JP2006324552A - Red semiconductor laser element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-hetero structured red semiconductor laser element which has superior linearity in the optical output vs. current characteristic, while having high output power, and to provide a method of manufacturing the same. <P>SOLUTION: The red semiconductor laser element 10 comprises at least a first conductivity-type AlGaInP cladding layer 13, a GaInP active layer 17, and a second conductivity-type AlGaInP cladding layer 18, sequentially stacked on a GaAs semiconductor substrate 11. The semiconductor laser element also has a ridge 21, consisting of a ridged second conductivity-type AlGaInP clad layer 18', a second conductivity-type GaInP contact layer 19', and a second conductivity-type GaAs capping layer 20', stacked sequentially on the second conductivity-type AlGaInP clad layer 18. The side surfaces of the ridge 21 and the surface of the second conductivity-type AlGaInP clad layer 18 are covered by a first conductivity-type AlInP layer 23, a first conductivity-type GaAs current blocking layer 24, and a GaInP layer 25, stacked sequentially thereon. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a red semiconductor laser element for use as a light source for optical information terminal equipment such as a DVD-R and a method for manufacturing the same, and particularly to a double having excellent linearity of optical output-current characteristics while having high output. The present invention relates to a red semiconductor laser element having a terror structure and a method for manufacturing the same.

  Semiconductor laser elements have excellent characteristics such as small size, light weight, high efficiency, high response speed, and wide wavelength selectivity, and therefore are actively being introduced into the fields of optical discs, optical communications, laser printers, etc. In particular, for writing on a high-density optical disk such as a DVD-R, an AlGaInP-based high-power red semiconductor laser element having an oscillation wavelength region of 650 nm is used.

  As an example of such an AlGaInP red semiconductor laser element, for example, a semiconductor laser element having a double hetero structure as shown in FIG. 4 is known (see, for example, Patent Document 1). The semiconductor laser element 50 is usually formed by a crystal growth method such as MOCVD (Metal Organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), or HVPE (Hydride Vapor Phase Epitaxy). It is created by the following process.

  That is, on the GaAs substrate 51, a first conductivity type GaInP buffer layer 52, a first conductivity type AlGaInP cladding layer 53, an undoped AlGaInP light guide layer 54, a GaInP strained quantum well (TQW) active layer 55, and an undoped AlGaInP light guide layer 56. Then, the second conductivity type AlGaInP clad layer 57 and the second conductivity type GaInP contact layer 58 are sequentially epitaxially laminated, and a ridge (waveguide) portion 60 is formed on the second conductivity type AlGaInP clad layer 57 by etching. Of these, the portion composed of the undoped AlGaInP light guide layer 54, the GaInP strained quantum well (TQW) active layer 55, and the undoped AlGaInP light guide layer 56 is generally referred to as a GaInP active layer.

  Thereafter, the first conductivity type GaAs current block layer 61 is embedded and grown in the portion removed by etching, and the second conductivity type GaAs is formed on the first conductivity type GaAs current block layer 61 and the second conductivity type GaInP contact layer 58. A cap layer 59 is laminated, and a second conductive side electrode 62 is provided on the surface of the second conductivity type GaAs cap layer 59, and a first conductive side electrode 63 is provided on the bottom of the GaAs substrate 51. Yes.

  This semiconductor laser device 50 is good at the interface between the second conductivity type AlGaInP cladding layer 57 and the first conductivity type GaAs current blocking layer 61 and at the interface between the second conductivity type GaInP contact layer 58 and the second conductivity type GaAs cap layer 59. It has been found that no crystallinity can be obtained. This is because the group V element is As (arsenic) different from P on the second conductivity type AlGaInP cladding layer 57 made of a group III-V compound semiconductor whose group V element is P (phosphorus). In order to form the first conductive type GaAs current blocking layer 61 made of a compound semiconductor in a separate process after etching without continuously forming the second conductive type GaAs current blocking layer 61, and a second group consisting of a III-V group compound semiconductor in which the V group element is P. This is because the second conductivity type GaAs cap layer 59 made of a III-V group compound semiconductor whose group V element is As is formed discontinuously on the conductivity type GaInP contact layer 58. Thus, when the crystallinity at the interface is impaired, the reactive current that does not contribute to the laser emission increases, resulting in a problem that the yield of the device is reduced.

  On the other hand, a compound semiconductor laser device that solves such problems of the prior art is disclosed in Patent Document 2 below. Here, a semiconductor laser device 70 disclosed in the following Patent Document 2 will be described with reference to FIG. 5. In FIG. 5, the same reference numerals are given to the same components as those of the semiconductor laser device 50 shown in FIG. A detailed description thereof will be omitted.

The semiconductor laser element 70 disclosed in the following Patent Document 2 is different in configuration from the semiconductor laser element 50 described above.
(A) By introducing the second conductivity type GaInP layer 65 between the second conductivity type AlGaInP cladding layer 57 and the first conductivity type GaAs current blocking layer 61, the group V element of the second conductivity type AlGaInP cladding layer 57 The group V element of the introduced second conductivity type GaInP layer 65 is made of the same P, and the group III element of the second conductivity type AlGaInP cladding layer 57 and the group III element of the introduced second conductivity type GaInP layer 65 Keeping the crystallinity between the two good by making the group elements consist of the same Ga,
(B) By introducing the second conductivity type GaInP layer 66 between the second conductivity type GaInP contact layer 58 and the second conductivity type GaAs cap layer 59, the V group element of the second conductivity type GaInP contact layer 58 and The introduced group V element of the second conductivity type GaInP layer 66 is made of the same P, and the group III element of the second conductivity type GaAs cap layer 59 and the introduced group III element of the second conductivity type GaInP layer 66 are made III. The group element is made of the same Ga, and in addition to this, the introduced second conductivity type GaInP layer 66 and the second conductivity type GaAs cap layer 59 are formed by a continuous process, so that the crystallinity between the two is improved. Keep
(C) The second conductivity type GaInP layer 67 and the second conductivity type GaInP layer 66 are interposed between the first conductivity type GaAs current blocking layer 61 and the second conductivity type GaAs cap layer 59, thereby providing a first conductivity type GaAs current. The block layer 61 and the second conductivity type GaInP layer 67 are formed by a continuous process, and the second conductivity type GaInP layer 66 and the second conductivity type GaAs cap layer 59 are also formed by a continuous process, whereby the second conductivity type GaInP layer is formed. The crystallinity of the layer 66 and the second conductivity type GaAs cap layer 59 is improved.
Japanese Patent Laid-Open No. 05-041560 (claims, paragraphs [0014] to [0019], FIGS. 1 to 4) JP 07-027033 (Claims, paragraphs [0004] to [0005], [0014] to [0015], FIG. 5)

  In the semiconductor laser device 70 disclosed in Patent Document 2, the second conductivity type GaInP layer 65 is epitaxially grown between the second conductivity type AlGaInP cladding layer 57 and the first conductivity type GaAs current blocking layer 61. The crystallinity of the first conductivity type GaAs current block layer 61 is increased (see (a) above), and the second conductivity type GaInP layer is further interposed between the first conductivity type GaAs current block layer 61 and the second conductivity type GaAs cap layer 59. 67 and the second conductivity type GaInP layer 66 are interposed, and the first conductivity type GaAs current blocking layer 61 and the second conductivity type GaInP layer 67 are formed by a continuous process, and the second conductivity type GaInP layer 66 and the second conductivity type GaInP layer 66 By forming the conductive type GaAs cap layer 59 in a continuous process, the second conductive type GaInP layer 66 and the second conductive type GaAs cap layer 59 are formed. The crystallinity of the gate layer 59 is improved (see (c) above), but the introduced second conductivity type GaInP layers 65, 66 and 67 are the same as the first conductivity type GaAs current blocking layer 61 and the lattice. It is necessary to use a matching composition.

  However, in the composition of the second conductivity type GaInP for lattice matching with the first conductivity type GaAs current blocking layer 61, the far field pattern is disturbed due to insufficient absorption of the laser beam, and an ideal waveform cannot be obtained. Therefore, there is a problem that defects such as ripples occur.

  Accordingly, the present invention has been made to solve such problems, and in particular, protects a current blocking layer having low crystallinity so as to increase the light absorption of laser light, and a high-output red semiconductor with a small kink. It is an object of the present invention to provide a laser element and a manufacturing method thereof.

  The first object of the present invention can be achieved by the following configuration. That is, according to the first aspect of the present invention, at least a first conductivity type AlGaInP cladding layer, a GaInP active layer, and a second conductivity type AlGaInP cladding layer are sequentially laminated on a GaAs semiconductor substrate, and the second conductivity type AlGaInP In the red semiconductor laser device having a ridge portion comprising a ridge-shaped second conductivity type AlGaInP clad layer, a second conductivity type GaInP contact layer, and a second conductivity type GaAs cap layer sequentially stacked on the clad layer, the ridge portion The side surface and the surface of the second conductivity type AlGaInP clad layer are covered with a first conductivity type AlInP layer, a first conductivity type GaAs current blocking layer and a GaInP layer which are sequentially stacked.

The invention according to claim 2 is the red semiconductor laser device according to claim 1, wherein the GaInP layer has a composition of Ga _x In _(1-x) P (where x = 0.42 to 0.48). And is in a lattice mismatch state with the first conductivity type GaAs current blocking layer. At this time, if it is out of the range of x = 0.42 to 0.48, the absorption of the laser beam is not sufficient, so that an ideal waveform cannot be obtained and defects such as ripples are generated, which is not preferable.

  According to a third aspect of the present invention, in the red semiconductor laser device according to the first or second aspect, support portions having the same layer structure as the ridge portion are provided on both sides of the ridge portion, and the surface of the support portion and The side surface facing the ridge portion is also covered with a first conductivity type AlInP layer, a first conductivity type GaAs current blocking layer, and a GaInP layer sequentially.

Furthermore, the second object of the present invention can be achieved by the following production method. That is, the invention of a method for manufacturing a red semiconductor laser device according to claim 4 is characterized by having at least the following steps (1) to (3).
(1) At least a first conductivity type AlGaInP cladding layer, a GaInP active layer, a second conductivity type AlGaInP cladding layer, a second conductivity type GaInP layer, and a second conductivity type GaAs layer are sequentially and sequentially stacked on a semiconductor substrate. To form a red double hetero laminated structure,
(2) A ridge portion comprising a second conductivity type AlGaInP clad layer, a second conductivity type GaInP contact layer, and a second conductivity type GaAs cap layer by etching in a ridge shape partway through the second conductivity type AlGaInP clad layer. Further,
(3) The first conductivity type AlInP layer, the first conductivity type GaAs current blocking layer, and the GaInP layer are successively coated on the side surface of the ridge portion and the surface of the second conductivity type AlGaInP cladding layer.

According to a fifth aspect of the present invention, in the method for manufacturing a red semiconductor laser device according to the fourth aspect, the GaInP layer has a composition of Ga _x In _(1-x) P (where x = 0.42 to _0). 48), and in a lattice mismatch with the first conductivity type GaAs current blocking layer.

  According to a sixth aspect of the present invention, in the method for manufacturing a red semiconductor laser device according to the fourth or fifth aspect, support portions are formed on both sides of the ridge portion at the same time in the step (2), and the (3) In the step, the first conductive type AlInP layer, the first conductive type GaAs current blocking layer, and the GaInP layer are successively coated on the surface of the support portion and the side surface facing the ridge portion at the same time. .

  By providing the above configuration, the present invention has the following excellent effects. That is, according to the first aspect of the present invention, the GaInP layer provided on the first conductivity type GaAs current blocking layer efficiently absorbs light in the wavelength band where the red semiconductor laser element develops color and has low crystallinity. Since the GaAs current blocking layer can be protected from being eroded by chemicals, a high output type red semiconductor laser device having a good manufacturing yield and good characteristics such as kink can be obtained.

  Further, according to the invention of claim 2, a red semiconductor laser element capable of remarkably exhibiting the effect of the invention of claim 1 is obtained.

  According to the invention of claim 3, since the support portion also functions as a protection member for the ridge portion, the ridge portion is less damaged at the time of manufacturing, and a red semiconductor laser device having a good manufacturing yield can be obtained. In addition, according to the invention of claim 3, since the support portion has a surface area larger than that of the ridge portion, the red semiconductor laser element can be attached to the submount by the junction down method, so that the cooling efficiency is improved. To be very reliable.

  Furthermore, according to the invention of the method for manufacturing a red semiconductor laser device according to claims 4 to 6, the red semiconductor laser device having the effects of the inventions of claims 1 to 3 can be easily manufactured.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the embodiment and FIGS. 1 and 2. The embodiment described below is a red color for embodying the technical idea of the present invention. The semiconductor laser device and the manufacturing method thereof are illustrated, and the present invention is not intended to be specified in this embodiment. The present invention is not limited to the technical ideas shown in the claims. It can be equally applied to those that have been changed. 1 is a cross-sectional view of the red semiconductor laser device in the middle of the manufacturing process according to the embodiment, and FIG. 2 is a cross-sectional view of the red semiconductor laser device before the electrode is provided.

As the semiconductor laser device according to Example 1, an AlGaInP red semiconductor laser device 10 having a first conductivity type of n-type was manufactured through the following steps (1) to (3).
(1) First epitaxial growth step,
First, as shown in FIG. 1, an n-type GaInP buffer layer 12, an n-type AlGaInP first cladding layer 13, an undoped AlGaInP light guide layer 14, and a strained quantum well (TQW) are formed on a GaAs substrate 11 by using a low pressure MOCVD method. A red double layer is formed by sequentially laminating a GaInP active layer 17 composed of an active layer 15 and an undoped AlGaInP light guide layer 16, a p-type AlGaInP cladding layer 18, a p-type GaInP contact layer 19 and a p-type GaAs cap layer 20. A layered structure for hetero was formed. In the above example, the n-type semiconductor layer was manufactured by Si doping, and the p-type semiconductor layer was manufactured by Zn doping.
(2) etching process then depositing a SiO ₂ film, processing the SiO ₂ film by photolithography by etching up to the middle of the p-type AlGaInP cladding layer 18 as a mask, the surface of the p-type AlGaInP cladding layer 18 Further, a ridge portion 21 composed of a ridge-shaped p-type AlGaInP cladding layer 18 ′ having a width of about 2.50 μm, an n-type GaInP contact layer 19 ′ and an n-type GaAs cap layer 20 ′, and supports on both sides of the ridge portion 21. Part 22 was formed. The formation of the support portion 22 is optional, but it acts as a protective member for the thin ridge portion 21 during manufacture, and the resulting red semiconductor laser element is held by a holding body via a submount to provide cooling efficiency. This is useful when applying the so-called junction down method, so it is better to provide it.
(3) Thereafter, as shown in FIG. 2, the n-type Al _x In _(1-x) P having a film thickness of 0.45 μm is successively formed on the surface of the support portion 22 and the portion removed by the low pressure MOCVD method again. An n-type AlInP layer 23 (x = 0.51), an n-type GaAs current blocking layer 24 having a thickness of 0.55 μm, and a GaInP layer 25 made of Ga _x In _(1-x) P having a thickness of 0.35 μm. (However, x = 0.44) was continuously covered, and the red semiconductor laser device 10 before electrode formation shown in FIG. 2 was produced.

  Subsequently, an electrode was formed on the front surface of the p-type GaAs cap layer 20 ′ of the ridge portion 22 and the back surface of the GaAs substrate 11 by a conventional method to manufacture a red semiconductor laser device. The obtained red semiconductor laser device was a red semiconductor laser device having an oscillation wavelength of 655 nm, excellent linearity from a low output region to a high output region, and a small kink.

In Example 1, a GaInP layer 25 having a composition of Ga _x In _(1-x) P (x = 0.51) was used, but x = 0.42 to 0.48. If so, the same effect is produced. The thickness of the GaInP layer 25 needs to be 0.50 μm or less. If the thickness of the GaInP layer 25 exceeds 0.50 μm, the GaInP layer 25 is in a lattice mismatch with the n-type GaAs current blocking layer 19, so that the distortion becomes too large and the wafer becomes clouded. Although there is no critical limit to the lower limit of the film thickness of the GaInP layer 25, if the GaInP layer 25 is not present, not only the kink is increased, but also chemicals after the formation of the n-type GaAs current blocking layer 24 having low crystallinity. Since the n-type GaAs current blocking layer 24 is eroded by the process of, it is essential to provide the GaInP layer 25.

  Further, the red semiconductor laser device 10 obtained in Example 1 has a wavelength of 655 nm that is useful for writing on a high-density optical disk such as a DVD-R, but is a compact that is still widely used as an optical recording medium. A laser having an oscillation wavelength of 780 nm is required to be able to be used for a disc (CD), a recordable compact disc (CD-R), a mini disc (MD), and the like. Further, in order to realize simplification and miniaturization of the optical pickup, a two-wavelength laser device that can emit both wavelengths of 650 nm and 780 nm from one package is effective. A specific example of a two-wavelength semiconductor laser element in which the red semiconductor laser element obtained in Example 1 and a known laser element with an oscillation wavelength of 780 nm are integrated is shown in FIG. 3 as a reference example.

  The two-wavelength semiconductor laser element 30 includes a red semiconductor laser element 31 having an oscillation wavelength of 655 nm on the DVD side and an infrared semiconductor laser element 40 having an oscillation wavelength of 780 nm on the CD side. Among these, the red semiconductor laser element 31 has the same configuration as that of the red semiconductor laser element 10 manufactured according to Example 1, and the same reference numerals as those of the red semiconductor laser element 10 are given to the specific configuration. Description is omitted. The CD-side infrared semiconductor laser device 40 having an oscillation wavelength of 780 nm has a well-known configuration. On the GaAs substrate 11, an n-type GAlGaAs cladding layer 41, an AlGaAs active layer 42, and a p-type AlGaAs cladding layer 43 are sequentially formed. A ridge portion 45 comprising a ridge-shaped p-type AlGaAs cladding layer 43 ′ and a p-type GaAs contact layer 44 is provided on the surface of the p-type AlGaAs cladding layer 43, and a side portion of the ridge portion 45 and the p-type AlGaAs cladding. An n-type GaAs current blocking layer 47 is provided on the surface of the layer 43 via an n-type AlGaAs layer 46, and the p-type GaAs contact layer 44 and the n-type GaAs current blocking layer 47 are covered with a p-type GaAs layer 48. It has a buried configuration. The two-wavelength semiconductor laser device 30 having such a configuration can be held by a holding body via a submount (not shown) by a junction down method to increase the cooling efficiency. A wavelength semiconductor laser element is obtained.

1 is a diagram showing a structure in the middle of manufacturing a semiconductor laser device according to Example 1. FIG. 1 is a diagram illustrating a structure of a semiconductor laser device before electrode formation of a semiconductor laser device according to Example 1. FIG. It is a figure which shows the structure before electrode formation of the dual wavelength semiconductor laser element of a reference example. It is a figure which shows the structure of the AlGaInP type red semiconductor laser element of a prior art example. It is a figure which shows the structure of the AlGaInP type red semiconductor laser element of another prior art example.

Explanation of symbols

11 GaAs substrate 12 n-type GaInP buffer layer 13 n-type AlGaInP first cladding layer 14 undoped AlGaInP light guide layer 15 strained quantum well (TQW) active layer 16 undoped AlGaInP light guide layer 17 GaInP active layer 18 p-type AlGaInP cladding layer 19 p Type GaInP contact layer 20 p type GaAs cap layer 21 ridge portion 22 support portion 23 n type AlInP layer 24 n type GaAs current blocking layer 25 GaInP layer 30 two-wavelength semiconductor laser device

Claims (6)

  At least a first conductivity type AlGaInP cladding layer, a GaInP active layer, and a second conductivity type AlGaInP cladding layer are sequentially stacked on a GaAs semiconductor substrate, and a ridge-shaped second conductivity is sequentially stacked on the second conductivity type AlGaInP cladding layer. In a red semiconductor laser device having a ridge portion comprising a type AlGaInP cladding layer, a second conductivity type GaInP contact layer, and a second conductivity type GaAs cap layer, the side surface of the ridge portion and the surface of the second conductivity type AlGaInP cladding layer are sequentially laminated. A red semiconductor laser device, which is covered with the first conductivity type AlInP layer, the first conductivity type GaAs current blocking layer, and the GaInP layer. The GaInP layer has a composition of Ga _x In _(1-x) P (where x = 0.42 to 0.48) and is in a lattice mismatch state with the first conductivity type GaAs current blocking layer. The red semiconductor laser device according to claim 1.   Support portions having the same layer structure as the ridge portion are provided on both sides of the ridge portion, and the first conductive type AlInP layer and the first conductive type GaAs current are provided on the surface of the support portion and the side surface facing the ridge portion. The red semiconductor laser device according to claim 1, wherein the red semiconductor laser device is sequentially covered with a block layer and a GaInP layer. A method for manufacturing a red semiconductor laser device, comprising at least the following steps (1) to (3):
(1) At least a first conductivity type AlGaInP cladding layer, a GaInP active layer, a second conductivity type AlGaInP cladding layer, a second conductivity type GaInP layer, and a second conductivity type GaAs layer are sequentially and sequentially stacked on a semiconductor substrate. To form a red double hetero laminated structure,
(2) A ridge portion comprising a second conductivity type AlGaInP clad layer, a second conductivity type GaInP contact layer, and a second conductivity type GaAs cap layer by etching in a ridge shape partway through the second conductivity type AlGaInP clad layer. Further,
(3) The first conductivity type AlInP layer, the first conductivity type GaAs current blocking layer, and the GaInP layer are successively coated on the side surface of the ridge portion and the surface of the second conductivity type AlGaInP cladding layer. The GaInP layer has a composition of Ga _x In _(1-x) P (where x = 0.42 to 0.48) and is in a lattice mismatch state with the first conductivity type GaAs current blocking layer. A method for manufacturing a red semiconductor laser device according to claim 5. In the step (2), support portions are formed on both sides of the ridge portion at the same time. In the step (3), the surface of the support portion and the side surface facing the ridge portion are also sequentially formed in the first conductivity type AlInP. 6. The method of manufacturing a red semiconductor laser device according to claim 4, wherein the layer, the first conductivity type GaAs current blocking layer, and the GaInP layer are continuously coated.

Images