN layer 103, but is in contact with the n-type AlGaN cladding layer 104.
It is possible to reduce the leak current and the threshold value.

That is, in this embodiment, the GaN current blocking layer 110 is formed of the n-type cladding layer 10 made of n-type GaAlN.
It is formed by exposing the surface of No. 3 and regrowth on it. In this case, the current blocking layer 110 is preferably a substantially high resistance i-type layer such as Zn-doped GaN. Here, on the surface containing Al, GaAlN,
InGaAlN and the like. GaN on the surface containing Al
By forming the current blocking layer of (1), the generated recombination current can be suppressed by the heterobarrier, so that a better current constriction effect can be obtained.

Although the active layer portion in FIG. 3 has a structure in which the MQW active layer is sandwiched between the guide layers as in FIG. 1, it is not necessarily required to have a quantum well structure and may be a single layer active layer. Also, in this embodiment, various modifications as described in the first embodiment are possible.

Further, as shown in FIG. 18, by forming the p-type GaAlN layer 108 also on the current blocking layer 110, the effect of suppressing the generated recombination current by the heterobarrier becomes remarkable, and the current constriction effect. Can be increased.

(Third Embodiment) FIG. 4 shows a second embodiment of the present invention.
FIG. 2 is a perspective view (a) and a sectional view (b) showing an element structure of the gallium nitride-based compound semiconductor laser according to the embodiment.
The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

The present embodiment is different from the first embodiment in that the mesa-type double hetero structure part is located closer to the n-side electrode 111 than the center of the main part of the element composed of the double hetero structure part and the current block layer. It is formed unevenly. That is, the double hetero structure portion is formed not on the center of the element main portion but on the n-side electrode 111 side, and
The width of the current blocking layer on the first side is 10 μm.

With such a structure, the same effect as in the first embodiment can be obtained, and the stripe portion of the double hetero structure is closer to the electrode side than the center, so that the current path is shortened. The operating voltage can be lowered.

Here, the distance between the mesa type structure portion (stripe portion) formed in the double hetero structure portion and the end portion of the mesa type structure (element main portion) for forming the n-side electrode is equal to the distance of the stripe portion. It is desirable that the width is 3 times or more and 20 times or less. This is because when the stripe portion is close to the end portion of the element main portion, the reactive current path flowing on the side surface becomes longer than the current flowing through the stripe portion, which causes an increase in operating voltage. From this point of view, the width of the stripe portion may be 0.5 to 3.3 μm, and the length from the stripe portion to the end portion of the element main portion may be 10 μm.

In the structure shown in FIG. 4, the width of the stripe portion is set to 1/50 or less of the width of the main portion of the element for forming the n-side electrode 111. As a result, appropriate distortion is given to the stripe portion, and the threshold current can be suppressed. Furthermore, in the configuration of FIG.
By making the effective refractive index of the stripe portion smaller than the effective refractive index of the current block layer 110, a light guiding effect is generated without extremely narrowing the width of the stripe portion, and thus an element having a small astigmatic difference is obtained. It can be realized.

Although the MQW active layer portion is a single layer in FIG. 4, the MQW active layer may be sandwiched between the guide layers as in FIG. Also in this embodiment,
Various modifications as described in the first embodiment are possible. Further, the configuration in which the stripe portion is displaced from the center to the electrode side as in the present embodiment can be applied to the configurations shown in FIGS.

(Fourth Embodiment) FIG. 5 shows a fourth embodiment of the present invention.
3 is a cross-sectional view showing a device structure of a gallium nitride-based compound semiconductor laser according to the embodiment of FIG.

An n-type GaN layer contact layer 203 is formed on a sapphire substrate 201 via a GaN buffer layer 202, and an n-type AlGaN cladding layer 204, is formed thereon.
The double hetero structure portion in which the InGaN-MQW active layer 205, the p-type AlGaN cladding layer 206, and the p-type GaN layer 207 are laminated is processed into a mesa shape.

Both sides of the active layer 205 having a mesa structure are partially removed, and in this portion, a (Al, In) GaN layer (mass transport layer) 21 having a lower refractive index than the active layer 205 is formed.
1 is formed. Furthermore, p is on both sides of the mesa structure.
-Type GaN buried layer 212 and n-type GaN buried layer 21
A current block layer formed by stacking 3 is buried and formed.

A p-type GaN contact layer 208 is formed on the mesa structure portion and the n-type GaN layer 213, and each layer is removed by etching so that a part of the n-type GaN layer contact 203 is exposed. And the exposed n-type G
An n-side electrode 221 is formed on the aN contact layer 203, and a p-side electrode 22 is formed on the p-type GaN contact layer 208.
2 is formed.

In this embodiment, the (Al, In) GaN layer 211 having a lower refractive index than the active layer 205 is used as the active layer 2.
When it is formed in contact with 05, light can be confined in the active layer 205. Furthermore, the p-type GaN burying layer 212 and the n-type GaN burying layer 213 are used to form the active layer 20.
The current can be narrowed to 5 and the current can be efficiently injected into the active layer 205. That is, the p-side electrode 222 is formed on the entire surface of the p-type GaN contact layer 208, but current is effectively injected into the active layer 205 by the pn reverse junction of the buried layers 212 and 213. In such a structure, p
Since the contact area of the side electrode 222 can be widened, the contact resistance between the electrode and the semiconductor layer can be reduced, driving at low voltage is possible, and the reliability is greatly improved. In addition, p-type Ga
Since the element surface is flattened by the N contact layer 208, there is also an advantage that it is easy to form a chip.

In the manufacturing method, RIE is generally used as a method for etching the double hetero structure into a mesa shape, but at this time, the crystal surface is damaged. Therefore, the damaged layer on the surface is removed by wet etching, but it is difficult to remove the gallium nitride-based material by wet etching. Therefore, the present embodiment is characterized by performing etching and further crystal growth in a crystal growth furnace.

That is, when the mesas are formed by dry etching by RIE or the like and then the embedded growth is carried out by the MOCVD method or the like, the crystal is etched if the substrate temperature is kept at 800 ° C. and the NH ₃ gas flow rate is reduced. In particular, InGaN
The layer has a large etching rate and the active layer 205 in the mesa portion
Is easily etched, and the damaged layer can be easily removed by RIE. Subsequently, when the substrate temperature is kept at 800 ° C. and the NH ₃ gas flow rate is increased, crystals are grown at the corners of the active layer portion etched by mass transport and the mesa bottom portion. According to such a manufacturing method, the leak current on the side surface of the mesa is reduced, and the current is effectively injected into the active layer 205.

6 and 7 are sectional views showing the manufacturing process of the same embodiment. First, as shown in FIG. 6A, a GaN buffer layer 202 having a thickness of 50 nm and an n-type GaN layer contact 20 having a thickness of 4 μm are formed on a sapphire substrate 201.
3, n-type AlGaN clad layer 204 having a thickness of 1 μm, InGaN-MQW active layer 205 having a thickness of 0.3 μm, p-type AlGaN clad layer 206 having a thickness of 1 μm, thickness 0.5
The μ-type p-type GaN layer 7 is sequentially grown by the MOCVD method.

Then, as shown in FIG. 6B, p-type G
After forming the SiO ₂ film 231 on the surface of the aN layer 207,
Patterning by PEP method, etching and p-type G
The aN layer 207 is exposed and n-type GaN is formed by the RIE method.
Etch until layer 203 is exposed. Here, the patterning of the SiO ₂ film 231 may be performed using a three-layer resist as described later.

Next, when the temperature is kept at 800 ° C. in the MOCVD reaction furnace and the flow rate of NH ₃ gas is 2 l / min and the flow rate of N ₂ gas is ₂₀ l / min, the surface becomes gas, as shown in FIG. The active layer 205 is partially etched, especially on both sides.

Next, the flow rate of NH ₃ gas is 10 l / min, and N _{2 is}
When a gas flow rate of 20 l / min is applied, as shown in FIG. 6D, a crystal layer (mass transport layer) 211 grows so that the irregularities on the surface of the mesa are filled with the mass transport.

Then, as shown in FIG. 7E, p-type G
Current blocking layers of the aN buried layer 212 and the n-type GaN buried layer 213 are formed. The above-described gas etching on both sides of the active layer, formation of the mass transport layer, and formation of the current block layer can be continuously performed in the same reaction furnace to which the raw material gas for MOCVD is supplied. The sides of the mesa structure are not exposed to the atmosphere.

Then, as shown in FIG. 7F, the SiO ₂ film 231 on the surface is removed to remove the p-type GaN contact layer 2
Grow 08. Then, as shown in FIG.
After forming the SiO ₂ film 231, the p-type GaN contact layer 208 is formed by patterning and etching by the PEP method.
Are exposed, and etching is performed by RIE until the n-type GaN contact layer 203 is exposed.

Next, Ti / Au is used as the n-side electrode 221.
A laminated film is formed, and Ni / A is used as the p-side electrode 222.
The structure shown in FIG. 3 is obtained by applying heat treatment after forming the u laminated film.

The results of examining the current-optical power / voltage characteristics of the semiconductor laser thus obtained are shown in FIGS. 8 (a) and 8 (b), respectively. In this embodiment, good characteristics with a threshold current of about 1/2 of that of the conventional example were obtained. Further, since the surface of the wafer has few irregularities, the device yield at the time of chip formation was as good as 90% or more.

(Modification of Fourth Embodiment) In the fourth embodiment, the crystal layer 211 formed by mass transport is formed on the mesa bottom together with the side of the active layer 205.
As shown in (a), the crystal layer 211 may be formed only on the side portion of the active layer 205.

The current blocking layer is not limited to the one using the pn reverse junction, but as shown in FIG.
The high resistance layer 215 of GaN may be used. Furthermore, FIG.
As shown in (c), the crystal layer 211 may be formed by mass transport after performing gas etching to such an extent that the active layer 205 is not largely etched. Moreover, as described in the modification of the first embodiment,
The configuration of the active layer, the configuration and material of the current blocking layer, etc. can be appropriately changed according to the specifications.

(Fifth Embodiment) FIG. 10 is a sectional view showing the device structure of a gallium nitride-based compound semiconductor laser according to the fifth embodiment of the present invention. The basic structure is the same as that of the first embodiment shown in FIG.

In the figure, reference numeral 301 denotes a sapphire substrate, on which a GaN buffer layer 302, an n-type GaN contact layer 303, an n-type AlGaN cladding layer 304,
n-type GaN waveguide layer 305, MQW active layer 306 made of InGaN, p-type GaN waveguide layer 307, p-type AlGaN
Clad layer 308, AlGaN current blocking layer 310,
A p-type GaN contact layer 309 is formed. These crystal growths are performed by MOCVD method or MBE method.

The p-type AlGaN clad layer 308 to the n-type AlGaN clad layer 304 are removed by etching except for the mesa portion, and the high-resistance AlGaN current block layer 310 is formed on both sides thereof. The p-type GaN contact layer 309 to the n-type GaN contact layer 303 are partially removed, and the n-side electrode 311 is formed on the n-type GaN contact layer 303 and the p-side electrode 312 is formed on the p-type GaN contact layer 309. To be done.

The active layer portion of this laser is In _c Ga _{1 -c}
The SCH structure is provided with a multiple quantum well composed of N well layer / In _d Ga _1-d N barrier layer (c> d) and a GaN waveguide layer.

To give an example of the specific composition and the film thickness of each layer, the multiple quantum well is an In _0.2 Ga _0.8 N well layer (2n
m) / In _0.05 Ga _0.95 N barrier layers (4 nm), each of which has a thickness of 0.1 μm. Both clad layers are n-type Ga _0.85 Al _0.15 N
(0.3 μm), p-type Ga _0.85 Al _0.15 N (0.3 μm
m).

What is important here is the mesa width and the refractive index difference ΔN between the active layer portion / buried layer for obtaining stable fundamental transverse mode oscillation. Once the structure of the active layer portion is determined, ΔN is determined by the composition of the buried layer. In the example of the present embodiment, the buried layer is G
a _0.94 Al _0.06 N, and the stripe width was 1 μm.

Now, the relationship between the stripe width and the composition of the buried layer for realizing stable fundamental transverse mode oscillation will be described. FIG. 11 shows an In _0.2 Ga _0.8 N well layer (2n
m) / In _0.05 Ga _0.95 N barrier layer (4 nm) having a multiple quantum well structure (the parameters of the waveguide layer and the clad layer are the same as those in FIG. 10) is used in the active layer portion, Ga _1-x Al _x
It is a plot of the stripe width W that satisfies the condition that the first-order mode (higher-order mode) of the horizontal transverse mode is cut off with respect to the Al composition x of the N-buried layer, that is, the condition that only the basic transverse mode exists. In order to realize stable fundamental transverse mode oscillation, the stripe width W needs to be set smaller than the value shown by the curve in this figure.

The buried structure is a structure suitable for efficiently confining carriers and light and realizing oscillation at a low threshold value. However, in the gallium nitride-based compound semiconductor laser, a mesa for obtaining a fundamental transverse mode is obtained. Due to its narrow width, the manufacturing process requires strict control. The narrow mesa width is due to the short oscillation wavelength, which can be said to be an essential problem in gallium nitride-based compound semiconductor lasers.

In order to make the mesa width relatively large, the refractive index difference ΔN in the horizontal direction may be made small, that is, the Al composition of the buried layer may be made small. However, since the control of ΔN depends on the controllability of the composition and the film thickness, it is desirable to set the mesa width to 1 μm or less in order to surely cut off the higher-order mode, as can be seen from FIG.

As a method for increasing the mesa width, there is an anti-waveguide structure. The anti-waveguide structure is a structure in which the refractive index outside the stripe is larger than that inside the stripe. In this case, the refractive index difference ΔN has a negative value, which is the opposite of that of the ordinary optical waveguide.
A waveguide mode is formed by the loss difference or gain difference inside and outside the stripe. The anti-guiding structure is significantly different from a so-called gain guiding structure in which a guided mode is formed only by a gain difference. That is, the astigmatism is small and the threshold value can be lowered.

In order to compare the gain guided type, the real refractive index guided type and the anti-guided type, the astigmatic difference of each and the stripe width dependence of the loss difference between the primary mode and the fundamental mode are shown in FIG.
Shown in (a) and (b). The larger the loss difference, the easier it is to obtain oscillation in the fundamental transverse mode, and the smaller the astigmatic difference, the easier it is to use in applications such as optical discs. 12
As can be seen from (a) and (b), the gain waveguide type has a very large astigmatic difference and cannot be used for optical disk applications. On the other hand, in the real index guided type, the astigmatic difference can be set to a small value. However, in a region where the stripe width is large, the loss difference between the higher-order mode and the fundamental mode is essentially 0. Therefore, it is necessary to control the stripe width to an extremely small value as described with reference to FIG.

On the other hand, the anti-waveguide type has a characteristic that it is as small as the real index type and the loss difference between the higher-order mode and the fundamental mode can be increased even with a relatively wide stripe width. is there. An example of adopting such an anti-waveguide type will be described in the next sixth embodiment.

(Sixth Embodiment) FIG. 13 is a sectional view showing the device structure of a gallium nitride compound semiconductor laser according to the sixth embodiment of the present invention. The same parts as those in FIG. 10 are designated by the same reference numerals, and detailed description thereof will be omitted.

The present embodiment is different from the fifth embodiment shown in FIG. 10 in that the current blocking layer is made of high resistance In _0.2 G
a _0.8 N layer 359. As a result, the refractive index of the current blocking layer 359 becomes higher than the equivalent refractive index of the double hetero structure portion. In addition, the current blocking layer 359
Since the bandgap of is the same as the well layer that constitutes the quantum well, in the state where carriers are not injected due to high resistance,
It becomes a loss layer for the oscillation wavelength. That is, an anti-waveguiding structure in which the refractive index is within the stripe <outside the stripe and the loss is inside the stripe <outside the stripe is realized.

In this embodiment, the stripe width is 3 μm. Such a relatively wide stripe width is easy to create. Further, as described below, the anti-waveguide structure has a feature that the tolerance of the stripe width is large.

FIGS. 14A and 14B show astigmatism, fundamental mode loss, and loss between the primary mode and the fundamental mode when the parameters of the double hetero structure are the same as those of the present embodiment shown in FIG. This shows the dependence of the difference on each stripe width. As described in FIG. 12, the anti-waveguide structure has a small astigmatic difference, but as can be seen from FIG. 14B, the loss difference between the primary mode and the fundamental mode is close to the stripe width of 3 μm. It can be seen that the loss is large and the fundamental mode loss is also relatively small. Therefore, stable oscillation in the fundamental transverse mode and at a low threshold value is possible.

(Seventh Embodiment) FIG. 15 is a sectional view showing the device structure of a gallium nitride-based compound semiconductor laser according to the seventh embodiment of the present invention. The basic structure is the same as that of the fourth embodiment shown in FIG.

In the figure, 401 is a sapphire substrate, on which GaN buffer layer 402, n-type GaN contact layer 403, n-type GaAlN cladding layer 404,
n-type GaN waveguide layer 454, InGaN multiple quantum well 40
5, p-type GaN waveguide layer 456, p-type GaAlN cladding layer 406, p-type GaN cap layer 407, GaN buried layer 411, p-type InGaN buried layer 412, n-type GaN
A buried layer 413 and a p-type GaN contact layer 408 are formed. 421 is an n-side electrode and 422 is a p-side electrode.

In this embodiment, the anti-waveguide structure is realized by the loss of the p-type InGaN buried layer 412. That is, by making the bandgap of the buried layer 412 substantially equal to or smaller than the bandgap of the well layer portion of the active layer portion, it is possible to obtain a layer that gives a loss to the oscillation wavelength. Specifically, the In composition of the p-type InGaN buried layer 412 may be the same as or larger than that of the well layer. This makes it possible to obtain a gallium nitride-based compound semiconductor laser that has a low threshold and oscillates in the fundamental transverse mode.

(Eighth Embodiment) FIGS. 16 and 17 show
It is sectional drawing which shows the manufacturing process of the gallium nitride type compound semiconductor laser concerning the 8th Embodiment of this invention, and has shown the manufacturing process of the mesa structure of a double hetero structure part especially. The present embodiment can be applied to each of the embodiments described so far.

First, as shown in FIG. 16A, a GaN buffer layer 5 having a thickness of 50 nm is formed on a sapphire substrate 501.
02 is grown on the n-type GaN contact layer 503 having a thickness of 4 μm, the n-type AlGaN cladding layer 504 having a thickness of 1 μm, and the InGaN-MQW active layer 5 having a thickness of 0.3 μm.
05, p-type AlGaN cladding layer 506 having a thickness of 1 μm,
A p-type GaN layer 507 having a thickness of 0.5 μm is sequentially grown by the MOCVD method.

Next, as shown in FIG. 16B, a SiO ₂ film 531 is deposited on the p-type GaN layer 507 by thermal CVD to a thickness of 0.4 μm, and three layers of resist / intermediate layer / resist are formed thereon. A resist was formed. That is, SiO ₂
A first resist 532 having a thickness of 3 μm is applied on the film 531 and exposed to a nitrogen atmosphere at 250 ° C. for 20 minutes to cure the resist, and then a Ti (or Al) film 533 is formed by an electron beam evaporation method. Evaporation to a thickness of 100-200 nm,
A second resist 534 was applied thereon with a thickness of 1 μm. Then, the resist 534 is exposed to light by a light exposure process.
For example, a stripe pattern having a width of 1 μm was formed.

Then, as shown in FIG. 16C, reactive ion beam etching (RIB) using chlorine gas is performed.
As shown in E), the Ti film 533 was selectively etched using the resist 534 as a mask to transfer the stripe pattern.

Next, as shown in FIG. 17D, the resist 532 was selectively etched by RIBE using oxygen gas with the Ti film 533 as a mask to transfer the stripe pattern. At this time, since the resist 532 has already been cured, the resistance to chlorine plasma is good. Through these steps, a resist mask having substantially vertical sidewalls could be created.

Next, as shown in FIG. 17E, Si is formed by RIE using the resist 532 and the Ti film 533 as a mask.
The O ₂ film 531 is selectively etched, and then FIG.
As shown in, the selective etching for forming the mesa stripe was performed. As a result, a double hetero structure mesa structure having a width of 1 μm and vertical sidewalls could be obtained.

After that, the current block layer (embedded layer)
Growth, contact layer growth, and formation of a mesa-type structure for forming a substrate-side electrode (eg, steps shown in FIGS. 6 and 7)
Then, by further forming electrodes, a gallium nitride-based compound semiconductor laser can be produced.

As described above, according to the present embodiment, by using the three-layer resist, even a narrow mesa stripe can be formed with good controllability, and the embedded structure (as described in the first to seventh embodiments) can be formed. It is extremely effective in manufacturing a BH) laser. It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be carried out without departing from the scope of the invention.

[0093]

As described above in detail, according to the present invention, a mesa double heterostructure portion made of a gallium nitride compound semiconductor material is formed on a substrate through a buffer layer made of a gallium nitride compound semiconductor material. Since the structure is formed and both sides of the mesa structure are filled with the current blocking layer, carriers can be injected and light can be satisfactorily confined in the double hetero structure, and a short wavelength that oscillates at a low threshold value can be achieved. It is possible to realize a gallium nitride-based compound semiconductor laser that can be used as a light source of

[Brief description of drawings]

FIG. 1 is a sectional view showing a device structure of a compound semiconductor laser according to a first embodiment.

FIG. 2 is a sectional view of an element structure showing a modified example of the first embodiment.

FIG. 3 is a sectional view showing an element structure of a compound semiconductor laser according to a second embodiment.

FIG. 4 is a sectional view showing an element structure of a compound semiconductor laser according to a second embodiment.

5A and 5B are a perspective view and a sectional view showing a device structure of a compound semiconductor laser according to a third embodiment.

FIG. 6 is a sectional view showing a first half of a manufacturing process of a semiconductor laser according to a fourth embodiment.

FIG. 7 is a cross-sectional view showing the latter half of the manufacturing process of the semiconductor laser according to the fourth embodiment.

FIG. 8 is a diagram showing optical power and voltage characteristics of a semiconductor laser according to a fourth embodiment.

FIG. 9 is a sectional view of an element structure showing a modified example of the fourth embodiment.

FIG. 10 is a sectional view showing an element structure of a compound semiconductor laser according to a fifth embodiment.

FIG. 11 is a diagram showing high-order mode cutoff conditions.

FIG. 12 is a diagram showing a characteristic comparison among a gain waveguide type, a real refractive index waveguide type, and an anti-guided type.

FIG. 13 is a sectional view showing an element structure of a compound semiconductor laser according to a sixth embodiment.

FIG. 14 is a diagram showing characteristics of a gallium nitride-based compound semiconductor laser having an anti-waveguide structure.

FIG. 15 is a sectional view showing an element structure of a compound semiconductor laser according to a seventh embodiment.

FIG. 16 is a cross-sectional view showing the first half of the manufacturing process of the semiconductor laser according to the eighth embodiment.

FIG. 17 is a cross-sectional view showing the latter half of the manufacturing process of the semiconductor laser according to the eighth embodiment.

FIG. 18 is a cross-sectional view showing a modified example of the second embodiment.

[Explanation of symbols]

101, 201 ... Sapphire substrate 102, 202 ... GaN buffer layer 103, 203 ... n-type GaN contact layer 104.204 ... n-type AlGaN cladding layer 105 ... Undoped GaN guide layer 106, 205 ... MQW active layer 107 ... Undoped GaN guide layer 108, 206 ... p-type AlGaN cladding layer 109, 208 ... p-type GaN contact layer 110 ... GaN layer Current blocking layer 111,221 ... n side electrode 112, 222 ... P-side electrode 121, 212 ... p-type GaN buried layer layer 122, 213 ... N-type GaN buried layer layer 207 ... p-type GaN layer 211 ... (Al, In) GaN mass transport layer

─────────────────────────────────────────────────── ─── Continuation of front page (72) Shinya Nunoue 1 Komukai Toshiba Town, Komukai-ku, Kawasaki City, Kanagawa Prefecture Toshiba Research and Development Center, Inc. (72) Inventor Genichi Hatakoshi Komukai, Kawasaki City, Kanagawa Prefecture Toshiba Town No. 1 within Toshiba Research and Development Center (72) Inventor Masahiro Yamamoto No. 1 Komukai Toshiba Town, Komukai-ku, Kawasaki-shi, Kanagawa Within Toshiba Research and Development Center (56) Reference JP-A-8-148718 (JP , A) JP 2-219090 (JP, A) JP 6-152072 (JP, A) JP 5-29708 (JP, A) JP 55-82482 (JP, A) JP 62-92385 (JP, A) Jpn. J. Appl. Phys. Part 2, October 15, 1996, Vol. 35 No. 10B, p. L1315-1317 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 5/00-5/50 JISST file (JOIS)

Claims (12)

(57) [Claims] 1. A substrate, a mesa stripe formed on the substrate via a buffer layer, and having a double hetero structure having an active layer sandwiched between first and second cladding layers having different conductivity types, and the mesa. First and second current blocking layers filling both sides of the stripe, and first and second current sandwiching the double hetero structure.
A contact layer and a first layer provided on each of the first and second contact layers
And a second electrode, each of the buffer layer, the active layer, the first and second cladding layers, the first and second current blocking layers, and the first and second contact layers, In _x Ga _y Al _z B _1-xyz N, where 0 ≦ x, y, z, x + y + z ≦ 1, and the first contact layer is basically composed of a material represented by the following composition formula: Disposed on the buffer layer,
The mesa stripe and the first and second current blocking layers form an integral mesa disposed on the first contact layer, the first electrode being on the first contact layer next to the mesa. And the width of the first current blocking layer located between the first electrode and the mesa stripe is the second current facing the first current blocking layer with the mesa stripe in between. The width is smaller than the width of the block layer, and the lower portion of the first clad layer has the mesa stripe shape.
It has an extension part extending on both sides, and the first part is provided on this extension part.
First and second current blocking layers are formed, and the first cracks are formed.
The first layer and the second current block, the second layer containing Al.
A gallium nitride-based compound semiconductor laser, wherein the layer does not contain Al . 2. A part of both sides of the active layer is replaced by a mass transport layer, and the mass transport layer has a composition different from that of the active layer and is basically composed of a material represented by the composition formula. The gallium nitride-based compound semiconductor laser according to claim 1 , wherein 3. A substrate, a mesa stripe formed on the substrate via a buffer layer, and having a double hetero structure in which an active layer is sandwiched by first and second cladding layers having different conductivity types, and the mesa. First and second current blocking layers filling both sides of the stripe, and first and second current sandwiching the double hetero structure.
A contact layer and a first layer provided on each of the first and second contact layers
And a second electrode, each of the buffer layer, the active layer, the first and second cladding layers, the first and second current blocking layers, and the first and second contact layers, In _x Ga _y Al _z B _1-xyz N, where 0 ≦ x, y, z, x + y + z ≦ 1, and the first contact layer is basically composed of a material represented by the following composition formula: Disposed on the buffer layer,
The mesa stripe and the first and second current blocking layers form an integral mesa disposed on the first contact layer, the first electrode being on the first contact layer next to the mesa. And the width of the first current blocking layer located between the first electrode and the mesa stripe is the second current facing the first current blocking layer with the mesa stripe in between. The width is smaller than the width of the block layer, and both sides of the active layer are partially covered by the mass transport layer.
And the mass transport layer is replaced with the active layer.
Are materials having different compositions and represented by the above composition formula
A gallium nitride-based compound semiconductor laser having the following features. 4. The method of claim, wherein the width of the mesa stripe is 1/50 or less of the width of said integral Mesa 1
4. A gallium nitride-based compound semiconductor laser according to any one of items 1 to 3 . 5. The gallium nitride-based compound semiconductor according to claim 1, wherein the width of the first current blocking layer is 3 times or more and 20 times or less the width of the mesa stripe. laser. 6. A substrate, a mesa stripe formed on the substrate via a buffer layer, and having a double hetero structure in which an active layer is sandwiched between first and second cladding layers having different conductivity types, and the mesa. First and second current blocking layers filling both sides of the stripe, and first and second current sandwiching the double hetero structure.
A contact layer and a first layer provided on each of the first and second contact layers
And a second electrode, each of the buffer layer, the active layer, the first and second cladding layers, the first and second current blocking layers, and the first and second contact layers, In _x Ga _y Al _z B _1-xyz N, where 0 ≦ x, y, z, x + y + z ≦ 1, and the first contact layer is basically composed of a material represented by the following composition formula: Disposed on the buffer layer,
The mesa stripe and the first and second current blocking layers form an integral mesa disposed on the first contact layer, the first electrode being on the first contact layer next to the mesa. And the mesa stripes are formed to be closer to the first electrode side than the center of the mesa, and the lower portion of the first cladding layer is the mesa stripes.
It has an extension part extending on both sides, and the first part is provided on this extension part.
First and second current blocking layers are formed, and the first cracks are formed.
The first layer and the second current block, the second layer containing Al.
A gallium nitride-based compound semiconductor laser, wherein the layer does not contain Al . 7. A portion of both sides of the active layer is replaced by a mass transport layer, the mass transport layer having a composition different from that of the active layer, and basically consisting of a material represented by the composition formula. The gallium nitride-based compound semiconductor laser according to claim 6 , wherein 8. A substrate, a mesa stripe formed on the substrate via a buffer layer, and having a double hetero structure in which an active layer is sandwiched by first and second cladding layers having different conductivity types, and the mesa. First and second current blocking layers filling both sides of the stripe, and first and second current sandwiching the double hetero structure.
A contact layer and a first layer provided on each of the first and second contact layers
And a second electrode, each of the buffer layer, the active layer, the first and second cladding layers, the first and second current blocking layers, and the first and second contact layers, In _x Ga _y Al _z B _1-xyz N, where 0 ≦ x, y, z, x + y + z ≦ 1, and the first contact layer is basically composed of a material represented by the following composition formula: Disposed on the buffer layer,
The mesa stripe and the first and second current blocking layers form an integral mesa disposed on the first contact layer, the first electrode being on the first contact layer next to the mesa. That the mesa stripes are formed to be closer to the first electrode side than the center of the mesa in the mesa, and a part of both sides of the active layer is formed by a mass transport layer.
And the mass transport layer is replaced with the active layer.
Are materials having different compositions and represented by the above composition formula
A gallium nitride-based compound semiconductor laser having the following features. 9. to claim 1, characterized in that it has an extension portion that the second contact layer is located between the each of the mesa stripe and the first and second current blocking layer
9. The gallium nitride-based compound semiconductor laser according to any one of 8 . 10. The gallium nitride based compound semiconductor laser according to claim 1, wherein the first and second current blocking layers have a refractive index higher than that of the mesa stripe. 11. A step of forming a buffer layer on a substrate, a step of forming a double hetero structure in which an active layer is sandwiched between clad layers having different conductivity types, a step of forming the double hetero structure in a mesa shape. By selective etching to form a mesa stripe, and by leaving it in a vapor phase at high temperature to re-evaporate the crystal,
A step of partially removing both sides of the active layer; a step of forming a mass transport layer at least on both sides of the active layer by growing a crystal by leaving it in a vapor phase at a high temperature; Growing a current blocking layer on both sides of the mesa stripe, wherein each of the buffer layer, the active layer, the cladding layer, the current blocking layer, and the mass transport layer is represented by the following composition formula: consisting essentially of material which _{is, in x Ga y Al z B} 1-xyz N, where, 0 ≦ x, y, z , x + y + z ≦ 1, a manufacturing method of a gallium nitride-based compound semiconductor laser, wherein . 12. A resist / interlayer / resist layer for selectively etching the double hetero structure into a mesa.
The method for manufacturing a gallium nitride-based compound semiconductor laser according to claim 11 , wherein the mask pattern is formed using a layer resist.