JP2003264346A - Nitride based semiconductor laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride based semiconductor laser element wherein manufacturing yield can be improved by restraining impurity elements from being introduced deeply. <P>SOLUTION: This nitride based semiconductor laser element is provided with an MQW light emitting layer 4, a p-type clad layer 5 which is formed on the MQW light emitting layer 4 and composed of Al<SB>0.08</SB>Ga<SB>0.92</SB>N, a p-type contact layer 7 which is formed on the p-type clad layer 5 and composed of In<SB>0.05</SB>Ga<SB>0.95</SB>N, and an impurity implanted layer 8 which is formed by introducing impurity elements in at least a part of a region except current passing regions 9 of the p-type clad layer 5 and the p-type contact layer 7. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride-based semiconductor laser device, and more particularly to a nitride-based semiconductor laser device having an impurity-doped layer.

[0002]

2. Description of the Related Art In recent years, nitride semiconductor laser elements are expected to be used as light sources for next-generation large-capacity optical disks, and their development is being actively pursued.

In a nitride semiconductor laser device, light emission characteristics such as light emission efficiency and threshold value can be improved by strictly narrowing a current injected from a p-side region. Therefore, various structures for performing current confinement have been conventionally proposed. For example, JP-A-11-214800
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses a structure in which current is confined by a high-resistance layer formed by using an ion implantation method.

[0004] FIG.
FIG. 1 is a cross-sectional view showing a structure of a conventional nitride-based semiconductor laser device disclosed in Japanese Unexamined Patent Application Publication No. H11-157,036. Referring to FIG. 26, the structure of a conventional nitride-based semiconductor laser device will be described. In a conventional nitride-based semiconductor laser device, a sapphire substrate 1
The buffer layer 102 made of GaN is formed on the substrate 01. On the buffer layer 102, an n-type contact layer 103 made of n-type GaN, an n-type clad layer 104 made of n-type AlGaN, and an n-type light guide layer (n-type optical waveguide layer) 105 made of n-type GaN And In _X Ga _1-X N /
MQW (Multiple Q) made of In _Y Ga _1-Y N
(Quantum Well) Active Layer 106
, A p-type optical guide layer (p-type optical waveguide layer) 107 made of p-type GaN, a p-type cladding layer 108 made of p-type AlGaN, and a p-type contact layer 109 made of p-type GaN
Are formed in this order.

In a part of the p-type cladding layer 108 and the p-type contact layer 109, an impurity element (B: boron) is implanted with an implantation energy of 160 keV and a dose of 2
The high resistance layer 110 formed by ion implantation under the condition of × 10 ¹³ cm ^-2 is formed. The high-resistance layer 110 performs p-side current confinement.

On the upper surfaces of the p-type contact layer 109 and the high-resistance layer 110, a p-side electrode 112 is formed. An n-side electrode 113 is formed on the exposed upper surface of the n-type contact layer 103.

In the conventional nitride-based semiconductor laser device shown in FIG. 26, high-resistance layer 110 and MQW active layer 106
In the case where the distance in the depth direction with respect to the
Since the current confinement near 06 is insufficient, the injection current spreads in the MQW active layer 106 in the horizontal direction. As a result, the current density of the MQW active layer 106 decreases,
There is a problem that the threshold current increases. If the distance between the high-resistance layer 110 and the MQW active layer 106 is too short, a crystal defect due to ion implantation is likely to be introduced into the MQW active layer 106, which causes a problem that the life of the device is shortened. Therefore, in order to obtain a nitride-based semiconductor laser device having sufficient device characteristics, it is necessary to strictly control the distance in the depth direction between the high-resistance layer 110 and the MQW active layer 106 on the order of 0.01 μm.

[0008]

Conventionally, however, a channeling phenomenon occurs in which impurity ions are implanted deeply during the ion implantation for forming the high-resistance layer 110. Therefore, the impurity ions are implanted deeper than the design value. There was an inconvenience. Therefore, it is difficult to strictly control the depth of the high-resistance layer 110 with good reproducibility, and it is difficult to precisely control the distance in the depth direction between the high-resistance layer 110 and the MQW active layer 106. there were. As a result, MQ
Since it is difficult to strictly control the width of the current injection into the W active layer 106, there is a problem that the production yield of the nitride-based semiconductor laser device is reduced.

[0009] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide:
An object of the present invention is to provide a nitride-based semiconductor laser device capable of improving the production yield by suppressing the deep introduction of an impurity element.

Another object of the present invention is to prevent channeling at the time of implanting impurity ions in the above-described nitride semiconductor laser device.

[0011]

In order to achieve the above object, a nitride-based semiconductor laser device according to one aspect of the present invention includes a light emitting layer and a first nitride formed on the light emitting layer and containing Al. A first conductivity type cladding layer including a material-based semiconductor layer, a first conductivity type contact layer formed on the cladding layer and including a second nitride-based semiconductor layer containing In, and a cladding layer and a contact layer. An impurity introduction layer formed by introducing an impurity element is provided in at least a part of a region other than the current passage region.

In the nitride-based semiconductor laser device according to this aspect, as described above, the first conductivity type clad layer including the first nitride-based semiconductor layer containing Al and the second nitride-based nitride layer containing In are included. By providing the first conductivity type contact layer including the material-based semiconductor layer, the cladding layer and the contact layer have different lattice constants in the direction perpendicular to the substrate. For example, when the impurity element is introduced by ion implantation, ,
Channeling can be prevented. Thereby, the deep introduction of the impurity element can be suppressed.
As a result, the depth of the impurity-doped layer can be strictly controlled with good reproducibility, so that the production yield can be improved.

[0013] In the nitride semiconductor laser device according to the above aspect, preferably, the impurity-introduced layer has more crystal defects than the current passing region. According to this structure, when the impurity introduction layer is used as a light absorbing layer, light can be absorbed by crystal defects included in the light absorbing layer. With this configuration, when the impurity-introduced layer is used as a current blocking layer, the current blocking layer can have a high resistance due to crystal defects contained therein.

In the above-described nitride-based semiconductor laser device, preferably, the upper surface of the impurity introduction layer and the upper surface of the current passage region are formed to be substantially flush with each other. With this configuration, it is possible to easily reduce unevenness on the element surface. This allows the stress applied to the projections to be reduced when compared to the conventional ridge structure when the device is attached to the heat dissipation base from the surface side of the element close to the light emitting layer by a junction-down method. Deterioration of characteristics can be suppressed. In addition, since the contact area with the heat radiating base can be increased by reducing the unevenness on the element surface, good heat radiating characteristics can be obtained.

In the above-mentioned nitride semiconductor laser device, preferably, the impurity concentration of the impurity element is maximized in the cladding layer. With this configuration,
Since the number of crystal defects in the cladding layer increases, the number of crystal defects in the light emitting layer located below the cladding layer can be reduced.
Thereby, the life of the element can be improved. Further, since crystal defects can be generated at a sufficient density in the cladding layer, for example, a high-resistance current blocking layer can be easily formed in the cladding layer. Thus, the width of current injection into the light emitting layer can be easily controlled. In addition, since crystal defects can be generated at a sufficient density in the cladding layer, for example, a light absorbing layer having a sufficient light absorbing effect can be formed in the cladding layer. Since some light seeps into the cladding layer,
By providing the light absorbing layer in the cladding layer, the width of lateral confinement of light can be controlled.

In the above-described nitride-based semiconductor laser device, preferably, the impurity-doped layer is formed by ion-implanting an impurity element into at least a part of a region other than the current passage region of the cladding layer and the contact layer. I have. According to this structure, the ion implantation method has good reproducibility, so that the impurity-doped layer can be formed with good reproducibility.

[0017] In the nitride semiconductor laser device according to the above aspect, the contact layer may be made of InGaN, and the cladding layer may be made of AlGaN. In this case, the In composition of the contact layer is preferably higher. If the In composition of the contact layer is increased as described above, the difference in lattice constant between the contact layer and the cladding layer increases, so that channeling can be further suppressed. In this case, the band gap of the contact layer preferably has a size that does not absorb laser light. With this configuration, it is possible to prevent the threshold current from increasing due to absorption of laser light by the contact layer.

In the nitride semiconductor laser device according to the above aspect, the density of crystal defects may be maximized in the cladding layer. With this configuration, the number of crystal defects in the cladding layer increases, so that the number of crystal defects in the light emitting layer located below the cladding layer can be reduced. Thereby, the life of the element can be improved. Further, since crystal defects can be generated at a sufficient density in the cladding layer, for example, a high-resistance current blocking layer can be easily formed in the cladding layer. Thus, the width of current injection into the light emitting layer can be easily controlled. In addition, since crystal defects can be generated at a sufficient density in the cladding layer, for example, a light absorbing layer having a sufficient light absorbing effect can be formed in the cladding layer. Since light seeps into the cladding layer to some extent, by providing a light absorbing layer in the cladding layer, the width of lateral confinement of light can be controlled.

In the nitride-based semiconductor laser device according to the one aspect, the impurity introduction layer may be a current blocking layer formed by an ion implantation method. According to this structure, the ion implantation method has good controllability of the introduction depth, so that the distance between the current blocking layer and the light emitting layer in the depth direction can be strictly controlled with good reproducibility.

In the nitride-based semiconductor laser device according to the above aspect, the impurity-doped layer may be a light absorption layer formed by an ion implantation method. With this configuration, the ion implantation method has good controllability of the introduction depth, so that the distance between the light absorbing layer and the light emitting layer in the depth direction can be strictly controlled with good reproducibility.

In the nitride semiconductor laser device according to the above aspect, the impurity element may be an impurity element having a larger mass number than carbon. According to this structure, channeling of the impurity element can be effectively prevented, so that the deep introduction of the impurity element can be suppressed. As a result, the controllability of the implantation profile in the depth direction can be improved.

In the nitride semiconductor laser device according to the above aspect, ions may be implanted from a direction inclined from the [0001] direction of the nitride semiconductor. According to this structure, channeling of the impurity element can be further prevented, so that the deep introduction of the impurity element can be suppressed. As a result, the controllability of the implantation profile in the depth direction can be improved. In this case, the surface of the nitride-based semiconductor is a (0001) plane, and the impurity-doped layer is formed except for the stripe-shaped width. The ion implantation is performed in a plane including a vertical direction and a direction inclined from the [0001] direction of the nitride-based semiconductor. Thereby, channeling of the impurity element can be prevented while preventing ions from being introduced asymmetrically below the mask for forming the light absorbing layer except for the stripe-shaped width.

In the nitride semiconductor laser device according to the above aspect, the impurity element may be ion-implanted through the through film. According to this structure, channeling of the impurity can be further prevented, so that the deep introduction of the impurity element can be suppressed.

In the nitride semiconductor laser device according to the above aspect, the through film may be an insulating film. According to this structure, the insulating film used as the through film can be used as the insulating film on the light absorbing layer or the current blocking layer, so that the current can be blocked more reliably.

Further, in the nitride-based semiconductor laser device according to the above aspect, by forming the first film on the electrode layer, a mask layer including the through film made of the first film and the electrode layer is formed. May be. According to this structure, since the electrode layer serving as the mask layer can be used as the contact electrode, the manufacturing process can be simplified.

In the nitride-based semiconductor laser device according to the above aspect, it may be assembled by a junction-down method. In the configuration of the present invention, since the surface of the element region has little unevenness, the stress applied to the element region can be reduced by assembling by the junction down method, and as a result, deterioration of the element characteristics can be suppressed. In addition, when assembling by the junction down method, it can be uniformly fused to a submount or the like, so that the heat radiation characteristics of the element are improved.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view showing the structure of a nitride semiconductor laser device according to a first embodiment of the present invention. FIG. 2 is an enlarged sectional view showing the MQW light emitting layer of the nitride semiconductor laser device according to the first embodiment shown in FIG.

First, the structure of the nitride-based semiconductor laser device according to the first embodiment will be described with reference to FIGS. In the first embodiment, an n-type layer 2 made of GaN having a thickness of about 1 μm is formed on an n-type GaN substrate 1.
And an n-type cladding layer 3 of Al _0.08 Ga _0.92 N having a thickness of about 1 μm, and an MQW light emitting layer 4 are formed in this order. The MQW light-emitting layer 4 has three quantum well layers 4c made of In _x Ga ₁ -xN having a thickness of about 3.5 nm.
And an MQW active layer in which four barrier layers 4b made of In _Y Ga ₁ -YN having a thickness of about 20 nm are alternately stacked. In the MQW active layer of the present embodiment, X = 0.15,
Y = 0.05 is set. On the lower surface of the MQW active layer, an n-type optical guide layer 4a made of Al _0.01 Ga _0.99 N and having a thickness of about 0.1 μm is formed. Also, M
On the upper surface of the QW active layer, A having a thickness of about 20 nm
a p-type cap layer 4d of _0.1 g _0.9 Ga _0.9 N;
A p-type light guide layer 4e made of Al _0.01 Ga _0.99 N having a thickness of 1 μm is formed in this order. In addition,
The MQW light emitting layer 4 is an example of the “light emitting layer” of the present invention.

On the MQW light emitting layer 4, a p-type cladding layer 5 made of Al _0.08 Ga _0.92 N having a thickness of about 0.28 μm
When a p-type intermediate layer 6 made of In _0.01 Ga _0.99 N to about 0.067μm thickness, In about 3nm thickness _0.05 Ga
_A p-type contact layer 7 made of _0.95 N is formed. As described above, in the first embodiment, the band gap of the p-type intermediate layer 6 is set to be an intermediate band gap between the p-type cladding layer 5 and the p-type contact layer 7 by adjusting the In composition. Have been. Thus, the p-type intermediate layer 6 has a different lattice constant from the p-type cladding layer 5 and the p-type contact layer 7.

Here, in the first embodiment, about 0.1 nm formed by ion implantation of carbon (C).
An impurity implantation layer 8 having an implantation depth of 32 μm is provided. Note that carbon is an example of the “impurity element” of the present invention, and the impurity injection layer 8 is formed of the “impurity introduction layer” of the present invention.
This is an example. In this case, the peak depth of the ion-implanted carbon concentration is about 0.2 from the upper surface of the p-type contact layer 7.
It is located in the region of the 3 μm p-type cladding layer 5. The peak concentration at this peak depth is about 1.0 × 10 ²⁰
cm ^-3 . In this case, the impurity implantation layer 8 contains more crystal defects than other regions due to the implantation of a large amount of impurity elements into the semiconductor. In addition, a region not ion-implanted (a non-implanted region) serving as a current passage region 9.
Are formed with a width of about 2.1 μm.

FIG. 3 is an enlarged sectional view schematically showing an ion implantation region. The impurity implantation layer 8 indicates an ion implantation region, and the mask layer 10a indicates a mask layer at the time of ion implantation. FIG. 3 does not show the layer structure of the nitride-based semiconductor layer. In FIG. 3, Rp is the peak depth, and the position of the peak depth is indicated by a solid line 8a. In the nitride-based semiconductor laser device according to the embodiment of the present invention, Rp + ΔRp is set to the implantation depth (the impurity implantation layer 8).
Thickness). Here, ΔRp is the standard deviation of the range. Further, at the time of ion implantation, the ions spread laterally (ΔR) below the mask layer 10a at the time of ion implantation.
l) occurs. Here, the mask layer 10a at the time of ion implantation
Is W, the width B of the region 8a below the mask layer 10a where the ions are not implanted is B = W−2 × ΔRl. Note that, in the cross-sectional views other than FIG. 3, the spread of ions in the horizontal direction is not shown for simplification of the drawing.

The impurity-implanted layer 8 in the first embodiment functions as a light-absorbing layer due to crystal defects contained in the impurity-implanted layer 8 and also functions as a current confinement layer due to its high resistance. In order to sufficiently perform not only current confinement but also lateral confinement of light in the impurity-implanted layer 8, the maximum value of the impurity concentration of ion-implanted carbon must be about 5 × 10 ¹⁹ cm ⁻³ or more. Is preferred. As a result, the impurity implantation layer 8 has more crystal defects than the current passing region 9, so that light can be absorbed by the crystal defects contained in the impurity injection layer 8.

On the upper surface of the current passing region 9 of the p-type contact layer 7, a Pt layer having a thickness of about 1 nm, a Pd layer having a thickness of about 100 nm, and a An Au layer having a thickness of about 240 n
A p-side ohmic electrode 10 made of a Ni layer having a thickness of m is formed in a stripe shape (elongated shape) with an electrode width of about 2.2 μm. Also, the p-side ohmic electrode 10
So as to cover the side surface of P and the upper surface of p-type contact layer 7.
An insulating film 11 made of iO ₂ is formed. Insulating film 1
1, a Ti layer having a thickness of about 100 nm, a Pt layer having a thickness of about 150 nm, and a Pt layer having a thickness of about 150 nm from the lower layer to the upper layer so as to contact the upper surface of the p-side ohmic electrode 10. A p-side pad electrode 12 made of an Au layer is formed.

On the back surface of the n-type GaN substrate 1, n
An Al layer having a thickness of about 6 nm, a Si layer having a thickness of about 2 nm, a Ni layer having a thickness of about 10 nm, and a
-Side ohmic electrode 1 composed of an Au layer having a thickness of
3 are formed. On the back surface of the n-side ohmic electrode 13, approximately 1
An n-side pad electrode 14 composed of a Ni layer having a thickness of 0 nm and an Au layer having a thickness of about 700 nm is formed.

[0036] p in the nitride semiconductor laser device according to the first embodiment, as described above, the p-type cladding layer 5 made of Al _{0. 08} Ga _0.92 N, consisting of In _0.05 Ga _0.95 N
Since the difference in lattice constant from the mold contact layer 7 is large, channeling of carbon can be suppressed. This allows
Carbon can be prevented from being deeply injected into the device. As a result, the controllability of the implantation profile in the depth direction can be improved. Thereby, the implantation depth of the impurity implantation layer 8 having a function as a light absorption layer for confining light in the lateral direction can be strictly controlled with good reproducibility.

In the nitride-based semiconductor laser device according to the first embodiment, as described above, between the p-type cladding layer 5 and the p-type contact layer 7, a p-type semiconductor having a lattice constant different from these lattice constants is used. By forming the mold intermediate layer 6, channeling during ion implantation can be further prevented.

In the nitride-based semiconductor laser device according to the first embodiment, as described above, the p-type intermediate layer 6 having a band gap intermediate the band gap between the p-type cladding layer 5 and the p-type contact layer 7. With p-type cladding layer 5 and p
By forming between the p-type cladding layer 5 and the p-type contact layer 7, the discontinuity of the band gap between the p-type cladding layer 5 and the p-type contact layer 7 can be reduced. Thereby, the resistance to the current flowing from the p-type contact layer 7 to the p-type cladding layer 5 can be reduced, so that the current can easily flow.

In the nitride semiconductor laser device according to the first embodiment, as described above, the p-type cladding layer 5 and the p-type contact layer 7 formed on the MQW light emitting layer 4
Since the impurity implantation layer 8 formed by carbon ion implantation is provided in a region other than the current passing region 9 of the above, the ion implantation method has good reproducibility, and thus the impurity implantation layer 8 acting as a light absorption layer is reproduced. It can be formed well. This makes it possible to control the lateral confinement of light with good reproducibility. As a result, the production yield can be improved as compared with a conventional nitride-based semiconductor laser device having a ridge portion.

In the nitride semiconductor laser device according to the first embodiment, as described above, the structure having the ridge portion formed by the conventional etching is provided by providing the impurity implantation layer 8 formed by the ion implantation. Unlike the above, at the interface between the impurity injection layer 8 and the current passing region 9,
No irregularities or high-density crystal defects occur. As a result, generation of a leak current due to a crystal defect can be significantly suppressed.

In the nitride-based semiconductor laser device according to the first embodiment, as described above, the implanted ions have a peak in the p-type cladding layer 5, so that the crystal defects in the p-type cladding layer 5 have a sufficient density. Can be generated. Thereby, the impurity injection layer 8 having a sufficient light absorption effect can be formed in the p-type cladding layer 5. As a result, it has a sufficient lateral light confinement effect. In addition, the impurity implantation layer 8 is 0.03
It is formed in the depth direction at a first distance of μm, and the lower MQW light emitting layer 4 has few crystal defects, so that a reduction in the life of the element can be suppressed.

In the nitride-based semiconductor laser device according to the first embodiment, as described above, by providing the impurity-implanted layer 8 formed by ion implantation, the conventional convex ridge portion is not required. Thereby, MQW
When the device is attached to the heat dissipation base from the front surface side of the element close to the light emitting layer 4 by a junction down method, there is no inconvenience that the element characteristics are degraded due to stress applied to the convex ridge portion. In addition, there is no inconvenience that the heat dissipation characteristics are deteriorated due to the small contact area with the heat dissipation base due to the convex ridge portion.

In the nitride-based semiconductor laser device according to the first embodiment, as described above, the insulating film 11 is formed on the impurity injection layer 8, so that when a large current is injected into the device, a minute amount of current is injected. It is possible to prevent generation of a large leak current.

In the nitride semiconductor laser device according to the first embodiment, as described above, In _0.01 Ga _0.99 N
By forming the p-type intermediate layer 6 composed of GaN, the lattice constant between the p-type intermediate layer 6 and the p-type contact layer 7 composed of In _0.05 Ga _0.95 N is different from the case where the p-type intermediate layer 6 is composed of GaN. Can be reduced. Thereby, the strain of the p-type contact layer 7 can be reduced, so that the crystallinity of the p-type contact layer 7 can be improved. As a result, the carrier concentration of the p-type contact layer 7 can be increased, so that the contact resistance between the p-type contact layer 7 and the p-side ohmic electrode 10 can be reduced.

FIGS. 4 to 7 are sectional views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment shown in FIG. FIG. 8 is a graph showing a simulation result of a carbon concentration and a crystal defect concentration profile in the nitride semiconductor laser device according to the first embodiment shown in FIG. FIG. 9 is a graph showing the results of SIMS measurement of the carbon concentration profile of the nitride semiconductor laser device according to the first embodiment shown in FIG.

Next, the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment will be described with reference to FIGS.

First, as shown in FIG. 4, an MOCVD method (Metal Organic C) is formed on an n-type GaN substrate 1.
chemical Vapor Deposition:
An n-type layer 2 made of GaN having a thickness of about 1 μm and an n-type cladding layer 3 made of Al _0.8 GaN having a thickness of about 1 μm are sequentially formed using metal organic chemical vapor deposition. On this n-type cladding layer 3, as shown in FIG. 2, an n-type optical guide layer 4a made of Al _0.01 Ga _0.99 N having a thickness of about 0.1 μm and an In _x Ga ₁ layer having a thickness of about 8 nm a MQW active layer in _Y Ga _1-Y N 4 layers of the barrier layer 4b made with a thickness of the quantum well layer 4c and about 16nm of three layers consisting of _-X N are stacked, Al having a thickness of about 20nm _A p-type cap layer 4d made of _0.1 Ga _0.9 N and Al _0.01 Ga _0.99 having a thickness of about 0.1 μm;
An MQW light emitting layer 4 made of a p-type light guide layer 4e made of N is formed. On the MQW light emitting layer 4, about 0.28 μm
a p-type cladding layer 5 made of Al _0.08 Ga _0.92 N having a thickness of m and In _0.01 having a thickness of about 0.067 μm.
A p-type intermediate layer 6 made of Ga _0.99 N and a p-type contact layer 7 made of In _0.05 Ga _0.95 N having a thickness of about 3 nm.
Are sequentially formed. In addition, as an n-type dopant, Si
And Mg as a p-type dopant.

Next, as shown in FIG. 5, a thickness of about 1 nm from the lower layer to the upper layer is formed on the upper surface of the region serving as the current passage region 9 of the p-type contact layer 7 by using the lift-off method. Pt layer and Pd having a thickness of about 100 nm
A Au layer having a thickness of about 240 nm;
A p-side ohmic electrode 10 made of a Ni layer having a thickness of nm is formed in a stripe shape (elongated shape) with an electrode width of about 2.2 μm. If the electrode width of the p-side ohmic electrode 10 is in the range of about 1 μm to about 6 μm, a sufficient current path can be ensured, and light can be well confined in the lateral direction.

That is, when the electrode width of the p-side ohmic electrode 10 is set to about 1 μm or less,
Since the contact area between 0 and the p-type contact layer 7 decreases, the contact resistance increases. Further, as described later, when ion implantation is performed using the p-side ohmic electrode 10 as a mask, crystal defects are also implanted in the lateral direction. As a result, the resistance of this region becomes high, so that the effective width of the current passage region 9 becomes small, and therefore, the current density becomes excessive. As a result, the temperature rise becomes large, which causes an increase in operating current and a reduction in element life. In an extreme case, an effective current path cannot be secured, and as a result, current may not be injected into the element. On the other hand, when the electrode width of the p-side ohmic electrode 10 is larger than 6 μm, the width of the current passage region 9 becomes excessively large, so that the current density becomes excessively small. As a result, the threshold current may increase significantly. Further, since the impurity injection layer 8 is too far from the light emitting portion of the MQW light emitting layer 4, lateral light confinement may be insufficient. Therefore, the electrode width of the p-side ohmic electrode 10 is
Preferably, it is in the range of about 1 μm to about 6 μm.

Next, a through film 15 made of SiO ₂ having a thickness of about 60 nm is formed by plasma CVD so as to cover the entire upper surfaces of the p-side ohmic electrode 10 and the p-type contact layer 7.

Next, as shown in FIG. 6, using the p-side ohmic electrode 10 as a mask, the p-type contact layer 7, the p-type intermediate layer 6, and the p-type
By ion-implanting a large amount of carbon into the predetermined region, an impurity implantation layer 8 having an implantation depth of about 0.32 μm is formed from the upper surface of the p-type contact layer 7. Thereby, the current passage region 9 having a current passage width of about 2.1 μm
Is formed. Note that the ion implantation conditions of the first embodiment were such that the ion implantation energy was about 95 keV and the dose was about 2.3 × 10 ¹⁵ cm ⁻² . The direction of the ion implantation was inclined by about 7 ° from the direction perpendicular to the surface of the p-type contact layer 7 (the [0001] direction of the p-type contact layer 7) to the stripe direction of the p-side ohmic electrode 10. I went from the direction.

The ion implantation conditions of the first embodiment (implantation energy: about 95 keV, dose: about 2.3 ×
FIG. 8 shows a simulation result of the carbon concentration profile in the depth direction of the device when the ion implantation is performed at 10 ¹⁵ cm ⁻² ) and the crystal defect concentration profile generated in the crystal by the ion implantation. The simulation was performed using simulation software called TRIM generally provided by an engineer of IBM Corporation. Referring to FIG. 8, according to the simulation result under the ion implantation conditions of the first embodiment, the peak depth Rp of the carbon concentration is about 0.23 μm, and the carbon concentration at this peak depth Rp is about 1.
It becomes 0 × 10 ²⁰ cm ⁻³ . Further, the standard deviation ΔRp of this graph is about 0.1 μm.

Further, by simulating the spread distribution of carbon and crystal defects in the direction perpendicular to the ion implantation direction (lateral direction) by simulation using TRIM, as shown schematically in FIG. About 0.12μm
It has been found that a degree of lateral spread (ΔR1) occurs. Thereby, in the first embodiment, the impurity implantation layer 8
Of the current passing region 9 defined by the width of the mask layer at the time of ion implantation is a value in consideration of the implantation spread of the implanted ions in the lateral direction. In the nitride semiconductor laser device according to the first embodiment, the width of the p-side ohmic electrode 10 (about 2.2 μm) and the width of the p-side ohmic electrode 10
The total value (approximately 2.3 μm) of the thickness of the through film 15 (approximately 0.1 μm in total on the left and right sides) formed on the side surface becomes the width W of the mask layer during ion implantation. From the width of this mask layer, about 0.2 μm, which is twice the lateral implantation spread (ΔR1).
By subtracting m, the width (about 2.1) of the current passing region 9 which is the width B of the region below the mask layer where ions are not implanted.
μm) is obtained.

Referring to FIG. 8, in the simulation, the concentration distribution of the crystal defects is larger than that of carbon.
It was found that the peak depth became shallower. In the first embodiment, the p-type cladding layer 5 is designed so that both the carbon concentration and the crystal defect concentration have peaks.

Further, according to the ion implantation conditions of the first embodiment,
SIMS (Secondary Ion Ma)
carbon concentration by ss Spectroscopy) analysis
FIG. 9 shows the measurement results of the distribution. Note that S
The measurement conditions by the IMS analysis were as follows:⁺
Using ions and primary ion acceleration voltage of 15k
V, the primary ion current was 25 mA. This measurement condition
And the sample is 120 × 120 μm^TwoIn the area of
By performing raster scan of ions, primary ions
Was irradiated. At this time, a 60 μm diameter area on the sample
To detect C-ion (secondary ion) coming out of
The carbon concentration distribution in the depth direction was measured. In addition,
In FIG. 9, at an injection depth of about 0.6 μm or more,
Elemental concentration is constant (about 2 × 10¹⁷cm^-3), But
This is not implanted by ion implantation,
Originally present in nitride-based semiconductor layers formed by crystal growth
It is the carbon concentration that had been. Low concentration indicated by broken line in FIG.
Considering this, the concentration profile of the region
The concentration of carbon originally contained in the semiconductor layer (about 2 × 10¹⁷c
m ^-3) Is excluded.

Referring to FIG. 9, in the actual carbon concentration measurement by SIMS analysis, the peak of the carbon concentration distribution is similar to that of the simulation result described above.
I knew it was inside. The peak depth of the carbon concentration in the measurement result by the SIMS analysis is the p-type contact layer 7.
From the upper surface of the substrate.

As described above, according to the simulation result by TRIM, the peak depth Rp of the carbon concentration distribution is p
While the depth was about 0.23 μm from the upper surface of the p-type contact layer 7, the peak depth of the carbon concentration by SIMS analysis was about 0.15 μm from the upper surface of the p-type contact layer 7. As described above, when carbon is ion-implanted under the conditions of the first embodiment, a deviation of about 0.08 μm between the calculated value of the peak depth of the carbon concentration by TRIM and the measured value of the peak depth by SIMS analysis. Occurs. Note that the magnitude of this shift varies depending on the type of implantation element and implantation conditions. For example, implantation energy: 110 ke
V, dose amount: When silicon ions are implanted under the condition of 1 × 10 ¹⁵ cm ⁻² , the estimated value of the peak depth by TRIM is about 0.15 μm, and the measured value of the peak depth by SIMS is: , About 0.10 μm. As described above, the estimated value of the peak depth of the implanted ion concentration by TRIM does not always completely agree with the measured value of the peak depth of the implanted ion concentration by SIMS. On the other hand, a very high reproducibility can be obtained in the ion concentration profile by the ion implantation method as long as the implantation conditions are determined. Thus, it is known that a plurality of elements having the same implanted ion concentration profile can be easily obtained. In addition, in each embodiment according to the present invention, in principle, description will be made using the above-described estimated value by TRIM.

As described above, after the impurity implantation layer 8 is formed by ion implantation, the through film 15 is removed by wet etching using a hydrofluoric acid-based etchant. Then, as shown in FIG. 7, using a plasma CVD method,
S having a thickness of about 200 nm covers the entire upper surfaces of p-type contact layer 7 and p-side ohmic electrode 10.
An insulating film 11 made of iO ₂ is formed. Then, a resist film (not shown) having an opening is formed on the upper surface of the p-side ohmic electrode 10 by using a photolithography technique. Using this resist film as a mask, CF
RIE (Reactive Ion E) using ₄ gases
The insulating film 11 located on the upper surface of the p-side ohmic electrode 10 is removed by the (tching) method. This allows
The upper surface of the p-side ohmic electrode 10 is exposed.

Finally, as shown in FIG.
From the lower layer to the upper layer so as to contact the exposed upper surface of the p-side ohmic electrode
A p-side pad electrode 12 composed of a Ti layer having a thickness of about 150 nm, a Pt layer having a thickness of about 150 nm, and an Au layer having a thickness of about 3 μm is vacuum-deposited. And n-type G
The rear surface of the aN substrate 1 has a predetermined thickness (for example, 100 μm).
After polishing, the n-type GaN substrate 1 has an n-type Ga
From the side close to the back surface of the N substrate 1, an Al layer having a thickness of about 6 nm, a Si layer having a thickness of about 2 nm,
An n-side ohmic electrode 13 composed of a Ni layer having a thickness of m and an Au layer having a thickness of about 100 nm is formed. Further, on the back surface of the n-side ohmic electrode 13, an n-side pad electrode 14 composed of a Ni layer having a thickness of about 10 nm from the side close to the n-side ohmic electrode 13 and an Au layer having a thickness of about 700 nm is formed. Thus, the nitride-based semiconductor laser device according to the first embodiment is completed.

In the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment, as described above, carbon is implanted from a direction inclined by about 7 ° from the [0001] direction of the p-type contact layer 7 to thereby reduce carbon. Can be suppressed, so that carbon can be prevented from being deeply injected into the device. As a result, the controllability of the implantation profile in the depth direction is improved. In particular, by implanting ions from a direction inclined in the stripe direction of the p-side ohmic electrode 10, ions can be prevented from being implanted into the current passing region 9 below the p-side ohmic electrode 10.

In the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment, as described above, the upper surface of the device is covered with the through film 15 before the ion implantation, so that carbon is more effectively removed. Channeling can be prevented. Thereby, it is possible to further suppress the carbon from being deeply implanted into the element, so that the controllability of the implantation profile in the depth direction is further improved.

In the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment, as described above, the p-side ohmic electrode 10 used as a mask for ion implantation can be used as a contact electrode. Can be simplified.

(Second Embodiment) FIG. 10 shows a second embodiment of the present invention.
1 shows a structure of a nitride-based semiconductor laser device according to an embodiment.
FIG. In the second embodiment, the first embodiment
Unlike the form, the current confinement layer and the
Forming a light absorbing layer and _0.01Ga
_0.99Example in the case of forming a p-type intermediate layer made of N
explain. Other configurations of the second embodiment are similar to those of the first embodiment.
It is the same as the state.

First, referring to FIG. 10, in the second embodiment, an n-type layer 2, an n-type cladding layer 3, and an MQW light emitting layer 4 are formed on an n-type GaN substrate 1. . The thickness and composition of each of the layers 1 to 4 are the same as in the first embodiment.

On the MQW light emitting layer 4, a p-type cladding layer 5 made of Al _0.08 Ga _0.92 N having a thickness of about 0.28 μm and an Al _0.01 Ga _0.99 N having a thickness of about 0.067 μm
A p-type intermediate layer 16 made of, an In _0.05 to about 3nm thick
The p-type contact layer 17 made of Ga _0.95 N is formed in this order. Thus, in the second embodiment, p
The band gap of the mold intermediate layer 16 can be adjusted by adjusting the Al composition so that the p-type clad layer 5 and the p-type contact layer 17 can be formed.
Is set so as to be an intermediate band gap. Thus, the p-type intermediate layer 16 has a different lattice constant from the p-type cladding layer 5 and the p-type contact layer 17.

Here, in the second embodiment, boron is ion-implanted into a part of the region from the p-type cladding layer 5 to the p-type contact layer 17 so as to have an implantation depth of about 0.34 μm. One impurity implantation layer 18a is formed. Note that boron is an example of the “impurity element” of the present invention, and the first impurity implantation layer 18a is an example of the “impurity introducing layer” of the present invention. The peak depth of the boron concentration of the first impurity implantation layer 18a is located in a region of the p-type cladding layer 5 having a depth of about 0.25 μm from the upper surface of the p-type contact layer 17. The boron concentration at this peak depth is about 1.0 × 10 ¹⁹ cm ⁻³ . This first impurity implantation layer 1
As shown in FIG. 8A, a current passing region 19 is formed by performing current constriction with respect to the injection current from the p-side. The current passage area 19 is formed with a width of about 1.8 μm.

Furthermore, in the second embodiment, the carbon is ion-implanted, so that the first impurity-implanted layer 18a is
A second impurity implantation layer 18b having an implantation depth of about 0.32 μm is formed in a region apart from the MQW light emitting layer 4 and the current passing region 19. This second impurity implantation layer 18
The peak depth of the carbon concentration b is in the p-type cladding layer 5 having a depth of about 0.23 μm from the upper surface of the p-type contact layer 17. The carbon concentration at this peak depth is about 1.0
× 10 ²⁰ cm ^-3 . Thus, current confinement can be performed in the first impurity injection layer 18a, and lateral light confinement can be performed in the second impurity injection layer 18b. Here, the second impurity implantation layer 18b has a first width (width of about 2.8).
μm). The carbon ion-implanted when forming the second impurity-implanted layer 18b is an example of the “impurity element” in the present invention, and the second impurity-implanted layer 18b
Is an example of the “impurity introduction layer” of the present invention.

Current passing region 19 of p-type contact layer 17
A p-side ohmic electrode 20 is formed in a stripe shape on the upper surface of the substrate. Further, an insulating film 21 is formed so as to cover the side surface of the p-side ohmic electrode 20 and the upper surface of the p-type contact layer 17. A p-side pad electrode 22 is formed on the insulating film 21 so as to contact the upper surface of the p-side ohmic electrode 20. Also, the n-type GaN substrate 1
On the back surface of the n-type GaN substrate 1, the n-side ohmic electrode 13 and the n-side pad electrode 13
Is formed. The thicknesses and compositions of the layers 20 to 22 are the same as those of the layers 10 to 12 of the first embodiment.

[0069] p in the nitride semiconductor laser device according to the second embodiment, as described above, the p-type cladding layer 5 made of Al _{0. 08} Ga _0.92 N, consisting of In _0.05 Ga _0.95 N
Since the difference in lattice constant from the mold contact layer 17 is large, channeling of boron and carbon can be suppressed. Thereby, boron and carbon can be suppressed from being deeply implanted into the device. As a result, the controllability of the implantation profile in the depth direction can be improved.
Therefore, the injection depth of the first impurity injection layer 18a having a function as a current confinement layer near the light emitting region can be strictly controlled with good reproducibility.

In the nitride-based semiconductor laser device according to the second embodiment, as described above, between the p-type cladding layer 5 and the p-type contact layer 17, a p-type semiconductor having a lattice constant different from these lattice constants is used. By forming the mold intermediate layer 16, channeling during ion implantation can be further prevented.

In the nitride semiconductor laser device according to the second embodiment, as described above, the second impurity implantation layer 18b is formed except for the first width, and the current passing region 1
Except for the width 9 (the second width), the first impurity implantation layer 18a is formed. The first width is larger than the second width, and the region of the second width has the first width. Formed in the region.
Thus, the current constriction can be enhanced and the light absorption by the light absorbing layer can be reduced, so that the threshold current can be reduced and the slope efficiency can be improved.

In the nitride semiconductor laser device according to the second embodiment, as described above, the second impurity implantation layer 18b is separated from the MQW light emitting layer 4 by the first distance of 0.03 μm in the depth direction. Since the first impurity implantation layer 18a is formed and separated from the MQW light emitting layer 4 in the depth direction by a second distance of 0.01 μm, the first distance is larger than the second distance. Has become. Thus, the current constriction can be enhanced and the light absorption by the light absorbing layer can be reduced, so that the threshold current can be reduced and the slope efficiency can be improved.

In the nitride-based semiconductor laser device according to the second embodiment, as described above, two types of ion implantation conditions are used, and the respective implantation regions are changed to function as a light absorbing layer. Of the second impurity implantation layer 18b to be formed and the first
The shape of the impurity injection layer 18a can be easily and separately controlled. Specifically, for example, the current passage region 19
While keeping the width of the second impurity implantation layer 1 narrow and constant.
8b can be independently changed. Thus, the degree of the light confinement in the horizontal direction can be changed without greatly changing the threshold current, so that the spread angle of the laser light in the horizontal direction can be controlled.

In the nitride-based semiconductor laser device according to the second embodiment, as described above, the first ion implantation of boron and the second ion implantation of carbon make it possible to perform the first and second ion implantations. Since the impurity elements to be implanted are different, the concentration profiles of the implanted impurity elements can be easily changed.

In the nitride-based semiconductor laser device according to the second embodiment, as described above, a relatively light element such as boron is ion-implanted, so that crystal defects are excessively formed in the first impurity-implanted layer 18a. It can be prevented from being formed.

In the nitride-based semiconductor laser device according to the second embodiment, as described above, a relatively heavy element such as carbon is ion-implanted, so that the second impurity-implanted layer 18b has a low dose. Defects can be injected. As a result, the carbon injected into the second impurity injection layer 18b diffuses into the MQW light emitting layer 4, thereby
An adverse effect on the characteristics of the element can be suppressed.

In the nitride semiconductor laser device according to the second embodiment, as described above, Al _0.01 Ga _0.99 N
By forming the p-type intermediate layer 16 made of
P-type contact layer 17 made of _0.05 Ga _0.95 N and Al
The discontinuity of the band gap with the p-type cladding layer 5 made of _0.08 Ga _0.92 N can be reduced. In particular, Al
_The p-type intermediate layer 16 made of _0.01 Ga _0.99 N has a smaller band gap with the p-type clad layer 5 than the p-type intermediate layer made of GaN. Resistance to the current (holes) flowing through the holes can be reduced. Thereby, the p-type contact layer 17
Therefore, the resistance to the current (hole) flowing through the p-type cladding layer 5 can be reduced.

The other effects of the nitride semiconductor laser device according to the second embodiment are the same as those of the first embodiment.

FIGS. 11 to 14 are cross-sectional views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG. In the second embodiment, a description will be given of a manufacturing process when the current confinement layer and the light absorption layer are formed by separate ion implantation.

First, up to the p-type cladding layer 5 is formed by using the same process as in the first embodiment shown in FIG.
Then, as shown in FIG. 11, on the p-type cladding layer 5,
A p-type intermediate layer 16 made of Al _0.01 Ga _0.99 N having a thickness of about 0.067 μm and an In _0.05 Ga _{0.95 made} of about 3 nm thick
An N-type p-type contact layer 17 is formed. next,
The p-side ohmic electrode 20 is formed in a stripe shape with an electrode width of about 2.0 μm on the upper surface of the p-type contact layer 17 by using a lift-off method. Then, an SiO ₂ film 23a having a thickness of about 500 nm is formed by plasma CVD so as to cover the entire upper surfaces of the p-side ohmic electrode 20 and the p-type contact layer 17.

Next, as shown in FIG. 12, the SiO ₂ film 23a is anisotropically etched by the RIE method using CF ₄ gas, so that a width of about 500 nm is formed on the side wall of the p-side ohmic electrode 20. The non-injection region enlarged film 23 made of SiO ₂ having the above is formed. Then, in the second embodiment, ion implantation is performed using the p-side ohmic electrode 20 and the non-implanted region enlarged film 23 as a mask (width of the mask is about 3 μm). That is, the ion implantation energy is about 80 k
Carbon was ion-implanted under conditions of eV and a dose of about 2.3 × 10 ¹⁵ cm ⁻² . Thereby, the second impurity implantation layer 1
8b is formed. Thereafter, the non-implantation region enlarged film 23 is completely removed.

Next, as shown in FIG. 13, the p-side ohmic electrode 20 is used as a mask and the implantation energy is about 70 ke.
V ions are implanted under an ion implantation condition of a dose of about 2.3 × 10 ¹⁴ cm ⁻² . Thus, a first impurity implantation layer 18a is formed.

Next, as shown in FIG.
Using method D, an insulating film 21 made of SiO ₂ having a thickness of about 200 nm is formed so as to cover the side surface of the p-side ohmic electrode 20 and the upper surface of the p-type contact layer 17.
Then, the upper surface of the p-side ohmic electrode 20 is exposed using the photolithography technique and the RIE method using CF ₄ gas.

Finally, a p-side pad electrode 22 is formed on the p-side ohmic electrode 20 and the insulating film 21, and an n-type GaN substrate 1 By forming the n-side ohmic electrode 13 and the n-side pad electrode 14 in order from the side closer to the back surface of the substrate 1, the nitride-based semiconductor laser device according to the second embodiment shown in FIG. 10 is completed.

(Third Embodiment) FIG. 15 shows a third embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a structure of the nitride-based semiconductor laser device according to the embodiment. In the third embodiment, an example in which a step-shaped impurity implantation layer is formed by performing ion implantation using a convex p-side ohmic electrode having a step as a mask will be described.

First, referring to FIG. 15, in the third embodiment, an n-type layer 2, an n-type cladding layer 3, and an MQW light emitting layer 4 are formed on an n-type GaN substrate 1. . The thickness and composition of each of the layers 1 to 4 are the same as in the first embodiment.

On the MQW light emitting layer 4, a p-type cladding layer 5 of Al _0.08 Ga _0.92 N having a thickness of about 0.28 μm
And a p-type contact layer 26 of In _0.05 Ga _0.95 N having a thickness of about 0.07 μm. As described above, in the third embodiment, the lattice constant of the p-type contact layer 26 is set to be significantly different from that of the p-type cladding layer 5 by adjusting the In composition.

Here, in the third embodiment, silicon (S
A step-like impurity implantation layer 27 formed by ion implantation of i) is provided. Note that silicon is an example of the “impurity element” in the present invention. The impurity injection layer 27 is an example of the “impurity introduction layer” of the present invention. The region not ion-implanted as the current passage region 28 is approximately 0.3 mm from the upper surface of the p-type contact layer 26.
It has a width of about 1.4 μm up to an implantation depth of 3 μm, and has a stepped shape having a width of about 1.8 μm up to an implantation depth of about 0.77 μm. Note that current constriction is performed in a region where the interval between the upper surface of the p-type contact layer 26 of the impurity implantation layer 27 and the implantation depth of about 0.33 μm is narrow. The peak depth of the silicon concentration in this region is located in the region of the p-type cladding layer 5 having a depth of about 0.14 μm from the upper surface of the p-type contact layer 26. The silicon concentration at this peak depth is about 1.0 × 10 ²⁰ cm ⁻³ . Further, light is confined in the lateral direction by a region having a wide interval from the upper surface of the p-type contact layer 26 of the impurity implantation layer 27 to the implantation depth of about 0.33 μm to about 0.77 μm. . The peak depth of the silicon concentration in this region is about 0.59 from the upper surface of the p-type contact layer 26.
It is located in the region of the MQW light emitting layer 4 having a depth of μm. The silicon concentration at this peak depth is about 1.0 × 10 ²⁰ c
m ⁻³ .

Current passing region 28 of p-type contact layer 26
On the upper surface of the Pt electrode 29 a having a thickness of about 140 nm and a Pt electrode 29 a having a thickness of about 2.2 μm and a Ni electrode 29 b having a thickness of about 600 nm and an electrode width of about 1.8 μm. Are formed in a stripe shape. Also, the p-side ohmic electrode 2
An insulating film 30 is formed so as to cover the side surface 9 and the upper surface of the p-type contact layer 26. On the insulating film 30, the upper surface of the p-side ohmic electrode 29 is contacted.
A p-side pad electrode 31 is formed. Also, n-type Ga
On the back surface of the N substrate 1, an n-side ohmic electrode 13 and an n-side pad electrode 14 are formed in order from the side closer to the back surface of the n-type GaN substrate 1.

[0090] p in the nitride semiconductor laser device according to the third embodiment, as described above, the p-type cladding layer 5 made of Al _{0. 08} Ga _0.92 N, consisting of In _0.01 Ga _0.99 N
Since the difference in lattice constant from the mold contact layer 26 is large, channeling of silicon can be suppressed. This can prevent silicon from being deeply injected into the device. As a result, the controllability of the implantation profile in the depth direction can be improved. Accordingly, the position of the lower surface 27a of the region functioning as the current confinement layer in the impurity injection layer 27 can be strictly controlled with good reproducibility.
The distance between “a” and the upper surface of the MQW light emitting layer 4 can be strictly controlled with good reproducibility.

In the nitride-based semiconductor laser device according to the third embodiment, as described above, the impurity implantation layer 27 functioning as the current confinement layer and the ion implantation light absorption layer is formed in a stepped shape, so that the impurity implantation is performed. A sufficient current confinement can be performed in a region where the interval of the layer 27 is narrow, and a suitable lateral confinement of light can be performed in a region where the interval of the impurity injection layer 27 near the light emitting portion of the MQW light emitting layer 4 is wide.
As a result, the current density can be increased, and excessive light absorption can be suppressed. As a result, it is possible to reduce the threshold current and control the horizontal spread angle of the laser light.

The other effects of the nitride semiconductor laser device according to the third embodiment are the same as those of the first embodiment.

FIGS. 16 to 20 are sectional views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment shown in FIG. In the third embodiment, an example will be described in which a step-shaped impurity implantation layer having a current confinement function is formed by a single ion implantation by using a convex mask layer having a step portion. Other configurations of the third embodiment are the same as those of the first embodiment.

First, up to the p-type cladding layer 5 is formed by using the same process as in the first embodiment shown in FIG.
Then, as shown in FIG. 16, on the p-type cladding layer 5,
A p-type contact layer 26 of In _0.05 Ga _0.95 having a thickness of about 3 nm is formed. Next, about 140 nm is formed on the upper surface of the p-type contact layer 26 by using a lift-off method.
A p-side ohmic electrode 29 composed of a Pt electrode 29a having a thickness of about 5 nm and a Ni electrode 29b having a thickness of about 600 nm is formed in a stripe shape with an electrode width of about 2.2 μm.

Then, as shown in FIG. 17, Ni etching on the p-side ohmic electrode 29 is performed by wet etching.
By etching only the electrode 29b isotropically,
Only the electrode width of the Ni electrode 29b is about 1.8 μm. Thereby, the convex p-side ohmic electrode 29 including the step portion is formed.
To form Thereafter, a through film 32 having a thickness of about 10 nm and made of SiO ₂ is formed by a plasma CVD method so as to cover the entire upper surfaces of the p-side ohmic electrode 29 and the p-type contact layer 26.

Here, in the third embodiment, FIG.
Thus, the convex p-side ohmic electrode 29 having a step
Is used as a mask, and the silicon
By performing the ON implantation, the step-like impurity implantation layer 2 is formed.
7 is formed. In the third embodiment, the ion implantation
Energy is about 400 keV and dose is about 4.5 × 10 ¹⁵
cm^-2Silicon ion implantation under the same ion implantation conditions.
U. As a result, the step-like impurity implantation layer 27 is
It is formed by ON implantation. In this case, between the impurity implantation layers 27
Peak depth of silicon concentration implanted in narrow regions
Is approximately 0.14 μm from the upper surface of the p-type contact layer 26.
This is a region of the p-type cladding layer 5 having a depth. This peak depth
Is about 1.0 × 10²⁰cm^-3In
You. In addition, the impurity is implanted into a wide area of the impurity implantation layer 27.
The peak depth of the silicon concentration of the p-type contact layer 2
6 of the MQW light emitting layer 4 having a depth of about 0.59 μm from the upper surface.
Area. The silicon concentration at this peak depth is
About 1.0 × 10²⁰cm^-3It is. After this, the wet edge
The through film 32 is removed by ching.

Next, as shown in FIG.
Using the D method, about 200 nm is covered so as to cover the entire upper surfaces of the p-side ohmic electrode 29 and the p-type contact layer 26.
And has a thickness, the insulating film 30 made of SiO ₂
To form Then, as in the first embodiment, the upper surface of the p-side ohmic electrode 29 is exposed using the photolithography technique and the RIE method using CF ₄ gas.

Finally, as shown in FIG. 20, using the same process as in the first embodiment, the upper surface of the insulating film 30 is
The p-side pad electrode 31 is formed so as to be in contact with the upper surface of the p-side ohmic electrode 29. Then, the n-type GaN substrate 1
Is polished to a predetermined thickness, and then the n-side ohmic electrode 13 and the n-side pad electrode 1
By forming No. 4, the nitride-based semiconductor laser device according to the third embodiment shown in FIG. 15 is completed.

In the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment, as described above, the ion implantation is performed by using the mask including the convex p-side ohmic electrode 29 having the step. The step-like impurity implantation layer 27 including regions having different depths can be formed by a single ion implantation. Thus, the impurity implantation layer 27 that can individually control the width of the current passage region 28 and the amount of light absorption can be formed by a single ion implantation. Therefore, current constriction and lateral light confinement of laser light can be appropriately set, so that current density can be increased and excessive light absorption can be suppressed. This makes it possible to reduce the threshold current and control the spread angle of the laser light in the horizontal direction.

(Fourth Embodiment) FIG. 21 shows a fourth embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a structure of the nitride-based semiconductor laser device according to the embodiment. In the fourth embodiment, with a plurality of times of ion implantation, by performing each of the ion implantation from a different angle, so as to form an ion implanted light absorbing layer and the current confinement layer, made of Al _Z Ga1 over _Z N The case where the p-type intermediate layer is formed will be described. Note that p
The composition of the mold intermediate layer is continuously changed by changing Z. Other configurations of the fourth embodiment are the same as those of the first embodiment.

First, referring to FIG. 21, in the fourth embodiment, an n-type layer 2, an n-type cladding layer 3, and an MQW light emitting layer 4 are formed on an n-type GaN substrate 1. . The thickness and composition of each of the layers 1 to 4 are the same as in the first embodiment.

On the MQW light emitting layer 4, a p-type cladding layer 5 of Al _0.08 Ga _0.92 N having a thickness of about 0.28 μm is formed.
When, about a p-type intermediate layer 36 made of 0.067μm in thickness Al _Z Ga1 over _Z N, In _0.05 Ga _0.95 to about 3nm thick
An N-type p-type contact layer 37 is formed in this order. In the fourth embodiment, the composition of the p-type intermediate layer 36 is continuously changed from Z = 0.08 to Z = 0 from the p-type cladding layer 5 to the p-type contact layer 37. . Thereby, the p-type intermediate layer 36 has a lattice constant that is continuously changed and has a band gap intermediate between the p-type cladding layer 5 and the p-type contact layer 37.

Here, in the fourth embodiment, a part of the p-type cladding layer 5 and the p-type
A second impurity implantation layer 38a formed by ion implantation of phosphorus (P) and having a function as a light absorption layer having an implantation depth of about 0.32 μm is formed by removing a first width of about 2.8 μm. It is provided. Note that phosphorus is an example of the “impurity element” in the present invention, and the second impurity implantation layer 38 a
It is an example of the "impurity introduction layer" of the present invention. In this case, the peak depth of the ion-implanted phosphorus concentration is located in the region of the p-type cladding layer 5 having a depth of about 0.22 μm from the upper surface of the p-type contact layer 37. The phosphorus concentration at this peak depth is about 1.0 × 10 ²⁰ cm ⁻³ .

Further, inside the second impurity implanted layer 38a, carbon is ion-implanted into a partial region of the p-type clad layer 5, the p-type intermediate layer 36 and the p-type contact layer 37. A first impurity implantation layer 38b functioning as a current confinement layer having an implantation depth of about 0.28 μm is provided. Note that carbon is an example of the “impurity element” of the present invention, and the first impurity introduction layer 38b is an example of the “impurity introduction layer” of the present invention. In this case, the peak depth of the ion-implanted carbon concentration is located in the region of the p-type cladding layer 5 having a depth of about 0.2 μm from the upper surface of the p-type contact layer 37. The carbon concentration at this peak depth is about 1.0
× 10 ¹⁹ cm ^-3 . The first impurity injection layer 38b performs current constriction with respect to the injection current from the p-side, so that the width of the reversely trapezoidal current that changes in an inclined manner in the range of about 2.5 μm to about 2.0 μm. A region 39 is formed.

On the upper surface of the current passing region 39 of the p-type contact layer 37, the p-side ohmic electrode 40 is formed in a stripe shape with an electrode width of about 2.9 μm, as in the first embodiment. . The insulating film 41 is formed so as to cover the side surface of the p-side ohmic electrode 40 and the p-type contact layer 37.
Is formed. The p-side pad electrode 42 is formed on the insulating film 41 so as to contact the upper surface of the p-side ohmic electrode 40.
Is formed. On the back surface of the n-type GaN substrate 1, an n-side ohmic electrode 13 and an n-side pad electrode 14 are formed in order from the side closer to the back surface of the n-type GaN substrate 1. The thicknesses and compositions of the layers 40 to 42 are the same as those of the layers 10 to 12 of the first embodiment.

[0106] p in the nitride semiconductor laser device according to the fourth embodiment, as described above, the p-type cladding layer 5 made of Al _{0. 08} Ga _0.92 N, consisting of In _0.05 Ga _0.95 N
Since the difference in lattice constant from the mold contact layer 37 is large, channeling of phosphorus and carbon can be suppressed.
This can prevent phosphorus and carbon from being deeply injected into the device. As a result, the controllability of the implantation profile in the depth direction can be improved. Thus, the implantation depth of the impurity element in the first impurity implantation layer 38b having a function as a current confinement layer near the light emitting region can be strictly controlled with good reproducibility.

In the nitride-based semiconductor laser device according to the fourth embodiment, as described above, between the p-type cladding layer 5 and the p-type contact layer 37, a p-type semiconductor having a lattice constant different from these lattice constants is used. By forming the mold intermediate layer 36, channeling during ion implantation can be further prevented. Further, since the p-type intermediate layer 36 is formed of a layer whose lattice constant changes continuously, the effect of preventing channeling during ion implantation can be further enhanced.

Further, in the nitride semiconductor laser device according to the fourth embodiment, as described above, the p-type intermediate layer 36 having a band gap intermediate the band gap between the p-type cladding layer 5 and the p-type contact layer 37. To the p-type cladding layer 5
And between the p-type contact layer 37 and
The discontinuity of the band gap between the p-type cladding layer 5 and the p-type contact layer 37 can be reduced. This allows
Since the resistance to the current flowing from the p-type contact layer 37 to the p-type cladding layer 5 can be reduced, the current can easily flow.

The other effects of the nitride semiconductor laser device according to the fourth embodiment are the same as those of the first embodiment.

FIGS. 22 to 25 are sectional views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. Next, FIGS.
The manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment will be described with reference to FIG.

First, up to the p-type cladding layer 5 is formed by using the same process as in the first embodiment shown in FIG.
Next, as shown in FIG. 22, on the p-type cladding layer 5, a p-type intermediate layer 36 made of Al _Z Ga1 over _Z N having a thickness of about 0.067Myuemu. Here, the composition of the p-type intermediate layer 36 is continuously changed from Z = 0.08 to Z = 0 from the p-type cladding layer 5 to the p-type contact layer 37. Then, on the upper surface of the p-type intermediate layer 36, about 3 nm
A p-type contact layer 37 of In _0.05 Ga _0.95 N having a thickness of is formed. Then, the p-side ohmic electrode 40 is formed in a stripe shape with an electrode width of about 2.9 μm on the upper surface of the p-type contact layer 37 by using a lift-off method. Then, the upper surface of the p-side ohmic electrode 40 and p
A through film 43 made of SiO _{2 having} a thickness of about 60 nm is formed by plasma CVD so as to cover the entire upper surface of the mold contact layer 37.

Next, in the fourth embodiment, as shown in FIG. 23, a predetermined angle is inclined from a direction perpendicular to the p-side ohmic electrode 40 with the stripe direction of the p-side ohmic electrode 40 as an axis. Carbon is ion-implanted from the direction in which it was set. Specifically, using the p-side ohmic electrode 40 as a mask, the p-side ohmic electrode 40
In the plane perpendicular to the stripe direction, the p-type contact layer 3
7 (the [00] of the p-type contact layer 37).
01] direction) from the angle of about 30 ° clockwise from
A second ion implantation is performed. As a result, a high resistance layer 38c having an implantation depth of about 0.28 μm from the upper surface of the p-type contact layer 37 is formed. In the first ion implantation of the fourth embodiment, the ion implantation energy is about 95 ke.
V ions and carbon ions are implanted under ion implantation conditions of about 2.3 × 10 ¹⁴ cm ⁻² .

Next, in a plane perpendicular to the stripe direction of the p-side ohmic electrode 40, a counterclockwise rotation is performed in a direction perpendicular to the p-type contact layer 37 (the [0001] direction of the p-type contact layer 37). A second ion implantation is performed from an angle of 30 °. As a result, as shown in FIG. 24, a high resistance layer 38d having an implantation depth of about 0.28 μm from the upper surface of the p-type contact layer 37 is formed. The conditions for the second ion implantation of the fourth embodiment are the same as the conditions for the first ion implantation.

Further, as shown in FIG. 25, phosphorus ions were implanted from a direction inclined about 7 ° from the direction perpendicular to the p-type contact layer 37 to the stripe direction of the p-side ohmic electrode 40. In the third ion implantation, the ion implantation energy is about 200 keV and the dose is about 2.5.
Under the ion implantation conditions of × 10 ¹⁵ cm ⁻² , phosphorus ion implantation is performed. In this manner, the regions formed by the first to third ion implantations are overlapped with each other.
A first impurity implantation layer 38b and a second impurity implantation layer 38a are formed as shown in FIG.

Thereafter, the through film 43 is removed by wet etching using a hydrofluoric acid-based etchant. Then, the p-type contact layer 37 is formed by using the plasma CVD method.
Then, an insulating film 41 having a thickness of about 200 nm and made of SiO ₂ as shown in FIG. 21 is formed so as to cover the entire upper surface of the p-side ohmic electrode 40.
Then, as in the first embodiment, the upper surface of the p-side ohmic electrode 40 is exposed using the photolithography technique and the RIE method using CF ₄ gas.

Finally, the p-side pad electrode 42 is formed on the insulating film 41 so as to be in contact with the exposed upper surface of the p-side ohmic electrode 40 by using the same process as in the first embodiment. Also, on the back surface of the n-type GaN substrate 1 after being polished to a predetermined thickness, the n-side ohmic electrode 13 and the n-side pad electrode 14 are arranged from the side close to the back surface of the n-type GaN substrate 1.
Is completed, the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 21 is completed.

In the manufacturing process of the nitride-based semiconductor laser device according to the fourth embodiment, as described above, the width of the current passing region 39 can be easily reduced by changing the ion implantation angle and performing ion implantation a plurality of times. The width can be made smaller than the width of the p-side ohmic electrode 40 as a mask. Thus, sufficient current confinement can be performed without performing a complicated process such as forming a plurality of ion implantation mask layers.

It should be noted that the embodiments disclosed this time are illustrative in all aspects and are not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description of the embodiments, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

For example, in the above embodiment, the ion-implanted light-absorbing layer is formed by ion-implanting any of carbon, silicon, boron and phosphorus, but the present invention is not limited to this. Ion implantation may be performed.
Note that as an element to be implanted, a dopant having conductivity opposite to that of a semiconductor to be implanted is preferably used. This makes it possible to form an impurity-implanted layer having a function of current confinement by ion implantation at a low dose. Further, it is preferable to use a heavy element having a larger mass number than carbon. Thereby, channeling of implanted ions can be prevented. Alternatively, any of Group 3 elements such as Al, Ga, and In and Group 5 elements such as phosphorus, As, and Sb may be implanted. In particular, since phosphorus or As forms a deep level (isoelectronic trap), a sufficient light absorption layer can be formed with a low dose.

In the third embodiment, the first ion-permeable region (SiO _{2 of} 10 nm) having the first stopping power is used.
And a second ion-permeable region having a second stopping power (10 nm SiO ₂ and 60 nm Pt) having a second stopping power through which ions are less likely to penetrate than the first ion-permeable region. The present invention is not limited to this, and the first ion-permeable region may be formed of a thin through film, and the second ion-permeable region may be formed of a thick through film.
For example, the first ion transmission region is made of 10 nm SiO ₂ , and the second ion transmission region is made of 300 nm SiO 2.
It may be composed of _two, also in the first ion transmissive region without forming a through film, a second ion permeable regions may be composed of 60nm of Pt. Alternatively, the first ion-permeable region is formed of a through film made of a low-density material,
May be formed of a through film made of a material having a high density. For example, the first ion transmission region is 6
The second ion transmission region may be composed of 60 nm of Pt, and may be composed of 0 nm of SiO ₂ .

In the first, second and fourth embodiments, the p-type intermediate layer having a single-layer structure is formed. However, the present invention is not limited to this, and the p-type intermediate layer may be formed of a plurality of layers having different lattice constants. May be formed. Thereby, the effect of preventing channeling at the time of ion implantation can be further increased.

In the first embodiment, In _0.01 G
By forming a p-type intermediate layer made of a _0.99 N,
The contact resistance was reduced by reducing the lattice constant difference between the p-type intermediate layer and the p-type contact layer made of InGaN as compared with the case where the type intermediate layer was formed of GaN, but the present invention is not limited to this. , The lattice constant of the p-type intermediate layer is
It is sufficient that the lattice constant is between the lattice constant of the p-type contact layer and the lattice constant of the p-type cladding layer. For example, A
a p-type cladding layer composed of lGaN and having a lattice constant of a1;
When a p-type contact layer made of InGaN and having a lattice constant of a2 and a p-type intermediate layer made of InGaN and having a lattice constant of a3 are formed, the p-type contact layer is formed so that the lattice constant is a3> a2.
The In composition of the mold intermediate layer may be adjusted. In particular, the lattice constant difference between the p-type cladding layer and the p-type intermediate layer is represented by Δa1 = a1−
a3, when the lattice constant difference between the p-type contact layer and the p-type intermediate layer is Δa2 = a3-a2, if the In composition of the p-type intermediate layer is adjusted so that Δa1 ≒ Δa2, the p-type intermediate layer In addition, distortion of the p-type contact layer can be reduced, and as a result, contact resistance can be reduced, which is preferable.

In the second embodiment, Al _0.01 G
a The p-type intermediate layer made of _0.99 N reduces the band gap difference between the p-type intermediate layer and the p-type cladding layer, thereby reducing the resistance to the current (hole) flowing from the p-type contact layer to the p-type cladding layer. Although reduced, the present invention is not limited to this, and it is sufficient that the band gap of the p-type intermediate layer is a band gap between the band gap of the p-type contact layer and the band gap of the p-type cladding layer. For example, a p-type cladding layer of AlGaN having a band gap of EG1 and a band gap of InGaN having a band gap of E
When forming a p-type contact layer of G2 and a p-type intermediate layer of EG3 with a band gap made of AlGaN, the Al composition of the p-type intermediate layer may be adjusted so that the band gap satisfies EG1> EG3. In particular, the band gap difference between the p-type cladding layer and the p-type intermediate layer is given by ΔEG1 = EG1
-EG3, when the band gap difference between the p-type contact layer and the p-type intermediate layer is ΔEG2 = EG3-EG2,
By adjusting the Al composition of the p-type intermediate layer so that EG1 ≒ ΔEG2, the resistance to the current flowing from the p-type intermediate layer to the p-type cladding layer and the resistance to the current flowing from the p-type contact layer to the p-type intermediate layer Is preferred because it is possible to reduce

[0124]

As described above, according to the present invention, it is possible to provide a nitride-based semiconductor laser device capable of improving the production yield by suppressing the deep implantation of the impurity element. .

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing an MQW light emitting layer of the nitride-based semiconductor laser device according to the first embodiment shown in FIG.

FIG. 3 is an enlarged sectional view schematically showing an ion implantation region.

FIG. 4 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment shown in FIG.

FIG. 5 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment shown in FIG.

FIG. 6 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment shown in FIG.

FIG. 7 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment shown in FIG.

FIG. 8 is a graph showing a simulation result of a carbon concentration and a crystal defect concentration profile in the nitride semiconductor laser device according to the first embodiment shown in FIG.

FIG. 9 is a graph showing a SIMS of a carbon concentration profile in the nitride semiconductor laser device according to the first embodiment shown in FIG. 1;
5 is a graph showing the measurement results obtained by the measurement.

FIG. 10 is a sectional view showing a structure of a nitride-based semiconductor laser device according to a second embodiment of the present invention.

FIG. 11 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG.

FIG. 12 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG.

FIG. 13 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG.

FIG. 14 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the second embodiment shown in FIG.

FIG. 15 is a sectional view showing a structure of a nitride-based semiconductor laser device according to a third embodiment of the present invention.

FIG. 16 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment shown in FIG.

FIG. 17 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment shown in FIG.

FIG. 18 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment shown in FIG.

FIG. 19 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment shown in FIG.

FIG. 20 is a cross-sectional view for explaining the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment shown in FIG.

FIG. 21 is a sectional view showing the structure of a nitride-based semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 22 is a sectional view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 21;

FIG. 23 is a sectional view for illustrating the manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 21;

FIG. 24 is a cross-sectional view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 21;

FIG. 25 is a cross-sectional view for explaining the manufacturing process for the nitride-based semiconductor laser device according to the fourth embodiment shown in FIG. 21;

FIG. 26 is a sectional view showing the structure of a conventional nitride-based semiconductor laser device.

[Explanation of symbols]

4, MQW light emitting layer (light emitting layer) 5 p-type clad layer (first conductive type clad layer) 7, 17, 26, 37 p-type contact layer (second conductive type contact layer) 8, 18a, 18b, 27 , 38a, 38b Impurity injection layer (impurity introduction layer)

Claims (5)

[Claims] 1. A light emitting layer, a first conductivity type cladding layer formed on the light emitting layer and including a first nitride-based semiconductor layer containing Al, and formed on the cladding layer and containing In. An impurity element formed by introducing an impurity element into at least a part of a region other than a current passing region of the cladding layer and the contact layer, the first conductivity type contact layer including a second nitride-based semiconductor layer to be formed; A nitride semiconductor laser device comprising an introduction layer. 2. The nitride-based semiconductor laser device according to claim 1, wherein said impurity-introduced layer has more crystal defects than said current passage region. 3. The nitride-based semiconductor laser device according to claim 1, wherein an upper surface of said impurity introducing layer and an upper surface of said current passage region are formed to be substantially flush with each other. . 4. The nitride-based semiconductor laser device according to claim 1, wherein an impurity concentration of said impurity element is maximized in said cladding layer. 5. The impurity-doped layer according to claim 1, wherein said impurity-introduced layer is formed by ion-implanting an impurity element into at least a part of a region other than a current passage region of said clad layer and said contact layer. 12. The nitride-based semiconductor laser device according to claim 1.