JP2003031901A - Semiconductor laser device and method of manufacturing the same - Google Patents

Abstract

(57) Abstract: In a semiconductor laser having a window region, a decrease in forward rise voltage Vf is prevented. SOLUTION: In a semiconductor laser provided with a window region 32 formed by introducing zinc into a quantum well structure active layer 18 near a semiconductor laser end face and disordering the same, a GaInP / AlGaInP quantum well structure is formed on a semiconductor substrate 12. N-AlGa having a band gap larger than the band gap of the active layer 18 having an Al composition ratio of 0.3 or more
An As buffer layer 14 is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device and its manufacturing method, and more particularly to a semiconductor laser device used for optical information processing and its manufacturing method.

[0002]

2. Description of the Related Art In recent years, with the progress of multimedia, a DVD as an optical density optical disc system has been attracting attention. As a rewritable DVD-RAM / RW light source, a high output 63 with a pulse output of 50 mW or more is used.
A red semiconductor laser of 0 nm to 690 nm band is used. One of the main factors limiting the increase in the output of the red semiconductor laser is deterioration at the chip end surface of the semiconductor laser.
This deterioration is referred to as COD (Catastrophic Optical Damage) deterioration, and is caused by light absorption caused by a defect near the chip end surface.

That is, in the case of high-power operation, the temperature rises and the end face is destroyed due to the surface recombination of the emitting end face and the increase of the light absorption in the vicinity of the end face. In order to prevent this, zinc is diffused near the emission facet to form a window region in which the active layer near the emission facet is disordered, and the effective bandgap energy of the active layer near the facet is increased to increase near the facet. The absorption of the laser light is reduced to suppress the end face deterioration.

FIG. 8 is a sectional view of a conventional semiconductor laser. In FIG. 8, reference numeral 100 is a semiconductor laser. The semiconductor laser 100 is a ridge type semiconductor laser,
Year OECC (M.Kato et al .: Fifth Optoelectrics an
d Communication Conference, Chiba, Japan, 2000, p.
534).

Reference numeral 102 denotes a Si-doped n-type GaAs substrate (hereinafter, n conductivity type is "n-" and p conductivity type is "p-".
Will be written). 104 is a Si-doped n-GaAs buffer layer, 106 is a lower cladding layer of n-AlGaInP,
108 is an MQW active layer, 110 is an upper cladding layer of p-AlGaInP, 112 is a contact layer of p-GaAs,
114 is a p-side front electrode, 116 is an n-side back electrode, 1
18 is a window region by zinc diffusion, and 120 is an insulating film.

Next, an outline of a conventional method of manufacturing the semiconductor laser 100 will be described. N-GaAs on the GaAs substrate 102
The buffer layer 104 is provided, and the lower cladding layer 106 and MQW are provided.
Active layer 108, upper cladding layer 110, contact layer 11
2 are sequentially formed by an epitaxial growth method such as MOCVD. After that, ZnO is vapor-deposited on the wafer surface near the chip end surface, which is the laser emission end surface when divided into chips, and annealed to diffuse zinc from the wafer upper surface to the MQW active layer 108 and the lower cladding layer 106. The window region 118 is formed. Then the upper clad layer 11
0 and the contact layer 112 are etched to leave a stripe mesa shape to form an optical waveguide, an insulating film 120 is formed on the upper surface of the wafer, and a surface electrode 114 is further formed.
After forming the back electrode 116 and the back electrode 116, cleavage is performed so as to pass through the window region 118 perpendicularly to the optical waveguide to manufacture an element.

[0007]

The conventional semiconductor laser 1
00 is configured as described above, and when forming the window region 118, ZnO is vapor-deposited on the wafer surface and annealed to diffuse zinc from the upper surface of the wafer to the MQW active layer 108 and further to the lower cladding layer 106. Is performed to form the window region 118. At this time, the lower cladding layer 106 is A
It is formed of 1GaInP and has a Zn diffusion rate of Al.
Since it is early in GaInP, the diffusion of Zn reaches the inside of the n-GaAs buffer layer 104.

The diffusion of Zn depends on the n-GaAs buffer layer 10
4 to the p-type in the n-GaAs buffer layer 104.
An n-junction is formed. Normally, the forward-direction rising voltage Vf of the semiconductor laser is determined by the bandgap of the MQW active layer 108. However, since the bandgap of the n-GaAs buffer layer 104 is smaller than the bandgap of the MQW active layer 108, first the window region 118 is formed. The pn junction formed at the interface with the n-GaAs buffer layer 104 turns on, the forward-direction rising voltage Vf becomes small, which causes a leak current, and in some cases, this leak current adversely affects the characteristics of the semiconductor laser. There was a problem that it could happen.

The present invention has been made to solve the above problems, and a first object of the present invention is to provide a semiconductor laser having a window region, in which the forward-direction rising voltage Vf is less decreased and the leakage current is small. The second purpose is to manufacture a semiconductor laser with a small decrease in forward-direction rising voltage Vf and a small leakage current in a simple process even if a window region is formed.

In Japanese Patent Laid-Open Nos. 4-111378 and 1-1028982, an n-GaAs substrate, a lower cladding layer of n-AlGaInP, and GaIn are disclosed.
A semiconductor laser having a structure of an active layer of P is disclosed in JP-A-6-
No. 338655 discloses an n-GaAs substrate and n-AlG.
A semiconductor laser having a structure of a lower cladding layer of aAs and a GaAs-SQW active layer is also disclosed in JP-A-5-2838.
No. 07, gazette describes a semiconductor laser having an n-GaAs substrate, a lower cladding layer of n-AlGaAs, and a GaAs active layer.

[0011]

A semiconductor laser device according to the present invention includes a semiconductor substrate of a first conductivity type, a buffer layer of a first conductivity type provided on the semiconductor substrate, and a buffer layer on the buffer layer. A first clad layer of the first conductivity type disposed on the first clad layer, an active layer of a quantum well structure having a bandgap smaller than the bandgap of the buffer layer disposed on the first clad layer, A second clad layer of a second conductivity type disposed on the layer, and an active layer in the vicinity of an end face in the optical waveguide direction of a laser resonator including the first clad layer, the active layer and the second clad layer. And a disordered region arranged by introducing impurities into the stack, and even if the impurity introduced to form the disordered region reaches the buffer layer, the band gap of the buffer layer is Also active band Since flop is small, can reduce the degradation of the forward rise voltage Vf, leak current is suppressed.

Further, the impurity introduced into the disordered region is zinc, and even if the diffusion of zinc having a high diffusion rate reaches the buffer layer, the band gap of the active layer is larger than that of the buffer layer. Since it is small, it is possible to reduce the decrease of the forward-direction rising voltage Vf and suppress the generation of leak current.

Furthermore, in the red semiconductor laser having the window region, the active layer is made of a GaInP material and the buffer layer is made of an AlGaAs material. Is also suppressed.

Further, AlGaA constituting the buffer layer
Since the Al composition ratio of the s-based material is 0.3 or more, the decrease in the forward-direction rising voltage Vf in the red semiconductor laser can be effectively reduced, and the generation of leak current can be suppressed.

In the method of manufacturing a semiconductor laser device according to the present invention, a first conductivity type buffer layer, a first conductivity type first cladding layer, and a band gap of the buffer layer are formed on a first conductivity type semiconductor substrate. A step of sequentially forming an active layer of a quantum well structure having a small band gap and a second cladding layer of a second conductivity type, and an optical waveguide direction of a laser resonator including the first cladding layer, the active layer and the second cladding layer. A step of introducing impurities from above the second clad layer into a region to be an end face of the layer to disorder the stack including the active layer,
The window region can be formed without lowering the forward rising voltage Vf.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In a semiconductor laser according to this embodiment, a buffer layer having a bandgap larger than that of an active layer of a quantum well structure is provided on a semiconductor substrate, and a semiconductor laser near an end face of the semiconductor laser is provided. The quantum well structure active layer is provided with a window region formed by introducing impurities.

Embodiment 1. FIG. 1 is a partially cutaway perspective view of a semiconductor laser according to the present invention. FIG. 2 is a sectional view of the semiconductor laser device according to the present invention taken along the line II-II in FIG. 1 and 2, reference numeral 10 denotes a semiconductor laser, which is a ridge type semiconductor laser having an oscillation wavelength of 630 to 690 nm and a pulse output of 50 mW or more.
12 is a Si-doped n-GaAs substrate, 14 is n-Ga
As a buffer layer provided on the As substrate 12, for example, a buffer layer made of Si-doped n-AlGaAs, and 16 as a first cladding layer, n-AlGaIn.
It is a lower clad layer of P. Reference numeral 18 is an MQW active layer provided on the lower cladding layer 16. The MQW active layer 18 is
The MQW structure is GaInP / AlGaInP.

The buffer layer 14 is made of a material having a bandgap larger than that of the MQW active layer 18. In this embodiment, n-AlGaAs having an Al composition ratio of 0.3 or more is used as the buffer layer 14. In addition, AlGaAs is Z compared to AlGaInP.
It is a material with a low diffusion rate of n. Reference numeral 20 denotes a p-type second clad layer disposed on the MQW active layer 18.
-AlGaInP upper cladding layer. 22 is p-G
In the contact layer of aAs, the upper clad layer 20 and the contact layer 22 are formed in a stripe mesa shape to form an optical waveguide 24. Except for the contact layer 22 on the top of the optical waveguide 24, the side surface of the optical waveguide 24, the upper clad layer 24 exposed by the formation of the optical waveguide 24 and the p-GaAs layer 26 formed at the same time as the contact layer 22 are made of SiO.
It is covered with an insulating film 28 such as ₂ .

A p-side surface electrode 30 is disposed on the surfaces of the contact layer 22 and the insulating film 28, and the contact layer 2
2 and a current path to the MQW active layer 18 via the optical waveguide 24. Reference numeral 32 is a window region provided in the vicinity of both end faces of the chip, which are emission end faces on both sides of the optical waveguide 24. The window region 32 is a region where the MQW active layer 18 is disordered by introducing zinc as an impurity from the surface of the upper cladding layer 24 by diffusion. The window region 32 includes the upper cladding layer 24, the MQW active layer 18, and the lower cladding layer 16.
including. Since the diffusion rate of Zn becomes smaller in the buffer layer 14, it becomes easier to control the diffusion of zinc at the boundary between the lower cladding layer 16 and the buffer layer 14 in some cases, but in some cases, the diffusion of Zn may occur in the buffer layer 14. It may extend.

On the surface of the window region 32, the contact layer 22 is removed and the insulating film 28 is provided. 34 is nG
It is an n-side back surface electrode provided on the back surface side of the aAs substrate 12. Next, an outline of a method of manufacturing the semiconductor laser 10 will be described. N as the buffer layer 14 on the GaAs substrate 12
-Providing an AlGaAs layer and n as the lower cladding layer 16;
-AlGaInP layer, MQW active layer 18, n-AlGaInP layer as upper cladding layer 20, contact layer 22
P-GaAs layers are sequentially formed by an epitaxial growth method such as MOCVD. After that, ZnO is vapor-deposited on the wafer surface near the both end surfaces of the chip, which becomes the laser emission end surface when divided into chips, and annealed to form n as the lower cladding layer 16 from the upper surface of the wafer through the MQW active layer 18. -Zinc is diffused to the AlGaInP layer to form the window region 32.

Then, n-Al as the upper cladding layer 20 is formed.
P-GaAs as GaInP layer and contact layer 22
The optical waveguide 24 is formed by etching while leaving the layer in a stripe mesa shape. After that, the insulating film 2 is formed on the upper surface of the wafer except for the contact layer 22 on the top of the optical waveguide 24.
8 is formed, and a surface electrode 30 is further formed on the contact layer 22 and the insulating film 28 on the top of the optical waveguide 24.
The back surface of the -GaAs substrate 12 is ground to a predetermined thickness, and the back electrode 34 is formed on the back surface of the n-GaAs substrate 12.
Finally, cleavage is performed so as to pass through the window region 32 perpendicularly to the optical waveguide 24 to complete the device.

Next, prior to the description of the operation of the semiconductor laser 10, the basic matters leading to the present invention will be described. FIG. 3 is a graph showing the IV characteristic of the conventional semiconductor laser. This semiconductor laser uses n-GaAs as a buffer layer.
The semiconductor laser 100 has the same structure as the semiconductor laser 100 having a layer and a window region which is a zinc diffusion region. FIG. 4 is a graph showing the IV characteristic of another conventional semiconductor laser. The semiconductor laser having the IV characteristic shown in FIG. 4 has an n-type buffer layer.
-The structure is the same as that of the semiconductor laser 100 having a GaAs layer, but has a structure having no zinc diffusion window region (provisionally named semiconductor laser 100X).

Comparing the graphs of FIGS. 3 and 4, when the forward-direction rising voltage Vf of the semiconductor laser 100X of FIG. 4 exceeds 1.5 × 10 ⁻⁵ V, the current value Log is changed.
I increased from 1.5 × 10 ⁻⁵ V to 3 × 10
^In the semiconductor laser 100 of FIG. 3, the forward-direction rising voltage Vf is less than 1 × 10 ⁻⁵ V, and the current value Lo is low, while the saturation level is slightly saturated near ⁻⁵ V and reaches LogI = −2.
The value of g I rises at a stroke at first, but 1.5 × 10
^The rate of increase becomes a little saturated from the point where it exceeds ⁻⁵ V, and the current value Log I rises with a decreasing gradient, resulting in 3 ×
In the vicinity of 10 ⁻⁵ V, a tendency similar to that of the graph of the semiconductor laser 100X is shown and reaches Log I = −2.

From this comparative study, considering that the semiconductor laser 100 having the window region has a high diffusion rate of Zn in AlGaInP, zinc is diffused to the n-GaAs buffer layer, which causes n-GaAs. Since the pn junction is formed in the buffer layer and the band gap of the n-GaAs buffer layer is smaller than that of the MQW active layer, when the voltage is increased, the interface between the window region and the n-GaAs buffer layer is first displayed. Turned on at the pn junction formed in, the current started to flow in the window region, and when the voltage was further increased, turn-on occurred at the MQW active layer,
It was considered that the shift was toward the graph of the semiconductor laser 100X. If the formation of the window region is stopped to prevent the decrease of Vf, COD deterioration will occur. Based on this consideration, the invention of the semiconductor laser according to this embodiment has been achieved.

Next, the operation of the semiconductor laser according to the present invention will be described. In the semiconductor laser 10, after the p-GaAs layer as the contact layer 22 is formed by the epitaxial growth method such as MOCVD, ZnO is vapor-deposited and annealed on the wafer surface in the vicinity of the chip end face which is the laser emission end face when divided into chips. As a result, zinc is diffused from the upper surface of the wafer to disorder the MQW active layer 18, widen the band gap, and form the window region 32 that is transparent to the laser light.

Since the lower cladding layer 16 is formed of an n-AlGaInP layer, the diffusion rate of zinc is high in the n-AlGaInP layer, but n-A as the buffer layer 14 is used.
Since the lGaAs layer has a low zinc diffusion rate, it is controlled so as to stop at the boundary between the lower cladding layer 16 and the buffer layer 14, but in some cases zinc diffuses into the buffer layer 14 and pn is formed in the buffer layer 14. It may form a bond.

FIG. 5 is a graph showing the IV characteristic of the semiconductor laser according to the first embodiment. Comparing FIG. 5 with FIGS. 3 and 4 shown above, the semiconductor laser 1 of FIG.
The forward-direction rising voltage Vf of 0 is slightly lower than 1.5 × 10 ⁻⁵ V, which is slightly lower than the forward-direction rising voltage Vf of the semiconductor laser 100X of FIG. 4, but the semiconductor laser 1 of FIG.
Considering that the forward-direction rising voltage Vf is less than 1 × 10 ⁻⁵ V in 00, it is considerably higher than the forward-direction rising voltage Vf of the semiconductor laser 100 and close to the forward-direction rising voltage Vf of the semiconductor laser 100X in FIG. Has become.

The slope of the current value Log I with respect to the voltage V of the semiconductor laser 10 of FIG.
X and that of the semiconductor laser 100 shown in FIG.
The rate of increase becomes a little saturated from the point of exceeding 10 ⁻⁵ V, the slope of Log I rises while becoming slightly smaller, and becomes close to 3 × 10 ⁻⁵ V, and the semiconductor laser 100X is reached.
The same tendency as the graph of No. 1 is shown and Log I = -2 is reached.

The tendency of the IV characteristic that the slope of Log I with respect to V of the semiconductor laser 10 in FIG. 5 becomes slightly smaller from about 2 × 10 ⁻⁵ V to the V of the semiconductor laser 100 in FIG. This is the same as the tendency that the slope of Log I decreases from about 1.5 × 10 ⁻⁵ V. However, in the semiconductor laser 10, the forward rising voltage Vf of the semiconductor laser 10 is higher than the forward rising voltage Vf of the semiconductor laser 100 of FIG.
The −V characteristic is shifted to the higher voltage side than that of the semiconductor laser 100, and the leakage current of the semiconductor laser 10 is small.

That is, with respect to the GaInP MQW active layer 18, an n-type having an Al composition ratio of 0.3 or more having a band gap larger than that of the MQW active layer 18.
By using AlGaAs as the buffer layer,
In the semiconductor laser provided with the window region 32 by Zn diffusion, the forward rising voltage Vf is suppressed from decreasing and the leakage current is reduced.

Therefore, in the semiconductor laser 10, as the buffer layer 14, n-AlGaA having an Al composition ratio of 0.3 or more is used.
Since s is used, zinc is more likely to be controlled so that zinc does not diffuse into the buffer layer 14, and even if a pn junction is formed in the buffer layer 14, the buffer layer 14 has a higher density than the MQW active layer 18. Since the semiconductor laser 10 has a large band gap, the MQW does not occur in the pn junction in the buffer layer without the first turn-on.
The first turn-on occurs in the active layer 18. Therefore, the decrease in the forward rising voltage Vf is suppressed, and the generation of the leak current due to the decrease in the voltage Vf is suppressed.

As described above, in the ridge type red semiconductor laser according to the first embodiment, the buffer layer 14
Since n-AlGaAs having an Al composition ratio of 0.3 or more is used as the above, it becomes easy to control so that zinc does not diffuse into the buffer layer 14, and even if the buffer layer 1
The zinc, which is an impurity, is diffused up to 4 and the buffer layer 14
Even if the pn junction is formed in the inside, by forming the buffer layer 14 to have a band gap larger than that of the MQW active layer 18, a decrease in the forward rising voltage Vf is suppressed, and the forward rising voltage is reduced. Generation of a leak current due to a decrease in Vf is also suppressed. As a result, a ridge-type red semiconductor laser in which the characteristics of the semiconductor laser and the operating efficiency are suppressed can be formed. In addition, it is possible to prevent a decrease in reliability at the time of high output.

Further, since the forward rising voltage Vf can be suppressed from being lowered by a simple process of forming n-AlGaAs having an Al composition ratio of 0.3 or more as the buffer layer 14, the characteristic deterioration of the semiconductor laser and the operating efficiency can be achieved. It is possible to manufacture a red semiconductor laser with less deterioration in a simple process, and there is little deterioration in the characteristics of the semiconductor laser or operation efficiency.
A highly reliable ridge-type red semiconductor laser at high output can be provided at low cost.

Embodiment 2. FIG. 6 is a perspective view of a semiconductor laser according to the present invention. In addition, in the following figures, FIG.
And the same reference numerals as in FIG. 2 are the same or equivalent. In FIG. 6, reference numeral 40 denotes a semiconductor laser having an oscillation wavelength of 630 to 690 nm and a pulse output of 50 mW or more.
It is an AS (Self-Aligned Structure) type semiconductor laser. 42 is an etching stopper layer of GaInP, 44 is a current blocking layer of AlInP, and 46 is a stripe groove.

On the Si-doped n-GaAs substrate 12, S
n-AlGaAs having an i-doped Al composition ratio of 0.3 or more
Buffer layer 14 of n-AlGaInP and GaInP are provided on the buffer layer 14.
MQW active layer 18 and first upper clad layer 20a, p which is a lower upper clad layer 20 made of p-AlGaInP.
-GaInP etching stopper layer 42, n-AlI
The nP current blocking layers 44 are sequentially arranged. A stripe groove 46 is provided in the center of the current block layer 44 along the optical waveguide direction, and the etching stopper layer 42 is exposed on the bottom surface of the stripe groove 46 to form a current path for flowing an operating current to the MQW active layer 18. ing.

The window region 32 including the MQW active layer 18 in which zinc is diffused and disordered is provided immediately below the stripe groove 46 in the vicinity of both end faces in the optical waveguide direction of the chip. A second upper clad layer 20b, which is an upper upper clad layer 20 made of p-AlGaInP, is provided on the surfaces of the stripe groove 46 and the current blocking layer 44, and the stripe groove 46 is embedded therein. Second upper cladding layer 20
A p-GaAs contact layer 22 is provided on the surface b, and a p-side surface electrode 30 is further provided thereon. An n-side back electrode 34 is provided on the back side of the n-GaAs substrate 12.

Next, an outline of a method of manufacturing the semiconductor laser 40 will be described. An n-AlGaAs layer as the buffer layer 14 is provided on the GaAs substrate 12, an n-AlGaInP layer as the lower cladding layer 16, an MQW active layer 18 of GaInP, and an n-AlGaInP as the upper cladding layer 20a.
Layer, p-GaInP as etching stopper layer 42
Layer and the n-AlInP layer as the current blocking layer 44 are sequentially formed by an epitaxial growth method such as MOCVD. Thereafter, ZnO is vapor-deposited and annealed on the wafer surface in the vicinity of both end surfaces of the chip, which becomes the laser emission end surface when divided into chips, and is annealed, so that the n-AlInP as the current block layer 44 has a width of about a stripe groove 46 to be formed later. The lower clad layer 16 from the layer upper surface through the MQW active layer 18
Diffusion of zinc to the n-AlGaInP layer as
The MQW active layer 18 is disordered to form the window region 32.

Next, the p-GaInP layer is used as an etching stopper layer 42 by wet etching, and stripe grooves 46 are formed in the n-AlInP layer as the current blocking layer 44.
To form a current inflow region. Then, n-AlInP as the stripe groove 46 and the current blocking layer 44 is formed.
P-AlGaI as the second upper cladding layer 20b on the layer
An nP layer and a p-GaAs layer as a contact layer are sequentially formed by an epitaxial growth method such as MOCVD to fill the stripe groove 46.

Further, p-GaAs as a contact layer
The surface electrode 114 is formed on the layer, and the n-GaAs substrate 1
The back surface of No. 2 is ground to a predetermined thickness, the back surface electrode 34 is formed on the back surface of the n-GaAs substrate 12, and finally the substrate is cleaved perpendicularly to the stripe groove 46 so as to pass through the window region 32.
Complete the device.

In the SAS type red semiconductor laser according to the second embodiment, as in the ridge type red semiconductor laser according to the first embodiment, A is used as the buffer layer 14.
By using n-AlGaAs having an l composition ratio of 0.3 or more, zinc can be easily controlled so as not to diffuse into the buffer layer 14, and zinc as an impurity is diffused even into the buffer layer 14, so that Pn in 14
Even if a bond is formed, the SAS according to the second embodiment
Type red semiconductor laser, the buffer layer 14 has a bandgap larger than that of the MQW active layer 18, so that the forward-direction rising voltage V is increased.
It is possible to suppress the decrease in f, and suppress the occurrence of leakage current due to this. As a result, it is possible to configure a SAS type red semiconductor laser in which the characteristics of the semiconductor laser are not degraded and the operation efficiency is reduced. In addition, it is possible to prevent a decrease in reliability at the time of high output.

Further, since the forward rising voltage Vf can be prevented from lowering by a simple process of forming n-AlGaAs having an Al composition ratio of 0.3 or more as the buffer layer 14, the characteristic deterioration and operating efficiency of the semiconductor laser can be prevented. It is possible to manufacture a SAS type red semiconductor laser in which the deterioration of power consumption is suppressed in a simple process, and there is little deterioration in the characteristics of the semiconductor laser and the decrease in operating efficiency, and a highly reliable SAS type red semiconductor laser at high output is inexpensive. Can be provided to.

Embodiment 3. FIG. 7 is a perspective view of a semiconductor laser according to the present invention. In FIG. 7, reference numeral 50 denotes a semiconductor laser, which is an embedded semiconductor laser having an oscillation wavelength of 630 to 690 nm and a pulse output of 50 mW or more.
Reference numeral 52 is a p-GaInP etching stopper layer, and 54 is an n-AlInP current blocking layer. A buffer layer 14 of n-AlGaAs having a Si-doped Al composition ratio of 0.3 or more is disposed on a Si-doped n-GaAs substrate 12, and a lower cladding layer 16 of n-AlGaInP is provided on the buffer layer 14. GaInP MQW active layer 18, p
A first upper clad layer 20a, which is a lower upper clad layer 20 made of -AlGaInP, and an etching stopper layer 42 of p-GaInP are sequentially arranged.

Striped mesa-shaped p-AlGaIn is formed in the center of the etching stopper layer 42 along the optical waveguide direction.
A second upper clad layer 20b, which is an upper upper clad layer 20 made of P, is provided, and the second upper clad layer 20b is provided on both sides of the stripe mesa of the second upper clad layer 20b.
N-AlInP current blocking layer 54 so that
Is provided. A p-GaAs contact layer is provided on the second upper cladding layer 20b and the current blocking layer 54, and a p-side surface electrode 30 is further provided thereon. An n-side back electrode 34 is provided on the back side of the n-GaAs substrate 12.

Next, an outline of a method of manufacturing the semiconductor laser 50 will be described. An n-AlGaAs layer as the buffer layer 14 is provided on the GaAs substrate 12, an n-AlGaInP layer as the lower cladding layer 16, an MQW active layer 18 of GaInP, and an n-AlGaInP as the upper cladding layer 20a.
Layer, p-GaInP as etching stopper layer 52
Layer, n-AlGaIn as the second upper cladding layer 20b
P layers are sequentially formed by an epitaxial growth method such as MOCVD. Thereafter, ZnO is vapor-deposited and annealed on the wafer surface in the vicinity of both end surfaces of the chip, which is the laser emission end surface when divided into chips, and the second upper clad layer 20b is then annealed.
As the lower cladding layer 16 from the upper surface of the n-AlGaInP layer as the lower layer via the MQW active layer 18.
Zinc is diffused to the InP layer to disorder the MQW active layer 18 and form the window region 32.

Then, the p-GaInP layer is used as an etching stopper layer 52, and the n-AlGaInP layer as the second upper cladding layer 20b is etched in a stripe mesa shape to form an optical waveguide. Next, on both sides of the stripe mesa of the n-AlGaInP layer as the second upper cladding layer 20b, the n-AlI as the current blocking layer 54 is formed.
The nP layer is formed by an epitaxial growth method such as MOCVD, and n-AlGaI as the second upper cladding layer 20b is formed.
The nP layer is buried leaving the top.

Further, as the second upper cladding layer 20b, n
On the -AlGaInP layer and the n-AlInP layer as the current blocking layer 54, p as the contact layer 22 is formed.
-The GaAs layer is formed by an epitaxial growth method such as MOCVD. Next, p-G as the contact layer 22
A surface electrode 114 is formed on the aAs layer, and n-GaAs
The back surface of the substrate 12 is ground to a predetermined thickness, and the n-GaA
A back electrode 34 is formed on the back surface of the s substrate 12, and is cleaved so as to pass through the window region 32 in a direction perpendicular to the optical waveguide direction of the second upper cladding layer 20b to complete the device.

Also in the buried type red semiconductor laser according to the third embodiment, as in the ridge type red semiconductor laser according to the first embodiment, n having an Al composition ratio of 0.3 or more is used as the buffer layer 14. By using -AlGaAs, it is easy to control zinc so that it does not diffuse into the buffer layer 14, and zinc that is an impurity is diffused even into the buffer layer 14, so that the p layer is diffused into the buffer layer 14.
Even if the n-junction is formed, the buried type red semiconductor laser according to the third embodiment has the MQW buffer layer 14.
With the structure having a bandgap larger than that of the active layer 18, it is possible to suppress a decrease in the forward-direction rising voltage Vf, and suppress the occurrence of a leak current due to this. As a result, it is possible to configure an embedded red semiconductor laser in which the characteristics of the semiconductor laser are not degraded and the operating efficiency is reduced. In addition, it is possible to prevent a decrease in reliability at the time of high output.

Further, the forward rise voltage Vf can be prevented from lowering by a simple process of forming n-AlGaAs having an Al composition ratio of 0.3 or more as the buffer layer 14, so that the characteristics of the semiconductor laser and the operating efficiency are lowered. It is possible to manufacture a buried type red semiconductor laser that suppresses the deterioration of power consumption in a simple process, and there is little deterioration in the characteristics of the semiconductor laser and the decrease in operating efficiency, etc. Can be provided to.

In the above description of the embodiment,
The red semiconductor laser having an oscillation wavelength of 630 to 690 nm, which uses AlGaAs having an Al composition ratio of 0.3 or more as the buffer layer, in which the MQW active layer is formed of GaInP, has been described.
The same effect can be obtained with an AlGaAs-based 780 nm band semiconductor laser using AlGaAs having an Al composition ratio of 0.15 or more as a buffer layer having a bandgap larger than that of the W active layer. Further, in the above-described embodiment, when the window region is formed, the impurity is introduced by diffusion, but the same effect can be obtained when the impurity is introduced by ion implantation.

[0050]

Since the semiconductor laser device and the method of manufacturing the same according to the present invention have the above-described configurations or steps, they have the following effects. In the semiconductor laser device according to the present invention, a first conductivity type semiconductor substrate, a first conductivity type buffer layer provided on the semiconductor substrate, and a first conductivity type provided on the buffer layer. Type first clad layer, an active layer having a quantum well structure having a bandgap smaller than that of the buffer layer, the active layer being disposed on the first clad layer, and being disposed on the active layer. A second clad layer of a second conductivity type, and a first
A disordered region disposed by introducing an impurity into a stack including an active layer in the vicinity of an end face in the optical waveguide direction of a laser resonator including a clad layer, an active layer and a second clad layer. Even if the impurities introduced to form the disordered region reach the buffer layer, the bandgap of the active layer is smaller than the bandgap of the buffer layer, so that the decrease in the forward-direction rising voltage Vf can be reduced. Generation of leak current is also suppressed. Further, it is possible to construct a semiconductor laser that has a window region in which the active layer is disordered by impurities, and that suppresses deterioration of laser characteristics and operation efficiency. In addition, it is possible to prevent a decrease in reliability at the time of high output.

Further, the impurity introduced into the disordered region is zinc, and even if zinc with a high diffusion rate reaches the buffer layer, the band gap of the active layer is larger than that of the buffer layer. Since it is small, it is possible to reduce the decrease of the forward-direction rising voltage Vf and suppress the generation of leak current. Further, it is possible to construct a semiconductor laser which has a window region in which the active layer is disordered by zinc and in which deterioration of laser characteristics and deterioration of operation efficiency are suppressed. In addition, it is possible to prevent a decrease in reliability at the time of high output.

Furthermore, in the red semiconductor laser having the window region, the active layer is made of GaInP-based material and the buffer layer is made of AlGaAs-based material. Generation is also suppressed. Further, it is possible to construct a red semiconductor laser which is provided with a window region in which the active layer is disordered by impurities and in which deterioration of laser characteristics and operation efficiency are suppressed. In addition, it is possible to prevent a decrease in reliability at the time of high output.

Further, AlGaA forming the buffer layer
Since the Al composition ratio of the s-based material is 0.3 or more, the decrease in the forward-direction rising voltage Vf can be effectively reduced in the red semiconductor laser. Further, it is possible to configure a red semiconductor laser that includes a window region in which the active layer is disordered by impurities, and effectively suppresses deterioration of laser characteristics and operation efficiency. In addition, it is possible to prevent a decrease in reliability at the time of high output.

Further, according to the method of manufacturing a semiconductor laser device of the present invention, the first conductivity type buffer layer, the first conductivity type first clad layer, and the band gap of the buffer layer are formed on the first conductivity type semiconductor substrate. A step of sequentially forming an active layer of a quantum well structure having a small band gap and a second cladding layer of a second conductivity type, and an optical waveguide direction of a laser resonator including the first cladding layer, the active layer and the second cladding layer. A step of introducing impurities from above the second clad layer into a region to be an end face of the layer to disorder the stack including the active layer,
The window region can be formed without lowering the forward rising voltage Vf. In addition, since it is possible to suppress the decrease in forward-direction rising voltage by a simple process of forming the buffer layer with a material larger than the band gap of the active layer of the quantum well structure, it is possible to reduce the characteristics of the semiconductor laser and the operation efficiency. A laser can be manufactured by a simple process, and a red semiconductor laser having high reliability at high output can be provided at a low cost with less deterioration of the characteristics and operating efficiency of the semiconductor laser.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG. 1 of the semiconductor laser according to the embodiment of the present invention.

FIG. 3 is a graph showing an IV characteristic of a conventional semiconductor laser.

FIG. 4 is a graph showing an IV characteristic of a conventional semiconductor laser.

FIG. 5 is a graph showing IV characteristics of the semiconductor laser according to the embodiment of the present invention.

FIG. 6 is a perspective view of a semiconductor laser according to an embodiment of the present invention.

FIG. 7 is a perspective view of a semiconductor laser according to an embodiment of the present invention.

FIG. 8 is a sectional view of a conventional semiconductor laser.

[Explanation of symbols]

12 semiconductor substrate, 14 buffer layer, 16 first
Clad layer, 18 active layer, 20 second clad layer,
32 window area.

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Claims (5)

[Claims] 1. A first-conductivity-type semiconductor substrate, a first-conductivity-type buffer layer provided on the semiconductor substrate, and a first-conductivity-type first clad provided on the buffer layer. Layer, an active layer of a quantum well structure having a bandgap smaller than that of the buffer layer, which is disposed on the first cladding layer, and a second conductivity type disposed on the active layer. Of the second clad layer and the first clad layer, the active layer and the second clad layer, which are disposed in the vicinity of the end face in the optical waveguide direction of the laser resonator and in which impurities are introduced into the stack including the active layer. And a disordered region. 2. The semiconductor laser device according to claim 1, wherein the impurity introduced into the disordered region is zinc. 3. The semiconductor laser device according to claim 1, wherein the active layer is made of a GaInP type material and the buffer layer is made of an AlGaAs type material. 4. The semiconductor laser device according to claim 3, wherein the Al composition ratio of the AlGaAs material forming the buffer layer is 0.3 or more. 5. An active of a quantum well structure having a band gap smaller than that of the first conductivity type buffer layer, the first conductivity type first cladding layer, and the buffer layer on the first conductivity type semiconductor substrate. A layer and a second of a second conductivity type
The step of sequentially forming the clad layer is performed. Impurities are introduced from above the second clad layer into a region serving as an end face in the optical waveguide direction of the laser resonator including the first clad layer, the active layer and the second clad layer to form the active layer. A method of manufacturing a semiconductor laser device, comprising: