JPH11168256A - Light-emitting element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration at the end face part of a semiconductor light-emitting element by making different the layer configuration of an end face that continues from one light emission end face and a layer configuration at regions other than the end face in the direction of an element thickness. SOLUTION: A second 2p-type clad layer 8, a second etching stop layer 9, a third 3p-type clad layer 10, and a p-type semiconductor layer 11 are laminated on a first etching stop layer 7 at a first site (I). The second 2p-type clad layers 8 and 9 are laminated on the layer 7 at a second site (II). Therefore, the distribution of an effective refractive index, an execution cavity loss, or the like differs at the first and second sites (I) and (II) and can be prescribed independently for each site. More specifically, the distribution of the effective refractive index, the execution cavity loss, or the like occurs at the first and second sites (I) and (II) especially at an active layer 5 based on the layer configuration in the thickness direction of an element and the amount of absorption of light, a refractive index, or the like at each site can be adjusted appropriately, thus suppressing the deterioration in structure at the end face part of a light-emitting element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-emitting element (particularly, a semiconductor laser) used for, for example, an optical disk pickup or a display, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Lasers for magneto-optical recording represented by a DVD (digital video disk) are required to operate at a high optical output (hereinafter, referred to as high-output operation). D
Semiconductor lasers having a wavelength of 650 nm used for VD video, RAM (random access memory) and the like are generally composed of (Al _1-x Ga _x ) _1-y In _y P-based material. In particular, it is difficult to perform high-output operation with high stability.

FIG. 19 schematically shows a general semiconductor laser. This semiconductor laser 50 has an active layer 59 between a first cladding layer 56 and a second cladding layer 57,
Further, a current confinement layer 58 for limiting the current injection width is provided as shown in the figure, and has a single vertical structure in the resonator length direction.

In general, in this material, the active layer 59 has a distortion (the lattice constant deviates from the intrinsic value of the material).
And the distortion is relaxed near the end face (returning to the original lattice constant), so that the band gap near the end face is smaller than that at the center.

[0005] The distribution of the band gap in the resonator length direction serves to increase the amount of light absorption at the end face. Then, the absorbed light generates electron-hole pairs to promote non-radiative recombination, or acts to induce diffusion and mutual diffusion by giving energy to impurities (for example, Fukushima et al., Electron. See the IEICE Transactions C-1vol. J78 C-1 No.3 pp.143).

That is, as shown in FIG. 19, in a semiconductor laser having a single vertical structure in the cavity length direction, the structure is likely to be destroyed due to a large amount of light absorption particularly near the end face, and the stability (reliability) ) And a semiconductor laser capable of high-power operation.

Hereinafter, the "resonator length direction", the "vertical direction (or element thickness direction)" used for the vertical structure, and the "horizontal direction" used for the horizontal structure are defined as shown in FIG.

[0008]

Therefore, as means for controlling the amount of light absorbed at the end face, a so-called "window structure" in which the effective refractive index (effective refractive index) is changed in the longitudinal direction of the resonator.
(See, for example, A. Shima; JEE January, 100 (1993))
Structure.

This "window structure" will be briefly described. This material system has a composition within the miscibility gap (mixed crystal composition range that cannot be produced in a thermal equilibrium state), and therefore, a composition separation called a natural superlattice occurs. There is a correlation between the degree of composition separation and the band gap, and it is generally known that the greater the degree of composition separation, the smaller the band gap.

Further, when Zn is doped into this material system, its superlattice structure is eliminated, and as a result, the band gap becomes large. Therefore, this natural superlattice is eliminated by diffusing Zn only near the end face, and in some cases,
By disordering the active layer structure (quantum well structure), the band gap in the vicinity of the end face of the semiconductor laser can be made larger than the band gap in the central part, and thus the amount of light absorption can be suppressed. This is a general window structure.

However, in a semiconductor laser having a “window structure”, if a large amount of Zn necessary for forming the window structure is contained in or near the active layer, optical loss or non-radiative recombination center may occur. (See, for example, A. Shima; JEE January, 100 (1993)).

As a result, the threshold carrier density increases, the operating current increases accordingly, and at the same time, the carrier overflow (current amount, ie, the carrier amount increases, overflows from the active layer to reach the cladding layer). That is, the operating current at a high temperature is increased, and further, the heat generation at the time of operating the laser is increased, so that the device characteristics at a high temperature are greatly changed.

Further, since more loss and non-radiative recombination center are generated at the end face, heat generation at the end face is increased. In general, the band gap becomes smaller as the temperature becomes higher. Therefore, when the heat generated at the end face increases, the band gap at the end face becomes smaller and the light absorption increases. An increase in the amount of light absorption promotes further heat generation and further reduces the band gap. By repeating this cycle, finally, there is a problem that the element structure is destroyed at the end face portion and the laser operation is stopped.

As described above, a general “window structure” is formed by diffusing zinc (Zn) into a part of the active layer and a layer near the active layer. Conversely, device characteristics and reliability are reduced. Therefore, careful attention must be paid to the diffusion amount, diffusion region, diffusion temperature, diffusion method, and the like, and technical difficulty is required. .

On the other hand, in addition to a semiconductor laser having a “window structure”, as a laser having a refractive index distribution in the cavity length direction, a current injection width called a TAPS (tapered stripe) structure is used. A laser whose structure has been changed in the device length direction, in other words, a laser whose horizontal structure has been changed in the resonator length direction, has already been commercialized (for example, a product name SLD112).
2VS: manufactured by Sony Corporation).

A laser whose lateral structure is typified by a TAPS generally has a structure as shown in FIGS.

For example, the first clad layer 63, the active layer 64, and the second clad layer 65 are formed on a GaAs substrate 62.
Are laminated, the second clad layer 65
Is patterned into a predetermined shape using photolithography, an ion-implanted high-resistance region (current constriction layer) 66 is provided outside the current injection region, and the current injection width W is changed in the resonator length direction (W _1). And W ₂ ).

The laser beam 67 emitted from the active layer 64 has a horizontal width x (corresponding to a horizontal radiation angle) and a vertical width y (corresponding to a vertical radiation angle) as shown in FIG. The light is emitted as an elliptical (or circular) light beam. In general, a semiconductor laser having a TAPS structure emits an elliptical laser beam that is large in the vertical direction (y in the figure) and small in the horizontal direction (x in the figure).

That is, as shown in FIGS. 20 and 21, in a semiconductor laser in which the lateral structure is changed in the resonator length direction, the current injection width is changed by changing the stripe width (W) in the resonator length direction. I have.

Further, by changing the stripe width W in the resonator length direction, a distribution occurs in the effective refractive index in the resonator length direction. At this time, when the stripe width W is reduced, a so-called loss index guide mechanism operates, and a distribution is formed in the effective refractive index (effective refractive index) in the lateral direction. Further, the relationship is such that as the stripe width W decreases, the effective cavity loss increases and the effective refractive index also increases. That is, in order to reduce the amount of light absorbed at the end face, the effective cavity loss may be reduced, that is, the stripe width W at that portion may be increased.
The loss index guide refers to a method of changing the refractive index by changing the absorption coefficient when changing the refractive index inside and outside the stripe in order to confine light in the stripe.

However, the stripe width W at the end face is
When the value of is increased, the effective refractive index in that portion is reduced, so that the current density is increased. Therefore, the heat generation amount distribution is increased, and the amount of decrease in the band gap is increased.

Further, as shown in FIG. 22, when the stripe width W is increased, the emission angle of light becomes larger in the vertical direction and becomes smaller in the horizontal direction, so that the aspect ratio (y / x) becomes larger. Therefore, inconvenience increases from the viewpoint of application to magneto-optical recording and optical disks.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to suppress a deterioration of an end face of a semiconductor light-emitting element in particular, and to provide a high-output and highly reliable light-emitting element (in particular, a semiconductor laser). ) And a method for producing the same.

[0024]

That is, the present invention provides a first portion which is continuous from at least one light emitting end face, and a second portion which is present on the opposite side of the first portion from the light emitting end face.
A light-emitting element (hereinafter, referred to as the present invention) in which the portions are sequentially arranged in the resonator length direction on the active layer, and the layer configuration of the first portion and the layer configuration of the second portion are different from each other in the device thickness direction. ).).

According to the light emitting device of the present invention, the first portion (end face portion) continuous from at least one light emitting end face and the second portion present on the opposite side of the first portion from the light emitting end face. Sites (regions other than the end surface portions: intermediate portions) are sequentially arranged in the resonator length direction with respect to the active layer, and the layer configuration of the first region and the layer configuration of the second region are arranged in the element thickness direction (hereinafter, referred to as the element thickness direction). In the vertical direction.), The distributions of the effective refractive index and the effective cavity loss are different between the first portion and the second portion, and these can be defined independently for each portion. .

That is, based on the layer structure in the element thickness direction (longitudinal direction), particularly in the active layer, distributions such as an effective refractive index and an effective cavity loss occur in the first portion and the second portion, Since the amount of light absorption, the refractive index, and the like at each portion can be appropriately adjusted, structural deterioration (for example, destruction of the element structure) at the end face of the light-emitting element is suppressed, and a high-output and highly reliable light-emitting element (particularly, Laser).

The above-mentioned layer configuration is a layer configuration in the vertical direction (element thickness direction) of each layer constituting the layered structure, and the difference in the layer configuration in the horizontal direction (for example, stripe width or the like) in the resonator length direction. Does not mean.

According to the present invention, as a method for manufacturing the light emitting device of the present invention with good reproducibility, a first portion continuous from at least one of the light emitting end faces, and the first portion is opposite to the light emitting end face. The second part present on the side is sequentially arranged on the active layer in the resonator length direction, and the layer constitution of the first part and the layer constitution of the second part are different from each other in the element thickness direction. The present invention provides a method for manufacturing a light-emitting element (hereinafter, referred to as a manufacturing method of the present invention).

The "effective refractive index" means a refractive index particularly averaged by a ratio of light occupying each layer of the semiconductor laser, and the "effective cavity loss" means only each area. “Casy and Panish;“ Heterostructure Lasers ”Chap
ter 7 (Academic Press) etc.].

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION In the light emitting device of the present invention and the manufacturing method of the present invention, it is desirable that the first portion and the second portion have different effective refractive index distributions. The effective refractive index distribution can be distributed in the cavity length direction.

The length L ₁ of the first portion in the resonator length direction is preferably from ₁₀ μm to 50 μm, and
The length of the portion L ₂ is 200μm~700μm is desirable.
The desirable lower limit of the length of the first portion, 10 μm, is the amount of light confinement, that is, the length required to modulate the transverse mode,
In the case of a semiconductor laser provided with a current non-injection region at the end face, the longitudinal mode is bistable, particularly by setting the length of the region to about 10 μm [light output-current characteristics (L−
Kink appears on the I-curve). Therefore, from this analogy, the length L _{1 of} the first portion
Is 10 μm or more, the mode of light can be sufficiently affected.

In a red high-power laser, the threshold current density becomes minimum at a cavity length of about 700 μm. Therefore, a desirable upper limit of the length of the second portion is 700 μm, and furthermore, it is expected that the cavity length will be shortened in the future, and it is considered that the cavity length will eventually be about 250 μm. Is a desirable lower limit of 200 μm.

Further, the effective refractive index of the first part is made larger than the effective refractive index of the second part, and the effective cavity loss of the first part is made smaller than the effective cavity loss of the second part. It is desirable.

As described above, if the distributions of the effective refractive index and the effective cavity loss are different between the first portion and the second portion, the first portion (end face portion) and the second portion (including the end face portion). (A portion where no light is emitted), it is possible to reduce the amount of light absorption at the first portion by reducing the band gap difference, and at the same time, since the refractive index at this portion is increased, light emission in the vertical direction is performed. The angle (corresponding to y in FIG. 21) is reduced, and the emission angle of light in the lateral direction (corresponding to x in FIG. 21) is increased, so that a perfect circular light beam with a small aspect ratio can be emitted.

Further, the semiconductor device has a laminated structure in which a first clad layer, an active layer, and a second clad layer are sequentially laminated on a semiconductor substrate, and both sides of the second clad layer are sandwiched between current confinement layers. The portion where the upper surface of the second clad layer is covered with the current injection layer may be referred to as the second portion. In the second portion, the upper surface portion may be covered with the current injection layer, and the other portions (both sides) may be covered with the current constriction layer.

Here, the first cladding layer is a layer component for injecting electrons (or holes) into the active layer, and the second cladding layer is This is a layer component for injecting holes (or electrons) into the active layer. In particular, the thickness of the second cladding layer at the first portion may be larger than the thickness of the second cladding layer at the second portion.

Further, the light emitting device and the manufacturing method of the present invention
At least one element selected from the group consisting of aluminum (Al), gallium (Ga) and indium (In), and at least one element selected from the group consisting of arsenic (As) and phosphorus (P) May be a compound semiconductor light-emitting device comprising a Group 5 element of the periodic table.

Next, the operation of the light emitting device of the present invention will be described.

Here, the two types of vertical structures shown in FIG. 3 will be described as an example. FIG. 3A shows a vertical structure a having a larger effective refractive index and a small effective cavity loss.
FIG. 3B shows a vertical structure b having a smaller effective refractive index and a large effective cavity loss.

As a laser using these vertical structures, FIG. 4A shows a laser having a structure A composed entirely of a vertical structure a in the resonator length direction, and FIG. B in which the structures of the vertical structures a and b are simply connected to each other
Are shown, respectively. In the structures A and B, the vertical structures are connected at the position z,
Further, the direction of the emitted light from each laser is defined as an arrow c direction in the figure, and the reflectances of the laser light on the emission surface 21 side and the opposite surface (reflection surface) 22 side are represented by Rf and Rr, respectively.
<Rr.

First, the light intensity distribution of the laser having the structure A and the structure B is shown in FIG. The solid line in the drawing indicates the case of the structure A, and the broken line in the diagram indicates the case of the structure B. The structure A is a single laser having a single longitudinal structure (layer structure in the element thickness direction) in the resonator length direction. Is a laser having portions having different longitudinal structures in the cavity length direction (the same applies hereinafter).

That is, in the laser of the structure B having the vertical structure b having a low effective refractive index, the light intensity distribution is reduced, and the emitted light amount is the same in the structures A and B. The relationship is as shown in FIG. From this, the structure B
It can be seen that the laser of (1) has a higher light intensity (that is, higher power can be output) especially at a portion having a vertical structure b having a smaller effective refractive index than the laser of structure A.

FIG. 6 shows the carrier distribution. Structure B
Since the vertical structure b is added and the effective cavity loss is increased, it is considered that the carrier distribution is particularly increased in the portion of the vertical structure b, as shown by a broken line in the figure.

Next, FIG. 7 shows a band gap distribution without considering light absorption. The bandgap distribution may be considered mainly by the effect of the relaxation of the lattice at the laser end face and the distribution of the calorific value resulting from the current density distribution. Then, when the band gap distribution in the structure A is represented by a solid line from the relationship shown in FIG. That is, the structure A
In this case, the band gap difference between the end face portion and the intermediate portion is large, while in the structure B, the band gap difference can be reduced.

The light absorption distribution is obtained from the light intensity distribution shown in FIG. 5 and the band gap distribution shown in FIG.
It is thought that it becomes. That is, in particular, in the laser having the structure B, the amount of light absorption on the laser emission side can be reduced, and therefore, the deterioration of the laser at the end face portion due to the light absorption can be suppressed.

On the other hand, the emission angle of light depends on the stripe width, but as the effective refractive index at the end face increases, the emission angle in the vertical direction decreases and the emission angle in the horizontal direction increases. Accordingly, compared with the semiconductor laser having the TAPS structure having the structure A (see FIG. 21), the laser having the structure B has a smaller emission angle in the vertical direction and a larger emission angle in the horizontal direction. A perfectly circular light beam is obtained.

Next, a preferred embodiment of the present invention will be specifically described. Here, a description will be given by taking the refractive index guided compound semiconductor laser shown in FIG. 1 as an example.

As shown in FIG. 1A, the light emitting device according to the present embodiment has a first portion (I) and a second portion (I) having different layer structures in the device thickness direction (vertical direction: the same applies hereinafter). II)
And the semiconductor laser 20 having the following in the cavity length direction.

FIG. 1B shows a layer structure of a first portion (I) which is a continuous portion including an end face (a sectional view taken along line BB).
FIG. 1 (C) shows a second portion which does not include the end face.
The layer structure (sectional view taken along the line CC) of the portion (II) is shown.

Here, the layer structure of the first portion (I) in the semiconductor laser 20 is such that, as shown in FIG. 1B, a first buffer layer 2, a second buffer layer 3, an n-type An active layer (eg, an active layer having an MQW structure: an active layer having a multiple quantum well structure) 5, a first p-type clad layer 6, and a first etching stop layer (which are The second p-type cladding layer 8 and the second etching stop layer (which may also serve as the saturable absorption layer: the same applies hereinafter) 9 and the second p-type cladding layer 8 may be used. It has a laminated structure of a compound semiconductor in which a 3p-type clad layer 10, a p-type semiconductor layer 11, and a second clad layer including a contact layer 12 are laminated. Injection of holes from the p-electrode 16 Sandwiched current confinement layer (n-type) 13 for limiting the width.

The layer structure of the second portion (II) is shown in FIG.
As shown in (C), on the substrate 1, the first cladding layer including the first buffer layer 2, the second buffer layer 3, and the n-type cladding layer 4, and an active layer (for example, an active layer having an MQW structure: Multiple quantum well structure active layer) 5, first p-type cladding layer 6, and first etching stop layer (or saturable absorption layer)
7, a second p-type cladding layer 8 and a second cladding layer composed of a second etching stop layer (or saturable absorption layer) 9 and a compound semiconductor laminated structure. Is covered with a current confinement layer (n-type) 13 as shown in the figure. However, in order to inject holes from the p-electrode 16, the n-type current confinement layer 13 is provided with a p-type current injection layer 14.

FIG. 2 shows a partially laminated structure of the semiconductor laser 20 according to the present embodiment. That is, as shown in the drawing, the second cladding layer is formed on the first etching stop layer 7 at the first portion (I), on the second p-type cladding layer 8, the second etching stop layer 9, the third p-type cladding layer. It has a layer configuration in which a layer 10 and a p-type semiconductor layer 11 are stacked. On the other hand, in a second portion (II), a second p-type cladding layer is formed on the first etching stop layer 7. 8 and a second etching stop layer 9.

Specifically, in the active layer, the effective refractive index is relatively large and the effective cavity loss is relatively small in the first portion (I), and the effective refractive index is relatively small in the second portion (II).
The effective refractive index is relatively small and the effective cavity loss is relatively large, so that a semiconductor laser having a distribution of the effective refractive index and the effective cavity loss in the cavity length direction can be obtained.

Therefore, when a forward voltage is applied between the n-electrode 15 and the p-electrode 16, current is injected into both the first and second portions, and electrons (holes) and holes (holes) are regenerated in the active layer. Combines and emits light. When a voltage is further applied to increase the amount of injected current, laser oscillation occurs. At this time, looking at the respective regions of the first portion and the second portion, since the refractive index in the stripe is high, light is confined in the stripe and a mode is formed. In addition, the amount of light confinement differs depending on the refractive index difference between the inside and outside of the stripe at each portion, and furthermore, the amount of light seeping out of the stripe differs, and the light in the buried layer outside the stripe differs. Different absorption.

That is, since the effective refractive index of the first portion is higher than that of the second portion, the amount of light confined in the stripe increases, and the efficiency of stimulated radiation at the end face can be increased. This can reduce the current density at the end face, in other words, the amount of carrier recombination.
Therefore, the amount of carriers that do not contribute to light emission and that do not emit light and recombine among carriers that recombine is reduced. Further, the first portion has a lower effective cavity loss than the second portion, and therefore has a smaller light absorption amount. Therefore, heat generated from light absorption is also reduced.

Therefore, in the semiconductor laser 20 according to the present embodiment, structural deterioration (particularly, destruction of the element structure due to heat generation) at the end face can be suppressed.
Since the refractive index at the end face portion can be made sufficiently large, the emitted laser light can be made into a perfect circular shape or a nearly perfect circular shape, and a high-power laser light can be emitted.

Next, a method of manufacturing a semiconductor laser (AlGaInP-based compound semiconductor laser) according to the present embodiment will be described with reference to FIGS.

First, in order to form the laminated structure 30 shown in FIG. 9, for example, the substrate 1 is made of n-conductivity type (001) GaAs having a plane orientation that is just or slightly inclined.
After the organic cleaning of the s substrate, for example, MOCVD (Metal Organic Chemical Vapor Dep.
osition) equipment, MBE (molecular beam epitaxy: Mo)
(Lecular Beam Epitaxial) device or other compound semiconductor thin film growth equipment.

Next, a GaAs buffer layer is formed on the GaAs substrate 1 as the first buffer layer 2 by, for example, 30 nm.
And then, as a second buffer layer 3, GaI
An nP buffer layer is grown to, for example, 30 nm.

Next, as the n-type cladding layer 4, (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P, for example, 3 × 10 ⁻¹⁷
An n-type conductive cladding layer doped with an n-type conductive impurity of a group 6 of the periodic table such as Se or Si at a concentration of cm ^-3 is grown.

[0061] Thereafter, although the active layer is grown 5, wherein, as shown in FIG. 9 (B), for example, (Al _0.5 Ga
_0.5 ) Optical guide layers 25 and 26 made of _0.5 In _0.5 P
Next, a quantum well layer 27 made of GaInP and (Al _0.5 G
a _{0.5) 0.5} In _0.5 called an MQW multiple quantum well structure is sandwiched between the barrier layer 28 made of P (MultipleQu
An active layer having an antum well structure is grown.

Thereafter, as the first p-type cladding layer (p-type conductive cladding layer) 6, for example, the concentration is 5 × 10 ⁺¹⁷ cm.
^-3 Zn as a p-type conductive impurity (Al _0.7
Ga _0.3 ) _0.5 In _0.5 P is grown to a thickness of, for example, 300 nm.

Further, as the first etching stop layer (or saturable absorption layer) 7, for example, a concentration of 5 × 10 ⁺¹⁷ c
GaIn doped with m ^-3 Zn as a p-type conductive impurity
A P layer is grown to a thickness of, for example, 15 nm.

Thereafter, as the second p-type cladding layer (p-type conductive cladding layer) 8, for example, a concentration of 5 × 10 ⁺¹⁷
cm ⁻³ of Zn was added as a p-type conductive impurity (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P with a thickness of, for example, 300 nm
To grow.

Further, as the second etching stop layer (or saturable absorption layer) 9, for example, a concentration of 5 × 10 ⁺¹⁷ c
GaIn doped with m ^-3 Zn as a p-type conductive impurity
A P layer is grown to a thickness of, for example, 15 nm.

Further, as the third p-type cladding layer (p-type conductive cladding layer) 10, for example, a concentration of 5 × 10 ⁺¹⁷ c
m ⁻³ Zn was added as a p-type conductive impurity (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P with a thickness of, for example, 800 nm
To grow.

Thereafter, as the p-type semiconductor layer 11, for example, a GaInP layer to which Zn having a concentration of 5 × 10 ⁺¹⁷ cm ^-3 is added as a p-type conductive impurity is grown to a thickness of, for example, 15 nm.

Thereafter, as the contact layer 12, for example, a p-type GaAs layer to which Zn having a concentration of 5 × 10 ⁺¹⁷ cm ^-3 is added as a p-type conductive impurity is grown to a thickness of, for example, 250 nm.

In this way, FIGS. 9A and 9B
The laminated structure 30 of the compound semiconductor shown in FIG.

Next, this laminated structure 30 is shown in FIGS.
Through the process shown in FIG. 4, patterning into a predetermined shape is performed. (I) shows the layer configuration of the first portion, and (II)
Indicates the layer configuration of the second portion.

First, on the upper surface 40a of the laminated structure 30, FIG.
5, a mask 31 made of, for example, SiO _{2 is formed} by using photolithography. Thereafter, when the second etching stop layer 9 is etched by wet or dry etching, as shown in FIG. 10, at the second part (II), the etching is performed up to the second etching stop layer 9, but at the first part (I). Then, the third p-type cladding layer 10, the p-type semiconductor layer 11, and the contact layer 12 are patterned into a predetermined shape by a mask (photoresist) 31.

Next, after the mask 31 is removed (or left as it is), a mask 32 shown in FIG. 16 is formed on the upper surface 40b of the laminated structure 30 (the upper surface portion of the second etching stop layer 9) using photolithography. Then, the first etching stop layer 7 is etched by wet or dry etching. The first part (I) at this time
FIG. 11 shows the layer configuration at the second portion (II). That is, in the second portion (II), the mask 32 is used to etch up to the first etching stop layer 7 while leaving the second p-type cladding layer 8 and the second etching stop layer 9 in a predetermined shape. Then, by the mask 32,
Further, the second p-type cladding layer 8 and the second etching stop layer 9 are patterned into a predetermined shape.

Next, after removing the mask 32, the mask 32 is put into a semiconductor thin film growing apparatus, and as shown in FIG.
As the current confinement layer 13a, for example, a GaAs layer doped with Se of 8 × 10 ⁺¹⁶ cm ^-3 is grown to a thickness of 1380 nm, for example. Note that the current confinement layer 13a at this time is an n-type G
aAs layer.

Thereafter, a mask is formed by using the photolithography technique, and the convex portion of the current confinement layer 13a in FIG. 12 is etched by wet or dry etching to achieve flattening. As shown in FIG. A laminated structure having the flattened current confinement layer 13b is created.

Thereafter, as shown in FIG. 17, a mask 33 made of, for example, silicon nitride (especially SiN) is formed and Zn
Use a diffusion method, especially at the end of the diffusion, at least 1 × 1
A flow of Zn at a flow rate of 0 ⁻¹⁹ cm ⁻³ is ^supplied , and n
The type conductive GaAs is inverted to p-type, and a p-type current injection layer 14 is formed in the second portion (II) as shown in FIG.

Thereafter, for example, Ti, P
A metal is deposited by a vapor deposition method in the order of t and Au to form a p-type ohmic electrode (p electrode 16). After that, after lapping the substrate to make it thinner, and further performing organic cleaning,
For example, an n-type ohmic contact (n-electrode 15) is formed by depositing a metal on a substrate in the order of Au-Ge, Ni, and Au by an evaporation method.

As described above, the compound semiconductor structure shown in FIG. 1 can be formed. In this semiconductor laser, the active layer has a separated confinement structure.
(Separate Confinement Heterostructure) type semiconductor laser.

The above-described manufacturing method is an example, and the impurity species, impurity concentration, composition of each semiconductor layer, film thickness, manufacturing process, and the like are not limited to these. For example, in the manufacturing process, first, the entire layered structure 30 shown in FIG. 9 is not grown, and, for example, after the crystal is grown up to the first etching stop layer 7, a mask having a predetermined shape is formed using photolithography technology. And a second p-type cladding layer 8,
Second etching stop layer 9, second p-type cladding layer 1
After growing the p-type semiconductor layer 11 and the contact layer 12 in a predetermined shape, the mask is removed and the current confinement layer 13 is removed.
And the current injection layer 14 may be formed.

Next, the subsequent steps are shown in FIGS. 18 (1) to 18 (4).
Shown in

First, after the wafer 41 having the layer structure shown in FIG. 1 formed based on the above-described steps is cleaved to a desired resonator length (1), the light-emitting end face of the cleaved wafer 42 is protected. A film is deposited (2).

The end face protective film is provided for the purpose of preventing the oxidation and the like of each layer and at the same time increasing the output of the semiconductor laser. For example, one side is covered with an Al ₂ O ₃ / Si multilayer film 44 to cover it. the reflectance for example, 85% to 95%, the reflectance may be 5-10% over the opposite side Al ₂ O ₃ single layer film 43.

Then, the semiconductor laser is formed into chips (3), semiconductor laser chips 45a, 45b,... Are formed and mounted (assembled) in a package to complete a semiconductor laser (4).

Although the present invention has been described with reference to the preferred embodiments, the light emitting device of the present invention is not limited to the above embodiments.

For example, the stripe width of the semiconductor laser may be constant in the cavity length direction, but may have a different stripe width in the cavity length direction as shown in FIG. 21, for example.

The semiconductor laser described above has two types of layer configurations in the resonator length direction. For example, the first portion or the second portion has a plurality of layer configurations in the resonator length direction. Alternatively, three or more layer configurations may be provided as a whole. Alternatively, a structure in which the layer configuration is changed stepwise in the resonator length direction may be used.

Although the semiconductor material is made of AlGaInP, materials having different lattice constants include ZnSe-based compound semiconductors of Group II-VI compounds of the periodic table (blue light emission),
There is an aN-based periodic table group III-V group compound semiconductor (blue light emission) and the like, and the physical mechanism is considered to be the same as in the example described here. For example, a group 3 to group 6 compound semiconductor of the periodic table, a GaN group 3 to group 5 compound semiconductor of the blue periodic table, or the like may be used.

[0087]

According to the light emitting device of the present invention, the first portion continuous from at least one light emitting end face and the second portion present on the opposite side of the first portion from the light emitting end face. Are sequentially arranged in the resonator length direction on the active layer, and the layer configuration of the first portion and the layer configuration of the second portion are different from each other in the element thickness direction (longitudinal direction). In the part and the second part, a distribution such as an effective refractive index and an effective cavity loss is generated, and the amount of light absorption and the refractive index in each part can be appropriately adjusted,
Therefore, a highly reliable high-output light-emitting element can be obtained by suppressing end face deterioration of the light-emitting element.

According to the manufacturing method of the present invention, the first part continuous from at least one light emitting end face and the second part present on the opposite side of the first part from the light emitting end face are activated. The layers are sequentially arranged on the layer in the resonator length direction. At this time, since the layer configuration of the first portion and the layer configuration of the second portion are processed so as to be different from each other in the element thickness direction,
The light emitting device of the present invention can be manufactured with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a semiconductor laser according to the present invention (A), a cross-sectional view showing a layer configuration of a first portion (B), and a cross-sectional view (C) showing a layer configuration of a second portion.

FIG. 2 is a schematic perspective view of a first portion (I) and a second portion (II).

FIGS. 3A and 3B are a schematic diagram (A) and a schematic diagram (B) illustrating the operation of the light emitting device of the present invention.

4A and 4B are a schematic diagram showing a structure A and a schematic diagram showing a structure B, respectively.

FIG. 5 is a graph showing a light intensity distribution.

FIG. 6 is a graph showing a carrier density distribution.

FIG. 7 is a graph showing a band gap distribution.

FIG. 8 is a graph showing a light absorption distribution.

FIG. 9 is a schematic sectional view in a manufacturing process of the semiconductor laser according to the present invention.

FIG. 10 is another schematic cross-sectional view of the first part (I) and the second part (II) in the manufacturing process.

FIG. 11 is another schematic cross-sectional view of the first part (I) and the second part (II) in the manufacturing process.

FIG. 12 is another schematic cross-sectional view of the first part (I) and the second part (II) in the manufacturing process.

FIG. 13 is another schematic cross-sectional view of the first part (I) and the second part (II) in the manufacturing process.

FIG. 14 is another schematic cross-sectional view of the first part (I) and the second part (II) in the manufacturing process.

FIG. 15 is a schematic view showing a mask pattern used in the manufacturing process.

FIG. 16 is a schematic view showing another mask pattern used in the manufacturing process.

FIG. 17 is a schematic view showing another mask pattern used in the manufacturing process.

FIG. 18 is a flowchart showing a post process.

FIG. 19 is a schematic perspective view of a conventional semiconductor laser having a single longitudinal structure in a cavity length direction.

FIG. 20 is a schematic cross-sectional view showing an end face structure.

FIG. 21 is a schematic perspective view of another semiconductor laser.

FIG. 22 is a graph showing the relationship between the stripe width W and the horizontal and vertical radiation angles.

[Explanation of symbols]

1, 62: substrate, 2: first buffer layer, 3: second buffer layer, 4: n-type cladding layer, 5, 64: active layer, 6
... first p-type cladding layer, 7 ... first etching stop layer, 8 ... second p-type cladding layer, 9 ... second etching stop layer, 10 ... third p-type cladding layer, 11 ... p-type semiconductor layer, 12 ... contact layer , 13, 13a, 13b... N-type current confinement layer, 14... P-type current injection layer, 15.
6 p-electrode, 20, 50, 61 semiconductor laser, 21
Outgoing surface, 22 ... Reflective surface, 25 ... First light guide layer, 26 ...
2nd optical guide layer, 27 ... quantum well layer, 28 ... barrier layer,
30 ... layer structure, 31, 32, 33 ... mask (photoresist), 40a, 40,40c ... top, 41, 42 ... wafer, 43 ... Al ₂ O ₃ single layer _{film, 44 ... Al 2 O 3 /} S
i multilayer film, 45a, 45b ... semiconductor laser chip, 5
6, 63: first cladding layer, 57, 65: second cladding layer, 58, 66: current confinement layer, 67: laser beam,
a, b: vertical structure, (I): first part, (II): second part

Claims (12)

[Claims] 1. A first portion continuous from at least one light emitting end face, and a second portion present on a side opposite to the light emitting end face with respect to the first portion has a resonator length direction on an active layer. A light emitting element, wherein a layer configuration of the first portion and a layer configuration of the second portion are different from each other in a device thickness direction. 2. The light emitting device according to claim 1, wherein an effective refractive index distribution is different between the first portion and the second portion. 3. An effective refractive index of the first part is larger than an effective refractive index of the second part, and an effective cavity loss of the first part is smaller than an effective cavity loss of the second part. The light emitting device according to claim 1, wherein 4. A laminated structure in which a first clad layer, an active layer, and a second clad layer are sequentially laminated on a semiconductor substrate, and both sides of the second clad layer are current confinement layers. The light emitting device according to claim 1, wherein a portion sandwiched between the first portion and the portion in which an upper surface of the second clad layer is covered with a current injection layer is the second portion. 5. The light emitting device according to claim 4, wherein the thickness of the second cladding layer at the first portion is larger than the thickness of the second cladding layer at the second portion. 6. Aluminum (Al), gallium (G)
a) and at least one element of Group 3 of the periodic table selected from the group consisting of indium (In) and at least one element of Group 5 of the periodic table selected from the group consisting of arsenic (As) and phosphorus (P) The light emitting device according to claim 1, wherein the light emitting device is a compound semiconductor light emitting device comprising: 7. A first portion continuous from at least one light emitting end face and a second portion present on a side opposite to the light emitting end face with respect to the first portion are arranged on the active layer in a resonator length direction. A method of manufacturing a light emitting device, wherein the layer structure of the first portion and the layer structure of the second portion are processed so as to be different from each other in the device thickness direction. 8. The method according to claim 7, wherein the first portion and the second portion have different effective refractive index distributions. 9. An effective refractive index of the first part is larger than an effective refractive index of the second part, and an effective cavity loss of the first part is smaller than an effective cavity loss of the second part. A method for manufacturing the light emitting device according to claim 7. 10. A first cladding layer on a semiconductor substrate,
An active layer and a second cladding layer are sequentially laminated to form a laminated structure, and a portion where both sides of the second cladding layer are sandwiched by current constriction layers is defined as the first portion, and the second cladding is formed. The method for manufacturing a light-emitting element according to claim 7, wherein a portion in which the upper surface of the layer is covered with the current injection layer is the second portion. 11. The second clad layer in the laminated structure such that the thickness of the second clad layer in the first portion is larger than the thickness of the second clad layer in the second portion. The method for manufacturing a light-emitting device according to claim 10, wherein the method is performed. 12. Aluminum (Al), gallium (G)
a) and at least one element of Group 3 of the periodic table selected from the group consisting of indium (In) and at least one element of Group 5 of the periodic table selected from the group consisting of arsenic (As) and phosphorus (P) The method for manufacturing a light emitting device according to claim 7, wherein the light emitting device is formed using a compound semiconductor comprising: