JP2000164986A - Semiconductor light emitting device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the existence of a protective film and improve the yield with the cleavage, assembling, etc., by forming a semiconductor layer to be a current block layer outside the protective film at the outsides of ridges. SOLUTION: On a substrate 21 a first conductivity-type clad layer 11 and an active layer 12 are laminated, a protective film 31 which is an insulation layer is deposited thereon, the protective film 31 on a ridge dummy region at an outer part of the protective film 31 is removed through photolithography, a semiconductor layer to be a current block layer 16 is formed on the ridge dummy region, a ridge-forming opening is bored in a central part of the protective film by the photolithography, a second conductive clad layer 13a and a contact layer 14a are deposited on the ridge part and layers 13b, 14b corresponding to them are deposited on the ridge dummy region. Thus the yield with the cleavage and assembling can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device and a method of manufacturing the same, and more particularly to a semiconductor light emitting device having a ridge-type stripe structure suitable as a semiconductor laser and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 4 shows the structure of a conventional ridge waveguide type semiconductor laser having a stripe structure and a method of manufacturing the same. As shown in FIG. 4A, after a first conductive type first clad layer 11, an active layer 12, a second conductive type second clad layer 13, and a second conductive type contact layer 14 are grown on a substrate 21, As shown in FIG. 4B, the ridge portion is formed by etching the second conductivity type contact layer 14 and the second conductivity type second cladding layer 13 by etching. At this time, the portion other than the ridge is etched to the middle of the second conductivity type second cladding layer 13 above the active layer 12, and then the side surface of the ridge portion and the surface of the portion other than the ridge are etched with the insulating layer 31.
To prevent current from flowing, and to form an electrode 32 thereon including the upper part of the ridge (FIG. 4).
(C)).

[0003] With such a structure, current is injected into the active layer 12 through the ridge portion, and light corresponding to the composition of the active layer 12 is generated in the active layer 12 below the ridge portion.
On the other hand, since the insulating layer 31 having a smaller refractive index than the semiconductor portion is formed, the effective refractive index of the active layer other than the ridge is smaller than the effective refractive index of the ridge portion. As a result, the generated light is confined in the optical waveguide below the ridge.

In this ridge waveguide type semiconductor light emitting device having a stripe structure, since the ridge portion is formed by etching, it is difficult to make the thickness of the etched cladding layer portion other than the ridge on the active layer constant. Met.
As a result, a slight difference in the thickness of the cladding layer in a portion other than the ridge significantly changes the effective refractive index of the active layer in this portion. In addition, the width of the bottom of the ridge that determines the width of current injection also fluctuates, which makes it difficult to produce a laser with a low threshold and a constant light spread angle with good reproducibility.

In order to solve such a problem, the thickness of the cladding layer above the active layer is determined by using the crystal growth rate at the time of crystal growth, a protective film is formed other than the ridge portion, and the ridge portion is re-formed. A growing method has been proposed (Japanese Unexamined Patent Application Publication No.
-121822, JP-A-9-199791). FIG. 5 shows the structure of such a laser and a method for producing the same.
Shown in First, a first conductive type first clad layer 11, an active layer 12, and a second conductive type first clad layer 13 are formed on a substrate 21.
After growing (FIG. 5A), the surface of the second conductive type first cladding layer 13 is covered with a protective film 31 such as SiO ₂ , and a stripe-shaped window is opened by photolithography. Only the second conductivity type second cladding layer 13a and the second conductivity type contact layer 14 are selectively grown (FIG. 5B).
Next, the protective film 31 covering portions other than the ridge, the side surface of the second conductive type second cladding layer 13a forming the ridge, and the entire surface of the second conductive type contact layer 14 are covered with an insulating layer 31a such as SiN _x , After removing the SiN _x insulating layer on the top of the ridge again by photolithography, the electrode 32 is formed on the entire surface (FIG. 5C).

As described above, if current is prevented from flowing to portions other than the ridge by the insulating layer, the surface is covered with the insulating layer, making cleavage difficult, and there are problems such as peeling of electrodes. In addition, when a pinhole or the like is present in the insulating layer, a current flows to a portion other than the ridge, and there is a problem that the current cannot be sufficiently confined at the ridge portion. Further, as shown in FIG. 9 (b), when assembled by j-down (junction down) with the substrate side up and the epitaxial layer side down, the solder material just goes around by the thickness of the electrode and the protective film, and the This is not a preferable state because it tends to reach the lower compound semiconductor layer and cause current leakage, and the ridge portion is more likely to be degraded by stress because it protrudes as compared with other portions.

[0007]

As described above, even when the conventional ridge stripe type semiconductor light emitting device having the ridge stripe type waveguide is formed by regrowth, current does not flow to portions other than the ridge by the insulating layer or the like. In the case of the LD, the cleavage and assembling are difficult, and the current may not be sufficiently confined by the protective film or the like, and the yield may decrease. Also, when assembled in j-down, current leakage to parts other than the ridge and deterioration due to stress may be caused, and sufficient LD characteristics may not be obtained.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a structure in which a semiconductor layer serving as a current blocking layer is formed further outside a protective film outside a ridge. By having a semiconductor light emitting device having
It has been found that the presence of a protective film is minimized to improve the yield of cleavage, assembly, etc., and that sufficient LD characteristics are obtained when assembled by j-down.
The present invention has been reached.

That is, the gist of the present invention is a semiconductor light emitting device having a ridge stripe type waveguide structure whose structure and manufacturing method are shown in FIG. 1 and an example of a manufacturing method thereof. Specifically, a semiconductor light emitting device having a compound semiconductor layer including an active layer on a substrate, a ridge type compound semiconductor layer formed on an opening through which current is injected, and protective films covering both sides of the opening Forming a semiconductor light emitting device having a current blocking layer formed outside the protective film, a compound semiconductor layer including an active layer and a protective film having an opening on a substrate in this order. A semiconductor comprising a step of selectively growing a current blocking layer on both sides of a film, a step of removing a portion corresponding to an opening of the protective film, and a step of selectively growing a ridge type compound semiconductor layer in the opening. A method for manufacturing a light emitting device, and a step of laminating a compound semiconductor layer including an active layer and a current block layer on a substrate in this order, a step of removing a part of the current block layer, Forming a protective film having an opening, a manufacturing method of the semiconductor light emitting device characterized by comprising the step of selectively growing a compound semiconductor layer of the ridge-type opening.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The structure of the present invention is created by regrowth.
That is, as shown in FIG. 1, a compound semiconductor layer including an active layer, which is first formed on a substrate, usually includes layers having a lower refractive index than the active layer above and below the active layer. Layer functions as a first conductivity type cladding layer, and the other epitaxial side layer functions as a second conductivity type first cladding layer. In addition, a layer functioning as a light guide layer may be included. Usually, a double hetero (DH) structure in which an active layer is sandwiched between two cladding layers,
A conductive clad layer 11, an active layer 12, and a second conductive clad layer 13 are sequentially laminated. At this time, an antioxidant layer having a function of preventing surface oxidation may be further included on the second conductivity type cladding layer 13.
5 can be stacked, which is preferred (FIG. 1 (a)). Next, a protective film 31 serving as an insulating layer is deposited, and the protective film in the ridge dummy region is removed from the outer portion of the protective film by photolithography. As shown in FIG. 8, the ridge dummy region includes a portion outside the protective film including the epitaxial layer from the substrate as viewed from the epitaxial layer side, and is referred to as a ridge dummy region. It includes an epitaxial layer grown so as to cover the protective film 31. A current block layer 16 is formed in the ridge dummy region (FIG. 2B). Further, an opening for forming a ridge is formed in the central portion of the protective film by photolithography. The shape of the opening is not limited to the stripe, and may be, for example, partly widened or narrowed. On this, a ridge type compound semiconductor layer, that is, a second conductivity type second clad layer which is usually a compound semiconductor layer having a lower refractive index than the active layer, and a contact layer for reducing resistance are formed. In addition, a layer functioning as a light guide layer may be included. By doing so, the second conductivity type cladding layer 13a and the contact layer 14
However, corresponding layers 13b and 14b are deposited in the ridge dummy region.

As shown in FIG. 2, first, a first conductive type clad layer 11, an active layer 12, a second conductive type clad layer 13, an antioxidant layer 15, and a current blocking layer 16 are formed on a substrate 21 as needed. Is formed (FIG. (A)). Next, the ridge portion and the portion where the protective film is to be formed are removed by using a photolithography method and an etching technique (FIG. 2B). Then, a protective film 31 which is an insulator is deposited, and the ridge dummy region is formed by the photolithography method. And open the opening in the ridge. A second conductivity type cladding layer and a contact layer are formed thereon. By doing so, the second conductivity type cladding layer 13a and the contact layer 14 are provided in the ridge portion, and the corresponding layers 13b are provided in the ridge dummy region.
And 14b are deposited (FIG. (C)). In FIGS. 1D and 2D, reference numerals 32 and 33 denote electrodes, which are formed by deposition by a known method.

A known growth method such as MOCVD or MBE may be used for forming and regrowing the double heterostructure. Also, the substrate may be used as long as it has conductivity. However, since a crystal thin film is preferably grown thereon, it has a semiconductor single crystal substrate such as GaAs, InP, Si, ZnSe, and particularly has a zinc blende structure. It is preferable to use a semiconductor crystal substrate, in which case the crystal growth surface of the substrate is (1).
The (00) plane or a plane crystallographically equivalent thereto is preferable.
In the present specification, the (100) plane does not necessarily have to be strictly the (100) plane.
The case including an off-angle of about ° is included.

The substrate may be a hexagonal substrate, in which case it is also formed on Al ₂ O ₃ , 6H-SiC or the like.

The cladding layer, active layer, current blocking layer,
If necessary, reduce the second conductivity type second crack to reduce contact resistance.
The second conductivity type contact layer formed on the
Without limitation, AlGaAs, AlGaInP, Ga
InPAs, AlGaInN, BeMgZnSSe, C
General III-V and II-VI semiconductors such as dZnSeTe
May be used to create the DH structure. At this time,
The current blocking layer concentrates the current on the ridge,
Materials that can cause laser oscillation only in the
It is good, but if it is too thick, for example, Ridges
The controllability of the trip width deteriorates, and if it is thin, it becomes j-down.
Reduces stress on the ridge stripe during assembly
The effect of avoidance diminishes. Therefore, the thickness of the current block layer
The lower limit is preferably 100 nm or more, and 300 nm or more.
Is more preferable, and 500 nm or more is most preferable. Also
The upper limit is preferably 2000 nm or less, 1500
nm or less, more preferably 1000 nm or less.
New The current blocking layer may be an insulating layer, but may be a semiconductor layer.
It is preferred that In this case, the first conductivity type
Conductive or high resistance, under carrier concentration
Limit value is 1 × 10¹⁷cm^-3More preferably, 5 × 10¹⁷
cm^-3More preferably, 7 × 10¹⁷cm ^-3Above
Is also preferred. The upper limit is 1 × 10¹⁹cm^-3Less than
Is preferably 5 × 10¹⁸cm^-3The following is more preferable, and 3
× 10¹⁸cm^-3The following are most preferred. In addition, protective film and
To prevent current leakage at the boundary of the flow block layer
The current blocking layer is formed so as to overlap the protective film.
More preferably.

The width d (FIG. 1B) of the protective film when growing the current blocking layer and the repetition width L of this protective film (FIG. 1)
(B)) is not particularly limited, but the ratio d / L of the width d of the protective film to the repetition width L of the protective film is 0.0.
If it is 02 or more and 0.5 or less,
This is preferable because the carrier concentration can be easily controlled. In addition, since it is necessary to open an opening for forming a ridge in this protective film, if the width d of the protective film is close to the width W of the opening, it is difficult to form the opening with high accuracy. It becomes impossible to perform selective growth such that a ridge portion or a ridge dummy region rides over the ridge portion. At this time, the width D (FIG. 1C) of the ridge regrowth protective film is d = 2D + W. Although the width of the protective film D is not particularly limited, the lower limit is preferably 5 μm or more, more preferably 7 μm, for the above-described reason.
m, most preferably 10 μm or more, and the upper limit is preferably such that the ratio of d / L is satisfied.

At this time, a material having a lower refractive index than the active layer is selected for the cladding layer. As the contact layer, a material having a band gap smaller than that of the cladding layer is usually selected, and a low resistance for obtaining ohmic properties with the metal electrode, a suitable carrier density and a lower limit of the carrier concentration are 1 ×. 10 ¹⁸ cm ⁻³ or more is preferable, and 5 × 1
0 ¹⁸ cm ^-3 or more is more preferable. The upper limit is 5
× 10 ¹⁹ cm ^-3 or less is preferable, and 2 × 10 ¹⁹ cm ^-3 or less is more preferable.

The second conductive type second clad layer may be made of the same material, a layer having a higher carrier concentration may be used as the contact layer, or a part of the second conductive type second clad layer on the surface side may be used. May be formed, and a portion having a high carrier concentration may be used as a contact layer. The active layer is not limited to a single layer, but may be a single quantum well structure (SQW) including a quantum well layer and optical guide layers sandwiching the quantum well layer from above and below, or a plurality of quantum well layers. A multi-quantum well structure (MQW) composed of a barrier layer sandwiched between them and an optical guide layer stacked above the uppermost quantum well layer and below the lowermost quantum well layer is also included. Furthermore, a structure in which the refractive index of the cladding layer at the ridge portion is lower than the refractive index of the cladding layer on the active layer can reduce variations in the light divergence angle caused by variations in the composition during laser fabrication. .

Although there is no particular limitation on the protective film, the current is confined by the protective films on both sides of the opening so that the current can be injected only into the region of the active layer below the ridge formed on the opening of the protective film. In order to stabilize the transverse mode of laser oscillation, it is necessary to have an insulating property in order to achieve the effective refractive index difference between the ridge portion and the protective film in the horizontal direction in the active layer. Is preferably smaller than the refractive index of the cladding layer. However, in practice, if the refractive index difference is too large, the effective refractive index step in the lateral direction in the active layer is likely to be large, so that the first cladding layer below the ridge must be thickened. On the other hand, if the difference in the refractive index is too small, it is necessary to increase the thickness of the protective film to some extent because light easily leaks to the outside of the protective film. Considering these facts, the lower limit of the difference in refractive index between the protective film and the cladding layer is set to 0.1.
1 or more is preferable, 0.2 or more is more preferable, 0.7
The above is most preferred. The upper limit is preferably 2.5 or less, more preferably 2.0 or less, and most preferably 1.8 or less.

There is no particular problem with the thickness of the protective film as long as it has sufficient insulating properties and does not leak light outside the protective film. The lower limit of the thickness of the protective film is preferably 10 nm or more, more preferably 50 nm or more, and most preferably 100 nm or more. The upper limit is preferably 50 nm or less, more preferably 300 nm or less, and most preferably 200 nm or less. The width D of the protective film and the repetition width L of the ridge portion are not particularly limited, but the ratio D / L of the width D of the protective film to the repetition width L of the ridge portion is 0.001 to 0.25. In some cases, the thickness of the ridge portion and the carrier concentration can be easily controlled, which is preferable. Here, the width D of the protective film and the repetition width L of the ridge portion are the same if the widths in the respective repetition units are the same, and if the widths in the respective repetition units vary, the respective widths are different. The average value may be used.

The protective film functions as an insulating layer, but is preferably a dielectric. Specifically, the protective film includes a SiNx film, a SiO ₂ film,
SiON film, Al ₂ O ₃ film, ZnO film, SiC film and amorphous Si
Selected from the group consisting of: The protective film is made of MO as a mask.
It is used when the ridge is formed by selective regrowth using CVD or the like, and is also used for the purpose of current constriction. From the viewpoint of simplicity of the process, it is preferable that the protective film for current confinement and the protective film for selective growth have the same composition. However, the protective films may have different compositions, and if necessary, may have different compositions. May be formed in multiple layers.

When a zinc blende type substrate is used and the substrate surface is a (100) plane or a plane crystallographically equivalent to the (100) plane, in order to facilitate the growth of a contact layer described later on the side face of the ridge, a protective film is required. It is preferable that the longitudinal direction of the stripe region preferably used as the opening extends in the [01-1] direction or a direction crystallographically equivalent thereto. In that case, most of the side surface of the ridge often becomes the (311) A plane, and the contact layer can be grown on substantially the entire surface of the second conductive type second clad layer forming the ridge, which can be grown. For the same reason, when a wurtzite type substrate is used, the direction in which the stripe region extends is, for example, [11-20] or [1-1] on the (0001) plane.
00] is preferred. HVPE (Hydride Vapor Phase Epitax
y) can be in either direction, but in MOVPE [11-
20] direction is more preferred.

This tendency is attributed to the fact that, for example, when a compound semiconductor containing Al, Ga and As as constituent elements, more specifically, an AlGaAs-based compound semiconductor is used as a cladding layer, the second conductivity type second cladding layer is made of AlGaAs, especially AlAs. The lower limit of the mixed crystal ratio is preferably 0.2 or more, more preferably 0.3 or more, and most preferably 0.4 or more. The upper limit is
1.0 or less is preferable, 0.9 or less is more preferable,
0.8 or less is most preferred. In this specification, the “[01-1] direction” refers to a general III-V direction.
Group and II-VI semiconductors, the (100) plane and [01-
[1-1] plane, the [11-1] plane exists between
The [01-1] direction is defined as a surface on which a group III or group VI element appears. Also, it is not necessary to be in the [01-1] just direction, and ± 10 ° from the [01-1] direction.
It is assumed that the directions up to the degree shifted are included.

The embodiment of the present invention is not limited to the case where the above-mentioned opening has a stripe shape and the stripe region is in the [01-1] direction. Hereinafter, other embodiments will be described. When the stripe region extends in the [011] direction or a direction crystallographically equivalent thereto, for example, the growth rate can have anisotropy depending on the growth conditions, and (10)
It can be made fast on the (0) plane and hardly grow on the (111) B plane. In this case, when the growth is selectively performed on the surface of the stripe-shaped window portion (100), (111)
A ridge-shaped second conductivity type second cladding layer having a side surface B is formed. Also in this case, the next time a contact layer is formed, by selecting a condition under which a more isotropic growth occurs, the entire ridge side surface composed of the (111) B surface as well as the ridge top surface of the (100) surface is contacted. A layer is formed. When a group III-V compound semiconductor layer is grown by MOCVD, the double hetero structure has a growth temperature of 700 °.
C and V / III ratio of about 25 to 45, the ridge portion is preferably grown at a growth temperature of 630 to 700 ° C., and the V / III ratio is preferably about 45 to 55. In particular, when the ridge portion selectively grown using the protective film is a III-V group compound semiconductor containing Al such as AlGaAs, introduction of a small amount of HCl gas during the growth reduces poly deposition on the protective film. Prevented and very favorable. In this case, if the introduction amount of the HCl gas is too large, the growth of the AlGaAs layer does not occur and the semiconductor layer is etched (etching mode).
Cl introduction amount included Al such as trimethylaluminum
It largely depends on the number of moles of Group III raw material supplied. In particular,
The lower limit of the ratio of the number of moles of HCl supplied and the number of moles of Group III raw material containing Al (HCl / Group III) is preferably 0.01 or more, more preferably 0.05 or more, and most preferably 0.1 or more. preferable. The upper limit is preferably 50 or less, more preferably 10 or less, and most preferably 5 or less.

In addition to the structure of the present invention, it is also possible to form an antioxidant layer which makes it difficult to oxidize the regrown surface of the double heterostructure surface or can easily remove the oxide film even if it is oxidized. In addition, a structure in which the refractive index of the cladding layer in the ridge portion is lower than the refractive index of the cladding layer on the active layer can also reduce the variation in the light divergence angle due to the variation in the composition at the time of forming the laser. Furthermore, the cladding layer of the regrown portion is grown so as to cover the upper surface of the protective film using a known method such as the MOCVD method,
Improve the controllability of the distribution of light that seeps into the vicinity of the protective film and the ridge, or grow the contact layer of the regrown part so as to cover the upper surface of the protective film, prevent oxidation of the side surface of the cladding layer, and prevent The contact area with the electrode can be increased. The growth of the clad layer and the contact layer of the regrown portion so as to cover the upper part of the protective film may be performed independently, or both may be combined. Thus, the present invention can be applied to various ridge stripe type waveguide structure semiconductor light emitting devices. This structure can also be applied as an edge-emitting LED.

The present invention is characterized in that an area for using the insulating film is minimized by forming a current blocking layer outside the protective film which is an insulating film. Since there is no protective film in the direction parallel to the vertical direction and only a minimal protective film exists in the vertical direction, cleavage is facilitated. Further, the ridge dummy region can be made thicker than the ridge stripe portion due to the presence of the current block layer. When assembled by j-down as shown in FIG. Has the advantage of preventing In addition, since the ridge dummy region has a thyristor structure due to the presence of the current block layer, there is an advantage in that current leakage due to the leakage of the solder material when assembled in a j-down structure is advantageous.

As the most desirable mode to which the present invention is applied, as shown in FIG. 3, an antioxidant layer 15 is provided on the DH surface, and the regrown clad layer 13a and contact layer 14a are formed.
Is formed so as to reach the upper part of the protective film 31, and the refractive index of the ridge clad layer 13a is made lower than the refractive index of the clad layer 13 on the active layer. The structure is such that it covers the upper part of the base 31.

The ridge type compound semiconductor layer is usually mostly the second conductivity type second cladding layer, but substantially the entire side surface and upper surface of the ridge type compound semiconductor layer is covered with other portions. It is preferable that a contact layer having a lower resistance is formed. Thus, through the contact layer,
By providing a sufficient contact area between the adjacent electrode and the second cladding layer of the second conductivity type, the resistance of the entire device can be reduced.

Incidentally, it is possible to further cover a part of the side surface and the upper surface of the ridge on which the contact layer is formed, with a layer for the purpose of preventing oxidation or the like. Even in such a case, the resistance of the entire device can be reduced as compared with forming an electrode without forming a contact layer on the side surface of the ridge, and the present invention is included in such a range. In particular, AlGaInP and AlGaInN
For a material having a high specific resistance (particularly in the p-type) such as a system, it is effective for reducing the resistance of the entire device.

A part of the ridge type compound semiconductor layer, which is the second conductive type second cladding layer, regrown using a known technique such as the MOCVD method described above is formed so as to cover the protective film. Is preferred. Second conductivity type, second
The lower limit of the overlapping portion of the cladding layer on the protective film is
It is preferably at least 0.01 μm, more preferably at least 0.1 μm. The upper limit is preferably less than 2.0 μm, more preferably 1.0 μm or less. By being formed as described above, the contact area between the contact layer and the electrode can be increased, the contact resistance between the contact layer and the electrode is reduced, and the light distribution that seeps out near the boundary between the protective film and the bottom of the ridge. Controllability can be improved. When a contact layer having a band gap smaller than the energy of light emitted from the active layer is used,
Light absorption of the contact layer formed on the side surface of the ridge can be reduced, and laser characteristics and reliability can be improved. In this case, it is not always necessary to form a protective film on the side surface of the ridge type compound semiconductor layer as in the conventional ridge waveguide type laser. In the present invention, the protective film is formed on the bottom of the side surface of the ridge-shaped portion. Is effective in simplifying the process and reducing costs.

In a preferred embodiment of the present invention, the refractive index of the second conductive type first cladding layer is larger than the refractive index of the second conductive type second cladding layer. The lower limit of the difference in the refractive index between the first cladding layer of the second conductivity type and the second cladding layer of the second conductivity type is:
0.005 or more is preferable, 0.01 or more is more preferable, and 0.02 or more is most preferable. The upper limit is
0.15 or less is preferable, 0.1 or less is more preferable,
Most preferably 0.08 or less. As a result, it is possible to suppress the tailing of the light distribution (near-field image) to the ridge portion, improve the symmetry of the vertical spread angle (far-field image), suppress the side peak of the horizontal spread angle (far-field image), Alternatively, laser characteristics and reliability can be improved by suppressing light absorption in the contact layer.

In another preferred embodiment of the present invention, the second
An antioxidant layer is provided at least immediately below the opening of the protective film on the conductive type first cladding layer, that is, in the stripe region and preferably on both sides thereof. Accordingly, when the cladding layer of the ridge portion is formed by regrowth, it is possible to prevent the generation of a high-resistance layer that increases the passage resistance at the regrowth interface. Also, if a large amount of impurities such as oxygen are present at the regrowth interface, light absorption (heat generation) at the interface due to deterioration of crystal quality or diffusion of impurities through defects will be promoted, resulting in deterioration of characteristics and reliability. I will. By providing an antioxidant layer,
Crystal quality degradation at these interfaces can be reduced.

The present invention can be applied to various ridge waveguide type semiconductor light emitting devices, for example, it can be combined with the following embodiments. (1) By forming a current blocking layer of a semiconductor, a dielectric, or the like, preferably a semiconductor, further outside the protective film covering both sides of the stripe region, the cleavage and the yield at the time of assembly are improved, and the assembly at the time of assembly at the junction down is improved. Stress on the ridge portion can be reduced and the life can be extended. (2) By adopting a substrate whose surface has an off-angle with respect to a low-order plane orientation, even if the regrown ridge portion has an asymmetric shape in the left-right direction, the light density distribution (or beam profile) is symmetric in the horizontal direction. In this case, the device can be oscillated in a stable fundamental transverse mode up to a high output, and the device yield and reliability can be improved. (3) By forming a structure having a ridge dummy region in which a current block layer is formed outside the protective film covering both sides of the stripe region, the thickness, composition, and carrier concentration of the stripe portion can be easily controlled.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. (Embodiment) This embodiment is shown in FIG. A 350 μm thick n-type GaAs (n
= 1 × 10 ¹⁸ cm ⁻³ ) Si-doped Al _x Ga _{1 -x} As (x = 0.55: n = 5) on the substrate 21 by MOCVD.
N-type first cladding layer 11 having a thickness of 1 × 10 ¹⁸ cm ⁻³ ) and a thickness of 1.5 μm, and undoped Al _x Ga ₁ -x As (x = 0.1
4) In 0.06 μm thick active layer 12, Zn-doped Al
_X Ga _1-X As (x = 0.55: p = 1 × 10 ¹⁸ c
m ⁻³ ) and a p-type first cladding layer 13 having a thickness of 0.25 μm;
10 nm thick Zn-doped Al _X Ga _{1 -X} As (x =
0.2: p = 1 × 10 ¹⁸ cm ⁻³ ). Next, a 200 nm SiN _x film 31 is deposited as a protective film, and [0] is formed on the SiN _x protective film by photolithography.
1-1] SiN _{x in} a stripe shape having a width of 22 μm in the B direction
The membrane was left. Here, the [01-1] B direction is (100)
[11-1] existing between the [01-1] plane and the [01-1] plane is As
A surface is defined so that it appears on the surface. The repetition width L of the ridge portion was set every 250 μm. (D / L
= 0.088). A 0.5 μm-thick Si-doped GaAs (n = 1 × 10 ¹⁸ cm) is formed thereon by MOCVD.
^-3 ) 16 were selectively grown. Next, [01] was formed at the center of the striped SiN _x film by photolithography.
-1] A 2.2 μm-wide striped window was opened in the B direction. On top of this, selective growth is performed by MOCVD, and when the entire surface is grown on a normal substrate in the form of a ridge stripe, Zn-doped Al _x Ga ₁ -x As (x = 0.
57: p-type second cladding layer 13a having a thickness of 1.25 μm at p = 1 × 10 ¹⁸ cm ⁻³ ) and a carrier concentration of 1 ×
A p-type contact layer 14 having a thickness of 0.5 μm was formed using Zn doped GaAs of 10 ¹⁹ cm ⁻³ . As a result of measuring the thickness of the cladding layer and the contact layer grown on the ridge portion by cross-sectional observation, the thickness was in agreement with the case where the entire surface was grown on a normal substrate within an error range. Thereafter, a p-side electrode was deposited and the substrate was thinned to 100 μm, and then an n-side electrode was deposited. FIG. 10 shows a cross-sectional view of the semiconductor light emitting device of this example. When chips were cut out from the wafer created in this way by cleavage, there was no damage due to cleavage,
There was no electrode peeling due to assembly. When the near-field image was confirmed, light emission was observed only in the ridge portion, and it was confirmed that the current was confined only in the lip portion by the current block. Further, assembling with j-down as shown in FIG. 9 (a), it was confirmed that a very good current-voltage characteristic was exhibited as shown in FIG. 6, and no current leaked to the non-ridge portion. It was confirmed that the product yield was good.

(Comparative Example) A laser was produced in the same process as in the example. At this time, the semiconductor layer 1 as a current blocking layer
6 on the p-type contact layer 14 without selective growth.
An N _x insulating film XY is deposited to a thickness of 200 nm, and [0-1-1] A is formed on the SiN _x insulating film by photolithography.
A stripe-shaped window having a width of 10 μm was opened on the ridge stripe in the direction. Except for this, it was completely the same as the example. FIG. 11 shows a sectional view of the semiconductor light emitting device of this comparative example. As a result of cleavage and assembling, an SiN _x film and an electrode are formed on the p-side surface, resulting in poor cleavage,
Problems such as peeling of the _X film occurred. When the near-field image was confirmed, it was confirmed that the entire active layer was emitting light due to current leakage in the ridge dummy region, and many lasers whose current was not sufficiently confined by the SiNx insulating film were observed.
Also, when assembled by j-down as shown in FIG. 9 (b),
As shown in FIG. 7, current leakage occurs, and a large number of current-voltage characteristics cannot be obtained. Since the thickness of the ridge stripe and the portions grown on both sides of the ridge stripe are the same, deterioration due to stress or the like from the solder material is prevented. Invited, sufficient laser characteristics could not be obtained, and the yield was reduced.

[0035]

According to the present invention, since the insulating layer for the purpose of current confinement in the ridge stripe type waveguide semiconductor light emitting device is not used, the yield by cleavage and assembling is improved, and the current flows outside the ridge stripe. Since the block layer exists and is thicker than the ridge stripe portion, j-down
In the case of assembling, the stress on the ridge stripe portion is reduced, and high output and long life can be achieved.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention, in which a ridge portion is formed by regrowth, at the stage when growth of a double heterostructure has been completed. b is a cross-sectional view of the semiconductor light emitting device according to the embodiment of the present invention in which the ridge portion is formed by regrowth, at the stage when the current block layer has been regrown. c is a cross-sectional view of the semiconductor light emitting device according to the embodiment of the present invention in which the ridge portion is formed by regrowth, at the stage when the ridge regrowth is completed. d is a cross-sectional view of a completed semiconductor light emitting device according to an embodiment of the present invention in which a ridge portion is formed by regrowth.

FIG. 2A is a cross-sectional view of a semiconductor light emitting device according to an embodiment of the present invention, in which a ridge portion is formed by regrowth, at a stage where a double heterostructure has been grown. b is a cross-sectional view of the semiconductor light emitting device according to the embodiment of the present invention in which the ridge portion is formed by regrowth at the stage when the formation of the current blocking layer is completed. c is a cross-sectional view of the semiconductor light emitting device according to the embodiment of the present invention in which the ridge portion is formed by regrowth, at the stage when the ridge regrowth is completed. d is a cross-sectional view of a completed semiconductor light emitting device according to an embodiment of the present invention in which a ridge portion is formed by regrowth.

FIG. 3 is a cross-sectional view of a completed semiconductor light emitting device according to one embodiment of the present invention in which a ridge portion is formed by regrowth.

FIG. 4A is a cross-sectional view of a conventional semiconductor light emitting device in which a ridge portion is formed by etching, after DH growth is completed. b is a cross-sectional view of the conventional semiconductor light emitting device in which the ridge portion is formed by etching, after the ridge etching is completed. c is a cross-sectional view of a completed conventional semiconductor light emitting device in which a ridge is formed by etching.

FIG. 5A is a cross-sectional view of a conventional semiconductor light emitting device in which a ridge portion is formed by regrowth at the stage when DH growth is completed. b
FIG. 3 is a cross-sectional view of a conventional semiconductor light emitting device in which a ridge portion is formed by regrowth at a stage where ridge regrowth is completed. c is a cross-sectional view of a completed conventional semiconductor light emitting device in which a ridge is formed by regrowth.

FIG. 6 shows current-voltage characteristics of a semiconductor light emitting device manufactured in an example of the present invention in which a ridge portion is formed by regrowth.

FIG. 7 shows current-voltage characteristics of a conventional semiconductor light emitting device in which a ridge portion is formed by regrowth as a comparative example.

FIG. 8 is a view of the semiconductor light emitting device of the present invention as viewed from the epitaxial layer side, showing a protective film and a ridge dummy region.

9A is a diagram showing a state in which the semiconductor light emitting device of the present invention is assembled in a junction down type, and FIG. 9B is a diagram showing a comparative example of the semiconductor light emitting device in the present invention assembled in a junction down type. FIG.

FIG. 10 is a cross-sectional view of a completed semiconductor light-emitting device of the present invention, which is a light-emitting semiconductor device used in Examples.

FIG. 11 is a cross-sectional view of a completed semiconductor light emitting device used in a comparative example.

[Explanation of symbols]

Reference Signs List 11 First conductivity type first cladding layer 12 Active layer 13 Second conductivity type first cladding layer 13a Second conductivity type second cladding layer 13b Second conductivity type second cladding layer formed in ridge dummy region 14 Second conductivity type Contact layer 14a Second conductivity type contact layer formed in ridge portion 14b Second conductivity type contact layer formed in ridge dummy region 15 Oxidation prevention layer 16 Current blocking layer 21 Substrate 31 Protective film 31a Insulating layer 32 Epitaxial layer side electrode 33 Substrate Side electrode 34 Solder material 35 Heat sink 36 Bonding wire

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsuji Fujii 1000 Higashikanamachi, Ushiku City, Ibaraki Prefecture Mitsubishi Chemical Corporation Tsukuba Office (72) Inventor Kazumasa Kiyomi 1000 Higashinakaanacho, Ushiku City, Ibaraki Mitsubishi Chemical Corporation Tsukuba Office

Claims (9)

[Claims] In a semiconductor light emitting device having a compound semiconductor layer including an active layer on a substrate, a ridge type compound semiconductor layer formed in an opening, and a protective film covering both sides of the opening area, A semiconductor light emitting device having a current block layer formed outside. 2. The compound semiconductor layer including the active layer,
2. The semiconductor light emitting device according to claim 1, further comprising a layer having a lower refractive index than the active layer above and below the active layer. 3. A layer having a lower refractive index than the active layers above and below the active layer, the layer on the substrate side is a first conductive type clad layer, and the other layer is a second conductive type first clad layer. 3. The semiconductor light emitting device according to claim 2, wherein: 4. The semiconductor light emitting device according to claim 1, wherein said ridge type compound semiconductor layer includes a layer having a smaller refractive index than an active layer. 5. A layer having a lower refractive index than the active layer,
The semiconductor light emitting device according to claim 4, wherein the semiconductor light emitting device is a second conductive type second clad layer. 6. The semiconductor light emitting device according to claim 1, wherein said current blocking layer is a semiconductor layer. 7. The semiconductor light emitting device according to claim 6, wherein the current blocking layer is a first conductivity type semiconductor layer or a high resistance semiconductor layer. 8. A step of forming, in this order, a compound semiconductor layer including an active layer and a protective film covering at least the opening on the substrate, a step of selectively growing current blocking layers on both sides of the protective film, and an opening in the protective film. Forming a portion, and selectively growing a ridge type compound semiconductor layer in the opening. 9. A step of laminating a compound semiconductor layer including an active layer and a current block layer on a substrate in this order, a step of removing a part of the current block layer, and a step having an opening in the removed portion. A method for manufacturing a semiconductor light emitting device, comprising: forming a protective film; and selectively growing a ridge type compound semiconductor layer in the opening.