JP2000124553A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a refractive index distribution and a carrier-trapping mechanism in lateral direction in an active layer itself by making an As composition ratio of an area along an inclined plane of a well layer higher than that of an area along a principal plane using a multiple quantum well active layer. SOLUTION: When (n) is taken to be a real number of n>7, n' is taken to be a real number of 2<=n'<=7 and n" is taken to be a real number of 3<=n"<=7, an active layer 4 which has either a (100) surface or a (n11) A surface acting as a principal plane 2 and a (n"11) A surface acting as an inclined plane is formed on a step-contained substrate 1 which has either the (100) surface or the (n11) A surface acting as the principal plane 2 and the (n11) A surface acting as an inclined plane 3. And using a multiple quantum well structure active layer whose well layer comprises InGaAsP as the active layer 4, an As composition ratio of an area along the inclined plane 3 of the well layer is made higher than that of an area along the principal plane 2. As a result, a refractive index distribution and a carrier-trapping mechanism in lateral direction are formed in the active layer 4 itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device and a method of manufacturing the same, and more particularly, to a lateral mode control type using a stepped substrate having an oscillation wavelength in an infrared region used as a light source of an optical fiber communication system. The present invention relates to a semiconductor laser device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, the capacity and cost of optical communication have been increasing, and in the future, so-called FTTH (Fiber To The Home) which introduces an optical fiber into each home.
In order to achieve this goal, it is essential to provide a high-performance optical communication module at a low price. For a semiconductor laser for optical communication that constitutes the optical communication module, Low price and high temperature operation are required.

Here, a semiconductor laser for optical communication that has been conventionally proposed will be described with reference to FIG. See FIG. 3A. FIG. 3A is a diagram showing a mainstream InP / InGaAsP semiconductor laser for optical communication, which is a BH (Buried Hete).
FIG. 1 is a cross-sectional view of a (ro) type semiconductor laser, in which n-type In
After an n-type InP buffer layer 32 also serving as an n-side cladding layer, an InGaAsP strained MQW (multiple quantum well structure) active layer 33, and a p-type InP cladding layer 34 are sequentially deposited on a P substrate 31, an SiO ₂ mask is formed. A ridge-shaped mesa 35 is formed by performing mesa etching reaching the n-type InP buffer layer 32 using a mask (not shown) as a mask.

Next, using an SiO ₂ mask as a selective growth mask, an n-type InP buried buffer layer 36 also serving as a clad layer, a p-type InP buried layer 37 also serving as a clad layer, After sequentially growing an n-type InP current blocking layer 38 also serving as a layer and a p-type InP buried protective layer 39 also serving as a cladding layer,
The basic laminated structure is formed by removing the O ₂ mask and then sequentially growing a p-type InP cladding layer 40 and a p-type InGaAs contact layer 41 on the entire surface.

[0005] In such a BH type semiconductor laser,
There semiconductor layer having a composition different from the active layer in the vertical and horizontal of the active layer, and, since the volume itself of the active layer is small, has a characteristic of oscillation threshold current I _th is small. This is because a semiconductor layer having a different composition on both sides of the active layer and, therefore, a different refractive index has a function of confining light in the lateral direction and emits light by reducing the volume of the active layer. It is possible to reduce the current and thereby improve the frequency characteristics.

FIG. 3B is a sectional view of a ridge type semiconductor laser.
First, on an n-type InP substrate 51, an n-type InP buffer layer 52 also serving as an n-side cladding layer, an InGaAsP strained MQW
Active layer 53, p-type InP cladding layer 54, p-type InGa
After the AsP etching stop layer 55 and the p-type InP cladding layer 56 are sequentially deposited, the p-type InP cladding layer 56 is reached using the SiO ₂ mask (not shown) as a mask so as to reach the p-type InGaAsP etching stop layer 55. A ridge-shaped mesa is formed by mesa etching, and then the exposed portion of the p-type InGaAsP etching stop layer 55 is etched away.

Next, using a SiO ₂ mask as a selective growth mask, a p-type InP buried layer 57 also serving as a cladding layer and an n-type I
nP current blocking layer 58 and p serving also as a cladding layer
Type InP buried protective layer 59 is grown sequentially,
_{(2) A} basic laminated structure is formed by removing the mask and then sequentially growing a p-type InP cladding layer 60 and a p-type InGaAs contact layer 61 on the entire surface.

In such a ridge type semiconductor laser, since the active layer is not directly processed, the effect of deterioration of device characteristics due to crystal defects and the like is relatively small. This is a stripe structure that is often used when crystal defects strongly affect the life of the laser.

However, there are various problems in such a conventional semiconductor laser, for example, the B type shown in FIG.
In the case of the H-type semiconductor laser, since the active layer is processed by etching, there is a problem that the element characteristics are slightly deteriorated due to crystal defects or impurities generated in the active layer.

In the ridge-type semiconductor laser shown in FIG. 3B, the active layer itself extends in a lateral direction other than the laser oscillation region, and the p-type InP buried layer 57 is formed.
And n-type InP current blocking layer 58 is p-type clad layer 5
6 is composed of the same InP layer as that of the active layer 6, an equivalent refractive index distribution is not formed in the lateral direction of the active layer, and the anti-guide structure is formed. . In addition, since the volume of the active layer is large, the threshold current I _th is relatively high, so that it is not widely used as an InP-based optical communication semiconductor laser.

As described above, the BH type semiconductor laser and the ridge type semiconductor laser each have problems. However, it is considered that an ideal configuration can be obtained by simultaneously employing only the advantages of both. Ideally, the stripe width can be reduced without the process of directly processing and forming the active layer, and the refractive index can be changed in the lateral direction of the active layer.

Therefore, the present inventors have proposed a single-growth semiconductor laser which employs at the same time only the advantages of the BH type semiconductor laser and the ridge type semiconductor laser in the AlGaInP-based short wavelength semiconductor laser (if necessary). For example, see Japanese Patent Application Laid-Open No. 6-45708), this once-growth semiconductor laser, that is, a bent-waveguide type S ³ laser (Self-aligned Stepped Sub) is used.
(Strate Laser) will be described with reference to FIGS. 4 to 6. FIG.

FIG. 4A is a perspective view of a single growth type semiconductor laser.
After a step having a slope of substantially (311) A plane is formed on an n-type GaAs substrate 71 having a (100) plane as a main surface, an n-type GaAs substrate is formed thereon by MOVPE (metal organic chemical vapor deposition).
aAs buffer layer 72, n-type GaInP intermediate layer 73, n
Type AlGaInP cladding layer 74, MQW active layer 75,
p-type AlGaInP cladding layer 76, peripheral portion is n-type Al
A GaInP current block layer 77 is formed and the center is p-type Al
P-side second cladding layer to be a GaInP current channel layer 78, p-type AlGaInP cladding layer 79, p-type GaIn
The P intermediate layer 80 and the p-type GaAs contact layer 81 are sequentially grown. The (311) A surface is
Group III elements (Ga in this case) appear on the surface (3
11) surface.

In this case, in the growth step of the p-side second cladding layer in which the peripheral portion is the n-type AlGaInP current block layer 77 and the central portion is the p-type AlGaInP current channel layer 78, the crystal plane orientation dependence of impurity doping is used. Since the current confinement mechanism is formed in one crystal growth step, this situation will be described with reference to FIG. See FIG. 4B. FIG. 4B shows a case where Zn and Se are simultaneously doped to form Al _0.35.
Al _0.35 Ga when a Ga _0.15 In _0.5 P layer is grown
FIG. 4 is a diagram showing the plane orientation dependence of the carrier concentration in a _0.15 In _0.5 P layer, where the horizontal axis is from (100) plane to (111) A.
It represents the off angle in the plane direction.

In the figure, as indicated by white circles and black circles, the carrier concentration is lowest near the (711) A plane, so that when the same amount of impurity is doped, n> 7
On the (n11) A plane, an n-type layer is obtained, and m ≦ 7 (m1
1) On the A-side, a p-type layer is obtained, and n-type GaAs
The Al _0.35 Ga _0.15 In _0.5 P layer grown along the slope of the s substrate 71, that is, the (311) A plane is almost (411) A
Although it becomes a surface and becomes a p-type layer, the portion grown along the flat surface of the n-type GaAs substrate 71, that is, the (100) plane,
Since it is a (100) plane, it becomes an n-type layer. Since the values of n and m depend on the doping amount of the impurity, the doping ratio, and the like, they have no special critical meaning.

The dependence of the carrier concentration on the plane orientation is as follows.
This is because the efficiency of taking in the impurities depends on the plane orientation. This situation will be described with reference to FIG. FIG. 5A is a diagram showing the plane orientation dependence of the efficiency of taking in Zn and Mg as p-type impurities, from the (100) plane to the (111) A plane and (111). A substrate having an off angle in the B-plane direction is subjected to A from a growth gas containing Zn and Mg.
FIG. 9 shows the relative incorporation efficiency of impurities in an AlGaInP layer when an lGaInP layer is grown.

Black circles and black squares indicate relative carrier concentrations measured by CV measurement (capacitance measurement).
The white circles and white squares indicate SIMS (Secondary).
This is a relative impurity concentration measured by yIon Mass Spectroscopy, and the difference between them indicates the activation rate of the impurity, and the difference in impurity concentration depending on the crystal plane orientation, that is, the relative impurity incorporation efficiency depends on the plane orientation. I understand the nature. Note that a circle indicates the A direction and a square indicates the B direction.

As is apparent from the figure, in the case of Zn,
In the A direction, as the off angle increases, that is, as n of (n11) decreases, the impurity concentration and the carrier concentration increase, and the off angle becomes 25 °, that is, the maximum near the (311) plane. , And thereafter decreases, but the density of the (111) A plane is about six times that of the (100) plane. In this case, since there is almost no difference between the impurity concentration and the carrier concentration, that is, since the activation rate of the impurity does not depend on the plane orientation, this result indicates the dependence of the impurity incorporation efficiency on the plane orientation. Will be.

On the other hand, in the B direction, the dependence of the impurity incorporation efficiency on the plane orientation is not so much observed.
1) On the B plane, it is half of the (100) plane. In the case of Mg, the same tendency as that of Zn is observed, but the orientation dependence is smaller than that of Zn.

FIG. 5B is a diagram showing the dependence of the incorporation efficiency of Se, which is an n-type impurity, on the plane orientation. Se has a tendency opposite to that of the p-type impurity. In the direction A, the efficiency of capturing impurities decreases as the off-angle increases. On the other hand, in the direction B, the efficiency of capturing impurities increases as the off-angle increases.

Therefore, a p-type impurity made of Zn or Mg and Se
The result of FIG. 4B that the p-type region and the n-type region can be grown at the same time by simultaneously doping the n-type impurity consisting of

As described above, the conventional one-time growth type semiconductor laser forms the current confinement mechanism by utilizing the plane orientation dependence of the impurity doping in the MOVPE method. Since both the current confinement mechanism and the refractive index distribution can be formed in the lateral direction of the active layer in a single continuous growth step, a semiconductor laser can be manufactured at a high yield and at a low price.

Further, since the once-growth semiconductor laser is not a loss guide structure, that is, a complex refractive index waveguide structure due to light absorption loss, it is not necessary to consider light absorption loss, and therefore, high efficiency and low efficiency are obtained. It has the advantage of low power consumption and low astigmatism characteristics.

[0024]

The technical matters relating to such a once-growth semiconductor laser are described in InP / InGaAsP.
It is expected that a semiconductor laser for optical communication having excellent characteristics can be obtained at low cost by applying the present invention to a system semiconductor laser, and the present applicant has already suggested it as a general theory (see, for example, JP-A-7-263805). However, the detailed configuration was not always clear.

That is, in the publication, it is simply described that an InP substrate may be used as a substrate and that an InP cladding layer may be used as a cladding layer. The target content is not disclosed at all.

Further, even if the InP / InGaAsP-based semiconductor laser is simply constituted as a once-growth semiconductor laser,
The lateral current confinement and the lateral refractive index distribution of the active layer itself, i.e., the carrier confinement and the refractive index distribution between the region along the slope of the active layer and the region along the flat main surface,
It was considered that this was not always sufficient as a semiconductor laser for optical communication.

Accordingly, an object of the present invention is to provide a pseudo-BH semiconductor laser in which a lateral carrier confinement mechanism and a refractive index distribution are formed in an active layer itself at a low cost.

[0028]

FIG. 1 is an explanatory view of the principle configuration of the present invention. Referring to FIG. 1, means for solving the problems in the present invention will be described. See FIG. 1 (1) In the present invention, n is a real number of n> 7, and n ′ is 2 ≦
When a real number of n ′ ≦ 7 and n ″ is a real number of 3 ≦ n ″ ≦ 7, either the (100) plane or the (n11) A plane is defined as the principal plane 2 and the (n′11) A plane is defined as The active layer 4 and the active layer 4 on which the (100) plane or the (n11) A plane is the principal plane 2 and the (n ″ 11) A plane is the slope 3 while using the step substrate 1 having the inclined plane 3 In addition, the p-side first cladding layer 5 in which the hole concentration in the region along the slope 3 is higher than the hole concentration in the region along the main surface 2, and the n-type current blocking layer 8 on the main surface 2, In the semiconductor laser device provided with at least the p-side second cladding layer 6 serving as the p-type current channel layer 7, an InP substrate is used as the step substrate 1, and the active layer 4 has a multiple quantum well structure in which the well layer is made of InGaAsP. Layer at least along the slope 3 of the well layer. As the composition ratio of areas is equal to or higher than the As composition ratio of the area along the main surface 2.

As described above, the plane orientation of the step substrate 1 is selected as described above, and the active layer 4 is made of InGaAs.
A multiquantum well structure active layer made of sP is used. At least a region along the slope 3 of the well layer is a high As composition region 9 and a region along the main surface 2 by utilizing the plane orientation dependence of As incorporation efficiency. Is formed in the low As composition region 10, a refractive index distribution and a forbidden band width distribution can be formed in the lateral direction of the active layer 4 itself. A quasi-BH semiconductor laser with enhanced confinement and carrier confinement can be obtained, thereby improving device characteristics.

In the case of a normal p-type impurity, the off-angle of the surface A increases as the off-angle increases.
Since the impurity concentration and the carrier concentration increase as n ′ or n ″ becomes smaller, the hole concentration in the region along the slope 3 can be reduced by simply setting n ′, n ″ <n. It can be higher than the hole concentration. The (100) plane corresponds to a case where n of the (n11) plane is set to infinity ∞.

(2) Further, according to the present invention, in the above (1), the n-type current blocking layer 8 and the p-type current channel layer 7
Contains one of Zn, Mg, and Cd and one of S and Se at the same time.

In general, on the A-plane, the plane orientation dependence of the p-type impurity incorporation efficiency and the plane orientation dependence of the n-type impurity incorporation efficiency are opposite to each other. Co-doping, the region growing along the main surface 2 can be an n-type layer and the region growing along the slope 3 can be a p-type layer, thereby forming a current confinement mechanism. Can be.

(3) The present invention relates to the above (1), wherein n
In the p-type current blocking layer 8, a layer doped with one of Zn, Mg, and Cd and a layer doped with any one of S and Se are alternately stacked. , Zn, Mg, Cd, a layer doped with one of Zn, Mg, Cd, and a layer doped simultaneously with any of S, Se are alternately stacked. And

When the p-side second cladding layer 6 is alternately doped with p-type impurities and n-type impurities, the p-type second cladding layer 6 is formed due to the plane orientation dependence of the efficiency of taking in the p-type impurities and n-type impurities and the difference in tendency. According to the carrier concentration distribution obtained, in the region along the slope 3, the p-type impurity enters the n-type layer by the diffusion principle due to the impurity concentration difference, and the p-type impurity and n
It becomes the p-type current channel layer 7 in which the type impurities are mixed.
On the other hand, in the region along the main surface 2, the p-type impurity is blocked by the impurity concentration difference and does not diffuse, and the n-type impurity hardly diffuses.
Although the doping profile has a pn .. structure, since these layers are all thin, the p-type doped portion is depleted due to the diffusion of carriers to form a uniform n-type current blocking layer 8.

(4) In the present invention, in any one of the above (1) to (3), an InP clad layer having a thickness of 0.5 μm or more is provided between the step substrate 1 and the active layer 4. It is characterized by having.

As described above, by providing the InP clad layer having a thickness of 0.5 μm or more between the step substrate 1 and the active layer 4, variations in the plane orientation of the slope 3 can be suppressed, and the device characteristics can be improved. A semiconductor laser excellent in reproducibility can be manufactured with good reproducibility.

Further (5), in the above (1) to (4), at least one of the barrier layer and the light guide layer of the active layer _{4, Al 1-xy In x} Ga y A
s (where 0 <x <1, 0 ≦ y <1).

(6) Further, according to the present invention, in any one of the above (1) to (5), a part of the p-side cladding layer is
Al _1-vw In _{v G aw} As (where 0 <v <1,0 ≦
w <1).

When the active layer 4 is a multiple quantum well structure active layer using InGaAsP as a well layer, and at least the p-side second cladding layer constituting the current confinement mechanism is formed of InP, Hardly sees the dependence of the impurity incorporation efficiency on the plane orientation, but the AlI has a large forbidden band width and a small spike caused by ΔE _C.
By using nGaAs as a barrier layer or a light guide layer constituting the active layer 4, or as a part of the p-side cladding layer, it becomes possible to constitute a semiconductor laser having more excellent characteristics.

(7) According to the present invention, n is a real number of n> 7, n 'is a real number of 2≤n'≤7, and n "is 3≤n".
If the real number is ≦ 7, the (100) plane or (n11)
A stepped substrate 1 having one of the A surfaces as the main surface 2 and the (n'11) A surface as the inclined surface 3 is used, and one of the (100) surface or the (n11) A surface as the main surface 2; n "1
1) In a method for manufacturing a semiconductor laser device provided with at least the active layer 4 having the A-plane as the slope 3, the p-side first cladding layer 5, and the p-side second cladding layer 6, an InP substrate is used as the step substrate 1. At the same time, a multiple quantum well structure active layer whose well layer is made of InGaAsP is used as the active layer 4, and the As composition ratio of at least the region along the slope 3 of the well layer is higher than the As composition ratio of the region along the main surface 2. It is characterized by being manufactured using a metal organic chemical vapor deposition method.

As described above, by using the metal organic chemical vapor deposition (MOVPE) method as the growth method, the active layer 4 can be formed.
Can be made higher in the region along the inclined surface 3 than in the region along the main surface 2. In particular, by disposing the active layer 4 in a multiple quantum well structure, Can be formed without causing the generation of the As composition distribution.

That is, the present inventor discovered a plane orientation dependency of As incorporation efficiency, which cannot be predicted from the conventional knowledge, and combined this phenomenon with a multiple quantum well structure to use a single growth method. InGaAsP for optical communication with good carrier confinement and light confinement in the lateral direction of the active layer 4
This makes it possible to manufacture a semiconductor laser without generating dislocations or the like in the active layer 4.

(8) Further, according to the present invention, in the method of the above (7), when growing the p-side first cladding layer 5, the plane orientation of the stepped substrate 1 is utilized by utilizing the plane orientation dependency of the efficiency of taking in impurities. 3 is characterized in that the hole concentration in the region along the main surface 2 is higher than the hole concentration in the region along the main surface 2.

(9) In the present invention according to (7) or (8), when the p-side second cladding layer 6 is grown, the plane orientation dependence of the efficiency of taking in the p-type impurity and the n-type impurity. Utilizing this difference, a region along the slope 3 of the step substrate 1 is defined as a p-type current channel layer 7, and a region along the main surface 2 is defined as an n-type current block layer 8.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pseudo BH type semiconductor laser according to an embodiment of the present invention will be described with reference to FIG. FIG. 2A is a cross-sectional view of the pseudo BH type semiconductor laser, and FIG. 2B is an explanatory diagram of the plane orientation dependence of the impurity incorporation efficiency in InP. Referring to FIG. 2A, first, a photoresist (not shown) is applied on an Sn-doped n-type InP substrate 11 having a main surface turned off by 6 ° from the (100) plane to the (111) A plane, and the photoresist is applied at intervals of 150 μm. Width 1
A resist pattern having a 50 μm stripe-shaped opening is formed by a photolithography process.

Next, etching is performed using an HCl-based etchant with the resist pattern as a mask so that the inclination angle with respect to the main surface is about 14 ° or more, ie, (10
0) A groove having a depth of 0.3 μm and a slope having an off angle of 20 ° or more with respect to the plane is formed.

Next, all layers from the buffer layer to the contact layer are continuously grown by the MOVPE method. In this case, the growth pressure is 50 Torr, the growth efficiency is about 800 μm / mol, and the carrier gas is throughout the entire growth process. Is 8000 sccm including hydrogen.

First, an n-type InP substrate 1 having a step formed thereon
1 and a substrate temperature of 620 ° C., using TMI (trimethyl indium) and PH ₃ to obtain PH ₃ / T
The raw material gas is flowed so that the MI ratio becomes 120 and the growth rate becomes 1 μm / hour, and the carrier concentration is 7 × 10 ¹⁷ cm ⁻³ and the thickness is 0.5 μm by flowing Si ₂ H ₆ as an impurity source. As described above, for example, the n-type InP buffer layer 12 also serving as the 0.5 μm n-side cladding layer is grown.

In this case, by growing the n-type InP buffer layer 12 to a thickness of 0.5 μm or more, the plane appearing on the slope becomes settled in the plane direction near the (411) A plane, and as an impurity. Si ₂ H ₆ , that is, Si
Is used, the dependence of the capturing efficiency on the plane orientation is small, and the electron concentration on the slope and the electron concentration on the main surface are almost uniform.

Next, the InGaAs PMQW active layer 13
First, the substrate temperature is set to 620 ° C.
TMI, TEG (triethyl gallium), A
sH _Three, And PH_ThreeAnd the V / III ratio is 80
So that the growth rate is 0.5 μm / hour.
Flow and Si_TwoH₆Flowing as a source of impurities
5 × 10¹⁷cm^-3With a thickness of 70
Non-strained n-type In with a 1.05 μm PL wavelength
_0.893Ga_0.107As_0.23P_0.77Grow the light guide layer
After that, under the same conditions,_TwoH₆Supply stopped
With a thickness of 30 nm and a PL wavelength of 1.05 μm without distortion
Non-doped In_0.893Ga_0.107As _0.23P_0.77light
Grow the guide layer. In InGaAsP,
The composition ratio indicates the composition ratio in the area along the slope.
The same applies hereinafter.

Next, with the substrate temperature also set to 620 ° C., using TMI, TEG, AsH ₃ and PH ₃ , the V / III ratio becomes 70 and the growth rate becomes 0.5.
A non-doped In _0.899 Ga _0.101 As _0.53 P _0.47 well layer having a thickness of 6 nm (= 60 _° ) and a compressive strain of 1% by flowing a source gas at a rate of μm / hour, and
With the substrate temperature also set to 620 ° C., TMI, TE
By using G, AsH ₃ , and PH ₃ to flow a source gas so that the group V / III ratio becomes 80 and the growth rate becomes 0.5 μm / hour, the thickness becomes 10 nm (= 10 nm).
In 0 Å), a non-doped _{In 0.855 Ga 0.145 As 0.32 P 0.} 68 barrier layer of unstrained the PL wavelength is 1.1μm composition,
A strained MQW region is grown by alternately growing eight well layers and seven barrier layers.

Next, with the substrate temperature also set to 620 ° C., using TMI, TEG, AsH ₃ and PH ₃ , the V / III ratio becomes 80 and the growth rate becomes 0.5.
By flowing the source gas at a rate of 1.0 μm / hour, the thickness is 100 nm (= 0.1 μm) and the PL wavelength is 1.05
Non-strained non-doped In _0.893 Ga _0.107 A with μm composition
By growing a s _0.23 P _0.77 light guide layer,
An nGaAs PMQW active layer 13 is formed.

In the growth process of the InGaAs PMQW active layer 13, the As concentration increases in the region along the slope to become the high As composition region 21, while the As concentration in the region along the main surface becomes relatively low. Low As
Since the composition region 22 is provided, the effective bandgap of the high As composition region 21 which is a laser oscillation region along the slope can be made 50 meV or more higher than that of the low As composition region 22 along the main surface. Since the movement of carriers in the layer in the lateral direction is eliminated, and a factor other than the step, that is, the refractive index distribution in the lateral direction can be formed by the As composition distribution, current confinement and light confinement close to the BH structure can be achieved. Will be possible.

Next, the state where the substrate temperature was set to 620 ° C.
And TMI and PH_ThreeUsing the PH _Three/ TMI ratio is 1
20 so that the growth rate is 1 μm / hour.
And DEZn (diethyl zinc) as an impurity source
Carrier concentration at the slope
7 × 10¹⁷cm^-30.3μm thick p-side first crack
A p-type InP cladding layer 14 serving as a doped layer is grown.

In this growth process, as shown in the figure, the efficiency of taking in Zn depends on the plane orientation. Therefore, the impurity concentration in the region along the slope of the p-type InP cladding layer 14 is mainly The concentration becomes higher by one digit or more than the impurity concentration in the region along the surface.

Next, a state in which the substrate temperature was set to 620 ° C.
And TMI and PH_ThreeUsing the PH _Three/ TMI ratio is 1
20 so that the growth rate is 1 μm / hour.
And DEZn and H_TwoSe flow alternately
Each pair is grown by 30 pairs of 10 nm each to obtain a total thickness of 0.
A 60 μm p-side InP second cladding layer is grown.

In the p-side InP second cladding layer, the Zn concentration in the region along the slope is 1.4 × 10 4
^While controlling the flow rate of DEZn to ¹⁸ cm ^-3 ,
Se concentration in a region along the main surface is 7 × 10 ¹⁷ cm ⁻³
It is controlled to become.

Referring again to FIG. 2B, by setting the impurity concentration in this manner, the Zn concentration in the region along the slope becomes one or more digits higher than the Se concentration. After entering the p-type doped layer, the p-type carrier concentration of 1.4 × 10 ¹⁸ cm ⁻³ is averaged to 7 × 10 ¹⁷ cm ⁻³ , and the entire portion along the slope is p-type InP It is converted to a current channel layer 16.

On the other hand, in the portion along the main surface, Zn
Since the concentration is one digit lower than 1.4 × 10 ¹⁸ cm ⁻³ ,
Blocked by Se of × 10 ¹⁷ cm ^-3, no diffusion occurs,
In addition, since the diffusion of Se hardly occurs, pnpnpn
.. The structure has a doping profile, but since these layers are all thin, the p-type doped portion is depleted by carrier diffusion to form a uniform n-type InP current blocking layer 15. Stenosis is performed.

Referring again to FIG. 2A, the TMI and the substrate temperature are set to 620 ° C.
PH_ThreeUsing the PH _Three/ TMI ratio becomes 120,
When the source gas is flowed so that the long speed is 2 μm / hour,
Then, by flowing DEZn as an impurity source,
Carrier concentration at 7 × 10¹⁷cm^-3And the thickness is 2.
A 0 μm p-type InP buffer layer 17 is grown.

Next, with the substrate temperature kept at 620 ° C., using TMI, TEG, AsH ₃ and PH ₃ , the V / III ratio becomes 80 and the growth rate becomes 0.5 μm.
m / hr and DEZn as an impurity source to provide a carrier concentration at the slope of 1 × 10 ¹⁸ cm ⁻³ , a thickness of 50 nm, and a PL wavelength of 1.20 μm. of p-type InGaAsP intermediate layer 18, i.e., p-type _{in 0.78 3 Ga 0.217 As 0.48 P} 0.52
Grow the intermediate layer. The p-type InGaAsP intermediate layer 18 is provided to reduce the influence of a spike serving as a barrier to holes formed by the difference in electron affinity χ.

Next, with the substrate temperature kept at 600 ° C., TMI, TEG, and AsH ₃ were used to form a group V / I
A source gas is flown so that the group II ratio becomes 40 and the growth rate becomes 0.5 μm / hour, and DMZn (dimethyl Z
By flowing n) as an impurity source, a strain-free p-type InGaAs contact layer 19 having a carrier concentration of 2 × 10 ¹⁹ cm ⁻³ at a slope and a thickness of 0.1 μm is grown.

Finally, the state where the substrate temperature is set to 600 ° C.
And TMI and PH_ThreeUsing the PH _Three/ TMI ratio is 1
20 so that the growth rate is 1 μm / hour.
0.1 μm thick undoped InP protective layer
20 and grown continuously by the MOVPE method.
After a long time, PH_ThreeAnd lower the temperature to 400 ° C.
PH when cut_ThreeSupply to the room, and then
After the temperature is lowered by the MOVPE apparatus,
The formed n-type InP substrate 11 is taken out.

Then, although not shown, after completely removing the undoped InP cap layer 20 with an HBr solution, an element isolation region having a width of 10 μm is formed, and a T-type insulating layer 19 is formed on the exposed p-type InGaAs contact layer 19 as a p-side electrode.
An i / Pt / Au-based electrode is provided, while an n-type InP substrate 1 is provided.
On the back surface of No. 1, the back surface is polished to reduce the thickness including the growth layers 12 to 19 to about 100 μm, and then n
An Au.Ge/Au electrode is formed as a side electrode.

Next, the wafer is cleaved into chips having a width of 300 μm and a length of 400 μm, and p-side-up (p-side u).
By bonding to the heat sink in p), the semiconductor laser device is completed.

As described above, the embodiment of the present invention has been described.
This is believed to have been confirmed for the first time by the present inventor, and cannot be recognized at all from the conventional knowledge. In addition to utilizing such a novel phenomenon, As and P are substantially included as the active layer. By using an InGaAsP layer and having an MQW structure having a plurality of thin well layers, an As composition sufficient to obtain an effective carrier confinement effect at room temperature in the lateral direction of the active layer by single growth without dislocations. By forming a distribution, a lateral carrier confinement mechanism and a lateral optical confinement mechanism close to the BH structure can be simultaneously formed.

That is, when the composition ratio of As in InGaAsP is small, A which causes a band gap difference of about 50 meV to such an extent that an effective carrier confinement mechanism or a lateral optical confinement mechanism is formed at room temperature.
When the InGaAsP layer cannot be formed as the active layer and the bulk is an InGaAsP layer,
Since the strain applied to the active layer becomes unbalanced with the occurrence of the composition distribution, dislocations and the like easily occur in the active layer.

Further, since the active layer has a strained MQW structure, an effect of expanding the As composition distribution due to the strain can be expected, and the characteristics required for the semiconductor laser for optical communication can be achieved by the above specific configuration. InP / InGaAs having
An sP-based semiconductor laser can be provided at low cost, and the commercial value of the present invention is very large.

In the above description of the embodiment, the n-type current blocking layer and the p-type current channel layer are formed by alternately doping Zn and Se. A current blocking layer and a p-type current channel layer may be formed. In this case, Zn and Se are simultaneously doped as shown in FIG. The region along the main surface becomes an n-type current block layer due to the difference in the tendency of the plane orientation dependence of the take-in efficiency, and current constriction is performed by the n-type current block layer.

In the above description of the embodiment, Zn is used as a p-type impurity, but Mg or Cd may be used, and Se is used as an n-type impurity. However, S may be used.

Further, in the above description of the embodiment, the substrate whose main surface is off by 6 ° from the (100) plane in the direction of the (111) A plane is used, but the (100) plane is used. Alternatively, a substrate may be used in which the (n11) A plane (where the real number n is n> 7) is off by a predetermined angle in the direction from the (100) plane to the (111) A plane. The plane orientation of the slope is not limited to the (411) A plane, but the (n′11) A plane (where the real number n ′ is 2 ≦ n ′).
≤ 7).

[0072] Also, in the description of the above embodiment, although using InP as a cladding layer, Al _1-vw part of the cladding layer In _v Ga _w As (where, 0 <v
<1, 0 ≦ w <1), and InG
aAsP barrier layer or InGaAsP light guide layer
_{l 1-xy In x Ga y} As ( where, 0 <x <1,0 ≦ y
<1, x <v), as long as the well layers constituting the MQW active layer contain As and P at substantially the same concentration.

Such an AlInGaAs-based semiconductor is a material suitable for the cladding layer because of its wide bandgap and small occurrence of spikes due to ΔE _C.
When GaAs is used, it is difficult to grow the side surface of the growth layer after processing because it contains Al, and the current confinement mechanism is self-formed because there is almost no dependence of the impurity orientation on the plane orientation. However, as described above, As and P are contained in the well layer constituting the MQW active layer at substantially the same concentration, and the p-type layer forming the current confinement mechanism is formed.
If the second side cladding layer is made of InP, another cladding layer, or a barrier layer and a light guide layer may be made of AlInGaAs.
Even if it is composed of s, a semiconductor laser having a confinement structure similar to the BH structure can be manufactured by the single growth method.

[0074]

According to the present invention, the MQW active layer is formed by utilizing the plane orientation dependency of the As composition distribution.
By the epitaxial growth method, a lateral carrier confinement structure and an optical confinement structure can be self-formed in the active layer without generating dislocations in the growth layer, whereby the characteristic temperature and low temperature required for a semiconductor laser for optical communication can be obtained. Semiconductor lasers satisfying element characteristics such as current threshold can be manufactured at a high yield and at a low price, which greatly contributes to the spread and development of FTTH.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is an explanatory diagram of a pseudo BH type semiconductor laser according to an embodiment of the present invention.

FIG. 3 is an explanatory view of a conventional semiconductor laser for optical communication.

FIG. 4 is an explanatory diagram of a conventional single growth semiconductor laser.

FIG. 5 is an explanatory diagram of the plane orientation dependence of the impurity incorporation efficiency in a conventional AlGaInP.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 step substrate 2 main surface 3 slope 4 active layer 5 p-side first cladding layer 6 p-side second cladding layer 7 p-type current channel layer 8 n-type current blocking layer 9 high As composition region 10 low As composition region 11 n type InP substrate 12 n-type InP buffer layer 13 InGaAs PMQW active layer 14 p-type InP cladding layer 15 n-type InP current blocking layer 16 p-type InP current channel layer 17 p-type InP cladding layer 18 p-type InGaAsP intermediate layer 19 p-type InGaAs contact layer REFERENCE SIGNS LIST 20 Undoped InP cap layer 21 High As composition region 22 Low As composition region 31 n-type InP substrate 32 n-type InP buffer layer 33 InGaAsP strained MQW active layer 34 p-type InP cladding layer 35 ridge-shaped mesa 36 n-type InP embedded buffer layer 37 p-type InP buried layer 38 n-type InP current Lock layer 39 p-type InP buried protective layer 40 p-type InP cladding layer 41 p-type InGaAs contact layer 51 n-type InP substrate 52 n-type InP buffer layer 53 InGaAsP strained MQW active layer 54 p-type InP cladding layer 55 p-type InGaAs etching Stop layer 56 p-type InP clad layer 57 p-type InP buried layer 58 n-type InP current blocking layer 59 p-type InP buried protective layer 60 p-type InP clad layer 61 p-type InGaAs contact layer 71 n-type GaAs substrate 72 n-type GaAs buffer layer 73 n-type GaInP intermediate layer 74 n-type AlGaInP cladding layer 75 MQW active layer 76 p-type AlGaInP cladding layer 77 n-type AlGaInP current blocking layer 78 p-type AlGaInP current channel layer 79 p-type AlGaInP cladding layer 8 p-type GaInP intermediate layer 81 p-type GaAs contact layer

Claims (9)

[Claims] 1. n is a real number with n> 7, and n ′ is 2 ≦ n ′
When a real number of ≦ 7 and n ″ is a real number of 3 ≦ n ″ ≦ 7, either the (100) plane or the (n11) A plane is a main plane, and the (n′11) A plane is a slope. An active layer using a stepped substrate, having either the (100) plane or the (n11) A plane as a main surface and the (n ″ 11) A plane as a slope;
On the active layer, a p-side first cladding layer having a higher hole concentration in a region along the slope than the hole concentration in a region along the main surface, and an n-type current blocking layer on the main surface. The p-side second which becomes the p-type current channel layer on the slope
In a semiconductor laser device provided with at least a cladding layer, an InP substrate is used as the step substrate, and a multiple quantum well structure active layer in which a well layer is made of InGaAsP is used as the active layer, and at least along the slope of the well layer. A semiconductor laser device, wherein the As composition ratio of the region along the main surface is higher than the As composition ratio of the region along the main surface. 2. The method according to claim 1, wherein the n-type current blocking layer and the p-type current channel layer are formed of one of Zn, Mg, and Cd and S, Se.
2. The semiconductor laser device according to claim 1, wherein the semiconductor laser device includes at least one of the following. 3. The method according to claim 2, wherein the n-type current blocking layer has
a layer doped with one of n, Mg and Cd;
e are alternately stacked with layers doped with any one of Zn, Mg, and C in the p-type current channel layer.
2. The semiconductor device according to claim 1, wherein a layer doped with one of d, one of Zn, Mg, and Cd, and a layer doped with any of S and Se are alternately stacked. 13. The semiconductor laser device according to claim 1. 4. The semiconductor according to claim 1, wherein an InP cladding layer having a thickness of 0.5 μm or more is provided between the step substrate and the active layer. Laser device. 5. at least one of the barrier layer and the optical guide layer of the active _{layer, Al 1-xy In x Ga} y A
5. The semiconductor laser device according to claim 1, wherein s (where 0 <x <1, 0 ≦ y <1). 6. 6. A part of the p-side cladding layer is made of Al
_{1-vw In v Ga w As} ( where, 0 <v <1,0 ≦ w <
The semiconductor laser device according to any one of claims 1 to 5, wherein the semiconductor laser device is configured from (1). 7. Let n be a real number with n> 7, and n ′ be 2 ≦ n ′
When a real number of ≦ 7 and n ″ is a real number of 3 ≦ n ″ ≦ 7, either the (100) plane or the (n11) A plane is a main plane, and the (n′11) A plane is a slope. An active layer using a stepped substrate, having either the (100) plane or the (n11) A plane as a main surface and the (n ″ 11) A plane as a slope;
In a method of manufacturing a semiconductor laser device provided with at least a p-side first cladding layer and a p-side second cladding layer, an InP substrate is used as the step substrate, and a multiple quantum well in which a well layer is made of InGaAsP is used as the active layer. A well structure active layer is manufactured using a metal organic chemical vapor deposition method so that at least the As composition ratio in the region along the slope of the well layer is higher than the As composition ratio in the region along the main surface. A method for manufacturing a semiconductor laser device, comprising: 8. When growing the p-side first cladding layer, utilizing the plane orientation dependency of the impurity incorporation efficiency,
8. The method of manufacturing a semiconductor laser device according to claim 7, wherein a hole concentration in a region along the slope of the step substrate is higher than a hole concentration in a region along the main surface. 9. When growing the p-side second cladding layer, a region along the slope of the step substrate is formed by utilizing a difference in plane orientation dependence of efficiency of taking in p-type impurities and n-type impurities. 9. The method according to claim 7, wherein a p-type current channel layer is formed, and a region along the main surface is formed as an n-type current block layer.