JP2008294322A - Multi-wavelength laser, optical pickup device and optical disk device - Google Patents

Abstract

A multi-wavelength laser capable of miniaturizing a mounted device is provided.
A laser structure LD1 formed on a GaN substrate 10 by crystal growth on the GaN substrate 10 and formed by crystal growth on a substrate (GaAs substrate 130) different from the GaN substrate 10. On the GaN substrate 10, there are provided laser structure portions LD2 and LD3 disposed through a laminated structure including an insulating layer 11, an adhesive layer 12, and an electrode layer 13. In other words, since the laser structure LD1 and the laser structures LD2 and LD3 are formed by crystal growth on different substrates, the wavelength difference between the laser structure LD1 and the laser structures LD2 and LD3 is increased. Can do. Further, since the laser structure portions LD1, LD2, and LD3 are provided on the common GaN substrate 10, the interval between the optical axes of the laser beams emitted from the laser structure portions LD1, LD2, and LD3 is sufficiently narrowed. be able to.
[Selection] Figure 2

Description

  The present invention relates to a multi-wavelength laser including a plurality of laser structures, and an optical pickup device and an optical disc apparatus including the multi-wavelength laser.

In recent years, in the field of semiconductor lasers (LDs), multi-wavelength lasers having a plurality of laser structures having different emission wavelengths on the same substrate (or base) have been actively developed. For example, in Patent Document 1, a laser having a plurality of wavelengths is formed by forming a plurality of laser structures having different spacer layer thicknesses on an active layer by crystal growth on the same substrate made of GaAs (gallium arsenide). Is going to be able to get
JP 2006-73965 A

  However, in the multi-wavelength laser described in Patent Document 1, since each laser structure is formed by crystal growth on the same substrate, the wavelength difference between the laser structures cannot be increased so much. Therefore, the multi-wavelength laser described in Patent Document 1 is used for an application that requires a plurality of laser beams having a very large wavelength difference (for example, an optical disc apparatus that requires three laser beams in the 700 nm band, the 600 nm band, and the 400 nm band). It cannot be applied to a light source.

  Therefore, in order to increase the wavelength difference between the laser structure portions, it is conceivable that laser chips each having the laser structure portions formed on separate substrates are arranged side by side on a support base (heat sink). However, in this case, it is not easy to narrow the interval between the optical axes of the laser beams emitted from the laser structure portions to, for example, about several tens of μm. Therefore, when each laser chip is simply arranged side by side on the support base, it is necessary to provide an optical system for each laser chip when inputting laser light emitted from each laser structure to another device. Therefore, the device on which the multi-wavelength laser is mounted is increased in size.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a multi-wavelength laser that enables downsizing of a mounted device, and an optical pickup device and an optical disc apparatus including the multi-wavelength laser. It is in.

  The multi-wavelength laser of the present invention is formed by crystal growth on a GaN substrate, a first laser structure formed by crystal growth on the GaN substrate, and a crystal growth on a substrate different from the GaN substrate, and on the GaN substrate. And one or a plurality of second laser structures disposed on the surface.

  The optical pickup device of the present invention includes a light source and an optical system provided between a region where the optical disk is placed and the light source. The light source includes the multi-wavelength laser.

  An optical disc apparatus according to the present invention includes the optical pickup device and an information processing unit that transmits input information to the optical pickup device or receives information written on an optical disc from the optical pickup device. is there.

  In the multi-wavelength laser, the optical pickup device, and the optical disk device of the present invention, the first laser structure formed on the GaN substrate by crystal growth on the GaN substrate and the substrate different from the GaN substrate. And one or more second laser structures formed by crystal growth. That is, since at least two laser structure parts are formed by crystal growth on different substrates, the wavelength difference between the laser structure parts can be increased. In addition, since each laser structure is provided on a common GaN substrate, each laser structure is more effective than the case where laser chips each formed on a separate substrate are arranged side by side on a support base or the like. The interval between the optical axes of the laser beams emitted from the structure portion can be sufficiently narrowed.

  According to the multi-wavelength laser, the optical pickup device, and the optical disk device of the present invention, the first laser structure formed on the GaN substrate by crystal growth on the GaN substrate and the substrate different from the GaN substrate. Since one or a plurality of second laser structure portions are formed by crystal growth in the laser, not only can the wavelength difference between the laser structure portions be increased, but also the laser emitted from each laser structure portion The interval between the optical axes of light can be made sufficiently narrow. As a result, the laser light emitted from each laser structure can be propagated by a single optical system, so that the mounted devices (optical pickup device and optical disk device) can be reduced in size.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a top view of a surface emitting semiconductor laser 1 according to the first embodiment of the present invention, and FIG. 2 shows a cross-sectional configuration of the semiconductor laser 1 in FIG. is there. 1 and 2 are schematically shown and are different from actual dimensions and shapes.

  This semiconductor laser 1 has a laser structure LD1 capable of emitting light having a wavelength of around 400 nm (for example, 405 nm) on a GaN substrate 10 and emitting light in a 700 nm band (for example, 780 nm) for CD. A laser structure LD2 capable of emitting light in the stacking direction and a laser structure LD3 capable of emitting light in a 600 nm band (for example, 650 nm) for DVD in the stacking direction are provided. Therefore, this semiconductor laser 1 has a function as a three-wavelength laser.

  In the semiconductor laser 1, the laser structure portions LD1, LD2, and LD3 are formed on the GaN substrate 10 so that the distance between the optical axes of the laser beams emitted from the laser structure portions LD1, LD2, and LD3 is as close as possible to each other. It is arranged on one surface side. For example, as shown in FIG. 1, the laser structure portions LD1, LD2, and LD3 are arranged so that the centers in the in-plane direction of the laser structure portions LD1, LD2, and LD3 correspond to the positions of the apexes of the triangle. ing. When the scale in the in-plane direction of the laser structure portions LD1, LD2, and LD3 is relatively small, it is not necessary to arrange the laser structure portions LD1, LD2, and LD3 as shown in FIG. For example, they may be arranged in a line in the in-plane direction.

(Laser structure LD1)
The laser structure LD1 is formed by crystal growth on the GaN substrate 10, and is composed of a nitride-based III-V group compound semiconductor. Note that the nitride-based III-V group compound semiconductor means at least one of the group 3B elements in the short period periodic table and at least N (nitrogen in the group 5B elements in the short period periodic table. For example, GaN, AlGaN (aluminum nitride / gallium), or AlGaInN (aluminum nitride / gallium / indium). The nitride-based III-V group compound semiconductor is a material that is transparent to light from visible to infrared.

  The laser structure LD1 is formed, for example, by laminating a lower DBR layer 20, a lower spacer layer 21, an active layer 22, an upper spacer layer 23, an upper DBR layer 24, and an upper contact layer 25 in this order from the GaN substrate 10 side. It has a laminated structure.

Here, the GaN substrate 10 is made of, for example, n-type GaN. The lower DBR layer 20 is configured by alternately laminating low refractive index layers (not shown) and high refractive index layers (not shown). Low refractive index layer is, for example, optical thickness is λ _1/4 (λ ₁ is an oscillation wavelength), an n-type _Al x1 _Ga 1-x1 N of (0 <x1 <1), the high refractive index layer is, for example, optical thickness There consisting lambda _1/4 of n-type _{Al x2 Ga 1-x2 n (} 0 ≦ x2 <x1). The lower spacer layer 21 is made of, for example, n-type Al _x3 Ga _1-x3 N (0 ≦ x3 <1). The GaN substrate 10, the lower DBR layer 20, and the lower spacer layer 21 contain an n-type impurity such as silicon (Si).

The active layer 22 includes, for example, a well layer (not shown) made of undoped In _x4 Ga _1-x4 N (0 <x4 <1) and an undoped In _x5 Ga _1-x5 N (0 <x5 <x4). It has a multiple quantum well structure in which barrier layers (not shown) are alternately stacked. In the active layer 33, the central portion in the in-plane direction of the stack is the light emitting region 22A.

The upper spacer layer 23 is made of, for example, p-type Al _x6 Ga _1-x6 N (0 ≦ x6 <1). The upper DBR layer 24 is configured by alternately laminating low refractive index layers (not shown) and high refractive index layers (not shown). , Low refractive index layer is, for example, optical thickness of lambda _1/4 p-type _{Al x7 Ga 1-x7 N (} 0 <x7 <1), the high refractive index layer is, for example, optical thickness of lambda _1/4 p It consists of type Al _x8 Ga _1-x8 N (0 ≦ x8 <x7). The upper contact layer 25 is made of, for example, p-type Al _x9 Ga _1-x9 N (0 ≦ x9 <1). The upper spacer layer 23, the upper DBR layer 24, and the upper contact layer 25 contain p-type impurities such as magnesium (Mg).

  In the laser structure portion LD1 of the present embodiment, an annular electrode layer 26 is formed on the upper surface of the upper contact layer 25. The electrode layer 26 is formed by, for example, laminating a titanium (Ti) layer, a platinum (Pt) layer, and a gold (Au) layer in this order, and is electrically connected to the upper contact layer 25. Yes.

  In the semiconductor laser 1 of the present embodiment, the insulating layer 11, the adhesive layer 12, and the electrode layer 13 are formed on the surface of the GaN substrate 10 on the laser structure LD1 side where the laser structure LD1 is not formed. They are formed in order from the substrate 10 side. An electrode layer 14 is formed on the surface of the GaN substrate 10 opposite to the laser structure LD1 side.

Here, the insulating layer 11 is made of an insulating material such as SiO ₂ (silicon oxide) or SiN (silicon nitride). The adhesive layer 12 is made of a semiconductor layer such as a polycrystalline silicon layer or an amorphous silicon layer, and has a high affinity with the insulating layer 11. As a result, the adhesive layer 12 has high adhesion strength between the electrode layer 13 and the insulating layer 11. The electrode layer 13 is made of, for example, a conductive material such as gold or palladium. The electrode layer 14 has a structure in which, for example, an alloy of Au and Ge (germanium), Ni (nickel), and Au are sequentially stacked from the GaN substrate 10 side.

(Laser structure LD2)
The laser structure LD2 is formed by crystal growth on a substrate different from the GaN substrate 10, for example, a GaAs substrate, and is composed of a GaAs III-V compound semiconductor. The GaAs III-V group compound semiconductor includes at least Ga of 3B group elements in the short period type periodic table and at least As (arsenic) of 5B group elements in the short period type periodic table. Point to. The GaAs III-V compound semiconductor is a material that is opaque to visible to infrared light.

  This laser structure portion LD2 is formed on the electrode layer 13, and for example, from the electrode layer 13 side, the lower contact layer 30, the lower DBR layer 31, the lower spacer layer 32, the active layer 33, the upper spacer layer 34, the current The constriction layer 35, the upper DBR layer 36, and the upper contact layer 37 are stacked in this order.

Here, the lower contact layer 30 is made of, for example, n-type Al _x10 Ga _1-x10 As (0 ≦ x10 <1). The lower DBR layer 31 is configured by alternately laminating low refractive index layers (not shown) and high refractive index layers (not shown). Low refractive index layer is, for example, optical thickness is λ _2/4 (λ ₂ is the oscillation wavelength), an n-type _Al x11 _Ga 1-x11 As the (0 <x11 <1), the high refractive index layer is, for example, optical thickness There consisting lambda _2/4 of n-type _{Al x12 Ga 1-x12 As (} 0 ≦ x12 <x11). The lower spacer layer 32 is made of, for example, n-type Al _x13 Ga _1-x13 As (0 ≦ x13 <1). The lower contact layer 30, the lower DBR layer 31, and the lower spacer layer 32 contain an n-type impurity such as silicon (Si).

The active layer 33 includes, for example, a well layer (not shown) made of undoped In _x14 Ga _1-x14 As (0 <x14 <1) and an undoped In _x15 Ga _1-x15 N (0 <x15 <x14). It has a multiple quantum well structure in which barrier layers (not shown) are alternately stacked. In the active layer 33, a region facing a current injection region 35A (described later) is a light emitting region 33A.

The upper spacer layer 34 is made of, for example, p-type Al _x16 Ga _1-x16 As (0 ≦ x16 <1). The upper DBR layer 36 is configured by alternately laminating low refractive index layers (not shown) and high refractive index layers (not shown). , Low refractive index layer is, for example, optical thickness of λ _2/4 p-type _{Al x17 Ga 1-x17 As (} 0 <x17 <1), the high refractive index layer is, for example, optical thickness of λ _2/4 p It is made of type Al _x18 Ga _1-x18 N (0 ≦ x18 <x17). The upper contact layer 37 is made of, for example, p-type Al _x19 Ga _1-x19 N (0 ≦ x19 <1). The upper spacer layer 34, the upper DBR layer 36 and the upper contact layer 37 contain a p-type impurity such as magnesium (Mg).

The current confinement layer 35 has a current confinement region 35B in its outer edge region and a current injection region 35A in its central region. The current injection region 35A is made of, for example, p-type Al _x20 Ga _1-x20 As (0 <x20 ≦ 1). The current confinement region 35B includes, for example, Al ₂ O ₃ (aluminum oxide), and is obtained by oxidizing high concentration Al contained in the current confinement layer 35D from the side surface, as will be described later. . Therefore, the current confinement layer 35 has a function of confining current.

  In the laser structure portion LD2 of the present embodiment, an annular electrode layer 38 is formed on the upper surface of the upper contact layer 37. For example, the electrode layer 38 is formed by laminating, for example, a Ti layer, a Pt layer, and an Au layer in this order, and is electrically connected to the upper contact layer 37.

(Laser structure LD3)
The laser structure LD3 is formed by crystal growth on a substrate different from the GaN substrate 10, for example, a GaAs substrate, and includes a GaAs III-V compound semiconductor and a GaP III-V compound semiconductor. It is configured. Note that the GaP-based III-V group compound semiconductor is at least Ga (gallium) of the 3B group elements in the short period type periodic table and at least P (phosphorus) of the 5B group elements in the short period type periodic table. The thing including The GaP III-V compound semiconductor is a material that is opaque to light from visible to infrared.

  The laser structure LD3 is formed on the electrode layer 13, and from the electrode layer 13 side, for example, the lower contact layer 40, the lower DBR layer 41, the lower spacer layer 42, the active layer 43, the upper spacer layer 44, the current The constriction layer 45, the upper DBR layer 46, and the upper contact layer 47 are stacked in this order.

Here, the lower contact layer 40 is made of, for example, n-type Al _x21 Ga _1-x21 As (0 ≦ x21 <1). The lower DBR layer 41 is configured by alternately laminating low refractive index layers (not shown) and high refractive index layers (not shown). An n-type _Al x22 _Ga 1-x22 As the low refractive index layer is, for example, optical thickness of λ _3/4 (λ ₃ is an oscillation wavelength) (0 <x22 <1) , the high refractive index layer is, for example, optical thickness There consisting lambda _3/4 of n-type _{Al x23 Ga 1-x23 As (} 0 ≦ x23 <x22). The lower spacer layer 42 is made of, for example, n-type Al _x24 Ga _1-x24 As (0 ≦ x24 <1). The lower contact layer 40, the lower DBR layer 41, and the lower spacer layer 42 contain an n-type impurity such as silicon (Si).

The active layer 43 includes, for example, a well layer (not shown) made of undoped In _x25 Ga _1-x25 As (0 <x25 <1) and undoped In _x26 Ga _1-x26 N (0 <x26 <x26). It has a multiple quantum well structure in which barrier layers (not shown) are alternately stacked. In the active layer 43, a region facing a current injection region 45A (described later) is a light emitting region 43A.

The upper spacer layer 44 is made of, for example, p-type Al _x27 Ga _1-x27 As (0 ≦ x27 <1). The upper DBR layer 46 is configured by alternately laminating low refractive index layers (not shown) and high refractive index layers (not shown). , Low refractive index layer is, for example, optical thickness of λ _3/4 p-type _{Al x28 Ga 1-x28 As (} 0 <x28 <1), the high refractive index layer is, for example, optical thickness of λ _3/4 p It is made of type Al _x29 Ga _1-x29 N (0 ≦ x29 <x28). The upper contact layer 47 is made of, for example, p-type Al _x30 Ga _1-x30 N (0 ≦ x30 <1). The upper spacer layer 44, the upper DBR layer 46, and the upper contact layer 47 contain a p-type impurity such as magnesium (Mg).

The current confinement layer 45 has a current confinement region 45B in its outer edge region and a current injection region 45A in its central region. The current injection region 45A is made of, for example, p-type Al _x31 Ga _1-x31 As (0 <x31 ≦ 1). The current confinement region 45B includes, for example, Al ₂ O ₃ (aluminum oxide), and is obtained by oxidizing high concentration Al contained in the current confinement layer 45D from the side surface, as will be described later. . Therefore, the current confinement layer 45 has a function of confining current.

  In the laser structure portion LD3 of the present embodiment, an annular electrode layer 48 is formed on the upper surface of the upper contact layer 47. For example, the electrode layer 48 is formed by laminating, for example, a Ti layer, a Pt layer, and an Au layer in this order, and is electrically connected to the upper contact layer 47.

A protective film 15 is formed over the entire surface of the GaN substrate 10 on the laser structure portions LD1, LD2, and LD3 side including the surfaces of the laser structure portions LD1, LD2, and LD3 and the electrode layers 26, 38, and 49. The protective film 15 is made of an insulating material such as SiO ₂ (silicon oxide) or SiN (silicon nitride). An opening is formed in a part of the protective film 15 where the laser structure portions LD1, LD2, and LD3 are not formed, and a part of the electrode layer 13 (electrode pad 13A) is exposed from the opening. ing. An opening is also formed in a part of the protective film 15 facing the electrode layers 26, 38, and 49, and the electrode electrically connected to the electrode layer 26 through the opening. A pad 27, an electrode pad 39 electrically connected to the electrode layer 38, and an electrode pad 49 electrically connected to the electrode layer 48 are formed on the surface of the protective film 15 (see FIG. 1).

  The semiconductor laser 1 having such a configuration can be manufactured as follows, for example.

First, the laser structure LD2 is manufactured. For this purpose, a laminated structure is formed by, for example, the MOCVD method. At this time, for example, TMA (trimethylaluminum), TMG (trimethylgallium), TMIn (trimethylindium), or AsH ₃ (arsine) is used as a raw material for the GaAs III-V compound semiconductor.

  Specifically, on the GaAs substrate 130, the oxide peeling layer 131D, the lower contact layer 30, the lower DBR layer 31, the lower spacer layer 32, the active layer 33, the upper spacer layer 34, the current confinement layer 35D, the upper DBR layer 36, and The upper contact layer 37 is stacked in this order (FIG. 3A).

  Here, the above-described current confinement layer 35D is made of the same material as that of the current injection region 35A, and becomes the current confinement layer 35 by an oxidation process described later. Further, like the current injection region 35A, the oxide peeling layer 131D is made of a material that is easily oxidized. It is thicker than the thickness. The thickness of the oxidized release layer 131D at this time is set so that the diameter of the unoxidized region in the flow constriction layer 35D becomes a desired value when almost all of the oxidized release layer 131D is oxidized in the oxidation treatment described later. Has been.

  As described above, the oxide peeling layer 131D is preferably thicker than the flow constriction layer 35D, but may be substantially the same thickness as the flow confinement layer 35D. However, in this case, the oxide peeling layer 131D needs to be made of a material that is more easily oxidized than the current confinement layer 35D.

  Next, the mesa shape is formed by selectively etching the upper contact layer 37 to a part of the GaAs substrate 130 by, for example, dry etching (FIG. 3B). As a result, the oxidized release layer 131D is exposed on the side surface of the mesa.

  Next, an oxidation process is performed at a high temperature in a water vapor atmosphere to selectively oxidize the current confinement layer 35D and the oxidation release layer 131D from the side surface of the mesa. At this time, the oxidation treatment is performed until almost all of the oxide peeling layer 131D is oxidized and the diameter of the unoxidized region of the current confinement layer 35D becomes a desired value. Thereby, almost all of the oxide peeling layer 131D becomes an insulating layer (aluminum oxide), and the oxide peeling layer 131 is formed (FIG. 4A). Further, since the outer edge region of the oxidized constricting layer 35D becomes an insulating layer (aluminum oxide), the current confining region 35B is formed in the outer edge region, and the central region becomes the current injection region 35A. In this manner, the laser structure portion LD2 is formed on the GaAs substrate 130 (FIG. 4A).

  Next, the laser structure portion LD2 is peeled off from the GaAs substrate 130 using, for example, vacuum suction or a photo-curing adhesive sheet (FIG. 4B). At this time, the oxide peeling layer 131 and the lower contact layer 30 are not in contact with each other at the interface between the oxide peeling layer 131 and the lower contact layer 30 among the interfaces of the layers constituting the laser structure LD2. That is, an intermediate layer in which both materials are mixed does not exist at the interface between the oxidized peeling layer 131 and the lower contact layer 30, or even if it exists, it is compared with the thickness of the intermediate layer at the other interface. There are few that can be ignored. For this reason, stress caused by oxidation is applied to the interface between the oxidized peeling layer 131 and the lower contact layer 30, and this peeling step makes it relatively easy at the boundary between the oxidized peeling layer 131 and the lower contact layer 30. The laser structure LD2 can be peeled off.

  In addition, you may heat (alloy) at about 300 to 400 degreeC before a peeling process. In this case, since the stress at the boundary between the oxidized peeling layer 131 and the lower contact layer 30 is further increased, the laser structure LD2 can be peeled more easily. When the oxide peeling layer 131 remains on the laser structure LD2 side, the oxide peeling layer 131 remaining on the laser structure LD2 side is removed by wet etching or the like.

Next, the laser structure portion LD3 is manufactured. For this purpose, a laminated structure is formed by, for example, the MOCVD method. At this time, the raw materials for the GaAs III-V compound semiconductor are the same as those described above, and the raw materials for the GaP III-V compound semiconductor are, for example, TMA (trimethylaluminum), TMG (trimethyl). Gallium), TMIn (trimethylindium), and PH ₃ (phosphine) are used.

  Specifically, on the GaAs substrate 130, the oxide peeling layer 141D, the lower contact layer 40, the lower DBR layer 41, the lower spacer layer 42, the active layer 43, the upper spacer layer 44, the current confinement layer 45D, the upper DBR layer 46, and The upper contact layer 47 is stacked in this order (FIG. 5A).

  Here, the above-described current confinement layer 45D is made of the same material as that of the current injection region 45A, and becomes the current confinement layer 45 by an oxidation process described later. The oxide peeling layer 141D is made of a material that is easily oxidized, like the current injection region 45A. For example, the current confinement layer 45D is formed so that the oxidation rate in the in-plane direction of the stack is faster than that of the current confinement layer 45D. It is thicker than the thickness. The thickness of the oxidized release layer 141D at this time is set so that the diameter of the unoxidized region in the flow confinement layer 45D becomes a desired value when almost all of the oxidized release layer 141D is oxidized in an oxidation process described later. Has been.

  As described above, the oxide peeling layer 141D is preferably thicker than the flow constriction layer 45D, but may be substantially the same thickness as the flow confinement layer 45D. However, in this case, the oxide peeling layer 141D needs to be made of a material that is more easily oxidized than the current confinement layer 45D.

  Next, the mesa shape is formed by selectively etching from the upper contact layer 47 to a part of the GaAs substrate 130 by, for example, dry etching (FIG. 5B). Thereby, the oxide peeling layer 141D is exposed on the side surface of the mesa.

  Next, oxidation treatment is performed at a high temperature in a water vapor atmosphere to selectively oxidize the current confinement layer 45D and the oxidation release layer 141D from the side surface of the mesa. At this time, the oxidation treatment is performed until almost all of the oxidized peeling layer 141D is oxidized and the diameter of the unoxidized region of the current confinement layer 45D becomes a desired value. Thereby, almost all of the oxide peeling layer 141D becomes an insulating layer (aluminum oxide), and the oxide peeling layer 141 is formed (FIG. 6A). Further, since the outer edge region of the oxidized constricting layer 45D is an insulating layer (aluminum oxide), the current confining region 45B is formed in the outer edge region, and the central region is the current injection region 45A. In this way, the laser structure LD3 is formed on the GaAs substrate 130 (FIG. 6A).

  Next, the laser structure portion LD3 is peeled off from the GaAs substrate 130 using, for example, vacuum suction or a photo-curing adhesive sheet (FIG. 6B). At this time, the oxide peeling layer 141 and the lower contact layer 40 are not in contact with each other at the interface between the oxide peeling layer 141 and the lower contact layer 40 among the interfaces of the layers constituting the laser structure LD3. That is, an intermediate layer in which both materials are mixed does not exist at the interface between the oxide peeling layer 141 and the lower contact layer 40, or even if it exists, the thickness is compared with the thickness of the intermediate layer at the other interface. There are few that can be ignored. For this reason, stress generated by oxidation is applied to the interface between the oxidized peeling layer 141 and the lower contact layer 40, and this peeling step makes it relatively easy at the boundary between the oxidized peeling layer 141 and the lower contact layer 40. The laser structure LD3 can be peeled off.

  In addition, you may heat (alloy) at about 300 to 400 degreeC before a peeling process. In this case, since the stress at the boundary between the oxidized peeling layer 141 and the lower contact layer 40 is further increased, the laser structure LD3 can be peeled off more easily. Further, when the oxide peeling layer 141 remains on the laser structure LD3 side, the oxide peeling layer 141 remaining on the laser structure LD3 side is removed by wet etching or the like.

  Next, the laser structure portion LD1 is manufactured. For this purpose, a laminated structure is formed by, for example, the MOCVD method. At this time, for example, TMA (trimethylaluminum), TMG (trimethylgallium), TMIn (trimethylindium), or ammonia (NH3) is used as a raw material for the nitride III-V compound semiconductor.

  Specifically, the lower DBR layer 20, the lower spacer layer 21, the active layer 22, the upper spacer layer 23, the upper DBR layer 24, and the upper contact layer 25 are stacked in this order on the large GaN substrate 10 (FIG. 7). . Thereafter, the mesa shape is formed by selectively etching the upper contact layer 25 to the lower DBR layer 20 by, for example, dry etching (FIG. 8). Thereby, the laser structure portion LD1 is formed (FIG. 8).

  Next, an insulating layer 11, an adhesive layer 12 and an electrode layer 13 are formed in this order from the GaN substrate 10 side in a region where the laser structure portion LD1 is not formed on the surface of the GaN substrate 10 on the laser structure portion LD1 side (FIG. 9). Subsequently, the laser structures LD2 and LD3 are disposed on the electrode layer 13 with the lower contact layers 30 and 40 side down (FIG. 10).

  Next, electrode layers 26, 38, and 49 are formed on the upper surfaces of the laser structure portions LD1, LD2, and LD3. Subsequently, after forming the protective film 15 over the entire surface of the GaN substrate 10 on the laser structure part LD1, LD2, LD3 side including the surfaces of the laser structure parts LD1, LD2, LD3 and the electrode layers 26, 38, 49, An opening is formed in a part of the region where the laser structure parts LD1, LD2, and LD3 are not formed to expose a part of the electrode layer 13 (electrode pad 13A), and the electrode layer 26 of the protective film 15 is exposed. , 38, 49 are also formed with openings (not shown) in part of the region facing the electrode layers 26, 38, 49 in the protective film 15. Electrode pads 27, 39, and 49 are formed on the surface of the protective film 15. In this way, the semiconductor laser 1 of the present embodiment is manufactured.

In the semiconductor laser 1 of the present embodiment, when a predetermined voltage is applied between the connection pad 27 electrically connected to the electrode layer 26 and the electrode layer 14, a current is injected into the active layer 22, As a result of light emission due to electron-hole recombination and repeated stimulated emission within the device, laser oscillation occurs at a predetermined wavelength λ ₁ , and laser light having a wavelength λ ₁ (wavelength of about 400 nm (for example, 405 nm)) is applied to the electrode. The light is output from the opening of the layer 26 to the outside. In addition, when a predetermined voltage is applied between the connection pad 39 electrically connected to the electrode layer 38 and the electrode layer 13, a current is injected into the active layer 33, and light is emitted by electron-hole recombination. As a result of repeated stimulated emission in the device, laser oscillation occurs at a predetermined wavelength λ ₂ , and laser light of wavelength λ ₂ (700 nm band (for example, 780 nm)) is output to the outside from the opening of the electrode layer 38. Is done. Further, when a predetermined voltage is applied between the connection pad 49 electrically connected to the electrode layer 48 and the electrode layer 13, a current is injected into the active layer 43, and light is emitted by electron-hole recombination. As a result of repeated emission within the device, laser oscillation occurs at a predetermined wavelength λ ₃ , and laser light of wavelength λ ₃ (600 nm band (for example, 650 nm)) is output to the outside from the opening of the electrode layer 48. Is done.

  By the way, in the present embodiment, the laser structure LD1 formed by crystal growth on the GaN substrate 10 and the crystal growth on a substrate (GaAs substrate 130) different from the GaN substrate 10 are formed. The formed laser structures LD2 and LD3 are provided. That is, since the laser structure LD1 and the laser structures LD2 and LD3 are formed by crystal growth on different substrates, the wavelength difference between the laser structure LD1 and the laser structures LD2 and LD3 is increased. be able to. Thereby, for example, a laser beam of 400 nm band is emitted from the laser structure portion LD1, a laser beam of 700 nm band is emitted from the laser structure portion LD2, and a laser beam of 600 nm band is independently emitted from the laser structure portion LD3. Therefore, the semiconductor laser 1 can be applied to the light source of the optical disk apparatus.

  In the present embodiment, since each laser structure part LD2, LD3 is provided on a common GaN substrate 10, each laser structure part LD1, LD2, LD3 is formed on a separate substrate, respectively. As compared with the case where the laser beams are arranged side by side on a support base or the like, the interval between the optical axes of the laser beams emitted from the laser structure portions LD1, LD2, and LD3 can be sufficiently narrowed. As a result, the laser light emitted from each of the laser structure portions LD1, LD2, and LD3 can be propagated by a single optical system, so that the mounted devices (optical pickup device and optical disk device) can be downsized. be able to.

[Modification of First Embodiment]
In the above embodiment, the GaAs substrate 130 is peeled from the laser structure portions LD2 and LD3 by utilizing the property of the interface between the lower contact layers 30 and 40 and the oxide peeling layers 131 and 141. , 40 and the oxide release layers 131 and 141 may be used to remove or thin the GaAs substrate 130 from the laser structures LD2 and LD3 by wrapping the GaAs substrate 130. When the laser structure portions LD2 and LD3 obtained by such a method are applied to the semiconductor laser 1, for example, as shown in FIG. 11, the GaAs substrate 130 remains slightly at the bottom of the laser structure portions LD2 and LD3. The GaAs substrate 130 is in electrical contact with the electrode layer 13. Also, as shown in FIG. 12, the laser structures LD2 and LD3 of FIG. 11 are formed on the common GaAs substrate 130, and are disposed on the electrode layer 13 with the common GaAs substrate 130 remaining. You may do it.

[Second Embodiment]
FIG. 13 shows a top view of a surface emitting semiconductor laser 2 according to a second embodiment of the present invention. 14 shows a cross-sectional configuration of the semiconductor laser 2 in FIG. 13 in the direction of arrows AA, and FIG. 15 shows a cross-sectional configuration of the semiconductor laser 2 in FIG. 13 in the direction of arrows BB. 13 to 15 are schematic representations, and are different from actual dimensions and shapes.

  In this semiconductor laser 2, the laser structure portion LD2 of the first embodiment is disposed on the back side of the GaN substrate 10 (the surface opposite to the laser structure portions LD1 and 3 of the GaN substrate 10). In this respect, the configuration is mainly different from the configuration of the semiconductor laser 1 of the above embodiment. Therefore, in the following, description of configurations, operations, and effects common to the above embodiment will be omitted as appropriate, and differences from the above embodiment will be mainly described.

  In the semiconductor laser 2 of the present embodiment, each of the laser structure portions LD1, LD2, and LD3 has a GaN substrate so that the distance between the optical axes of the laser beams emitted from the laser structure portions LD1, LD2, and LD3 is as close as possible to each other. 10 on both sides. For example, the laser structure portions LD1 and LD3 are disposed on one surface side of the GaN substrate 10 with the electrode layers 14 and 48 facing away from the GaN substrate 10, and the laser structure portion LD2 includes the electrode layer 38. It is arranged on the other surface side of the GaN substrate 10 toward the GaN substrate 10 side, and each laser structure part LD1, LD2, LD3 is arranged in a line in the in-plane direction. That is, the laser structure portions LD1, LD2, and LD3 are arranged in a line on the GaN substrate 10 so that the light emission directions of the laser structure portions LD1 and LD3 and the light emission direction of the laser structure portion LD2 face each other. Has been. Further, each laser structure portion LD1, LD2, LD3 is formed on the GaN substrate 10 so that the laser light emitted from each laser structure portion LD1, LD2, LD3 is not blocked by the other laser structure portions LD1, LD2, LD3. It is alternately arranged on both sides.

  Here, unlike the case of the first embodiment, the laser structure portion LD2 is not formed by peeling off the GaAs substrate 130 or thinning it by lapping, but is formed on the GaAs substrate 130. The back surface is bonded via an adhesive layer 53. Further, the GaAs substrate 130 on which the laser structure portion LD2 is formed is larger than the GaN substrate 10, and wire bonding to electrode pads 56 and 57, which will be described later, is not blocked by the GaN substrate 10.

  As shown in FIGS. 13 and 14, an insulating layer 51 is formed on the side surface of the laser structure portion LD2 and the surface of the portion of the GaAs substrate 130 where the laser structure portion LD2 is not formed. An extraction electrode 54 and an electrode pad 56 electrically connected to the extraction electrode 54 are formed on the surface of the insulating layer 51 where the laser structure portion LD2 is not formed. Further, bumps 55 that are in contact with the electrode layer 14 formed on the back surface of the GaN substrate 10 are formed on the extraction electrode 54. Thus, the electrode layer 14 is drawn out to the surface on the laser structure LD2 side on the GaAs substrate 130 by the bump 55, the extraction electrode 54, and the electrode pad 56. The bump 55 also has a function as a support member for stabilizing the direction of the optical axis of the laser structure portion LD2.

  Further, as shown in FIGS. 13 and 15, the electrode electrically connected to the electrode layer 38 on the laser structure LD2 is formed on the surface of the insulating layer 51 where the laser structure LD2 is not formed. A pad 57 is formed. Therefore, each electrode pad 13A, 27, 49, 56, 57 is formed on the surface of the laser structure portion LD1, LD2, LD3 on the side where the laser beam is emitted.

  In the semiconductor laser 2 of the present embodiment, when the laser structure LD2 is driven, the laser light from the laser structure LD2 passes through the GaN substrate 10 and the surface of the GaN substrate 10 on the laser structure LD1 and LD3 side. Ejected from. At this time, since the laser structure portion LD2 is disposed on a different surface from the laser structure portions LD1 and LD3, the gap between the laser structure portion LD1 and the laser structure portion LD3 is made smaller than in the above embodiment, The interval between the optical axes of the laser structure portions LD1, LD2, and LD3 can be made narrower than in the above-described embodiment. As a result, for example, an image display panel having three laser structure portions LD1, LD2, and LD3 as one pixel can be constructed.

  In each of the above embodiments, the case where the present invention is applied to a surface emitting semiconductor laser has been described. However, the case where the present invention is applied to an edge emitting semiconductor laser will be described below.

[Third Embodiment]
FIG. 16 is a top view of an edge-emitting semiconductor laser 3 according to the third embodiment of the present invention, and FIG. 17 shows a cross-sectional configuration of the semiconductor laser 3 in FIG. is there. 16 and 17 are schematically shown and are different from actual dimensions and shapes.

  The semiconductor laser 3 includes a laser structure LD4 capable of emitting light having a wavelength of about 400 nm (for example, 405 nm) on the GaN substrate 10 in a direction in the stacking plane, and a 700 nm band (for example, 780 nm) for CD. A laser structure LD5 capable of emitting light toward the in-plane direction of the laminate and a laser structure LD6 capable of emitting light of 600 nm band (for example, 650 nm) for DVD toward the in-plane direction of the laminate. is there. Therefore, this semiconductor laser 3 has a function as a three-wavelength laser.

  Further, in this semiconductor laser 3, the laser structure portions LD4, LD5, and LD6 are formed on the GaN substrate 10 so that the distances between the optical axes of the laser beams emitted from the laser structure portions LD4, LD5, and LD6 are as close as possible to each other. It is arranged in parallel on one surface side.

(Laser structure LD4)
The laser structure LD4 is formed by crystal growth on the GaN substrate 10, and is composed of a nitride III-V compound semiconductor. The laser structure LD4 has, for example, a laminated structure in which a lower cladding layer 60, an active layer 61, an upper cladding layer 62, and an upper contact layer 63 are laminated in this order from the GaN substrate 10 side. Strips extending in the in-plane direction of the laminated surface and in the opposite direction of the front end face 91 and the rear end face 92 which are cleavage planes on the upper part (specifically, the upper part of the cladding layer 62 and the upper contact layer 63). The ridge portion 65 is provided. Note that a portion of the active layer 61 corresponding to the bottom of the ridge portion 65 is a light emitting region 61A.

  Here, the lower cladding layer 60 is made of, for example, n-type AlGaN. The active layer 61 has, for example, an undoped GaInN multiple quantum well structure. The upper cladding layer 62 is made of, for example, p-type AlGaN. The upper contact layer 63 is made of, for example, p-type GaN. Although not shown, a lower guide layer made of, for example, n-type GaN is provided between the lower cladding layer 60 and the active layer 61, and, for example, p-type GaN is interposed between the upper cladding layer 62 and the active layer 61. A lower guide may be provided.

  Further, both side surfaces of the ridge portion 65 and side surfaces of the lower cladding layer 60, the active layer 61, and the upper cladding layer 62 are covered with the insulating film 15. As will be described later, the insulating film 15 also covers the side surfaces of the laser structure portions LD5 and LD6.

Further, on the upper surface of the ridge portion 65, a strip-shaped electrode layer 64 extending in the extending direction of the ridge portion 65 is formed. The electrode layer 64 is formed with a connecting portion 64A extending across the laser structure portions LD5 and LD6. The connecting portion 64A is formed on the surface of the insulating film 15 with the laser structure portions LD4 and LD4. It is electrically connected to an electrode pad 66 formed corresponding to a portion where LD5 and LD6 are not formed. In addition, insulating layers 77 and 87 are formed on the surfaces of the electrode layers 75 and 85 facing the connecting portion 64A, thereby preventing the electrode layers 75 and 85 and the connecting portion 64A from being short-circuited with each other. is doing. Here, the electrode layer 64 and the electrode pad 66 are configured, for example, by laminating a palladium (Pd) layer and a platinum (Pt) layer in this order. The insulating layers 77 and 87 are made of an insulating material such as SiO ₂ (silicon oxide) or SiN (silicon nitride).

  In the present embodiment, the insulating layer 11, the adhesive layer 12, and the electrode layer 13 are formed from the GaN substrate 10 side on the surface of the GaN substrate 10 on the laser structure portion LD 4 side where the laser structure portion LD 4 is not formed. It is formed in order. An electrode layer 14 is formed on the surface of the GaN substrate 10 opposite to the laser structure LD4 side.

(Laser structure LD5)
The laser structure LD5 is formed by crystal growth on a substrate different from the GaN substrate 10, for example, a GaAs substrate, and is composed of a GaAs III-V group compound semiconductor. The laser structure portion LD5 is formed on the electrode layer 13, and, for example, the lower contact layer 70, the lower cladding layer 71, the active layer 72, the upper cladding layer 73, and the upper contact layer 74 are formed from the electrode layer 13 side. It is a laminated structure formed by laminating in order, and the front side that is in the in-plane direction of the laminated surface and is a cleavage plane on the upper part of the laminated structure (specifically, the upper part of the cladding layer 73 and the upper contact layer 74). It has a strip-shaped ridge portion 76 extending in the opposing direction of the end face 91 and the rear end face 92. Note that a portion of the active layer 72 corresponding to the bottom of the ridge portion 76 is a light emitting region 76A.

  Here, the lower contact layer 70 is made of, for example, n-type GaAs. The lower cladding layer 71 is made of, for example, n-type AlGaAs. The active layer 72 has, for example, an undoped AlGaAs multiple quantum well structure having a different composition ratio. The upper cladding layer 73 is made of, for example, p-type AlGaAs. The upper contact layer 74 is made of, for example, p-type GaAs.

  Further, both side surfaces of the ridge portion 76, and side surfaces of the lower contact layer 70, the lower cladding layer 71, the active layer 72, and the upper cladding layer 73 are covered with the insulating film 15. In addition, on the upper surface of the ridge portion 76, a strip-shaped electrode layer 75 extending in the extending direction of the ridge portion 76 is formed. The electrode layer 75 is formed with a connecting portion 75A extending across the laser structure portion LD6, and the connecting portion 75A is formed on the surface of the insulating film 15 with the laser structure portions LD4, LD5, LD5. It is electrically connected to an electrode pad 78 formed corresponding to the portion where the LD 6 is not formed. In addition, an insulating layer 87 is formed on a portion of the surface of the electrode layer 85 facing the connecting portion 75A to prevent the electrode layer 85 and the connecting portion 75A from being short-circuited with each other. Here, the electrode layer 75 and the electrode pad 78 are configured by, for example, stacking a Pd layer and a Pt layer in this order.

(Laser structure LD6)
The laser structure LD6 is formed by crystal growth on a substrate different from the GaN substrate 10, for example, a GaAs substrate, and is composed of a GaAs III-V compound semiconductor. The laser structure portion LD6 is formed on the electrode layer 13, and, for example, a lower contact layer 80, a lower cladding layer 81, an active layer 82, an upper cladding layer 83, and an upper contact layer 84 are formed from the electrode layer 13 side. It is a laminated structure formed by laminating in order, and the front side that is the in-plane direction of the laminated surface and is a cleavage plane on the upper part of the laminated structure (specifically, the upper part of the cladding layer 83 and the upper contact layer 84) It has a strip-shaped ridge portion 86 extending in the opposing direction of the end face 91 and the rear end face 92. Note that a portion of the active layer 82 corresponding to the bottom of the ridge portion 86 is a light emitting region 86A.

  Here, the lower contact layer 80 is made of, for example, n-type GaAs. The lower cladding layer 71 is made of, for example, n-type AlGaInP. The active layer 72 has, for example, an undoped AlGaInP multiple quantum well structure having a different composition ratio. The upper cladding layer 73 is made of, for example, p-type AlGaInP. The upper contact layer 74 is made of, for example, p-type GaAs.

  Further, both side surfaces of the ridge portion 86 and side surfaces of the lower contact layer 80, the lower cladding layer 81, the active layer 82, and the upper cladding layer 83 are covered with the insulating film 15. Further, a strip-shaped electrode layer 85 extending in the extending direction of the ridge portion 86 is formed on the upper surface of the ridge portion 86. The electrode layer 85 is formed with a connecting portion 85A extending in a direction intersecting with the extending direction of the laser structure portion LD6. The connecting portion 85A is a laser structure portion LD4 in the surface of the insulating film 15. , LD5, and LD6 are electrically connected to electrode pads 88 formed corresponding to the portions where LD6 and LD6 are not formed. Here, the electrode layer 85 and the electrode pad 88 are configured by, for example, stacking a Pd layer and a Pt layer in this order.

  The semiconductor laser 3 having such a configuration can be manufactured as follows, for example.

  First, the laser structure LD5 is manufactured by, for example, the MOCVD method. Specifically, an oxide peeling layer 171D, a lower contact layer 70, a lower cladding layer 71, an active layer 72, an upper cladding layer 73, and an upper contact layer 74 are stacked in this order on the GaAs substrate 130 (FIG. 18A). ). The oxide peeling layer 171D is made of a material that is easily oxidized.

  Next, for example, by dry etching, the ridge portion 76 is formed by selectively etching from the upper contact layer 74 to a part of the lower cladding layer 71, and further, a part of the GaAs substrate 130 is selectively etched. Thus, a mesa shape is formed (FIG. 18B). As a result, the oxidized release layer 171D is exposed on the side surface of the mesa.

  Next, an oxidation treatment is performed at a high temperature in a water vapor atmosphere to selectively oxidize the oxide peeling layer 171D from the side surface of the mesa. At this time, the oxidation treatment is performed until almost all of the oxidized peeling layer 171D is oxidized. Thereby, almost all of the oxide peeling layer 171D becomes an insulating layer (aluminum oxide), and the oxide peeling layer 171 is formed (FIG. 19A). In this way, the laser structure portion LD5 is formed on the GaAs substrate 130.

  Next, the laser structure portion LD5 is peeled off from the GaAs substrate 130 using, for example, vacuum suction or a photocurable adhesive sheet (FIG. 19B). At this time, the oxide peeling layer 171 and the lower contact layer 70 are not in contact with each other at the interface between the oxide peeling layer 171 and the lower contact layer 70 among the interfaces of the layers constituting the laser structure LD5. That is, at the interface between the oxidized peeling layer 171 and the lower contact layer 70, there is no intermediate layer in which both materials are mixed, or even if it exists, it is compared with the thickness of the intermediate layer at the other interface. There are few that can be ignored. For this reason, stress caused by oxidation is applied to the interface between the oxidized peeling layer 171 and the lower contact layer 70. Therefore, this peeling step makes it relatively easy at the boundary between the oxidized peeling layer 171 and the lower contact layer 70. The laser structure LD5 can be peeled off.

  In addition, you may heat (alloy) at about 300 to 400 degreeC before a peeling process. In such a case, since the stress at the boundary between the oxidized peeling layer 171 and the lower contact layer 70 is further increased, the laser structure LD5 can be peeled off more easily. If the oxide peeling layer 171 remains on the laser structure LD5 side, the oxide peeling layer 171 remaining on the laser structure LD5 side is removed by wet etching or the like.

  Next, the laser structure portion LD6 is manufactured by, for example, the MOCVD method. Specifically, the oxide peeling layer 181D, the lower contact layer 80, the lower cladding layer 81, the active layer 82, the upper cladding layer 83, and the upper contact layer 84 are stacked in this order on the GaAs substrate 130 (FIG. 20A). ). The oxide peeling layer 181D is made of a material that is easily oxidized.

  Next, the ridge portion 86 is formed by selectively etching from the upper contact layer 84 to a part of the lower cladding layer 81 by, for example, a dry etching method, and further, the part of the GaAs substrate 130 is selectively etched. To form a mesa shape (FIG. 20B). Thereby, the oxide peeling layer 181D is exposed on the side surface of the mesa.

  Next, an oxidation treatment is performed at a high temperature in a water vapor atmosphere to selectively oxidize the oxide release layer 181D from the side surface of the mesa. At this time, the oxidation treatment is performed until almost all of the oxide peeling layer 181D is oxidized. Thus, almost all of the oxide peeling layer 181D becomes an insulating layer (aluminum oxide), and the oxide peeling layer 181 is formed (FIG. 21A). In this way, the laser structure portion LD6 is formed on the GaAs substrate 130.

  Next, the laser structure portion LD6 is peeled off from the GaAs substrate 130 using, for example, vacuum suction or a photocurable adhesive sheet (FIG. 21B). At this time, the oxide peeling layer 181 and the lower contact layer 80 are not in contact with each other at the interface between the oxide peeling layer 181 and the lower contact layer 80 among the interfaces of the layers constituting the laser structure LD6. That is, the interface between the oxide peeling layer 181 and the lower contact layer 80 does not have an intermediate layer in which both materials are mixed, or even if it exists, it is compared with the thickness of the intermediate layer at the other interface. There are few that can be ignored. For this reason, stress caused by oxidation is applied to the interface between the oxidized peeling layer 181 and the lower contact layer 80, and this peeling step makes it relatively easy at the boundary between the oxidized peeling layer 181 and the lower contact layer 70. The laser structure LD6 can be peeled off.

  In addition, you may heat (alloy) at about 300 to 400 degreeC before a peeling process. In this case, since the stress at the boundary between the oxidized peeling layer 181 and the lower contact layer 80 is further increased, the laser structure LD6 can be peeled off more easily. If the oxide peeling layer 181 remains on the laser structure LD6 side, the oxide peeling layer 181 remaining on the laser structure LD6 side is removed by wet etching or the like.

  Next, the laser structure portion LD4 is manufactured by, for example, the MOCVD method. Specifically, a lower cladding layer 60, an active layer 61, an upper cladding layer 62, and an upper contact layer 63 are stacked in this order on a large GaN substrate 10 (FIG. 22). Thereafter, the mesa shape is formed by selectively etching the upper contact layer 63 to the lower cladding layer 60 by, for example, a dry etching method (FIG. 23). Subsequently, the upper contact layer 63 and a part of the upper cladding layer 62 are selectively etched to form a ridge portion 65 (FIG. 24). Thereby, the laser structure portion LD4 is formed.

  Next, the insulating layer 11, the adhesive layer 12, and the electrode layer 13 are formed in this order from the GaN substrate 10 side in the region where the laser structure portion LD4 is not formed on the surface of the GaN substrate 10 on the laser structure portion LD4 side (FIG. 25). Subsequently, the laser structure portions LD5 and LD6 are disposed on the electrode layer 13 with the lower contact layers 70 and 80 facing down (FIG. 26).

  Next, after forming the protective film 15 over the entire surface on the laser structure LD4, LD5, LD6 side, an opening is formed in a part of the region where the laser structure LD4, LD5, LD6 is not formed. In addition, a part of the electrode layer 13 (electrode pad 13A) is exposed, and an opening is formed in a region facing the upper portion of the ridge portions 65, 76, 86 (upper contact layers 63, 74, 84) of the protective film 15. (FIG. 27).

  Next, electrode layers 64, 75, 85 are formed on the ridge portions 65, 76, 86, and electrode pads 66, 75, 85 are formed on regions of the protective film 15 where the laser structure portions LD 4, LD 5, LD 6 are not formed. 78, 88 are formed. In this way, the semiconductor laser 3 of the present embodiment is manufactured.

In the semiconductor laser 3 of the present embodiment, when a predetermined voltage is applied between the connection pad 66 electrically connected to the electrode layer 64 and the electrode layer 14, a current is injected into the active layer 61, As a result of light emission due to electron-hole recombination and repeated stimulated emission within the device, laser oscillation occurs at a predetermined wavelength λ ₄ , and laser light having a wavelength λ ₄ (wavelength of around 400 nm (for example, 405 nm)) is on the front side. Output from the end face 91 to the outside. In addition, when a predetermined voltage is applied between the connection pad 78 electrically connected to the electrode layer 75 and the electrode layer 13, a current is injected into the active layer 72 and light is emitted by electron-hole recombination. As a result of repeated emission within the device, laser oscillation occurs at a predetermined wavelength λ ₅ , and laser light having a wavelength λ ₅ (700 nm band (for example, 780 nm)) is output from the front end face 91 to the outside. In addition, when a predetermined voltage is applied between the connection pad 88 electrically connected to the electrode layer 85 and the electrode layer 13, a current is injected into the active layer 82 and light is emitted by electron-hole recombination. As a result of repeated stimulated emission in the device, laser oscillation occurs at a predetermined wavelength λ ₆ , and laser light of wavelength λ ₆ (600 nm band (for example, 650 nm)) is output from the front end face 91 to the outside.

  By the way, in the present embodiment, the laser structure LD4 formed by crystal growth on the GaN substrate 10 and the crystal growth on a substrate (GaAs substrate 130) different from the GaN substrate 10 are formed. The formed laser structures LD5 and LD6 are provided. That is, since the laser structure LD4 and the laser structure LD5, LD6 are formed by crystal growth on different substrates, the wavelength difference between the laser structure LD4 and the laser structure LD5, LD6 is increased. be able to. Thereby, for example, laser light of 400 nm band is emitted from the laser structure part LD4, laser light of 700 nm band is emitted from the laser structure part LD5, and laser light of 600 nm band is independently emitted from the laser structure part LD6. Therefore, the semiconductor laser 3 can be applied to the light source of the optical disc apparatus.

  In the present embodiment, since the laser structure portions LD5 and LD6 are provided on the common GaN substrate 10, the laser chip in which the laser structure portions LD4, LD5, and LD6 are formed on separate substrates, respectively. As compared with the case where the laser beams are arranged side by side on a support base or the like, the interval between the optical axes of the laser beams emitted from the laser structure portions LD4, LD5, and LD6 can be sufficiently narrowed. As a result, the laser light emitted from each of the laser structure portions LD4, LD5, and LD6 can be propagated by a single optical system, so that the mounted devices (optical pickup device and optical disk device) can be downsized. be able to.

[Modification of Third Embodiment]
In the third embodiment, the GaAs substrate 130 is peeled off from the laser structures LD5 and LD6 by utilizing the property of the interface between the lower contact layers 70 and 80 and the oxide peeling layers 171 and 181. The GaAs substrate 130 may be removed or thinned from the laser structure portions LD5 and LD6 by wrapping the GaAs substrate 130 without using the contact layers 70 and 80 and the oxide peeling layers 171 and 181. When the laser structure portions LD5 and LD6 obtained by such a method are applied to the semiconductor laser 3, for example, as shown in FIG. 28, the GaAs substrate 130 remains slightly at the bottom of the laser structure portions LD5 and LD6. The GaAs substrate 130 is in electrical contact with the electrode layer 13. Also, as shown in FIG. 29, the laser structures LD5 and LD6 of FIG. 28 are formed on the common GaAs substrate 130, and are disposed on the electrode layer 13 with the common GaAs substrate 130 left. You may do it.

[Application example]
The semiconductor laser LD according to each of the above embodiments and the modifications thereof includes an information reproducing apparatus for reproducing information recorded on a recording medium (optical disk), an information recording apparatus for recording information on the recording medium, and both functions. The present invention can be applied to various devices such as an information recording / reproducing apparatus or a communication apparatus, and an example thereof will be described below.

  FIG. 30 illustrates an example of a schematic configuration of the information recording / reproducing apparatus 100 according to this application example, and includes an optical device 110 and an information processing unit 120.

  The information processing unit 120 acquires information recorded on the recording medium 101 from the optical device 100 and transmits input information to the optical device 110. On the other hand, the optical device 100 is used, for example, as an optical pickup device for high-density recording / reproduction using a DVD or the like, and includes a semiconductor laser LD as a light source, a region on which a recording medium 101 such as a DVD is placed, and a semiconductor laser. And an optical system provided between the laser diode and the LD. A large number of pits (projections) having a size of, for example, several μm are formed on the surface of the recording medium 101. The optical system is disposed in the optical path from the semiconductor laser LD to the recording medium 101. For example, a grating (GRT) 111, a polarization beam splitter (PBS) 112, a collimating lens (CL) 113, a quarter-wave plate (Λ / 4 plate) 114 and objective lens (OL) 115 are provided. In addition, this optical system includes a cylindrical lens (CyL) 116 and a light receiving element (PD) 117 such as a photodiode on the optical path separated by the polarization beam splitter (PBS) 112.

  In this optical device 100, light from the light source (semiconductor laser LD) is focused on the recording medium 101 through the GRT 111, PBS 112, CL 113, λ / 4 plate 114 and OL 115, and reflected by the pits on the surface of the recording medium 101. Is done. The reflected light enters the PD 117 through the OL 115, the λ / 4 plate 114, the CL 113, the PBS 112, and the CyL 116, and the pit signal, tracking signal, and focus signal are read.

  As described above, since the semiconductor laser LD is used as the light source in the optical device 100 of the present embodiment, each laser beam emitted from the semiconductor laser LD can be propagated by a single optical system. Thereby, the optical apparatus 100 can be reduced in size compared with the case where an optical system is provided for each type of laser light emitted from the semiconductor laser LD.

  While the present invention has been described with reference to the embodiment and the modifications, the present invention is not limited to the above embodiment and can be variously modified.

1 is a top view of a semiconductor laser according to a first embodiment of the present invention. It is sectional drawing of the AA arrow direction of the semiconductor laser of FIG. It is sectional drawing for demonstrating the manufacturing method of the semiconductor laser of FIG. It is sectional drawing for demonstrating the process following FIG. It is sectional drawing for demonstrating the process following FIG. It is sectional drawing for demonstrating the process following FIG. FIG. 7 is a cross-sectional view for explaining a step following the step in FIG. 6. It is sectional drawing for demonstrating the process following FIG. FIG. 9 is a cross-sectional view for explaining a step following the step in FIG. 8. It is sectional drawing for demonstrating the process following FIG. FIG. 6 is a cross-sectional view illustrating a modification of the semiconductor laser in FIG. 1. FIG. 10 is a cross-sectional view illustrating another modification of the semiconductor laser in FIG. 1. It is a top view of the semiconductor laser which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the AA arrow direction of the semiconductor laser of FIG. It is sectional drawing of the BB arrow direction of the semiconductor laser of FIG. It is a top view of the semiconductor laser which concerns on the 3rd Embodiment of this invention. It is sectional drawing of the AA arrow direction of the semiconductor laser of FIG. FIG. 17 is a cross-sectional view for illustrating the method for manufacturing the semiconductor laser of FIG. 16. It is sectional drawing for demonstrating the process following FIG. FIG. 20 is a cross-sectional view for explaining a process following the process in FIG. 19. It is sectional drawing for demonstrating the process following FIG. FIG. 22 is a cross-sectional view for explaining a process following the process in FIG. 21. FIG. 23 is a cross-sectional view for illustrating a process following the process in FIG. 22. FIG. 24 is a cross-sectional view for illustrating a process following the process in FIG. 23. FIG. 25 is a cross-sectional view for describing a step following the step in FIG. 24. FIG. 26 is a cross-sectional view for illustrating a process following the process in FIG. 25. FIG. 27 is a cross-sectional view for illustrating a process following the process in FIG. 26. FIG. 17 is a cross-sectional view illustrating a modification of the semiconductor laser in FIG. 16. FIG. 17 is a cross-sectional view illustrating another modification of the semiconductor laser in FIG. 16. It is a schematic block diagram of the optical apparatus which concerns on one application example.

Explanation of symbols

  1-3 ... Semiconductor laser, 10 ... GaN substrate, 11, 51 ... Insulating layer, 12, 53 ... Adhesive layer, 13, 14, 26, 38, 48, 52, 64, 75, 85 ... Electrode layer, 13A, 27 , 39, 49, 56, 57, 66, 78, 88 ... electrode pads, 15 ... protective film, 20, 31, 41 ... lower DBR layer, 21, 32, 42 ... lower spacer layer, 22, 33, 43, 61 , 72, 82 ... active layer, 22A, 33A, 43A, 61A, 72A, 82A ... light emitting region, 23, 34, 44 ... upper spacer layer, 24, 35, 45 ... current confinement layer, 35A, 45A ... current injection region 35B, 45B ... current confinement region, 24, 36, 46 ... upper DBR layer, 25, 37, 47, 63, 74, 84 ... upper contact layer, 130 ... GaAs substrate, 54 ... extraction electrode, 55 ... bump, 60 , 71, DESCRIPTION OF SYMBOLS 1 ... Lower clad layer, 62, 73, 83 ... Upper clad layer, 65, 76, 86 ... Ridge part, 91 ... Front side end surface, 92 ... Rear side end surface, 100 ... Information reproducing | recording recording apparatus, 101 ... Recording medium, 110 ... Optical device, 111 ... GRT, 112 ... PBS, 113 ... CL, 114 ... λ / 4 plate, 115 ... OL, 116 ... CyL, 117 ... PD, 120 ... Information processing unit, 131, 131D, 141, 141D, 171, 171D, 181, 181D ... oxidation peeling layer, LD ... semiconductor laser, LD1-LD6 ... laser structure.

Claims (10)

A GaN substrate;
A first laser structure formed by crystal growth on the GaN substrate;
A multi-wavelength laser comprising: one or a plurality of second laser structures formed by crystal growth on a substrate different from the GaN substrate and disposed on the GaN substrate. The multi-wavelength laser according to claim 1, wherein the second laser structure is formed by crystal growth on a GaAs substrate. 2. The multiwavelength laser according to claim 1, wherein the first and second laser structures are disposed on the same surface side of the GaN substrate. The first and second laser structures have a stacked structure including a first DBR layer, a first spacer layer, an active layer, a second spacer layer, and a second DBR layer in this order from the GaN substrate side. The multi-wavelength laser according to claim 3, wherein laser light is mainly emitted to the second DBR layer side in the stacking direction. The first and second laser structure parts include a lower clad layer, an active layer, and an upper clad layer in this order from the GaN substrate side, and extend in the in-plane direction of the upper layer of the upper clad layer. The multiwavelength laser according to claim 3, wherein a laser beam is emitted in a direction in which the ridge portion extends. The first and second laser structure portions are alternately arranged on both surfaces of the GaN substrate so that laser beams emitted from the first and second laser structure portions are not blocked by other laser structure portions. The multi-wavelength laser according to claim 1, wherein the multi-wavelength laser is provided. The first and second laser structures have a stacked structure including a first DBR layer, a first spacer layer, an active layer, a second spacer layer, and a second DBR layer in order from the GaN substrate side,
The laser structure portion formed on one surface side of the GaN substrate among the first and second laser structure portions mainly emits laser light to the second DBR layer side in the stacking direction of the stacked structure,
Of the first and second laser structure parts, the laser structure part formed on the other surface side of the GaN substrate mainly emits laser light to the first DBR layer side in the stacking direction of the stacked structure. The multi-wavelength laser according to claim 6. On the GaN substrate, comprising a laminated structure including an insulating layer, an adhesive layer and a metal layer in order from the GaN substrate side,
The multi-wavelength laser according to any one of claims 1 to 7, wherein the second laser structure section is disposed on the laminated structure. A light source;
An optical system provided between a region where an optical disk is placed and the light source;
An optical pickup device comprising: the light source including the multi-wavelength laser according to any one of claims 1 to 8. An optical pickup device;
An information processing unit that transmits input information to the optical pickup device or receives information written on an optical disc from the optical pickup device, and
The optical pickup device is provided between a light source configured to include the multi-wavelength laser according to any one of claims 1 to 8, a region where an optical disk is placed, and the light source. An optical disc apparatus comprising: an optical system.

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