JP3712686B2 - Planar optical semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a planar optical semiconductor device.
[0002]
[Prior art]
Conventionally, in order to realize a long-wavelength surface emitting laser, a GaInAs / AlGaAs / GaAs laser with a short wavelength is excited by current injection, and a laser beam generated from this is incident on a GaInAsP / InP laser with a long wavelength. There is something that oscillates.
[0003]
This surface-emitting laser can obtain laser light having a long wavelength by absorbing laser light having a short wavelength with a GaInAsp / InP-based laser and oscillating it.
[0004]
However, this surface emitting laser is not bonded to the fused interface in order to bond a GaInAs / AlGaAs / GaAs laser having a GaAs substrate as a supporting substrate and a GaInAsP / InP laser having an InP substrate as a supporting substrate. There is a problem in that the oscillation efficiency is low because a light emitting center is generated and the laser light is absorbed in this portion.
[0005]
In addition, since the difference in thermal expansion coefficient between the substrates is large, there is a problem that the substrates are warped as the temperature rises due to laser oscillation.
[0006]
In addition, the process of fusing the substrate is necessary during the manufacturing process, which not only makes the process extremely complicated, but also causes a large stress at the interface to fuse the substrates having different lattice constants, resulting in a decrease in reliability. There is.
[0007]
[Problems to be solved by the invention]
As described above, the conventional surface emitting laser has to be manufactured by fusing different substrates, and there are problems that the light emission efficiency is low, the substrate is warped, and the reliability is lowered.
[0008]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a planar optical semiconductor device that has high light emission efficiency, does not warp the substrate, and has improved reliability.
[0012]
[Means for Solving the Problems]
  To achieve the above objectiveThe present invention comprises a substrate,
  A first light emitting layer formed on the substrate and emitting light by current injection;
  A second light emitting layer formed on the substrate;
  A pair of first semiconductor multilayer film reflectors disposed so as to sandwich the first light emitting layer and the second light emitting layer;
  A pair of second semiconductor multilayer film reflectors arranged so as to sandwich the first light emitting layer, the second light emitting layer, and the pair of first semiconductor multilayer film reflectors;
  The pair of first semiconductor multilayer film reflecting mirrors absorbs light emitted from the first light emitting layer into the first light emitting layer and causes first laser oscillation,
  The second light emitting layer absorbs the first laser light oscillated by the first laser oscillation and emits light,
  The pair of second semiconductor multilayer film reflecting mirrors absorbs light emitted from the second light emitting layer into the second light emitting layer and causes second laser oscillation to generate second laser light. A planar optical semiconductor device is provided.
[0013]
At this time, the first light emitting layer is made of Al._xGa_1-xyIn_yAs_1-zP_z(0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ 1-xy ≦ 1, 0 ≦ z ≦ 1) layers, and the second light emitting layer is Ga_1-pIn_pAs_1-qN_qIt is preferable to have a layer (0 ≦ p ≦ 1, 0 <q <1).
[0014]
The second light emitting layer is preferably disposed at a position where the density of the first laser light is higher than the average light density.
[0015]
The second light emitting layer is preferably disposed at a position where the density of the second laser light is higher than the average light density.
[0016]
The second light emitting layer is disposed at a position where the density of the first laser light is higher than the average light density and the density of the second laser light is higher than the average light density. It is preferable.
[0017]
It is preferable that there are a plurality of the second light emitting layers.
[0018]
In addition, it is preferable that at least one of the second light emitting layers is capable of current injection.
[0019]
The substrate is preferably GaAs.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and can be used in various ways.
[0021]
(Embodiment 1)
FIG. 1 is a cross-sectional view of a planar optical semiconductor element according to Embodiment 1 of the present invention.
[0022]
As shown in FIG. 1, this planar optical semiconductor element is formed on a GaAs substrate 1 with Al._xGa_1-xyIn_yAs_1-zP_zA first light-emitting layer 4 made of (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ 1-xy ≦ 1, 0 ≦ z ≦ 1) is formed. A pair of first semiconductor multilayer film reflecting mirrors 2 and 3 are formed so as to sandwich the first light emitting layer 4. Examples of the substrate 1 include a GaAs / Si laminated structure, an InP substrate, and a GaP substrate in addition to a GaAs substrate. The same applies to the following embodiments.
[0023]
On the first light emitting layer 4, Ga_1-pIn_pAs_1-qN_qA second light emitting layer 6 made of (0 ≦ p ≦ 1, 0 <q <1) is formed. A pair of second semiconductor multilayer film reflecting mirrors 7 and 9 are formed so as to sandwich the second light emitting layer 6.
[0024]
A spacer layer 17 is formed on the first light emitting layer 4. A current confinement layer 10 made of an oxide is formed on the spacer layer 17 so that the current is confined in the semiconductor layer 11 that is not oxidized.
[0025]
A p-type conductive layer 5 is formed on the current confinement layer 10. A contact layer 13 is formed on the p-type conductive layer 5. A surface electrode 14 is formed on the contact layer 13. A back electrode 15 is formed on the back surface of the GaAs substrate 1.
[0026]
The second light emitting layer 6 is sandwiched between the phase adjusting semiconductor layers 8a and 8b.
A p-type impurity diffusion preventing layer 16 is formed between the contact layer 13 and the first semiconductor multilayer film reflecting mirror 3. A phase adjustment layer 18 is formed between the first semiconductor multilayer mirror 3 and the second semiconductor multilayer mirror 7.
[0027]
The pair of first semiconductor multilayer film reflecting mirrors 2 and 3 reflect the light emitted from the first light emitting layer 4 so as to absorb the feedback to the first light emitting layer 4 and cause the first laser oscillation. It has become.
[0028]
The second light emitting layer 6 absorbs and emits the first laser light oscillated by the first laser oscillation. The pair of second semiconductor multilayer film reflecting mirrors 7 and 9 reflect the light emitted from the second light emitting layer 6 to cause the second light emitting layer 6 to absorb the feedback and cause the second laser oscillation. Thus, it becomes possible to generate laser light having a long wavelength.
[0029]
The first light emitting layer 4 is made of Al._xGa_1-xyIn_yAs_1-zP_z(0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ 1-xy ≦ 1, 0 ≦ z ≦ 1), for example, the emission wavelength is 0.98 μm.
[0030]
The first semiconductor multilayer mirrors 2 and 3 have a low refractive index Al._xGa_1-xAs (0.7 ≦ x <0.9) layer and high refractive index Al_yGa_1-yThis is a laminated structure in which As (0.05 ≦ y ≦ 0.35) layers are alternately laminated. Low refractive index Al_xGa_1-xAs (0.7 ≦ x <0.9) layer and high refractive index Al_yGa_1-yThe thickness of each As (0.05 ≦ y ≦ 0.35) layer is set so that the refractive index × thickness is ¼ of the emission wavelength (here 0.98 μm) in the first light emitting layer 4. Designed.
[0031]
The current confinement layer 10 is made of Al having a high Al composition._zGa_1-zThis is an aluminum gallium oxide layer formed by oxidizing an As (0.9 <z <1) layer laterally from its side surface. Al is not oxidized_zGa_1-zThe As (0.9 <z <1) layer 11 is a current-carrying region having a diameter of 2 μm to 5 μm.
[0032]
The p-type conductive layer 5 is made of p-type Al._wGa_1-wIt is formed of an As (0.05 <w <0.35) layer. The contact layer 13 is formed of a p-type GaAs layer.
[0033]
The second light-emitting layer 6 includes two layers of Ga having a band gap of 0.99 eV to 0.86 eV._1-sIn_sAs_1-pN_p(0 <s <1, 0 <p <1, for example, p = 0.005) Ga between the quantum well layers with a band gap of 1.13 eV to 1.38 eV_1-uIn_uAs_1-vN_v(0 <u <1, 0 <v <1, e.g., v = 0.003) A barrier layer is sandwiched between the two quantum well layers and Ga gap having a band gap of 1.13 eV to 1.38 eV._1-uIn_uAs_1-vN_v(0 <u <1, 0 <v <1, for example, v = 0.003) This is a structure in which two light guide layers are formed. The second light emitting layer 6 has an emission wavelength of 1.3 μm. Here, although two quantum well layers are provided, three or more layers may be formed with a barrier layer interposed therebetween.
[0034]
As described above, there are a plurality of active layers inside the second light emitting layer 6, and the whole may be one light emitting layer. By doing so, the light density in one light emitting layer is lowered. For this reason, the maximum light output is increased, the temperature dependency is decreased, and a semiconductor element having excellent high temperature characteristics can be obtained.
[0035]
The second semiconductor multilayer mirrors 7 and 9 have a low refractive index Al._xGa_1-xAs (0.7 ≦ x <0.9) layer and high refractive index Al_yGa_1-yThis is a laminated structure in which As (0.05 ≦ y ≦ 0.35) layers are alternately laminated. Low refractive index Al_xGa_1-xAs (0.7 ≦ x <0.9) layer and high refractive index Al_yGa_1-yThe thickness of each As (0.05 ≦ y ≦ 0.35) layer is such that the refractive index × thickness is ¼ of the emission wavelength (1.3 μm in this case) in the second light emitting layer 6. Designed.
[0036]
The phase adjusting semiconductor layers 8a and 8b are made of Al._yGa_1-yIt is formed of an As (0.05 ≦ y ≦ 0.35) layer. The phase adjusting semiconductor layers 8a and 8b are configured to provide a second light emission at a peak position of the amplitude of the standing wave component of the standing wave component related to the amplitude of the laser light generated in the first light emitting layer 4 or the second light emitting layer 6. The thickness is adjusted so that the layer 6 is located.
[0037]
For example, among the second semiconductor multilayer film reflecting mirrors 7 and 9, the layer facing the second light emitting layer 6 side is made of Al having a low refractive index._xGa_1-xThe layer is assumed to be an As (0.7 ≦ x <0.9) layer. The sum of the thicknesses of the phase adjusting semiconductor layer 8a and the second light emitting layer 6 is an integral multiple of 0.75 μm, and the thickness of the phase adjusting semiconductor layer 8b is an integral multiple of 0.75 μm.
Thus, the second light emitting layer 6 can be provided at a position where the optical densities of the first laser beam and the second laser beam are higher than the average value in the resonator.
[0038]
  In this way, the light emitted from the first light emitting layer 4 causes a laser operation and thus has a standing wave component in the resonator. For this reason, the light emitted from the first light emitting layer 4 has a density in the resonator. Therefore, the first light emitting layer 4 and the second light emitting layer 4Light emissionIt is preferable that both layers 6 are provided so as to be located in a portion where the light density of the laser beam is high.
[0039]
In addition, the density of the light density also occurs with respect to the laser light emitted from the second light emitting layer 6. In this case, it is preferable that the second light emitting layer 6 is provided so that the laser light is located in a portion where the density is high.
[0040]
By doing so, the light absorption coefficient is increased and the carriers in the second light emitting layer 6 are efficiently excited. If the second light emitting layer 6 is provided at a position where the laser beam has a high light density, the light absorption coefficient is increased and the light loss is reduced, so that the threshold value can be lowered and the light output is increased.
[0041]
The p-type impurity diffusion prevention layer 16 is made of n-type Al._yGa_1-yIt is formed of an As (0.05 ≦ y ≦ 0.35) layer. Since the p-type impurity diffusion prevention layer 16 is formed of the n-type semiconductor layer in this manner, the p-type impurity can be prevented from diffusing from the lower layer to the second light emitting layer 6, and the light emission efficiency is reduced. Does not happen.
[0042]
The spacer layer 17 and the phase adjustment layer 18 are each made of Al._yGa_1-yIt is formed of an As (0.05 ≦ y ≦ 0.35) layer.
[0043]
In such a surface type semiconductor optical device, when the diameter of the AlGaAs layer 11 having a high Al concentration through which a current flows is 5 μm, the threshold current value is 0.1 mA, and the oscillation wavelength 1. 3 μm light can be obtained. The maximum light output is 0.3 mW or more.
[0044]
Al as the first light emitting layer 4_xGa_1-xyIn_yAs_1-zP_z(0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ 1-xy ≦ 1, 0 ≦ z ≦ 1), so that even if the operating temperature is raised, the first light emitting layer 6 is irradiated. The influence of the laser beam is small. Since the first light emitting layer 4 emits light with a larger energy than the second light emitting layer 6, the temperature dependence of the light emission intensity is small. In addition, since the second laser is an optically pumped laser using the first laser beam, the temperature dependency is smaller than that of the current pumped laser. For this reason, the temperature dependence of the second laser can be made smaller than when the current excitation operation is performed alone.
[0045]
When the temperature is raised to 85 ° C. under a driving condition in which a light output of 0.1 mW is obtained at room temperature, a very small value of 10% or less can be realized.
[0046]
Next, a method for manufacturing the planar optical semiconductor device of this embodiment will be described.
[0047]
First, a semiconductor multilayer structure for forming elements is formed on the GaAs substrate 1 by MOCVD.
[0048]
Specifically, the n-type GaAs substrate 1 is replaced with AsH.₃And H₂Cleaning is performed for 10 minutes by raising the temperature to 720 ° C. in an atmosphere. Then the substrate temperature is lowered to 680 ° C. and AsH₃And TMGa (tri-methyl-gallium) and SiH₄As a raw material, an n-type GaAs buffer layer to which Si is added is formed. This n-type GaAs buffer layer is a surface layer on the GaAs substrate 1 and is not shown in the drawing.
[0049]
Next, TMAl (trimethylaluminum), TMGa, AsH₃And SiH₄As a raw material, the n-side first semiconductor multilayer mirror 2 is formed. At this time, TMAl and TMGa sources having different flow rates are used for the two layers having different Al compositions.
[0050]
  Next, TMGa, TMIn (trimethylindium) and AsH₃As a raw materialFirst light emissionLayer 4 is formed. Next, TMGa, AsH₃And CBr₄Is used to form a GaAs spacer layer 17 to which carbon is added. Next, this spacer-Al doped with Zn on the layer 17_0.98Ga_0.02As layer is formed. This Al_0.98Ga_0.02The As layer is a high Al concentration layer and is oxidized in the subsequent process to become the current confinement layer 10.
[0051]
  Next, TMGa, TMAl, AsH₃And DMZn (di-methyl zinc)ElectricLayer 5 is formed. Next, using TMGa, AsH3 and DMZn, the carrier concentration is 1 × 10.¹⁹cm^-3The p-type GaAs contact layer 13 is formed.
[0052]
Next, TMGa, TMAl, AsH₄And SiH₄Is used to form the n-type AlGaAs diffusion prevention layer 16. Since the diffusion preventing layer 16 has a conductivity type opposite to that of the impurity of the GaAs contact layer 13, the effect of suppressing the diffusion of the impurity from the contact layer 13 to the semiconductor multilayer reflector 3 is increased. Here, the impurity concentration of the diffusion preventing layer 16 is 5 × 10.¹⁸cm^-3To 2 × 10¹⁹cm^-3Is preferred.
[0053]
When Zn diffuses from GaAs to AlGaAs, the Zn concentration in AlGaAs decreases from about 1/2 to about 1/3 near the interface. Therefore, the n-type impurity concentration of the diffusion preventing layer 16 is set to 5 × 10.¹⁸cm^-3This is because the opposite conductivity type impurity concentration in the diffusion preventing layer 16 becomes higher than the p type impurity concentration from the GaAs contact layer 13 and the effect of preventing diffusion is increased.
[0054]
Next, the first semiconductor multilayer film reflecting mirror 3 is formed in the same manner as the semiconductor multilayer film reflecting mirror 2, but without adding Si. Next, TMGa, TMAl and AsH₃Is used to form the AlGaAs phase adjusting layer 18.
[0055]
Next, TMGa, TMAl and AsH₃Then, the second semiconductor multilayer film reflecting mirror 7 is formed. Next, TMGa, TMAl and AsH₃Is used to form the phase adjusting clad layer 8a halfway. Thereafter, the growth temperature is lowered to 550 ° C. to form the remainder of the phase adjusting clad layer 8a.
[0056]
  Next, TMGa, TMIn and AsH₃And DMHy (dimethylhydrazine) and NH₃Simultaneously, GaInAsNSecond light emissionLayer 6 is formed. Where NH₃, It is possible to significantly reduce the incorporation of C into GaInAsN from DMHy, TMAl, or TMGa, and increase the light emission efficiency of the laser.
[0057]
Next, TMGa, TMAl and AsH are formed on the active layer 6.₃Is used to form the phase adjusting clad layer 8b halfway. Here, the growth temperature is raised to 680 ° C. to form the remainder of the phase adjusting clad layer 8b. Next, a second semiconductor multilayer film reflecting mirror 9 is formed.
[0058]
After each semiconductor layer is deposited, SiO patterned in a circle₂As a mask, a cylindrical mesa structure is formed by chlorine-based dry etching. The lower end of etching is performed up to the GaAs substrate 1. Thereafter, steam oxidation is performed, and the current confinement layer 10 is formed so as to oxidize the high Al concentration layer from the periphery and leave the central portion.
[0059]
Next, SiO patterned in a smaller circle than the above cylindrical mesa structure₂Is used as a mask to dry-etch the outer portion of the mesa structure up to the p-type contact layer 13. If impurities not used in other layers are added to the p-type contact layer 13, the end point can be easily detected. For example, Cp₂Mg may be added using Mg. Alternatively, C may be used as a p-type impurity other than the contact layer 13 to detect Zn.
[0060]
Next, SiO patterned in a smaller circle₂Is used as a mask, the outer portion of the mesa structure is dry-etched into the semiconductor multilayer reflector 9, the phase adjustment layers 8 a and 8 b, the active layer 6, and the multilayer reflector 7 into a cylindrical shape with a diameter of 5 μm. This is to increase the effect of lateral light confinement.
[0061]
Note that the current confinement layer is formed by providing a high Al concentration layer 11 in one or a plurality of layers of the semiconductor multilayer reflectors 9, 7 and 3, the phase adjusting layers 8 a and 8 b and the spacer layer 18, and performing oxidation. 10 can also be formed. Since this layer has a low refractive index, it functions as an optical confinement layer.
[0062]
Next, Pt / Au (a gold layer laminated on a platinum layer) is formed on the ring as the p-side electrode 14, and the AsH is formed at 420 ° C.₃And N₂Annealing inside. Next, Au-Ge-Ni (gold, germanium and nickel alloy) is deposited as the n-side electrode 15 and annealed at 380 ° C.
[0063]
In the present embodiment, TMGa is used as a Ga raw material for stacking the semiconductor layers, but TEGa (triethylgallium) may be used. Further, Zn is added as a p-type impurity and DMZn is used as a raw material, but DEZn (diethyl zinc) may be used. Further, it is possible to use C instead of Zn as the p-type impurity. In this case, as a raw material of C, TMAs or CBr₄Can be used.
[0064]
SiH as a raw material of Si₄Is used but Si₂H₆Can be used.
[0065]
In addition, the film is formed using the MOCVD method, but it is formed by the MBE method using Ga, Al, In, As metal and Be or C p-type impurity, n-type impurity Si metal, and plasma N. May be. Nitrogen source is NH₃But you can. In addition, the MO-MBE method, the gas source MBE method, the CBE method, or the like may be used.
[0066]
In the present invention, Al is formed on a GaAs substrate._xGa_1-xyIn_yAs_1-zP_zA surface emitting laser having a light emitting layer of (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ 1-xy ≦ 1, 0 ≦ z ≦ 1) is formed.
[0067]
In addition, Ga_1-pIn_pAs_1-qN_qA surface optical laser having a light emitting layer of (0 ≦ p ≦ 1, 0 <q <1) is formed. That is, these surface emitting lasers can be continuously epitaxially grown on the GaAs substrate.
[0068]
Therefore, it is not necessary to manufacture each surface emitting laser on different substrates and fuse them. Therefore, it is possible to solve the problems of low light emission efficiency, warping of the substrate, and deterioration of reliability.
[0069]
Since the two light emitting layers are epitaxially formed on the same GaAs substrate in this way, unlike the case of using a bonded substrate, there is no generation of a non-light emitting center at the substrate bonding surface between the two light emitting layers, There is no light scattering loss due to the influence of the interface.
[0070]
In addition, unlike the case of bonding different types of substrates, the only thick substrate is a GaAs substrate, so that the problem of substrate warpage due to fluctuations in operating temperature does not occur.
[0071]
The first light emitting layer 4 is made of Al._xGa_1-xyIn_yAs_1-zP_z(0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ 1-xy ≦ 1, 0 ≦ z ≦ 1), and the second light emitting layer 6 is formed of Ga._1-pIn_pAs_1-qN_q(0 ≦ p ≦ 1, 0 <q <1), so that each of them can be lattice-matched with the GaAs substrate or can be formed within the effective critical film thickness even when there is a lattice irregularity. Can be prevented.
[0072]
As a result of experiments by the inventors, it has been found that high-quality crystals can be grown when the emission wavelength of the first light-emitting layer 4 is 0.63 μm to 1.2 μm.
[0073]
Further, the first light emitting layer 4 is made of Ga._1-yIn_yWhen As (0 <y ≦ 1) and the emission wavelength is 0.87 μm to 1 μm, the band gap of the first light emitting layer 4 is smaller than the band gap of GaAs. GaAs can be used for a part of 5. Accordingly, since the same GaAs as that of the substrate 1 can be used for a part of the first semiconductor multilayer film reflecting mirrors 2 and 5, it has been found that a high-quality crystal can be grown without causing lattice mismatch with the GaAs substrate.
[0074]
(Embodiment 2)
FIG. 2 is a schematic cross-sectional view of a planar optical semiconductor device according to Embodiment 2 of the present invention.
[0075]
In this embodiment, the pair of first semiconductor multilayer film reflecting mirrors is provided between the pair of second semiconductor multilayer film reflecting mirrors, and both the first light emitting layer and the second light emitting layer are the first. The semiconductor multilayer film reflecting mirror is provided.
[0076]
As shown in FIG. 2, the planar optical semiconductor device includes a GaAs substrate 1, a first light emitting layer 4 formed on the GaAs substrate 1 and emitting light by current injection, and a first light emitting layer 4 formed on the GaAs substrate 1. Two light emitting layers 6, a pair of first semiconductor multilayer film reflecting mirrors 2 and 3 disposed so as to sandwich the first light emitting layer 4 and the second light emitting layer 6, and a pair of first semiconductor multilayer films A pair of second semiconductor multilayer film reflecting mirrors 7 and 9 are arranged so as to sandwich the reflecting mirrors 2 and 3 therebetween.
[0077]
The pair of first semiconductor multilayer film reflecting mirrors 2 and 3 are configured so that the light emitted from the first light emitting layer 4 is absorbed back into the first light emitting layer 4 to cause the first laser oscillation. The second light emitting layer 6 emits light by absorbing the first laser light oscillated by the first laser oscillation. The pair of second semiconductor multilayer film reflecting mirrors 7 and 9 feedbacks and absorbs the light emitted from the second light emitting layer 6 to the second light emitting layer to cause second laser oscillation, thereby generating the second laser. It is designed to generate light.
[0078]
A phase adjusting layer 19 is formed between the first light emitting layer 4 and the first semiconductor multilayer reflector 2 to adjust the phase of the first light emitting layer 4.
[0079]
A phase adjustment layer 20 is formed between the first semiconductor multilayer film reflector 2 and the second semiconductor multilayer film reflector 7, and the first semiconductor multilayer film reflector 2 and the second semiconductor multilayer mirror are formed. The phase between the film reflecting mirrors 7 is adjusted. Further, a phase adjusting layer 21 is formed between the first semiconductor multilayer reflector 3 and the second semiconductor multilayer reflector 9, and the first semiconductor multilayer reflector 3 and the second semiconductor multilayer reflector 3 The phase between the semiconductor multilayer film reflecting mirrors 9 is adjusted. These phase adjusting layers 19, 20 and 21 are made of Al._yGa_1-yIt is formed of an As (0.05 ≦ y ≦ 0.35) layer.
[0080]
The first light emitting layer 4 is formed of, for example, a GaAs layer having an emission wavelength of 0.87 μm.
[0081]
The pair of first semiconductor multilayer film reflecting mirrors 2 and 3 is made of Al having a low refractive index._xGa_1-xAs (0.7 ≦ x <0.9) layer and high refractive index Al_yGa_1-yThis is a laminated structure in which As (0.05 ≦ y ≦ 0.35) layers are alternately laminated. Low refractive index Al_xGa_1-xAs (0.7 ≦ x <0.9) layer and high refractive index Al_yGa_1-yAs (0.05 ≦ y ≦ 0.35) layers, each thickness is designed so that the refractive index × thickness is 3/4 of the emission wavelength of the first light emitting layer (here 0.87 μm) Has been.
[0082]
  Current confinement layer 10Al with high Al composition_zGa_1-zThis is an aluminum gallium oxide layer formed by oxidizing an As (0.9 <z <1) layer laterally from its side surface. Al is not oxidized_zGa_1-zThe As (0.9 <z <1) layer 11 is a current-carrying region having a diameter of 2 μm to 5 μm.
[0083]
The p-type conductive layer 5 is made of p-type Al._wGa_1-wIt is formed of an As (0.05 <w <0.35) layer. The contact layer 13 is formed of a p-type GaAs layer.
[0084]
The second light-emitting layer 6 includes two layers of Ga having a band gap of 0.99 eV to 0.89 eV._1-sIn_sAs_1-pN_p(0 <s <1, 0 <p <1, for example, p = 0.005) Ga between the quantum well layers with a band gap of 1.13 eV to 1.38 eV_1-uIn_uAs_1-vN_v(0 <u <1, 0 <v <1, e.g., v = 0.003) A barrier layer is sandwiched between the two quantum well layers and Ga gap having a band gap of 1.13 eV to 1.38 eV._1-uIn_uAs_1-vN_v(0 <u <1, 0 <v <1, for example, v = 0.003) This is a structure in which two light guide layers are formed. The second light emitting layer 6 has an emission wavelength of 1.3 μm. Here, although two quantum well layers are provided, three or more layers may be formed with a barrier layer interposed therebetween.
[0085]
As described above, there are a plurality of active layers inside the second light emitting layer 6, and the whole may be one light emitting layer. By doing so, the light density in one light emitting layer is lowered. For this reason, the maximum light output is increased, the temperature dependency is decreased, and a semiconductor element having excellent high temperature characteristics can be obtained.
[0086]
The second semiconductor multilayer mirrors 7 and 9 have a low refractive index Al._xGa_1-xAs (0.7 ≦ x <0.9) layer and high refractive index Al_yGa_1-yThis is a laminated structure in which As (0.05 ≦ y ≦ 0.35) layers are alternately laminated. Low refractive index Al_xGa_1-xAs (0.7 ≦ x <0.9) layer and high refractive index Al_yGa_1-yThe thickness of each As (0.05 ≦ y ≦ 0.35) layer is such that the refractive index × thickness is ¼ of the emission wavelength (1.3 μm in this case) in the second light emitting layer 6. Designed.
[0087]
The spacer layer 17 is made of Al._yGa_1-yIt is formed of an As (0.05 ≦ y ≦ 0.35) layer.
[0088]
The phase adjusting semiconductor layers 8a and 8b are made of Al._yGa_1-yIt is formed of an As (0.05 ≦ y ≦ 0.35) layer. The phase adjusting semiconductor layers 8a and 8b are arranged so that the second light emitting layer 6 is positioned at the peak position of the standing wave of the laser light generated in the first light emitting layer 4 or the second light emitting layer 6. The thickness can be adjusted.
[0089]
  For example, of the second semiconductor multilayer reflector 3 and the first semiconductor multilayer reflector 2, the layers facing the first light-emitting layer 4 are each made of Al having a low refractive index._xGa_1-xThe layer is assumed to be an As (0.7 ≦ x <0.9) layer. Lower reflective mirror 2 of the first surface optical elementAnd secondThe sum of the thicknesses of the phase adjustment layers 20 between the two surface optical elements and the lower reflecting mirror 7 is set to an integral multiple of 0.77 μm. The phase adjustment layer of the first active layer is set to 0.77 μm. The sum of the thicknesses of the first active layer 4, the spacer layer 17, and the high Al concentration layer 11 is set to 0.8 μm. The sum of the p-type conductive layer 5, the contact layer 13, the p-type impurity diffusion prevention layer 16, and the phase adjusting semiconductor layer 8a is set to an integral multiple of 0.77 μm.
[0090]
Further, the sum of the thicknesses of the second light emitting layer 6 and the phase adjusting semiconductor layer 8a is set to an integral multiple of 0.77 μm. Further, the thickness of the phase adjusting semiconductor layer 8b is set to an integral multiple of 0.77 μm.
[0091]
In this way, both the first light emitting layer 4 and the second light emitting layer 6 are provided in places where the optical densities of the first laser light and the second laser light are higher than the average value in the resonator. be able to.
[0092]
In such a surface type semiconductor optical device, when the diameter of the AlGaAs layer 11 having a high Al concentration through which a current flows is 5 μm, the threshold current value is 7 mA, and the oscillation wavelength is 1.3 μm from the second light emitting layer 6. Light can be obtained. The maximum light output is 3 mW or more.
[0093]
Such a large output can be obtained because the second light emitting layer 6 is provided between the pair of first semiconductor multilayer reflectors 2 and 3, and therefore the first semiconductor multilayer reflector 2 and This is because the loss component 3 is mostly due to absorption of the second light emitting layer.
[0094]
In the present embodiment, since a plurality of second light emitting layers 6 are provided, the volume of the active layer is large and output saturation is unlikely to occur, so that a large output can be obtained.
[0095]
Further, since GaAs is used as the first light emitting layer 4, even if the operating temperature is raised, the influence of the laser light emitted from the first light emitting layer 4 is small. For this reason, the change in the intensity of the laser light emitted from the second light emitting layer 6 with respect to the increase in operating temperature is small.
[0096]
When the temperature is raised to 85 ° C. under a driving condition in which a light output of 1 mW is generated at room temperature, a very small value of 15% or less can be realized.
[0097]
In addition, since the emission wavelength of the second emission layer 6 is 1.5 times the emission wavelength of the first emission layer 4, the emission of the second emission layer 6 is performed by the pair of first semiconductor multilayer film reflectors 2. And 3 are hardly reflected. Therefore, regardless of the configuration (for example, any number of layers) of the pair of first semiconductor multilayer film reflectors 2 and 3, the light from the second light-emitting layer 6 is transmitted to the pair of first semiconductors. It is hardly reflected by the multilayer reflectors 2 and 3 to reduce its strength. Therefore, in designing the pair of first semiconductor multilayer film reflectors 2 and 3, it is only necessary to consider confining light from the first light emitting layer 4 efficiently, and the influence on the second light emitting layer 6 is considered. You can design freely without doing.
[0098]
Next, a method for manufacturing the surface type semiconductor light emitting device will be described.
[0099]
First, a semiconductor multilayer structure is formed using the same method as in the first embodiment. However, the phase adjustment layer 8a and the active layer 6 are composed of a plurality of layers. The phase adjustment layers 8a and 8b and the active layer 6 are formed at 625 ° C. and a growth rate of 10 nm / second. This is due to the following reason.
[0100]
As a result of the study by the present inventors, it has been found that in the growth of GaInAsN, flattening of the mirror surface morphology of the crystal proceeds at a growth temperature between 600 ° C. and 625 ° C. Furthermore, considering uniformity and the like even within the wafer surface, it was desirable to exceed 620 ° C. On the other hand, it has been found that nitrogen is less likely to be incorporated as the growth temperature is higher. For this reason, it is desirable that the growth temperature be 605 ° C. or higher and 625 ° C. or lower.
[0101]
In addition, in the growth of GaInAsN, it has been found that the growth rate depends on the temperature when it exceeds 1.7 nm / second at 520 ° C., 5 nm / second at 570 ° C., and 16 nm / second at 620 ° C. On the other hand, in the thin film growth of GaInAsN, it was found that the higher the growth rate, the more homogeneous crystals can be grown. On the other hand, when a GaInAsN quantum well is formed, since the amount of strain increases, a film having a thickness of 20 nm or more cannot be substantially grown. In the MOCVD method, it is difficult to set the gas replacement time in the apparatus to 1 second or less. For this reason, it is not practical to set the growth rate of the quantum well to 20 nm / second or more. Therefore, it is desirable that the growth temperature is 600 ° C. or more and 625 ° C. or less, and the growth rate is 9 nm / second or more and 20 nm / second or less. In particular, within the error range, the growth temperature is 625 ° C. and the growth rate is 10 nm / second. It is desirable that the rate be 20 nm / second or less. In the experiment conducted by the present inventor, the temperature error is ± 3 ° C. and the speed error is ± 2%.
[0102]
Conventionally, with regard to GaInAsN, it is said that the luminous efficiency decreases as the N concentration increases. However, in the case of GaInAsN formed under this growth condition, a high-quality crystal is basically obtained, so the nitrogen concentration is 0.7%. GaInAsN also emitted lighter than crystals with a nitrogen concentration of 0.3% grown at 520 ° C. and annealed at 680 ° C.
[0103]
In the present embodiment, the entire structure on the contact layer 13 is a columnar structure. At this time, the diameter of the cylinder was 3 μm to 10 μm. 5 μm or less is desirable in terms of single mode stability, and 4 μm or more is desirable in terms of obtaining a large light output.
[0104]
After this, the entire SiO₂Passivation is performed, and then a current confinement layer 10 is formed by etching and oxidation of the high Al concentration layer 11. Finally, an electrode formation process is performed to complete the device.
[0105]
Since the two light emitting layers are epitaxially formed on the same GaAs substrate in this way, unlike the case of using a bonded substrate, there is no generation of a non-light emitting center at the substrate bonding surface between the two light emitting layers, There is no light scattering loss due to the influence of the interface.
[0106]
In addition, unlike the case of bonding different types of substrates, the only thick substrate is a GaAs substrate, so that the problem of substrate warpage due to fluctuations in operating temperature does not occur.
[0107]
The first light emitting layer 4 is made of Al._xGa_1-xyIn_yAs_1-zP_z(0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ 1-xy ≦ 1, 0 ≦ z ≦ 1), and the second light emitting layer 6 is formed of Ga._1-pIn_pAs_1-qN_q(0 ≦ p ≦ 1, 0 <q <1), so that each of them can be lattice-matched with the GaAs substrate or can be formed within the effective critical film thickness even when there is a lattice irregularity. Can be prevented.
[0108]
As a result of experiments by the inventors, it has been found that high-quality crystals can be grown when the emission wavelength of the first light-emitting layer 4 is 0.63 μm to 1.2 μm.
[0109]
Further, the first light emitting layer 4 is made of Ga._1-yIn_yWhen As (0 <y ≦ 1) and the emission wavelength is 0.87 μm to 1 μm, the band gap of the first light emitting layer 4 is smaller than the band gap of GaAs. GaAs can be used for a part of 5. Accordingly, since the same GaAs as that of the substrate 1 can be used for a part of the first semiconductor multilayer film reflecting mirrors 2 and 5, it has been found that a high-quality crystal can be grown without causing lattice mismatch with the GaAs substrate.
[0110]
(Embodiment 3)
FIG. 3 is a schematic cross-sectional view of a planar optical semiconductor device according to Embodiment 3 of the present invention.
[0111]
This embodiment is characterized in that in the planar optical semiconductor device shown in Embodiment 2, a modulation active layer is provided between the first light emitting layer and the second light emitting layer. The same parts as those in FIG.
[0112]
  As shown in FIG. 3, a p-type AlGaAs phase adjustment layer 24 is formed on the p-type impurity diffusion prevention layer 16. A modulation active layer 25 is formed on the p-type AlGaAs phase adjusting layer 24. The modulation active layer 25 has the same structure as the second light emitting layer 6. An n-type GaAs conductive layer 22 is formed on the modulation active layer 25. n-type GaAsGuidanceAn n-type electrode 23 is formed on the electric layer 22.
[0113]
The main optical output of this planar optical semiconductor device was obtained with excellent electrical characteristics and temperature characteristics almost the same as those of the planar optical semiconductor device described in the second embodiment.
[0114]
  In the planar optical semiconductor device described in the second embodiment,The secondWhen the current injected into one light emitting layer 4 is modulated, the energy transfer efficiency from the first laser to the second light emitting layer 6 is 10% or less, so the amount of energy modulation supplied to the second light emitting layer 6 The input modulation must be 10 times or more.
[0115]
On the other hand, in the planar optical semiconductor device described in this embodiment, since the current injected into the modulation active layer 25 can be directly modulated, the amount of input energy to be modulated is 1/10 or less. Mu
[0116]
When the current injected into the first light emitting layer 4 is modulated, energy modulation of about 10 mW is required at several mA × (energy of the wavelength of the first laser). When power is supplied to 25, 0. Energy modulation of several mA x 0.95 eV and 1 mW or less is sufficient. For this reason, in the former case, it is necessary to provide a cooling mechanism in the modulation power source, but in the latter case, natural heat dissipation is sufficient.
[0117]
  In the present embodiment, a semiconductor multilayer structure is formed as in the first embodiment. p-type impuritiesPrevention of diffusionFor layer 16, p-type impurities, not n-type, are added at 1 × 10¹⁸cm^-3Add to low concentration of. This is because current needs to flow through this layer.
[0118]
  The current confinement layer 10 was formed by etching in the shape of a cylinder halfway through the GaAs substrate 1. n-type leadElectricLayer 22, modulation active layer 25, phase adjusting layer 24, diffusion of p-type impurityPreventionLayer 16 was etched into a cylinder. The active layer 6, the phase adjusting layers 8a and 8b, the reflecting mirror 3, the inter-mirror phase adjusting layer 21, and the semiconductor multilayer film reflecting mirror 9 were etched into a cylindrical shape. The p-type electrode 14 was deposited and annealed. Thereafter, an n-type electrode 23 was deposited in a ring shape. Thereafter, the n-type electrode 15 was deposited, and the n-type electrode 23 and the n-type electrode 15 were annealed simultaneously at 380 ° C. to complete the device.
[0119]
In the first, second, and third embodiments, the second light emitting layer has an oscillation wavelength of 1.3 μm. However, the second light emitting layer may have a 1.55 μm band. In this case, by using AlGaAs as the first light emitting layer 4, the wavelength of the first light emitting layer 4 can be made half the wavelength of the second light emitting layer 6. Therefore, there is an advantage that it is easy to design a mirror having a high reflectance for the light emission of the first light emitting layer 4 and a high transmittance for the light emission of the first light emitting layer 4.
[0120]
In addition, by taking the relationship between the first laser light and the second emission wavelength to an appropriate integer ratio, the transmittance of one light is increased and the transmittance of one light is decreased or the transmittance of both is decreased. Although design is possible, this ratio is not limited to the above embodiment.
[0121]
【The invention's effect】
It is possible to provide a planar optical semiconductor device that has high light emission efficiency, does not warp the substrate, and has improved reliability.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a planar optical semiconductor device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a planar optical semiconductor device according to Embodiment 2 of the present invention.
FIG. 3 is a cross-sectional view of a planar optical semiconductor device according to Embodiment 3 of the present invention.
[Explanation of symbols]
1 ... GaAs substrate
2... First semiconductor multilayer film reflecting mirror
3... First semiconductor multilayer film reflecting mirror
4 ... 1st light emitting layer
5 ... p-type conductive layer
6 ... 2nd light emitting layer
7: Second semiconductor multilayer film reflecting mirror
8a, 8b ... Semiconductor layer for phase adjustment
9: Second semiconductor multilayer film reflecting mirror
10 ... Current confinement layer
11 ... High Al concentration semiconductor layer
13 ... Contact layer
14 ... Surface electrode
15 ... Back electrode
16..Diffusion prevention layer for p-type impurities
17 ... Spacer layer
18 ... Phase adjustment layer
19 ... Phase adjustment layer
20 ... Phase adjustment layer
21 ... Phase adjustment layer
22 ... n-type conductive layer
23 ... n-type electrode
24: Phase adjustment layer
25 ... Active layer for modulation

Claims (8)

A substrate,
Formed on said substrate, a first light-emitting layer you light by current injection,
A second light emitting layer formed on the substrate;
A pair of first semiconductor multilayer film reflectors disposed so as to sandwich the first light emitting layer and the second light emitting layer;
A pair of second semiconductor multilayer film reflectors arranged so as to sandwich the first light emitting layer, the second light emitting layer, and the pair of first semiconductor multilayer film reflectors;
The pair of first semiconductor multilayer film reflecting mirrors absorbs light emitted from the first light emitting layer into the first light emitting layer and causes first laser oscillation,
The second light emitting layer absorbs the first laser light oscillated by the first laser oscillation and emits light,
The pair of second semiconductor multilayer film reflecting mirrors absorbs light emitted from the second light emitting layer into the second light emitting layer and causes second laser oscillation to generate second laser light. surface optical semiconductor device, characterized in that letting. The first light-emitting layer is made of Al _x Ga _1-xy In _y As _1-z P _z (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ 1-xy ≦ 1, 0 ≦ z ≦ 1), and the second light emitting layer has a Ga _1-p In _p As _1-q N _q (0 ≦ p ≦ 1, 0 <q <1) layer. The planar optical semiconductor device described. 3. The planar optical semiconductor device according to claim 1 , wherein the second light emitting layer is disposed at a position where the density of the first laser light is higher than the average light density . 4. 3. The planar optical semiconductor device according to claim 1, wherein the second light emitting layer is disposed at a position where the density of the second laser light is higher than the average light density . Disposing the second light emitting layer at a position where the density of the first laser light is higher than the average light density and the density of the second laser light is higher than the average light density. The planar optical semiconductor device according to claim 1 or 2, characterized in that: 6. The planar optical semiconductor device according to claim 1, wherein there are a plurality of the second light emitting layers . The planar optical semiconductor device according to claim 6, wherein at least one of the second light emitting layers is capable of current injection . Surface optical semiconductor device according to any one of claims 1 to 7, wherein the substrate is GaAs.

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