JP3684519B2 - Semiconductor laser manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention provides a semiconductor laser.TheMore particularly, the present invention relates to a buried layer structure of a buried heterojunction structure (BH) type semiconductor laser and a semiconductor laser characterized by the buried layer manufacturing method.TheIt relates to a manufacturing method.
[0002]
[Prior art]
  In recent years, the development of optical communication technology based on semiconductor lasers and optical fibers has been remarkable, and optical fiber has almost replaced electric cables in mainline communication paths. With the increase, it is predicted that the optical fiber will extend to each home.
[0003]
  Also, in the transmission processing between computers, due to operating speed and mounting problems, development of optical parallel connection using optical fiber instead of the conventional coaxial cable is underway. Realization of such optical parallel connection For this purpose, it is important to reduce the power of the electro-optical conversion element.
[0004]
  A semiconductor laser having a BH (buried heterojunction) structure is generally used as a semiconductor laser used for such optical communication. However, for use on an individual basis, a large amount of BH structure semiconductor is provided at low cost. Establishment of a technique for producing a laser is required, and in order to realize optical parallel connection, realization of a high-efficiency BH structure semiconductor laser operating at a low threshold is required.
[0005]
  An FBH (Flat-Buried-Heterostructure) structure semiconductor laser as a typical example of a conventional BH structure semiconductor laser is illustrated.8Will be described with reference to FIG.
[0006]
  Figure8reference
  In this FBH structure semiconductor laser, an n-type InGaAsP light guide layer 72, an InGaAsP active layer 73, and a p-type InP clad layer 74 are sequentially formed on an n-type InP substrate 71 which also serves as an n-type clad layer. SiO2 after growth by phase growth method)₂Mesa etching is performed using a dielectric mask (not shown) such as a mask.
[0007]
  Next, using this dielectric mask as a selective growth mask, the p-type InP buried layer 75 and the n-type InP buried layer 76 are sequentially grown using the LPE method (liquid phase epitaxial growth method) or the MOVPE method, The dielectric mask is removed, and a p-type InP layer 77 and a p-type InGaAsP contact layer 78 serving as a cladding layer are grown on the entire surface. Finally, a p-side electrode 79 is provided on the p-type InGaAsP contact layer 78, and n An n-side electrode 80 is provided on the back surface of the type InP substrate 71 to complete the FBH structure semiconductor laser.
[0008]
  As another BH structure semiconductor laser, a semiconductor laser provided with a high-resistance buried layer is illustrated.9Will be described with reference to FIG.
  Figure9(A) Reference
  In the case of this BH structure semiconductor laser, first, an n-type InGaAsP light guide layer 72, an InGaAsP active layer 73, a p-type InP cladding layer 74, and a p-type are formed on an n-type InP substrate 71 that also serves as an n-type cladding layer. After sequentially growing the InGaAsP contact layer 78 by the MOVPE method,₂Mesa etching is performed using a dielectric mask (not shown) such as a mask.
[0009]
  Next, using this dielectric mask as a selective growth mask, an Fe-doped InP buried layer 81 is grown using the MOVPE method, and then the dielectric mask is removed. Finally, the p-type InGaAsP contact layer 78 is formed on the p-type InGaAsP contact layer 78. The p-side electrode 79 is provided, and the n-side electrode 80 is provided on the back surface of the n-type InP substrate 71 to complete the BH structure semiconductor laser.
[0010]
[Problems to be solved by the invention]
  Again, figure8reference
  However, in the conventional FBH structure semiconductor laser,aThe leakage current path of the path of the p-type InP clad layer 74 → p-type InP buried layer 75 → n-type InP substrate 71, indicated by the arrow of FIG.bThe leakage current path of the path of the p-type InP layer 77 → the n-type InP buried layer 76 → the p-type InP buried layer 75 → the n-type InP substrate 71, which is indicated by the arrow of FIG. There is a problem of increasing the size.
[0011]
  this house,bWhen a high current is injected into the semiconductor laser, the thyristor structure including the p-type InP layer 77-n-type InP buried layer 76-p-type InP buried layer 75-n-type InP substrate 71 is turned on. On the other hand, in the low current injection region near the threshold current,aThe leakage current path becomes the main path, which hinders the low threshold current.
[0012]
  thisaIn order to reduce the leakage current due to the leakage current path, the junction portion between the p-type InP cladding layer 74 and the p-type InP buried layer 75 may be narrowed, but the buried layer is formed using a normal growth method. When formed, it was difficult to grow the p-type InP buried layer 75 with good controllability.
[0013]
  Further, since the n-type InP buried layer 76 is normally located obliquely above the InGaAsP active layer 73,aThe leakage current path is greatly expanded in the p-type InP buried layer 75, and it is difficult to reduce the threshold current also from this point.
[0014]
  Further, when the striped mesa is formed by wet etching, it is easy to form a ridge portion, that is, an overhang portion, on the selective embedding growth mask, so that the surface of the embedding layer can be easily flattened. However, there is a problem that it is inferior to RIE (reactive ion etching) in terms of controllability of etching amount, reproducibility, and possibility of uniform etching in a large area.
[0015]
  In order to solve this problem of wet etching, when ethane-hydrogen RIE is used, in the mesa etching process, a dielectric mask as a mask for selective embedding growth is also etched to some extent. A new problem arises that the controllability of the width is not sufficient.
[0016]
  In order to solve such problems, a dielectric mask having a stripe-shaped opening having a width of about 2.5 μm is provided on an n-type InP substrate, and DH (double heterojunction) is formed on the opening by a selective growth method. It has been proposed to grow striped mesas containing structures (if necessary, see Y. Kondo, Applied Physics Letters, Vol. 62, 1993, p. 1188).
[0017]
  In this case, in order to grow the buried layer without mask, the buried layer is grown by highly doping Se.⁺There is a problem that the type buried layer causes a memory effect, and it is practically difficult to grow the p type buried layer by highly doping Se, which is an n-type impurity.WhenThere is also a problem.
[0018]
  In addition, when the stripe mesa is formed by RIE, it is difficult to grow the buried layer flat because the collar cannot be formed on the selective buried growth mask.WhenThere is a problem.
[0019]
  Figure9(B) Reference
  For example, when the n-type InP substrate 71 is etched by RIE to form a striped mesa and then the buried layer is grown by a normal MOVPE method, the buried layer, that is, the InGaAs layer 82 and the InP layer 83 are flat. The abnormal growth on the selective embedding growth mask 84 occurs.
[0020]
  Figure9(B) is a photomicrograph of a cross-section of a semiconductor laser. In this case, a thin InGaAs layer 82 and an InP layer having different compositions as buried layers so that the growth process can be clearly understood by the contrast. 83 is grown alternately.
[0021]
  In such a case, in order to grow the buried layer flatly, the growth temperature may be increased or the growth rate may be decreased. However, if the growth temperature is increased, impurities are diffused into the active layer during the growth process. In addition, there is a problem in that the mesa change during the temperature rise by the mass transport is promoted and the laser characteristics are deteriorated.
[0022]
  Further, when the growth rate is lowered, there is a problem that the growth time is increased, the productivity is lowered, and the diffusion of impurities is promoted to deteriorate the laser characteristics.
[0023]
  Accordingly, an object of the present invention is to reduce the leakage current in a BH structure semiconductor laser to lower the threshold current, and to form a flat buried layer with good productivity without adversely affecting the laser characteristics. .
[0024]
[Means for Solving the Problems]
  FIG. 1 is an explanatory view of the principle configuration of the present invention, and FIG. 2 is an explanatory view of the growth direction of the buried layer by the method of the present invention. In FIG. 1 and FIG. Means for solving the problem will be described.
  See Fig. 1 (a)
  (1) The present invention relates to a semiconductor laser.In this manufacturing method, at least the active layer 3 and the opposite conductivity type cladding layer 4 are grown on the one-conductivity-type semiconductor substrate 1 having the {100} plane as the main surface, and then the side surface is substantially {011} plane by etching. Next, the stripe-shaped mesa 5 is formed by covering the side surface of the stripe-shaped mesa 5 and the exposed {100} surface of the one-conductivity-type semiconductor substrate 1 by metal organic chemical vapor deposition. The opposite conductivity type layer 6 is grown in such a range that the {011} growth surface in the lateral direction of the substrate does not disappear, and then the opposite conductivity type buried layer is grown in the [100] direction while adding a gas containing chlorine to the growth gas atmosphere. Then, the one-conductivity type buried layer 7 is grown in the [100] direction while adding chlorine-containing gas in the growth gas atmosphere, and further, chlorine is formed on the one-conductivity type buried layer 7 in the growth gas atmosphere. Gas containing Growing opposite conductivity type buried layer 8 in the [100] direction while(Corresponding to the first embodiment).
[0025]
  See Fig. 2 (a)
  Figure 2 (a)After forming the striped mesa 12 whose side surface is in the vicinity of the (011) plane on the (100) plane InP substrate 11, monochloromethane (CH_ThreeThis is a photomicrograph of a cross-section when the buried layer is grown by the MOVPE method to which Cl) is added, and the thin InGaAs layer 13 and InP having different compositions as the buried layer can be seen by the contrast so that the growth direction can be seen by contrast. It can be seen that the layers 14 are grown alternately, and as is apparent from the figure, they are grown substantially parallel to the (100) plane, that is, only in the <100> direction.
[0026]
  Thus, when the side surface of the striped mesa 5 is in the vicinity of the {011} plane, for example, the growth temperature is set to 600 ° C. by adding a gas containing chlorine to the growth gas atmosphere and controlling the growth conditions. By setting the angle to ± 10 °, the growth on the side surface of the striped mesa 5 is suppressed, and the growth occurs only on the exposed {100} plane of the one conductivity type semiconductor substrate 1, that is, only in the [100] direction. By controlling the thickness of the opposite conductivity type layer 6 grown so as to cover the side surface of the striped mesa 5 and the exposed {100} surface of the one conductivity type semiconductor substrate 1, the leakage current path at the time of low current injection is controlled. The width, that is, the lateral distance of the one-conductive type buried layer 7 from the striped mesa 5 can be narrowed, and thus the threshold current can be reduced.
[0027]
  In particular, when an opposite conductivity type layer is further grown on the opposite conductivity type layer 6, the vertical position of the one conductivity type buried layer 7 can be arbitrarily controlled by the thickness of the opposite conductivity type layer. Further, by providing this opposite conductivity type layer, the thickness of the opposite conductivity type base layer of the thyristor structure constituting the leakage current path at the time of high current injection can be increased, so that the turn-on voltage becomes higher. , Leakage current can be reduced.
[0028]
  (2In addition, the present invention provides the above(1)In the above, either monochloromethane or monochloroethane is used as the gas containing chlorine added to the growth gas atmosphere.
[0029]
  As described above, monochloromethane or monochloroethane having one chlorine is preferable as the gas containing chlorine added to the growth gas atmosphere in order to grow the buried layer only in the [100] direction.
[0030]
  Refer to FIG.
  (3Further, according to the present invention, in the semiconductor laser manufacturing method, at least the one-conductivity-type cladding layer 2, the active layer 3, and the opposite-conductivity-type are formed on the one-conductivity-type semiconductor substrate 1 having a {100} plane as a main surface. After the clad layer 4 is selectively grown and the striped mesa 5 is grown, the opposite conductivity type layer 6 is grown on the entire surface by metal organic vapor phase epitaxy, and then a gas containing chlorine in the growth gas atmosphere. The one conductivity type buried layer 7 is grown only in the lateral direction of the stripe-shaped mesa 5 while adding, and the opposite conductivity type buried layer 8 is grown on the entire surface (first step).2Corresponding to the embodiment).
[0031]
  FIG.b)reference
  FIG.b) Shows a cross-sectional structure when stripe-like mesas 12 are formed on an InP substrate 11 and then a thin InGaAs layer 13 and an InP layer 14 are alternately grown by adding a gas containing chlorine in a growth gas atmosphere. As shown schematically, as shown in the figure, the growth hardly occurs on the upper surface of the striped mesa 12 and the exposed surface of the InP substrate 11, and the growth occurs only in the side surface direction of the striped mesa 12.
[0032]
  Therefore, the striped mesa 5 and the flat one-conductive type buried layer 7 can be formed by a simple manufacturing process without using a dielectric mask for etching and selective growth, so that the laser characteristics are made uniform. And productivity is improved.
[0033]
  (4Further, according to the present invention, in the semiconductor laser manufacturing method, at least the one-conductivity-type cladding layer 2, the active layer 3, and the opposite-conductivity-type are formed on the one-conductivity-type semiconductor substrate 1 having a {100} plane as a main surface. After the clad layer 4 is selectively grown and the striped mesa 5 is grown, the opposite conductivity type buried layer or the high resistance is added while adding a gas containing chlorine to the growth gas atmosphere using the metal organic chemical vapor deposition method. After the buried layer is grown only in the lateral direction of the striped mesa 5 and then the one-conductivity-type semiconductor layer is grown on the entire surface, the portion corresponding to the upper portion of the strip-shaped mesa 5 of this one-conductivity-type semiconductor layer is removed. Further, an opposite conductivity type layer is grown on the entire surface (first step)3Corresponding to the embodiment).
[0034]
  Thus, by adding a gas containing chlorine to the growth gas atmosphere, the opposite conductivity type buried layer or the high resistance buried layer can be provided directly only in the side surface direction of the striped mesa 5. When the resistance buried layer is provided, the leakage current can be further reduced.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
  Here, the first embodiment of the present inventionPremiseThe manufacturing process will be described with reference to FIGS.
  See Fig. 3 (a)
  First, on the n-type InP substrate 21 having a (100) plane as a main surface, the thickness is 100 to 300 nm, for example, 150 nm and the impurity concentration is 5.0 × 10 5 by the MOVPE method.¹⁷cm^-3N-type InGaAsP light guide layer 22, emission wavelength is 1.3 μm, thickness is 100 to 200 nm, for example, 100 nm undoped InGaAsP active layer 23, and thickness is 1.5 to 2.0 μm, for example, 1 Impurity concentration is 5.0 × 10 at 5μm¹⁷cm^-3The p-type InP cladding layer 24 is sequentially grown.
[0036]
  Refer to FIG.
  Next, a SiO film having a thickness of 0.3 μm is formed by a CVD method.₂After depositing the film, it is patterned and striped SiO2 with a width of 1.5 μm₂A mask 25 is formed and then this SiO 2₂Using the mask 25 as an etching mask, mesa etching is performed by RIE using an ethane-based gas composed of ethane + hydrogen + a trace amount of oxygen, and the height is, for example, 2.5 μm, and the side surface has a substantially (011) plane stripe. A mesa 26 is formed.
[0037]
  Next, TMI (trimethylindium), PH as source gases_ThreeAnd a MOVPE method using DMZn (dimethyl zinc) as a dopant at a growth temperature of 600 ° C., a thickness of 0.1 to 0.8 μm, for example, 0.3 μm and an impurity concentration of 1.0 × 10¹⁸cm^-3The p-type InP layer 27 is grown on the side surface of the striped mesa 26 and the exposed surface of the n-type InP substrate 21.
[0038]
  Refer to FIG.
  The dopant is then SiH_FourAnd monochloromethane (CH_ThreeCl) is added so that the ratio of TMI to the flow rate, that is, monochloromethane / TMI is 2 to 50, for example, 30 and the thickness is 0.1 to 1.0 μm, for example, 0.4 μm. Concentration is 2.0 × 10¹⁸cm^-3N-type InP buried layer 28 and a thickness of 0.5 to 2.0 μm, for example, 1.5 μm and an impurity concentration of 1.0 × 10¹⁸cm^-3The p-type InP buried layer 29 is sequentially grown to embed the stripe mesa 26.
[0039]
  Refer to FIG.
  Then SiO₂After removing the mask 25, the thickness is 0.5 to 3.0 μm, for example, 1.0 μm and the impurity concentration is 1.0 × 10 6 by the MOVPE method.¹⁸cm^-3P-type InP layer 30 and a thickness of 0.1 to 0.5 μm, for example, 0.3 μm and an impurity concentration of 1.0 × 10¹⁹cm^-3The p-type InGaAsP contact layer 31 is sequentially grown, and finally, a Ti / Pt / Au electrode 32 as a p-side electrode is provided on the p-type InGaAsP contact layer 31, and an n-side electrode is formed on the back surface of the n-type InP substrate 21. An Au · Ge / Au electrode 33 is provided.
[0040]
  See Fig. 4 (e)
  In FIG. 4E, a striped mesa 26 is provided under the same conditions as described above in order to confirm the growth state of the p-type InP layer 27, the n-type InP buried layer 28, and the p-type InP buried layer 29. FIG. 4 is a micrograph of a cross section when an embedded layer is grown on an n-type InP substrate 21, and as in FIG. 2, a thin p is used as an embedded layer to confirm the growth direction by contrast. A type InP layer 34, an InGaAs layer 35, an n-type InP layer 36, and a p-type InP layer 37 are alternately grown.
[0041]
  As can be seen from the figure, when monochloromethane is not included in the growth gas atmosphere, the p-type InP layer 34 and the InGaAs layer 35 extend along the side surface of the striped mesa 26 and the exposed surface of the n-type InP substrate 21. When growing and then adding monochloromethane to the growth gas atmosphere, the n-type InP layer 36, the InGaAs layer 35, and the p-type InP layer 37 are exposed surfaces of the n-type InP substrate 21 (100). It can be seen that it grows only on the surface, that is, only in the <100> direction.
[0042]
  That is, since the growth in the <011> direction is suppressed by adding monochloromethane, the n-type InP buried layer 28 can be grown in a substantially rectangular shape parallel to the (100) plane.
[0043]
  Therefore, in the first embodiment, when the p-type InP layer 27 is grown, the thickness thereof is controlled so that the lateral direction between the striped mesa 26 and the n-type InP buried layer 28 is increased. Can be arbitrarily narrowed, whereby the interval of the leakage current path at the time of low current injection can be narrowed, so that the threshold current can be lowered.
[0044]
  For example, a threshold current as low as 5.0 mA was obtained when the resonator length of the BH structure semiconductor laser fabricated in this way was set to 300 μm and oscillated without an end face coating.
[0045]
  Based on the above, next, the first embodiment of the present invention will be described. In the process of FIG.Before the n-type InP buried layer 28 is grown, the p-type InP buried layer is grown with monochloromethane added in the growth gas atmosphere.
[0046]
  Therefore, in the first embodiment of the present invention,The vertical position of the n-type InP buried layer 28 can be arbitrarily controlled by the thickness of the p-type InP buried layer, and by providing the p-type InP buried layer, a high current injection can be performed. Since the thickness of the p-type base layer of the thyristor structure constituting the leakage current path can be increased, the turn-on voltage is increased and the leakage current can be reduced.
[0047]
  In the first embodiment, the p-type InP buried layer 29 is also grown in an atmosphere to which monochloromethane is added, but the buried layer after the n-type InP buried layer 28 is formed. In this case, it is not always necessary to add monochloromethane, and a normal MOVPE method may be used.
[0048]
  Also, the above1'sIn the embodiment, monochloromethane is used as a gas to be added to the growth gas atmosphere, but monochloroethane (C₂H_FiveCl) may be used, and anyway, a chloride containing one chlorine is desirable.
[0049]
  Further, in order to grow the buried layer only in the <100> direction, it is necessary to control the growth temperature.1'sIn the embodiment, the growth temperature is 600 ° C., but it may be in the range of 600 ° C. ± 10 °.
[0050]
  Next, FIG.And FIG.A second embodiment of the present invention will be described with reference to FIG.
  Figure5(A) Reference
  First, on the n-type InP substrate 51 whose main surface is the (100) plane, a 0.2 μm thick SiO 2 film is formed by CVD.₂After providing the film, a stripe-shaped opening having a width of 2.5 μm is provided by patterning to form SiO 2₂The mask 52 is formed, and then the SiO 2₂By the MOVPE method using the mask 52 as a selective growth mask, the thickness is 500 to 1500 nm, for example, 1000 nm, and the impurity concentration is 5.0 × 10.¹⁷cm^-3An n-type InP buffer layer 53, an emission wavelength of 1.3 μm, an MQW active layer 54 provided with 10 periods of InGaAsP / InGaAs structures having thicknesses of 10 nm and 6 nm, respectively, and a thickness of 500 to 1000 nm, for example, 700 nm Impurity concentration is 5.0 × 10¹⁷cm^-3The p-type InP clad layer 55 is sequentially grown to form a stripe mesa 56 having a height of 1.0 to 2.5 μm, for example, 1.8 μm.
[0051]
  Figure5(B) Reference
  Then, using HF solution, SiO₂After removing the mask 52, TMI, PH as source gas_ThreeAnd a MOVPE method using DMZn as a dopant at a growth temperature of 600 ° C., a thickness of 0.1 to 0.5 μm, for example, 0.4 μm and an impurity concentration of 1.0 × 10¹⁸cm^-3The p-type InP layer 57 is grown on the entire surface.
[0052]
  Figure6(C) Reference
  The dopant is then SiH_FourAnd PCl_ThreeTo the flow rate ratio of TMI, that is, Cl / In is 0.2 to 1.0, for example, PCl so that 0.5._ThreeAnd a growth temperature of 550 to 600, for example, 575 ° C., and an impurity concentration of 2.0 × 10¹⁸cm^-3The n-type InP buried layer 58 is grown only in the side surface direction of the striped mesa 56.
[0053]
  In this case, the important conditions for growing the n-type InP buried layer 58 only in the lateral direction of the striped mesa 56 are the Cl / In ratio and the growth temperature. The flow rate of Cl is increased and the growth temperature is increased. By setting a low value, it is possible to grow crystals only in the lateral direction.
[0054]
  Figure6(D) Reference
  Then PCl_ThreeBy an ordinary MOVPE method in an atmosphere not containing oxygen, the thickness is 0.2 to 1.5 μm, for example, 1.0 μm and the impurity concentration is 1.0 × 10¹⁸cm^-3P-type InP layer 59 and a thickness of 0.1 to 0.5 μm, for example, 0.5 μm and an impurity concentration of 1.0 × 10¹⁹cm^-3The p-type InGaAsP contact layer 60 is sequentially grown, and finally, the p-type InGaAsP contact layer60A Ti / Pt / Au electrode 61 as a p-side electrode is provided thereon, and an Au · Ge / Au electrode 62 is provided as an n-side electrode on the back surface of the n-type InP substrate 51.
[0055]
  In the BH structure semiconductor laser manufactured in this way, the cavity length is 300 μm because the mesa width is uniform, and the threshold current distribution in the 2-inch wafer is 8. A very high uniformity of 0 ± 0.5 mA was exhibited, and a high yield was obtained.
[0056]
  This second2In this embodiment, since the flat buried layer is grown by a maskless and simple manufacturing process, the productivity is improved and a cheaper semiconductor laser can be manufactured.
[0057]
  Then figure7Referring to FIG.3The embodiment will be described.
  Figure7(A) Reference
  First, the above3In exactly the same manner as in the first embodiment, on the n-type InP substrate 51 having the (100) plane as the main surface, a 0.2 μm thick SiO 2 film is formed by CVD.₂After providing the film, a stripe-shaped opening having a width of 2.5 μm is provided by patterning to form SiO 2₂A mask (not shown) is used, and then this SiO₂The thickness is 500 to 1500 nm, for example, 1000 nm and the impurity concentration is 5.0 × 10 5 by the MOVPE method using the mask as a selective growth mask.¹⁷cm^-3An n-type InP buffer layer 53, an emission wavelength of 1.3 μm, an MQW active layer 54 provided with 10 periods of InGaAsP / InGaAs structures having thicknesses of 10 nm and 6 nm, respectively, and a thickness of 500 to 1000 nm, for example, 700 nm Impurity concentration is 5.0 × 10¹⁷cm^-3The p-type InP clad layer 55 is sequentially grown to form a stripe mesa 56 having a height of 1.0 to 2.5 μm, for example, 1.8 μm.
[0058]
  Then, using HF solution, SiO₂After removing the mask, TMI, PH as source gas_ThreeAnd PCl for ferrocene as the Fe dopant_ThreeThe growth temperature is set to 550 to 600, for example, 575 ° C., and the resistance value is 1 × 10 6 by the MOVPE method with the addition of⁸After the Ω · cm Fe-doped InP buried layer 63 is grown only in the lateral direction of the striped mesa, PCl_ThreeBy a normal MOVPE method in an atmosphere not containing oxygen, the thickness on the mesa is 0.1 to 0.5 μm, for example, 0.25 m and the impurity concentration is 1.0 × 10¹⁸cm^-3The n-type InP block layer 64 is grown.
[0059]
  Figure7(B) Reference
  Next, after selectively removing the portion of the n-type InP block layer 64 corresponding to the top of the striped mesa, an impurity having a thickness of 0.2 to 1.5 μm, for example, 1.0 μm, is formed by a normal MOVPE method. Concentration is 1.0 × 10¹⁸cm^-3P-type InP layer 59 and a thickness of 0.1 to 0.5 μm, for example, 0.5 μm and an impurity concentration of 1.0 × 10¹⁹cm^-3The p-type InGaAsP contact layer 60 is sequentially grown, and finally, the p-type InGaAsP contact layer60A Ti / Pt / Au electrode 61 as a p-side electrode is provided thereon, and an Au · Ge / Au electrode 62 is provided as an n-side electrode on the back surface of the n-type InP substrate 51.
[0060]
  This first3In this embodiment, since the flat Fe-doped InP buried layer 63 is grown only in the lateral direction of the striped mesa by a maskless and simple manufacturing process, the leakage current can be further reduced and the laser can be reduced. The characteristics are improved and an inexpensive semiconductor laser can be manufactured.
[0061]
  Note that the above3The Fe-doped InP buried layer 63 in this embodiment may be replaced with a p-type InP buried layer.
[0062]
  Also, the above2And the second3In the embodiment, the MQW active layer is used as the active layer.1'sAs in the embodiment, an InGaAsP active layer may be used, and a light guide layer may be provided.
[0063]
  Conversely, the above1'sThe active layer in the embodiment is an InGaAsP active layer.2And the second3As in the first embodiment, an MQW active layer may be used, and a light guide layer may not be provided, or may be provided on both sides of the active layer.
[0064]
  Also, the above1'sIn the embodiment, since the n-type InP substrate also serves as the n-type cladding layer, the n-type InGaAsP light guide layer is directly provided on the n-type InP substrate, but the n-type InP buffer is provided on the n-type InP substrate. The n-type InGaAsP light guide layer may be provided through the layer, and in this case, the n-type InP buffer layer functions as an n-type cladding layer.
[0065]
  In each of the above embodiments, an n-type InP substrate is used as a substrate. However, a p-type InP substrate may be used, and in that case, it is described in each embodiment. It is necessary to reverse the conductivity type of each layer.
[0066]
  In each of the above embodiments, most of the buried layer is formed of InP, but is not limited to InP, and a semiconductor layer generally represented by InGaAlAsP may be used.
[0067]
  Further, in each of the above embodiments, the semiconductor laser for optical communication is a main target.NoFor this reason, the InGaAsP / InP system has been described, but the present invention is not limited to the InGaAsP / InP system, but also covers the GaAs / AlGaAs system.
[0068]
【The invention's effect】
  According to the present invention, when the buried layer of the BH structure semiconductor laser is formed, the isotropic growth, the growth in the direction perpendicular to the substrate, or the lateral direction of the striped mesa is controlled by controlling the manufacturing conditions. By controlling the growth of semiconductors and combining them, semiconductor lasers with low leakage current and low threshold current can be manufactured, and the yield of semiconductor lasers with a flat buried layer surface and uniform device characteristics Since it can be manufactured well, it contributes to further development and spread of optical communication technology.
[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 growth direction of a buried layer according to the method of the present invention.
FIG. 3 shows the first embodiment of the present invention.Up to the middle of the manufacturing processIt is explanatory drawing.
FIG. 4 shows the first embodiment of the present invention.Fig. 3 and subsequent drawings of the premise manufacturing processIt is explanatory drawing.
[Figure 5]It is explanatory drawing of the manufacturing process to the middle of the 2nd Embodiment of this invention.
[Fig. 6]It is explanatory drawing of the manufacturing process after FIG. 5 of the 2nd Embodiment of this invention.
[Fig. 7]It is explanatory drawing of the manufacturing process of the 3rd Embodiment of this invention.
[Fig. 8]It is explanatory drawing of the conventional FBH structure semiconductor laser.
FIG. 9It is explanatory drawing of the conventional BH structure semiconductor laser.
[Explanation of symbols]
  1 One conductivity type semiconductor substrate
  2 One conductivity type cladding layer
  3 Active layer
  4 Opposite conductivity type cladding layer
  5 Striped mesa
  6 opposite conductivity type layer
  7 One conductivity type buried layer
  8 Reverse conductivity type buried layer
  9 electrodes
  10 electrodes
  11 InP substrate
  12 Striped mesa
  13 InGaAs layer
  14 InP layer
  21  n-type InP substrate
  22 n-type InGaAsP light guide layer
  23 InGaAsP active layer
  24 p-type InP cladding layer
  25 SiO₂mask
  26 Striped mesa
  27 p-type InP layer
  28 n-type InP buried layer
  29 p-type InP buried layer
  30 p-type InP layer
  31 p-type InGaAsP contact layer
  32 Ti / Pt / Au electrode
  33 Au / Ge / Au electrode
  34 p-type InP layer
  35 InGaAs layer
  36 n-type InP layer
  37 p-type InP layer
  51  n-type InP substrate
  52 SiO₂mask
  53 n-type InP buffer layer
  54 MQW active layer
  55 p-type InP cladding layer
  56 Striped Mesa
  57 p-type InP layer
  58 n-type InP buried layer
  59 p-type InP layer
  60 p-type InGaAsP contact layer
  61 Ti / Pt / Au electrode
  62 Au / Ge / Au electrode
  63 Fe-doped InP buried layer
  64 n-type InP block layer
  71 n-type InP substrate
  72 n-type InGaAsP light guide layer
  73 InGaAsP active layer
  74 p-type InP cladding layer
  75 p-type InP buried layer
  76 n-type InP buried layer
  77 p-type InP layer
  78 p-type InGaAsP contact layer
  79 p-side electrode
  80 n-side electrode
  81 Fe-doped InP buried layer
  82 InGaAs layer
  83 InP layer
  84 Mask for selective embedding growth

Claims (4)

After growing at least the active layer and the opposite conductivity type cladding layer on the one-conductivity-type semiconductor substrate having the {100} plane as the main surface, a striped mesa having substantially {011} planes is formed by etching. Next, by using metalorganic vapor phase epitaxy, the stripe-shaped mesa side surface and the exposed {100} surface of the one-conductivity-type semiconductor substrate are covered, and the {011} growth surface in the side surface direction of the stripe-shaped mesa is After growing the opposite conductivity type layer within the range that does not disappear, the opposite conductivity type buried layer is grown in the [100] direction while adding a gas containing chlorine in the growth gas atmosphere, and then chlorine is added in the growth gas atmosphere. The one conductivity type buried layer is grown in the [100] direction while adding a gas containing oxygen, and further, the opposite conductivity type buried layer is added on the one conductivity type buried layer while adding a gas containing chlorine in the growth gas atmosphere. Included The method of manufacturing a semiconductor laser, characterized in that growing the [100] direction. 2. The method of manufacturing a semiconductor laser according to claim 1 , wherein either monochloromethane or monochloroethane is used as the gas containing chlorine added to the growth gas atmosphere.   A striped mesa is formed by selectively growing at least a one-conductivity-type clad layer, an active layer, and an opposite-conductivity-type clad layer on a one-conductivity-type semiconductor substrate having a {100} plane as a main surface. Using a vapor phase growth method, an opposite conductivity type layer is grown on the entire surface, and then one conductivity type buried layer is grown only in the lateral direction of the striped mesa while adding a gas containing chlorine to the growth gas atmosphere. And further growing an opposite conductivity type layer on the entire surface.   A striped mesa is formed by selectively growing at least a one-conductivity-type clad layer, an active layer, and an opposite-conductivity-type clad layer on a one-conductivity-type semiconductor substrate having a {100} plane as a main surface. Using a vapor phase growth method, an opposite conductivity type buried layer or a high resistance buried layer is grown only in the lateral direction of the striped mesa while adding a gas containing chlorine to the growth gas atmosphere, A semiconductor laser comprising: growing one conductivity type semiconductor layer; removing a portion of the one conductivity type semiconductor layer corresponding to the upper portion of the striped mesa; and further growing an opposite conductivity type layer on the entire surface. Manufacturing method.

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