JP4967615B2 - Semiconductor light emitting device - Google Patents

Description

  The present invention relates to a semiconductor light emitting device including a light detection element for detecting laser light, and more particularly to a semiconductor light emitting device that can be suitably applied in applications that require high light detection accuracy.

  2. Description of the Related Art Conventionally, in semiconductor light emitting devices for applications such as optical fibers and optical disks, the laser light of a semiconductor laser is detected by a light detection mechanism as part of the purpose of keeping the light output level of the semiconductor laser incorporated therein. Things have been done. This light detection mechanism can be constituted by, for example, a reflecting plate that branches a part of the laser light and a semiconductor photodetector that detects the branched laser light. However, in this case, not only the number of parts increases, but also there is a problem that the reflector and the semiconductor photodetector must be arranged with high accuracy with respect to the semiconductor laser. Therefore, as one of the measures for solving such a problem, it is conceivable to integrally form the semiconductor laser and the semiconductor photodetector.

  However, if these are integrally formed, the semiconductor photodetector may detect not only stimulated emission light (laser light) that should be detected but also spontaneous emission light. In such a case, an error corresponding to the spontaneous emission light is included in the light output level of the semiconductor laser measured based on the photocurrent converted by the semiconductor photodetector. Here, the spontaneous emission light changes depending on the temperature, the operating current, etc., and the correlation between the laser light and the photocurrent is made non-linear, so this method is also required to control the light output level with high accuracy. Not suitable for use.

  Therefore, in Patent Document 1, a technique is proposed in which one photodetecting layer in the semiconductor photodetector is provided at the antinode of the standing wave of the laser light so that the stimulated emission light can be detected more easily than the spontaneous emission light. Yes. Patent Document 2 proposes a technique in which a control layer is provided in a semiconductor photodetector and a part of spontaneous emission light input from the semiconductor light emitting element is blocked before the semiconductor photodetector detects the part.

Special table 2003-522421 gazette Japanese Patent No. 2877785

However, in Patent Document 1, since the antinodes and nodes of the standing wave appear at half the oscillation wavelength λ ₀ , it is required to make the photodetection layer extremely thin. For example, when the oscillation wavelength λ ₀ is 850 nm, the wavelength in the semiconductor photodetector (λ ₀ / n: n is the refractive index in the semiconductor photodetector) is about 250 nm, and the antinodes and nodes have a period of 125 nm. Since it exists, the thickness of the photodetection layer is about 100 nm even if it is thick. Considering that the thickness of the photodetection layer is usually on the order of μm, it is difficult to convert a sufficient amount of stimulated emission light into photocurrent by the semiconductor photodetector in the technique of Patent Document 1, It is not easy to improve detection accuracy.

  Moreover, in patent document 2, a control layer is formed by oxidizing a part of semiconductor substance which comprises a semiconductor photodetector. However, since the oxidized semiconductor material cannot selectively reflect the spontaneous emission light, the spontaneous emission light is somewhat transmitted. Further, the non-oxidized portion of the control layer transmits the spontaneous emission light with almost no attenuation. For this reason, the technique of Patent Document 1 has a problem that the level of spontaneous emission light detected by the semiconductor photodetector cannot be sufficiently reduced, and the light detection accuracy cannot be improved.

  The present invention has been made in view of such problems, and an object thereof is to provide a semiconductor light emitting device capable of improving the light detection accuracy.

Semiconductors light emitting device of the present invention includes a laminated structure, a light-detecting layer. The laminated structure includes a first conductive type first semiconductor layer, an active layer, and a second conductive type second semiconductor layer in this order, and has a fundamental wave light and a wavelength that is ½ times the fundamental wave light. The SHG (Second Harmonic Generation) light is emitted. The photodetection layer has a band gap that is larger than the energy corresponding to the wavelength of the fundamental wave light and not more than twice the energy corresponding to the wavelength of the fundamental wave light.

In the semiconductor light emitting device of the present invention, a light detection layer having a band gap larger than the energy corresponding to the wavelength of the fundamental light and not more than twice the energy corresponding to the wavelength of the fundamental light is provided . As a result, the fundamental wave light out of the light generated in the laminated structure is not absorbed by the photodetection layer but is transmitted through the photodetection layer, but SHG light that is the second harmonic light having an intensity proportional to the square of the intensity of the fundamental wave light. Is absorbed by the photodetection layer and converted into a photocurrent.

According to the semiconductor light emitting device of the present invention, the photodetection layer having a band gap larger than the energy corresponding to the wavelength of the fundamental light and not more than twice the energy corresponding to the wavelength of the fundamental light is provided. SHG light can be absorbed by the light detection layer without being absorbed by the light detection layer among the light generated in the light, and converted into a photocurrent.

  Here, since the SHG light is generated with an intensity that is approximately proportional to the square of the intensity of the fundamental wave light, it is mainly generated by stimulated emission light having a high intensity among the fundamental wave light, and is hardly generated by spontaneous emission light having a low intensity. Absent. That is, SHG light is mainly generated by stimulated emission light mainly included in the fundamental wave light generated in the laminated structure. As a result, light with a high proportion of stimulated emission light can be detected by the photodetection layer, so that the photocurrent converted by the photodetection layer is hardly affected by spontaneous emission light that varies with temperature, operating current, etc. . As a result, the light detection accuracy is improved.

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

[First Embodiment]
FIG. 1 shows a cross-sectional configuration of a semiconductor light emitting device 1 according to a first embodiment of the present invention. The semiconductor light emitting device 1 is obtained by integrally forming a semiconductor photodetector 10 and a surface emitting semiconductor laser 20.

  The semiconductor light emitting device 1 emits laser light from the surface emitting semiconductor laser 20 from the n-side electrode 28 (described later) side to the outside and leaks to the semiconductor photodetector 10 side. A photocurrent corresponding to the output level of the leaked laser light is output from the semiconductor photodetector 10. That is, the semiconductor light emitting device 1 is configured by disposing the semiconductor photodetector 10 on the side opposite to the side where the laser light of the surface emitting semiconductor laser 20 is emitted to the outside. Note that FIG. 1 is a schematic representation and is different from actual dimensions and shapes.

(Surface emitting semiconductor laser 20)
The surface emitting semiconductor laser 20 includes a p-type DBR layer 21 (multilayer reflector), a current confinement layer 22, a lower cladding layer 23, an active layer 24, an upper cladding layer 25, an n-type DBR on the semiconductor photodetector 10. A layered structure in which the layer 26 (multilayer film reflecting mirror) and the n-type contact layer 27 are stacked in this order is provided.

The p-type DBR layer 21 is configured by alternately laminating low refractive index layers (not shown) and high refractive index layers (not shown). This low refractive index layer is, for example, p-type Al _x1 Ga _1-x1 As (0 <x1 ≦ 1) having a thickness of λ ₀ / 4n ₁ (where λ ₀ is an oscillation wavelength and n ₁ is a refractive index), a high refractive index. The layers are each composed of, for example, p-type Al _x2 Ga _1-x2 As (0 ≦ x2 <x1) having a thickness of λ ₀ / 4n ₂ (n ₂ is a refractive index). Examples of p-type impurities include zinc (Zn), magnesium (Mg), and beryllium (Be).

The current confinement layer 22 has a ring-shaped current confinement region 22A in a region from the side surface of the surface emitting semiconductor laser 20 to a predetermined depth, and the other region is a current injection region 22B. Here, the current injection region 22B is made of, for example, p-type Al _x3 Ga _1-x3 As (0 <x3 ≦ 1). The current confinement region 22A includes Al ₂ O ₃ (aluminum oxide), and is obtained by oxidizing a current confinement layer 22D made of p-type Al _x3 Ga _1-x3 As from its side surface, as will be described later. It is a thing. Therefore, the current confinement layer 22 has a function of confining current.

The lower cladding layer 23 is made of, for example, Al _x4 Ga _1-x4 As (0 ≦ x4 ≦ 1). The active layer 24 is made of, for example, Al _x5 Ga _1-x5 As (0 ≦ x5 ≦ 1), and has a light emitting region 24A in a region facing the current injection region 22B. The upper cladding layer 25 is made of, for example, Al _x6 Ga _1-x6 As (0 ≦ x6 ≦ 1).

The n-type DBR layer 26 is configured by alternately laminating low refractive index layers (not shown) and high refractive index layers (not shown). The low refractive index layer is, for example, an n-type Al _x7 Ga _1-x7 As (0 <x7 ≦ 1) having a thickness of λ ₀ / 4n ₃ (where n ₃ is a refractive index), and the high refractive index layer has a thickness of, for example, λ ₀ / 4n ₄ (n ₄ is a refractive index) n-type Al _x8 Ga _1-x8 As (0 ≦ x8 <x7). Examples of n-type impurities include silicon (Si) and selenium (Se).

  The n-type contact layer 27 is made of, for example, n-type GaAs. The surface emitting semiconductor laser 20 also has a ring-shaped n-side electrode 28 having an opening at the center of the surface of the n-type contact layer 27. Here, the n-side electrode 28 has a structure in which, for example, an alloy of gold (Au) and germanium (Ge), nickel (Ni), and gold (Au) are stacked in this order, and the n-type contact layer 27. And are electrically connected.

(Semiconductor photodetector 10)
The semiconductor photodetector 10 is configured by laminating an n-type buffer layer 12, an n-type DBR layer 13 (multilayer film reflector), a photodetection layer 14 and a p-type contact layer 15 in this order on an n-type inclined substrate 11. Has been.

The n-type inclined substrate 11 is a semiconductor substrate having a crystal plane that is slanted compared to a normal flat crystal plane (100). Here, when a GaAs substrate is used as the inclined substrate, examples of the crystal plane include a (011) plane, a (211) plane, a (311) plane, and a (411) plane. The n-type buffer layer 12 is made of, for example, n-type GaAs. The n-type DBR layer 13 is configured by alternately laminating a low refractive index layer (not shown) and a high refractive index layer (not shown), and one of the resonators together with the p-type DBR layer 21. The mirror is configured. The low refractive index layer is, for example, an n-type Al _x9 Ga _1-x9 As (0 <x9 ≦ 1) having a thickness of λ ₀ / 4n ₃ (where n ₃ is a refractive index), and the high refractive index layer has a thickness of, for example, λ ₀ / 4n ₅ (n ₅ is a refractive index) n-type Al _x10 Ga _1-x10 As (0 ≦ x10 <x9). The p-type contact layer 15 is made of, for example, p-type GaAs.

The photodetection layer 14 is a semiconductor having a band gap larger than the band gap of the active layer 24 and not more than twice the band gap of the active layer 24, that is, greater than the energy corresponding to the oscillation wavelength λ ₀ and having an oscillation wavelength λ ₀ . It is made of a semiconductor having a band gap equal to or less than twice the corresponding energy. The photodetection layer 14 is substantially composed of a non-doped semiconductor. Here, “substantially non-doped semiconductor” means a semiconductor in which neither p-type or n-type impurities are doped at all, or so small that the absorbed light can be converted into a photocurrent. It is a concept that includes a semiconductor doped with impurities. The photodetection layer 14 may be made of a semiconductor doped with a p-type or n-type impurity having a lower concentration than the n-type DBR layer 13 and the p-type DBR layer 21.

Thus, since the photodetection layer 14 is composed of a semiconductor that is not doped with p-type or n-type impurities at all or is lightly doped, the photodetection layer 14 is composed of a surface emitting semiconductor laser 20. The second harmonic light (SHG light) having an intensity proportional to the square of the intensity of the fundamental wave light without absorbing the fundamental wave light (light having the oscillation wavelength λ ₀ ) of the laser light output from the laser light is absorbed. To convert photocurrent into photocurrent. The photocurrent generated in the photodetection layer 14 is input as a light output monitor signal to a light output arithmetic circuit (not shown) connected to the semiconductor photodetector 10, and the surface emitting semiconductor laser is used in the light output arithmetic circuit. This is used to measure the output level of the laser beam output from 20 to the n-side electrode 28 side (external).

Here, when the wavelength λ ₀ of the fundamental wave light is 980 nm, the wavelength of the SHG light is 490 nm which is ½ of λ _0. Therefore, the semiconductor does not absorb the light of wavelength 980 nm but absorbs the light of wavelength 490 nm. Examples include GaAs, GaInP, AlInP, AlGaAs, AlGaInP, and ZnMgSSe. If the wavelength λ ₀ of the fundamental wave light is other than 980 nm, the light detection layer 14 may be formed of a semiconductor that does not absorb light of that wavelength and absorbs light of a wavelength that is ½ of that wavelength.

  The photodetection layer 14 is disposed inside a resonator constituted by the n-type DBR layer 13, the p-type DBR layer 21 and the n-type DBR layer 26. For example, as shown in FIG. Provided between the type DBR layer 13 and the p-type DBR layer 21. For this reason, when the photodetection layer 14 is not used as a resonator mirror, it is preferable that the optical periodic structure of the resonator is not disturbed. However, when the photodetection layer 14 is used as a resonator mirror, it is n-type. The DBR layer 13 and the p-type DBR layer 21 are preferably configured so as to form an optical periodic structure of a resonator. However, the photodetection layer 14 need not be composed of a single layer, and may be composed of a plurality of layers. When the photodetection layer 14 is constituted by a plurality of layers as described above, each layer may be constituted by different impurity concentrations, or may be constituted by different semiconductor materials. In order to increase the amount of SHG light incident on the light detection layer 14, it is preferable to provide the light detection layer 14 closer to the active layer 24. However, the amount of SHG light incident on the light detection layer 14 is small. If the incident SHG light can be detected with high accuracy, the light detection layer 14 may be provided at the end of the resonator or outside. For example, as shown in the semiconductor light emitting device 2 of FIG. 2, the p-type DBR layer 21 is formed thick so that the n-type DBR layer 26 and the p-type DBR layer 21 alone constitute a resonator, and the p-type DBR layer 21 is formed. In addition, by providing the n-type semiconductor layer 18 that does not form the optical periodic structure of the resonator instead of the n-type DBR layer 13, the photodetection layer 14 can be disposed outside the resonator.

  The light detection layer 14 preferably has a configuration in which the difference in refractive index between the fundamental wave light and the SHG light is small, that is, the fundamental wave light and the SHG light are phase-matched. Further, as shown in the semiconductor light emitting device 3 of FIG. 3, the phase of the fundamental wave light and the SHG light is phase-adjusted on the surface of the light detection layer 14 on the active layer 24 side so as to be phase matched when incident on the light detection layer 14. The matching layer 19 may be provided in contact therewith. If the fundamental wave light and the SHG light are not phase-matched when entering the light detection layer 14, the SHG light generated in the surface-emitting type semiconductor laser 20 cancels each other, and light is emitted from the surface-emitting type semiconductor laser 20 side. This is because the intensity of the SHG light incident on the detection layer 14 may be extremely reduced. Here, the phase matching layer 19 includes, for example, a semiconductor layer in which the traveling speed of the fundamental wave light is relatively fast and the traveling speed of the SHG light is relatively slow, and the traveling speed of the fundamental wave light is relatively slow and the SHG light. And a semiconductor layer having a relatively fast traveling speed, and the fundamental wave light on the surface of the phase matching layer 19 on the light output side (interface between the light detection layer 14 and the phase matching layer 19). The traveling speeds of the SHG light and the SHG light are made substantially equal.

The photodetection layer 14 is preferably made of a material having a large SHG conversion efficiency η _SHG . This is because the fundamental wave light incident on the light detection layer 14 can be converted into SHG light in the light detection layer 14. The SHG conversion efficiency η _SHG can be expressed by the following equation (1).

Here, P _f ² is the light output (W) of the fundamental wave light, P _SH ² is the light output (W) of the SHG light, ε ₀ is the dielectric constant (F / m), and μ ₀ is the magnetic permeability (H / m). , Ω is the angular frequency (rad / s) of the fundamental wave light, d is the second-order nonlinear optical coefficient (m / V), l is the length of the SHG medium (m), and n _SH is the refractive index of the SHG light (none (Dimensional amount), Δk is a difference in propagation constant between fundamental wave light and SHG light (/ m), and A is a cross-sectional area (m ² ).

Table 1 lists some of the materials with large SHG conversion efficiency η _SHG . Table 1 also lists materials whose fundamental light absorption coefficient α is not zero, that is, materials that absorb part of the fundamental light. However, since the second-order nonlinear optical coefficient d in these materials is sufficiently large, It is possible to generate SHG light from fundamental light that has not been absorbed by the material. Therefore, even if the absorption coefficient α of the fundamental wave light is not zero, any material having a sufficiently large second-order nonlinear optical coefficient d can be used as the material of the light detection layer 14.

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

4, 5, and 6 show the manufacturing method in the order of steps. In order to manufacture the semiconductor light emitting device 1, a semiconductor layer made of a GaAs compound semiconductor is formed on an n-type inclined substrate 11 made of n-type GaAs, for example, by MOCVD (Metal Organic Chemical Vapor Deposition) method. It forms in a lump. At this time, for example, trimethylaluminum (TMA), trimethylgallium (TMG), or arsine (AsH ₃ ) is used as a raw material for the GaAs compound semiconductor, and for example, hydrogen selenide (H ₂ Se) is used as the source material for the donor impurity. As the acceptor impurity raw material, for example, dimethyl zinc (DMZn) is used.

  Specifically, first, an n-type buffer layer 12, an n-type DBR layer 13, a photodetection layer 14, a p-type contact layer 15, a p-type DBR layer 21, a current confinement layer 22D, a lower portion, The clad layer 23, the active layer 24, the upper clad layer 25, the n-type DBR layer 26, and the n-type contact layer 27 are laminated in this order (FIG. 4).

  Next, after forming a mask (not shown) in a predetermined region of the surface of the n-type contact layer 27, the n-type contact layer 27 to the p-type DBR layer 21 are selectively removed by, for example, a dry etching method. Then, a mesa shape is formed, and then the mask is removed (FIG. 5).

  Next, oxidation treatment is performed at a high temperature in a water vapor atmosphere to selectively oxidize the current confinement layer 22D from the side surface. Thereby, the outer edge region of the current confinement layer 22D becomes an insulating layer (aluminum oxide). As a result, a ring-shaped current confinement region 22A is formed in the outer edge region, and the central region becomes the current injection region 22B. In this way, the current confinement layer 22 is formed (FIG. 6).

  Next, for example, a ring-shaped n-side electrode 28 is formed on the surface of the n-type contact layer 27 by vapor deposition. Similarly, the p-side common electrode 16 is formed on the exposed surface of the p-type contact layer 15. N-side electrodes 17 are formed on the back surface of the n-type inclined substrate 11 (FIG. 1). In this way, the semiconductor light emitting device 1 of the present embodiment is manufactured.

  Hereinafter, the operation and effect of the semiconductor light emitting device 1 of the present embodiment will be described.

  In the semiconductor light emitting device 1, when a predetermined voltage is applied between the p-side common electrode 16 and the n-side electrode 28, the current confined by the current confinement layer 22 is light emission that is the gain region of the active layer 24. The light is injected into the region 24A, and light is emitted by recombination of electrons and holes. This light includes not only light generated by stimulated emission, but also light generated by spontaneous emission. As a result of repeated stimulated emission in the resonator, laser oscillation occurs at a predetermined wavelength, and the predetermined light is emitted. A laser beam having a wavelength is repeatedly incident on the light detection layer 14 provided in the resonator, and is output to the outside from the n-side electrode 28 side.

By the way, in the present embodiment, the surface emitting semiconductor laser 20 is formed by crystal growth on the n-type inclined substrate 11, so that the resonator of the surface emitting semiconductor laser 20 is illustrated as illustrated in FIG. The light traveling back and forth propagates through the asymmetric medium. For this reason, not only the fundamental wave light L1 (laser light having an oscillation wavelength λ ₀ ) but also a fundamental wave light generated by converting a part of the fundamental wave light L1 by an asymmetric medium is included in the light traveling back and forth in the resonator. SHG light L2 having a wavelength that is ½ times L1 is also included. Since the SHG light L2 is generated with an intensity that is approximately proportional to the square of the intensity of the fundamental wave light L1, it is mainly generated by stimulated emission light having a high intensity in the fundamental wave light L1, and is generated by spontaneous emission light having a low intensity. There is almost no. Accordingly, the SHG light is mainly generated by the stimulated emission light mainly included in the fundamental wave light L1 generated in the surface emitting semiconductor laser 20.

  Here, the photodetection layer 14 of the present embodiment is made of a semiconductor having a band gap larger than the band gap of the active layer 24 and not more than twice the band gap of the active layer 24. Of the reciprocating laser light, the fundamental wave light L1 is not absorbed, and the SHG light L2 having a high ratio of stimulated emission light is absorbed and converted into a photocurrent. That is, the spontaneous emission light slightly contained in the fundamental wave light generated in the surface emitting semiconductor laser 20 is not absorbed by the light detection layer 14. This photocurrent is output to the optical output arithmetic circuit as an optical output monitor signal through a wire (not shown) electrically connected to the p-side common electrode 16 and the n-side electrode 17. Thereby, the output level of the laser beam outputted to the outside from the n-side electrode 28 side is measured.

  From the above, in the semiconductor light emitting device 1 of the present embodiment, the surface emitting semiconductor laser 20 is formed by crystal growth on the n-type inclined substrate 11, and the light detection layer 14 is formed in the band of the active layer 24. Since it is configured by a semiconductor having a band gap larger than the gap and not more than twice the band gap of the active layer 24, SHG light generated mainly by stimulated emission light can be detected by the light detection layer 14. As a result, the photocurrent converted in the photodetection layer 14 is hardly affected by the spontaneous emission light that varies depending on the temperature, the operating current, etc., so that the photodetection accuracy is improved.

[Second Embodiment]
FIG. 8 shows a cross-sectional configuration of the semiconductor light emitting device 4 according to the second embodiment of the present invention. FIG. 8 is a schematic representation, which differs from actual dimensions and shapes. Moreover, in the following description, when the same code | symbol as the said embodiment is used, it has having the structure and function similar to the element of the same code | symbol.

  The semiconductor light emitting device 4 is configured by disposing a semiconductor photodetector 70 on the light emitting side surface of a light emitting diode (LED) 80 and integrally forming it. In the semiconductor light emitting device 4, light emitted from the light emitting diode 80 is emitted from the n-side electrode 18 (described later) side of the semiconductor photodetector 70 to the outside. Further, the semiconductor photodetector 70 outputs a photocurrent corresponding to the output level of the incident light.

  That is, this semiconductor light emitting device 4 is mainly different from the above embodiment in which the surface emitting semiconductor laser 20 is provided as a light source in that the light emitting diode 80 is provided as a light source. Therefore, hereinafter, the above differences will be mainly described in detail, and description of the same configurations, operations, and effects as those in the above embodiment will be appropriately omitted.

(Semiconductor photodetector 70)
The semiconductor photodetector 70 is configured by laminating an n-type buffer layer 12, a photodetection layer 14, and a p-type contact layer 15 in this order on an n-type inclined substrate 11. An n-side electrode 18 having an opening at a portion facing the light emitting diode 80 is formed on the back surface of the n-side inclined substrate 11. The n-side electrode 18 has a structure in which, for example, AuGe, Ni, and Au are laminated in this order, and is electrically connected to the n-side inclined substrate 11.

(Light emitting diode 80)
The light emitting diode 80 has a laminated structure in which a lower clad layer 81, an active layer 82, and an upper clad layer 83 are laminated in this order on a semiconductor photodetector 70. An n-side electrode 84 is formed on the upper cladding layer 83, and the insulating layer 85 covers the side surfaces of the lower cladding layer 81, the active layer 82, and the upper cladding layer 83.

The lower cladding layer 81 is made of, for example, Al _x11 Ga _1-x11 As (0 ≦ x11 ≦ 1). The active layer 82 is made of, for example, Al _x12 Ga _1-x12 As (0 ≦ x12 ≦ 1), and has a light emitting region 82 </ b> A in a region facing the n-side electrode 84. The upper cladding layer 83 is made of, for example, Al _x13 Ga _1-x13 As (0 ≦ x13 ≦ 1). The insulating layer 85 is made of, for example, SiN or SiO2. The n-side electrode 84 has a structure in which, for example, AuGe, Ni, and Au are stacked in this order, and is electrically connected to the upper cladding layer 83.

  The semiconductor light emitting device 4 having such a configuration can be manufactured, for example, as follows. First, the n-type buffer layer 12, the light detection layer 14, the p-type contact layer 15, the lower cladding layer 81, the active layer 82, and the upper cladding layer 83 are laminated on the n-type inclined substrate 11 in this order.

  Next, after forming a mask (not shown) in a predetermined region of the surface of the upper cladding layer 83, the upper cladding layer 83 to the lower cladding layer 81 are selectively removed by, for example, a dry etching method to form a trapezoidal shape. The mesa is formed, and then the mask is removed.

  Next, the n-side electrode 84 is formed on the upper surface of the upper clad layer 83 by, for example, vapor deposition, and the p-side common electrode 16 is formed on the exposed surface of the p-type contact layer 15 in the same manner. An n-side electrode 18 having an opening in a portion facing the light emitting diode 80 is formed on the back surface of the inclined substrate 11. In this way, the semiconductor light emitting device 4 of the present embodiment is manufactured.

  In this semiconductor light emitting device 4, when a predetermined voltage is applied between the p-side common electrode 16 and the n-side electrode 84, current is injected into the light emitting region 82 </ b> A that is the gain region of the active layer 82, thereby Light emission occurs due to recombination of holes with holes, and the light is output to the outside from the n-side electrode 18 side. This light mainly includes light generated by spontaneous emission, but also includes light generated by stimulated emission.

  By the way, in the present embodiment, since the light emitting diode 80 is formed by crystal growth on the n-type inclined substrate 11, the light in the light emitting diode 80 includes fundamental wave light (like the above embodiment). In addition to light having a wavelength corresponding to the energy of the band gap of the active layer 82, SHG light having a wavelength that is ½ times the fundamental light is also included. Since this SHG light is generated with an intensity approximately proportional to the square of the intensity of the fundamental wave light, it is mainly generated by stimulated emission light having a high intensity among the fundamental wave light, and is hardly generated by spontaneous emission light having a low intensity. . Therefore, SHG light is mainly generated by stimulated emission light slightly contained in the fundamental light generated in the light emitting diode 80.

  Here, the photodetection layer 14 of the present embodiment is composed of a semiconductor having a band gap larger than the band gap of the active layer 82 and not more than twice the band gap of the active layer 82. The fundamental wave light is not absorbed, but the SHG light is absorbed and converted into a photocurrent. That is, spontaneous emission light mainly included in the fundamental light generated in the light emitting diode 80 is not absorbed by the light detection layer 14. This photocurrent is output to the optical output arithmetic circuit as an optical output monitor signal through a wire (not shown) electrically connected to the p-side common electrode 16 and the n-side electrode 18. Thereby, the output level of the emitted light emitted from the n-side electrode 18 side to the outside is measured.

  From the above, in the semiconductor light emitting device 4 of the present embodiment, the light emitting diode 80 is formed by crystal growth on the n-type tilted substrate 11, and the photodetecting layer 14 is made larger than the band gap of the active layer 82. Since the semiconductor layer is made of a semiconductor having a band gap that is not more than twice the band gap of the active layer 82, the SHG light can be detected by the photodetection layer 14. As a result, the emitted light traveling toward the n-side electrode 18 is hardly absorbed when passing through the photodetection layer 14, and is thus emitted to the outside from the n-side electrode 18 side with almost no loss in the photodetection layer 14. The output level of emitted light can be measured.

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

  For example, in the above embodiment, the case where the semiconductor material is composed of a GaAs-based compound semiconductor has been described. However, the material is composed of another material system, for example, a red-based material such as AlGaAs or GaInP, or a blue-based material such as GaInN. It is also possible to do.

  In the first embodiment, the semiconductor photodetector 10 is provided on the back side of the surface-emitting type semiconductor laser 20, but may be provided on the side that outputs the laser light to the outside. In this case, as in the first embodiment, the photodetection layer can be provided inside or outside the resonator. Moreover, in the said 2nd Embodiment, although the semiconductor photodetector 10 was provided in the light emission side of the light emitting diode 30, you may provide in the back surface side of the light emitting diode 30. FIG.

  In the above embodiment, the case where the n-type inclined substrate 11 is used as the common substrate has been described. However, the present invention is also applicable to the case where a p-type inclined substrate is used as the common substrate. However, in that case, the conductivity type described in the above embodiment may be replaced from p-type to n-type and from n-type to p-type. Further, the semiconductor substrate does not need to be a tilted substrate, and may be any substrate that can epitaxially stack a semiconductor layer capable of generating SHG light or third-order or higher harmonic light. It may be a semiconductor substrate having a flat crystal face (100) that is not ideally grown.

Moreover, in the said embodiment, although the photon detection layer 14 was comprised so that SHG light could be absorbed, it seems that a semiconductor light-emitting device can generate | occur | produce nth-order (n is an integer greater than or equal to 3) harmonic light. In this case, the photodetection layer needs to be configured to be able to absorb the nth harmonic light. Specifically, a semiconductor in which the photodetection layer has a band gap larger than the band gap of the active layer and not more than n times the band gap of the active layer, that is, the oscillation wavelength λ ₀ greater than the energy corresponding to the oscillation wavelength λ _0. As long as it is made of a semiconductor having a band gap equal to or less than n times the energy corresponding to.

  In the above embodiment, the p-side common electrode 16 that can be used in common by the semiconductor photodetector 10 and the surface emitting semiconductor laser 20 or the light emitting diode 30 is provided. You may make it provide the p side electrode which applies a voltage separately to the type semiconductor laser 20 or the light emitting diode 30, respectively.

1 is a cross-sectional configuration diagram of a semiconductor light emitting device according to a first embodiment of the present invention. It is a cross-sectional block diagram of the semiconductor light-emitting device which concerns on one modification. It is a cross-sectional block diagram of the semiconductor light-emitting device which concerns on another modification. FIG. 3 is a cross-sectional configuration diagram for explaining a manufacturing process of the semiconductor light emitting device of FIG. 1. FIG. 5 is a cross-sectional configuration diagram for explaining a process following FIG. 4. FIG. 6 is a cross-sectional configuration diagram for explaining a process following FIG. 5. It is a cross-sectional block diagram for demonstrating the effect | action of the semiconductor light-emitting device of FIG. It is a cross-sectional block diagram of the semiconductor light-emitting device concerning the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1-4 ... Semiconductor light-emitting device, 10, 30, 50, 70 ... Semiconductor photodetector, 11 ... N-type inclination board | substrate, 12 ... N-type buffer layer, 13, 26 ... N-type DBR layer, 14 ... Photo detection layer, 15 ... p-type contact layer, 16 ... p-side common electrode, 17, 28, 84 ... n-side electrode, 18 ... n-type semiconductor layer, 19 ... phase matching layer, 20, 40, 60 ... surface emitting semiconductor laser, 21 ... p-type DBR layer, 22, 22D ... current confinement layer, 22A ... current confinement region, 22B ... current injection region, 23, 81 ... lower cladding layer, 24, 82 ... active layer, 24A, 82A ... light emission region, 25, 83: upper cladding layer, 27: n-type contact layer, 80: light emitting diode, 85: insulating layer, L1: fundamental light, L2: SHG light.

Claims (7)

The first-conductivity-type first semiconductor layer, the active layer, and the second-conductivity-type second semiconductor layer are included in this order , and the fundamental wave light and SHG (Second Harmonic Generation) a laminated structure that emits light including light, and
Greater than energy corresponding to the wavelength of the fundamental light, a semiconductor light emitting device Ru and an optical detection layer having a band gap of 2 times the energy corresponding to the wavelength of the fundamental light. A third semiconductor layer of a second conductivity type provided on the opposite side of the active layer with respect to the first semiconductor layer;
The photodetection layer is disposed between the first semiconductor layer and the third semiconductor layer and has a lower concentration than any of the first semiconductor layer, the second semiconductor layer, and the third semiconductor layer. the semiconductor light emitting device according to claim 1 impurity has been configured by the doped semiconductor. The photodetection layer is doped with a semiconductor in which neither impurity of the first conductivity type nor the second conductivity type is doped at all, or a small amount of impurities that can convert the absorbed light into a photocurrent. and that the semiconductor light-emitting device according to claim 2 that is composed of a semiconductor. Wherein the first semiconductor layer and the second semiconductor layer semiconductor light emitting device according to claim 1 that make up the pair of multilayer-film reflective mirror. It said first semiconductor layer and the light detection layer semiconductor light emitting device according to claim 1 that make up the multilayer reflector. Wherein the first semiconductor layer and the light detection layer semiconductor light emitting device according to claim 5 that have a periodic structure corresponding to the wavelength of light output from the active layer. The light between the detection layer and the active layer, a semiconductor light emitting device according to claim 1, Ru a phase matching layer for matching the respective phase of the fundamental wave light and SHG light.

Images