JP4281987B2 - Manufacturing method of semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to a semiconductor laser technology for optical communication, and more particularly to a method of manufacturing a surface emitting semiconductor laser, a surface emitting semiconductor laser formed by using the method, an optical transmission module using the surface emitting semiconductor laser element, and an optical The present invention relates to a transmission / reception module and an optical communication system.
[0002]
[Prior art]
In recent years, the amount of information handled as seen in the explosive spread of the Internet has increased dramatically, and is expected to accelerate further in the future. For this reason, optical fibers are introduced not only in trunk lines but also in subscriber lines such as homes and offices and transmission lines close to users such as LAN (Local Area Network), and between each device and in the devices. Large-capacity information transmission technology is extremely important.
[0003]
In order to increase the capacity of the optical network and optical wiring without worrying about the distance, the surface of the 1.3 .mu.m band and 1.55 .mu.m band, which has low transmission loss of silica fiber as a light source and good matching, is used. A light emitting semiconductor laser element (VCSEL: Vertical Cavity Surface Emitting Laser) is extremely promising. The surface-emitting type semiconductor laser device is 1Gbit, which is already a high-speed LAN in the 0.85 μm band that can be actually formed on a GaAs substrate. / s Ethernet (registered trademark), etc.
[0004]
In the 1.3 μm band, the material system on the InP substrate is common, and the edge-emitting laser has a track record. However, this conventional long-wavelength semiconductor laser has a major drawback that the operating current increases three times when the environmental temperature is changed from room temperature to 80 ° C. In addition, since there is no material suitable for a reflecting mirror in a surface-emitting type semiconductor laser element, it is difficult to achieve high performance, and a practical level of characteristics has not been obtained.
[0005]
For this reason, the current highest performance is obtained by the structure in which the active layer on the InP substrate and the AlGaAs / GaAs reflector on the GaAs substrate are directly bonded (V. Jayaraman, JCGeske, MHMacDougalF.H. Peters). , TDLowes, and TTChar, Electron. Lett., 34, (14), pp. 1405-1406, 1998.).
[0006]
However, this method is unavoidable in terms of mass productivity because of the inevitable increase in cost. Therefore, recently, a material system capable of forming a 1.3 μm band on a GaAs substrate has attracted attention, and (Ga) InAs quantum dots, GaAsSb and GaInNAs (for example, see JP-A-6-37355) have been studied. The new material GaInNAs is attracting attention as a material that can make the temperature dependence of laser characteristics extremely small.
[0007]
The GaInNAs semiconductor laser on the GaAs substrate has a band gap that is reduced by adding nitrogen, so that a long wavelength band such as a 1.3 μm band can be formed on the GaAs substrate. When the In composition is 10%, the nitrogen composition is about 3% and a 1.3 μm band can be formed. However, there is a problem that the threshold current density rapidly increases as the nitrogen composition increases. FIG. 15 is a graph showing the nitrogen composition dependence of the threshold current density experimentally obtained by the inventor. The horizontal axis indicates the nitrogen composition ratio (%), and the vertical axis indicates the threshold current density. Yes. The reason why the threshold current density rapidly increases as the nitrogen composition increases is that the crystallinity of the GaInNAs layer deteriorates as the nitrogen composition increases.
[0008]
For this reason, the issue is how to grow GaInNAs with high quality. As such GaInNAs crystal growth methods, MOCVD (Metal Organic Chemical Vapor Deposition) and MBE (Molecular Beam Epitaxy) have been tried.
[0009]
The MOCVD method does not require a high vacuum like the MBE method, and the MBE method only controls the material gas flow rate while controlling the material supply by changing the cell temperature, and increases the growth rate. It is a growth method that is extremely suitable for mass production because it can easily increase the throughput. The MOCVD method is used in all production of 0.85 μm band-emitting semiconductor laser devices that are actually put into practical use (in most cases).
[0010]
Recently, many reports of semiconductor lasers using this new GaInNAs-based material have been reported. However, most of these cases were due to the MBE method. Japanese Laid-Open Patent Publication No. 9-237942 proposes a surface emitting laser. Most recently, surface emitting semiconductor laser elements have been reported. First report from Hitachi (1.18μm) in 1998 (MCLarson, M. Kondow, T. Kitatani, K. Nakahara, K. Tamura, H. Inoue, and K. Uomi, IEEE Photonics Technol. Lett., 10, pp.188-190, 1998), reported in 2000 by Stanford (1.215 μm), Sandia & Cielo (1.294 μm), Tokyo Tech & Ricoh (1.262 μm), and Infineon (1.285 μm).
[0011]
[Problems to be solved by the invention]
However, this new GaInNAs surface emitting semiconductor laser device has only one report of MOCVD method suitable for mass production, and all others have been grown by MBE method and have sufficient characteristics. It is not a thing. In particular, those grown by the MBE method have a very high resistance of the p-side multilayer reflector, so a method that does not use the p-side multilayer reflector as a current path is used, but eventually the operating voltage increases. It had problems such as. However, a new GaInNAs surface-emitting type semiconductor laser element manufacturing method and manufacturing apparatus by MOCVD method that solves such problems and is suitable for mass production have not yet been established.
[0012]
  Therefore, the present invention improves the manufacturing technology of a surface emitting semiconductor laser device, and a method for manufacturing a GaInNAs surface emitting semiconductor laser device having a high quality and a practical level.TheIt is intended to provide.
[0013]
[Means for Solving the Problems]
First, the results of experiments by the inventors will be described as to the cause that hinders the high performance of GaInNAs surface emitting semiconductor laser elements by MOCVD.
FIG. 1 is a diagram showing an outline of a general MOCVD apparatus. The MOCVD method is a vapor phase growth method in which crystal growth is performed by thermal decomposition of a source gas and surface reaction with a substrate to be grown using at least a part of an organic metal source.
[0014]
  As shown in the figure, the MOCVD apparatus includes a source gas supply unit A to which source gas is supplied, a heating means (not shown) for heating the growth substrate, a heating unit (heating body B), a reaction This is a configuration having an exhaust part (exhaust pump or the like) C for exhausting exhausted gas. Usually, the substrate is introduced from the substrate loading / unloading port 11 so that air does not enter the growth chamber (reaction chamber) 12 and is transferred to the growth chamber (reaction chamber) 12 after being evacuated by the exhaust part C. The source gas supply unit A is usually divided into a group III line A1 and a group V line A2. Figure1In the growth chamber (reaction chamber) 12, the Group III and Group V raw materials are joined before the entrance.
[0015]
As the pressure in the growth chamber, a reduced pressure of about 50 Torr to 100 Torr is often used. As the group III material, an organic metal such as Ga: TMG (trimethylgallium), TEG (triethylgallium), Al: TMA (trimethylaluminum), or In: TMI (trimethylindium) is used. For Group V materials, AsH₃(Arsine), TBA (tertiary butyl arsine), PH₃Hydride gas and organic compounds such as (phosphine) and TBP (tertiary butylphosphine) are generally used.
[0016]
Carrier gas is hydrogen gas (H₂) Is usually used. Usually, impurities are removed and supplied through a hydrogen purifier. An organic compound such as DMHy (dimethylhydrazine) or MMHy (monomethylhydrazine) can be used as a raw material for nitrogen for growing a semiconductor layer containing nitrogen. The raw material is not limited to this.
[0017]
Liquid or solid raw materials such as organic metals and organic nitrogen compounds are supplied by being bubbled through a carrier gas in a bubbler. The hydride is supplied in a gas cylinder. In FIG. 1, TMG, TMA, TMI and DMHy use bubblers (liquid, solid material bubblers) and AsH₃15 and dopant gas 15 '(only one type is shown in FIG. 1) uses a gas cylinder.
[0018]
The path of the source gas is switched by the valve 16, and necessary materials and compositions are grown by controlling the supply amount with an MFC (mass flow controller) or the like. In general, each of group III line A1 and group V line A2 has main lines a1 and b1 for supplying gas to the reaction chamber, vent lines a2 and b2 for supplying to the exhaust pump, and a dummy line in addition to the raw material line (Refer to the dummy lines # 1 to # 4 in the figure) and the valve 16 is switched so as to merge with either the main lines a1 and b1 or the vent lines a2 and b2, respectively. By eliminating the pressure difference between a2 and b2, the gas flow is prevented from being disturbed as much as possible.
[0019]
The main lines a1, b1, vent lines a2, b2, and dummy lines # 1 to # 4 are also supplied with carrier gas. When growing a semiconductor light emitting device having a plurality of semiconductor layers, crystal growth is performed by supplying necessary raw materials for each layer to the main line side and supplying dummy lines for supplying carrier gas to the vent side. The growth thickness is controlled by the supply time of the source gas. As a result, the necessary structure can be grown, so the throughput is good and it can be said that the method is suitable for mass production.
[0020]
FIG. 2 shows a room temperature photoluminescence spectrum from an active layer having a GaInNAs / GaAs double quantum well structure composed of a GaInNAs quantum well layer and a GaAs barrier layer, which are semiconductor layers containing nitrogen produced by such an MOCVD apparatus. FIG.
[0021]
FIG. 3 is a diagram showing a sample structure. On the GaAs substrate 101, a lower cladding layer 102, an intermediate layer 103, an active layer 104 containing nitrogen, an intermediate layer 103, and an upper cladding layer 105 are sequentially stacked.
[0022]
In FIG. 2, A is a room temperature photoluminescence spectrum of a sample in which a double quantum well structure is formed on an AlGaAs cladding layer with a GaAs intermediate layer sandwiched, and B is 2 with a GaAs interlayer on a GaInP cladding layer. It is a room temperature photoluminescence spectrum of the sample which formed the quantum well structure continuously.
[0023]
As shown in FIG. 2, the photoluminescence intensity of sample A is reduced to less than half that of sample B. Therefore, if an active layer containing nitrogen such as GaInNAs is continuously formed on a semiconductor layer containing Al as a constituent element using a single MOCVD apparatus, the light emission intensity of the active layer will deteriorate. There was a problem. For this reason, the threshold current density of a GaInNAs laser formed on an AlGaAs cladding layer is several times higher than that formed on a GaInP cladding layer.
[0024]
Next, this cause will be examined.
FIG. 4 shows an example of the semiconductor light emitting device shown in FIG. 3, in which an epitaxial growth apparatus (device having a cladding layer made of AlGaAs, an intermediate layer made of GaAs, and an active layer made of a GaInNAs / GaAs double quantum well structure) It is the figure which showed the depth direction distribution of nitrogen and oxygen concentration when forming using MOCVD. The measurement was performed by SIMS (Secondary Ion-microprobe Mass Spectrometer (Spectrometry)).
[0025]
FIG. 5 is a diagram showing the measurement conditions. In FIG. 4, two nitrogen peaks are observed in the active layer corresponding to the GaInNAs / GaAs double quantum well structure. An oxygen peak is detected in the active layer. However, the oxygen concentration in the intermediate layer not containing N and Al is about one digit lower than the oxygen concentration in the active layer.
[0026]
On the other hand, when the depth direction distribution of oxygen concentration is measured for an element in which the cladding layer is made of GaInP, the intermediate layer is made of GaAs, and the active layer is made of a GaInNAs / GaAs double quantum well structure, the oxygen concentration in the active layer is measured. Was at the background level.
[0027]
That is, using a nitrogen compound raw material and an organometallic Al raw material, when a single crystal growth apparatus is used for continuous crystal growth of a semiconductor light emitting device in which a semiconductor layer containing Al is provided between a substrate and an active layer containing nitrogen Our experiments revealed that oxygen is incorporated into the active layer containing nitrogen. Oxygen incorporated into the active layer forms a non-radiative recombination level, which reduces the luminous efficiency of the active layer.
[0028]
It has been newly found that the oxygen incorporated into the active layer is a cause of lowering the light emission efficiency in the semiconductor light emitting device in which the semiconductor layer containing Al is provided between the substrate and the active layer containing nitrogen. The origin of this oxygen is considered to be a substance containing oxygen remaining in the apparatus or a substance containing oxygen contained as impurities in the nitrogen compound raw material.
[0029]
Next, the cause of oxygen uptake will be examined.
FIG. 6 is a diagram showing the depth direction distribution of the Al concentration of the same sample as FIG. The measurement was performed by SIMS. FIG. 7 is a diagram showing the measurement conditions.
[0030]
From FIG. 6, Al is detected in the active layer which is not originally introduced with the Al raw material. However, in the intermediate layer (GaAs layer) adjacent to the Al-containing semiconductor layer (cladding layer), the Al concentration is about one order of magnitude lower than that of the active layer. This indicates that Al in the active layer is not mixed by diffusion and substitution from a semiconductor layer (cladding layer) containing Al.
On the other hand, when an active layer containing nitrogen was grown on a semiconductor layer not containing Al, such as GaInP, Al was not detected in the active layer.
[0031]
Therefore, Al detected in the active layer is bonded to impurities (moisture, etc.) in the Al raw material, Al reactant, Al compound, or Al remaining in the apparatus. Incorporated into the active layer. That is, using a nitrogen compound raw material and an organometallic Al raw material, a single crystal growth apparatus continuously crystal-grows a semiconductor light-emitting element in which a semiconductor layer containing Al is provided between a substrate and an active layer containing nitrogen. It was newly found that Al is naturally incorporated in the active layer containing nitrogen.
[0032]
Compared with the depth distribution of nitrogen and oxygen concentration in the same element shown in FIG. 6, the two oxygen peak profiles in the double quantum well active layer do not correspond to the peak profile of nitrogen concentration. 6 corresponds to the Al concentration profile. From this, it became clear that the oxygen impurities in the GaInNAs well layer were incorporated together with Al incorporated in the well layer rather than being incorporated with the nitrogen source. .
[0033]
That is, when the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber comes into contact with the nitrogen compound raw material, the moisture contained in the Al and nitrogen compound raw material or the moisture remaining in the gas line or reaction chamber Al and oxygen are incorporated into the active layer by combining with oxygen-containing substances such as. Our experiment revealed for the first time that the oxygen incorporated into the active layer had reduced the luminous efficiency of the active layer.
[0034]
In the case of being manufactured by a normal MBE method, there has been no report on a decrease in light emission efficiency in a semiconductor light emitting element in which a semiconductor layer containing Al is provided between a substrate and an active layer containing nitrogen.
[0035]
While the MBE method grows crystals under ultra-low pressure (in a high vacuum), the MOCVD method usually has a pressure of several tens of Torr to atmospheric pressure, and the pressure in the reaction chamber is higher than the MBE method. This is presumably because the raw materials, carrier gas, etc. that are overwhelmingly short contact and react with the Al residue in the reaction chamber or the like.
[0036]
Therefore, in the case of a growth method such as the MOCVD method in which the pressure in the reaction chamber or the gas line is high, in order to improve this, at least Al remaining in the apparatus is included in the film together with oxygen during the growth of the active layer containing nitrogen. It was found that a step for removing the Al-based residue was necessary so as not to be taken in.
[0037]
In view of the above, the present invention is characterized by adopting the following configuration in order to achieve the above object. Hereinafter, each claim will be described in detail.
[0038]
(1) The method for manufacturing a semiconductor light emitting device according to claim 1 includes a substrate and nitrogen.Made of GaInNAs materialIn the method of manufacturing a semiconductor light emitting device in which a semiconductor layer containing Al is provided between the active layer and the semiconductor layer containing Al and the active layer containing nitrogen are grown using an organometallic Al raw material and a nitrogen compound raw material, respectively. And a semiconductor layer containing AlWhenActive layer containing nitrogenWhenBetweenDuring the growth of the provided semiconductor layerAl material remaining in the growth chamber, Al reactant, Al compound, or AlBy supplying organic nitrogen compound gas into the growth chamberIt is characterized by providing a step of removing.
[0039]
As described above, the Al-based residue causes oxygen that causes non-radiative recombination to be incorporated into the active layer containing nitrogen, so that after the growth of the semiconductor layer containing Al, the oxygen-containing residue contains nitrogen. Before the active layer is grown, the reaction chamber is supplied with a gas that can be removed by reacting with the Al-based residue remaining on the reaction chamber side wall, heating body, jig holding the substrate, etc. Incorporation of oxygen into the layer can be suppressed.
[0040]
By this method, the Al concentration in the active layer containing nitrogen is reduced to 1 × 10¹⁹cm^-3By reducing to the following, continuous oscillation at room temperature became possible. Furthermore, the Al concentration in the active layer containing nitrogen is 2 × 10¹⁸cm^-3By reducing to the following, light emission characteristics equivalent to those formed on a semiconductor layer not containing Al were obtained.
[0041]
FIG. 8 shows the result of evaluating the threshold current density by fabricating a broad stripe laser using AlGaAs as a cladding layer (a layer containing Al) and using a GaInNAs double quantum well structure (a layer containing nitrogen) as an active layer. . In a structure in which an active layer containing nitrogen is continuously formed on a semiconductor layer containing Al as a constituent element, 2 × 10¹⁹cm^-3Above Al and 1 × 10¹⁸cm^-3More oxygen is incorporated, and the threshold current density is 10 kA / cm²The value was significantly higher than 2.
[0042]
However, the Al concentration in the active layer is 1 × 10¹⁹cm^-3By reducing to the following, the oxygen concentration in the active layer becomes 1 × 10¹⁸cm^-3Reduced to a threshold current density of 2-3 kA / cm²The broad stripe laser oscillated. Broad stripe laser has a threshold current density of several kA / cm²Continuous oscillation at room temperature is possible with the following active layer quality. Therefore, the Al concentration in the active layer containing nitrogen is 1 × 10¹⁹cm^-3By suppressing to the following, a semiconductor laser capable of continuous oscillation at room temperature can be manufactured.
[0043]
  Also,The step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas is a step of supplying an organic nitrogen compound gas into the growth chamber.It may be.
[0044]
An example of a gas that can be removed by reacting with an Al-based residue is an organic compound gas. As described above, when the DMHy gas, which is one of the organic compound gases, is supplied using the DMHy cylinder during the growth of the active layer containing nitrogen, it is apparent that it reacts with the Al residue.
[0045]
Therefore, after the growth of the semiconductor layer containing Al and before the growth of the active layer containing nitrogen, when the organic compound gas is supplied using the organic compound gas cylinder, the jig for holding the reaction chamber side wall, the heating body, and the substrate Since it can be removed by reacting with the Al-based residue remaining in, etc., oxygen uptake into the active layer can be suppressed. Furthermore, it is preferable to use the same gas as the nitrogen raw material of the active layer containing nitrogen because it is not necessary to add a gas line.
[0046]
  AlsoThe step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas is a step of supplying a gas containing oxygen (O) into the growth chamber.It may be.
[0047]
One example of a gas that can be removed by reacting with an Al-based residue is O₂, H₂A gas containing oxygen such as O is raised. As described above, it is known that oxygen is taken into the active layer together with Al during the growth of the active layer containing nitrogen. So O₂, H₂It can be seen that a gas containing oxygen such as O reacts with an Al-based residue.
[0048]
Therefore, after the growth of the semiconductor layer containing Al and before the growth of the active layer containing nitrogen, O₂, H₂When oxygen-containing gas such as O is supplied, it can be removed by reacting with the Al-based residue remaining on the reaction chamber side wall, heating body, jig holding the substrate, etc., so that oxygen can be taken into the active layer. Can be suppressed. Therefore, oxygen uptake into the active layer can be suppressed.
[0049]
As can be seen from the SIMS profile in FIG. 6, a large amount of Al was taken into the first layer of the active layer containing nitrogen and was hardly taken into the second layer. Al-based residues can be removed simply by supplying gas. Of course, since the gas containing excessively supplied oxygen needs to be removed before the active layer growth, it is desirable to supply an appropriate amount that does not excessively increase. On the contrary, it is difficult to exclude the gas containing oxygen.
[0050]
  Also,A semiconductor that has undergone an Al removal process between a semiconductor region that has been subjected to the process of removing Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas, and an active layer containing nitrogen. Ga with a larger band gap than the region_xIn_{1- x}P_yGrowing As (0 <x ≦ 1, 0 <y ≦ 1) layerYou may do it.
[0051]
The step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas can be performed, for example, by interrupting the growth. In this case, the epi-substrate surface may be damaged by an etching gas or the like to cause a defect. If this interface is an active region into which carriers are injected, it becomes a non-radiative recombination center and the light emission efficiency is lowered when the light emitting element is operated.
[0052]
Ga with higher band gap energy than the surface material band gap energy during growth interruption_xIn_{1- x}P_yWhen the As (0 <x ≦ 1, 0 <y ≦ 1) layer is grown between the active layer containing nitrogen, the number of carriers injected into the growth interruption interface for removal by the etching gas is almost eliminated, so that the luminous efficiency is lowered. Things will disappear. If this growth interruption interface is analyzed by SIMS, oxygen (O) or nitrogen (N) or aluminum (Al) will be observed. It should be noted that other materials may be used as long as they do not contain Al and nitrogen and have a band gap energy higher than that of the surface material at the time of the growth interruption.
[0053]
  Further, in a semiconductor light emitting device in which a semiconductor layer containing Al is provided between a substrate and an active layer containing nitrogen, nitrogen that is not in direct contact with the active layer is interposed between the semiconductor layer containing Al and the active layer containing nitrogen. Including a semiconductor layer formedMay be.
[0054]
The step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas can be performed by crystal growth. For example, a semiconductor layer not containing nitrogen and Al is provided as an intermediate layer between the semiconductor layer containing Al and the active layer containing nitrogen, and organic nitrogen such as DMHy gas that is the etching gas at the same time as at least the Group III material in the middle When the compound gas is supplied, a semiconductor layer containing nitrogen is grown so as to take in Al and oxygen. As a result, Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber can be removed, so that oxygen incorporation into the active layer can be suppressed.
[0055]
In this case, it is necessary to set conditions so that the semiconductor layer containing nitrogen has a band gap larger than that of the active layer. In addition, it is preferable that the semiconductor layer containing nitrogen is not in direct contact with the active layer because oxygen that causes non-radiative recombination centers is incorporated.
[0056]
According to the semiconductor light emitting device of this configuration, the semiconductor layer containing nitrogen is formed between the semiconductor layer containing Al and the active layer containing nitrogen. That is, the step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas is used as a semiconductor layer containing nitrogen by supplying an organic nitrogen compound gas such as DMHy as a nitrogen raw material. Thus, a semiconductor layer containing nitrogen is grown in a form of taking in Al and oxygen.
[0057]
As a result, the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber can be removed, so that oxygen uptake into the active layer can be suppressed, and luminous efficiency can be increased. In the case of a semiconductor laser, the threshold current can be made sufficiently low.
[0058]
  In addition, a semiconductor layer having a larger band gap energy than the semiconductor layer containing nitrogen is formed between the semiconductor layer containing nitrogen and the active layer containing nitrogen.May be.
[0059]
  SaidofThus, the step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber is growth of a semiconductor layer containing nitrogen, and Al and oxygen are taken into the film. If the semiconductor layer containing nitrogen is in the active region where carriers are injected, oxygen becomes a non-radiative recombination center and the light emission efficiency is lowered when the light emitting element operates. When a semiconductor layer having a higher band gap energy and containing no Al and nitrogen than a semiconductor layer containing nitrogen is formed between the semiconductor layer containing nitrogen and the active layer containing nitrogen, carriers injected into the semiconductor layer containing nitrogen are formed. Almost disappears, so the luminous efficiency is not reduced.
[0060]
According to the semiconductor light emitting device of this configuration, between the semiconductor layer containing nitrogen and the active layer containing nitrogen in which oxygen that is a non-radiative recombination center that reduces the light emission efficiency during operation of the light emitting device is incorporated in the film. Since a semiconductor layer having a higher band gap energy than that of a semiconductor layer containing nitrogen was formed, carrier injection into the semiconductor layer containing nitrogen could be suppressed, and a decrease in light emission efficiency could be suppressed, so that the light emission efficiency could be increased. In the case of a semiconductor laser, the threshold current can be made sufficiently low.
[0061]
  Further, in a semiconductor light emitting device in which a semiconductor layer containing Al is provided between a substrate and an active layer containing nitrogen, a GaNAs layer or a GaInNAs layer is formed between the semiconductor layer containing Al and the active layer containing nitrogen.May be.
[0062]
The step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas can be performed while the crystal is growing. For example, when GaAs not containing nitrogen and Al is provided as an intermediate layer between the semiconductor layer containing Al and the active layer containing nitrogen, if DMHy gas as the etching gas is supplied during the growth of the GaAs layer or GaInAs layer, Al Then, a GaNAs layer or a GaInNAs layer is grown so as to take in oxygen.
[0063]
As a result, Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber can be removed, so that oxygen incorporation into the active layer can be suppressed. In this case, it is necessary to set conditions so that the GaNAs layer or the GaInNAs layer has a band gap larger than that of the active layer. For example, DMHy gas phase ratio: [DMHy] / ([DMHy] + [AsH₃]) Is reduced, the growth temperature is increased, and the In composition is increased, so that nitrogen incorporation is reduced.
[0064]
  Also, above, Any one of a GaAs, GaInAs, GaAsP, GaInPAs, and GaInP layer is formed between the GaNAs layer or GaInNAs layer and the active layer containing nitrogen.May be.
[0065]
  the aboveThe step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber as described above is growth of a GaNAs layer or a GaInNAs layer, and incorporates Al and oxygen into the film. If the GaNAs layer or the GaInNAs layer is in the active region where carriers are injected, oxygen becomes a non-radiative recombination center and the light emission efficiency is lowered during operation of the light emitting element.
[0066]
A GaAs, GaInAs, GaAsP, GaInPAs, or GaInP layer having a higher band gap energy and no Al and nitrogen than the GaNAs or GaInNAs layer is formed between the GaNAs or GaInNAs layer and the active layer containing nitrogen. Then, since almost no carriers are injected into the GaNAs layer or GaInNAs layer, the luminous efficiency is not lowered.
[0067]
  In a semiconductor light emitting device in which a semiconductor layer containing Al is provided between a substrate and an active layer containing nitrogen, a GaInNP layer or a GaInNPAs layer is formed between the semiconductor layer containing Al and the active layer containing nitrogen.May be.
[0068]
The step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas can be performed while the crystal is growing. For example, when a GaInP layer or GaInPAs layer not containing nitrogen and Al is provided as an intermediate layer between the semiconductor layer containing Al and the active layer containing nitrogen, when the DMHy gas as the etching gas is supplied during the growth of the intermediate layer, A GaInNP layer or a GaInNPAs layer is grown so as to take in Al and oxygen.
[0069]
As a result, Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber can be removed, so that oxygen incorporation into the active layer can be suppressed. In this case, it is necessary to set conditions so that the band gap is larger than the band gap of the active layer. For example, DMHy gas phase ratio: [DMHy] / ([DMHy] + [AsH₃] + [PH₃]) Is reduced, and the nitrogen uptake is reduced by increasing the growth temperature.
[0070]
  Also, above, A GaAsP, GaInPAs, and GaInP layer having a larger band gap energy than the GaInNP layer or GaInNPAs layer is formed between the GaInNP layer or GaInNPAs layer and the active layer containing nitrogen.May be.
[0071]
  the aboveThe step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber is growth of a GaInNP layer or a GaInNPAs layer, and Al and oxygen are taken into the film. If the GaInNP layer or the GaInNPAs layer is in the active region into which carriers are injected, oxygen becomes a non-radiative recombination center and the luminous efficiency is lowered when the light emitting element is operated.
[0072]
If any of the GaAsP, GaInPAs, and GaInP layers having a higher band gap energy and no Al and nitrogen than the GaInNP layer or GaInNPAs layer is formed between the GaInNP layer or GaInNPAs layer and the active layer containing nitrogen, the GaInNP Since almost no carriers are injected into the layer or GaInNPAs layer, the luminous efficiency is not lowered.
[0073]
  In addition, the surface emitting semiconductor laser element isManufacturing method of semiconductor light emitting device, orthe aboveIt is characterized by being formed using a configuration.
[0074]
Examples of the semiconductor layer containing nitrogen include GaNAs, GaInNAs, InNAs, GaAsNSb, GaInNAsSb, and GaInNPAs. For example, GaInNAs will be described below. By adding N to GaInAs, which has a larger lattice constant than GaAs, GaInNAs can be lattice-matched to GaAs, and its band gap can be reduced, enabling emission in the 1.3 μm and 1.55 μm bands. Become. Since it is a GaAs substrate lattice matching system, wide gap AlGaAs or GaInP can be used for the cladding layer.
[0075]
Furthermore, the addition of N reduces the band gap as described above, lowers the energy levels of both the conduction band and the valence band, and extremely increases the band discontinuity of the conduction band at the heterojunction. As a result, the temperature of the operating current of the laser The dependency can be made extremely small.
[0076]
Further, the surface-emitting type semiconductor laser device is advantageous for small size, low power consumption, and parallel transmission by two-dimensional integration. Although it is difficult to obtain performance that can be put to practical use in the conventional GaInPAs / InP system, a surface emitting semiconductor laser element is 0.85 μm band surface emitting semiconductor laser element using a GaAs substrate according to a GaInNAs material. Since the Al (Ga) As / (Al) GaAs semiconductor multilayer distributed Bragg reflector and the current narrowing structure by selective oxidation of AlAs can be applied, practical application can be expected.
[0077]
To achieve this, it is important to improve the crystal quality of the GaInNAs active layer, to reduce the resistance of the multilayer reflector, and to improve the crystal quality and controllability of the multilayer structure as a surface emitting semiconductor laser element. However, since the method for manufacturing a semiconductor light emitting device according to any one of claims 1 to 3 of the present invention or the configuration according to any one of claims 4 to 8 is used, the driving voltage is low and the driving voltage is low. A surface-emitting type semiconductor laser device with high emission efficiency and low threshold current operation and good temperature characteristics can be easily realized at low cost.
[0078]
  Also,A Ga region between a semiconductor region subjected to the step of removing Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas and an active layer containing nitrogen is formed._xIn_{1- x}P_yAn As (0 <x ≦ 1, 0 <y ≦ 1) layer is provided, and a region where the step of removing with the etching gas is performed is a semiconductor distributed Bragg reflector portion.1Formed using the method for manufacturing a semiconductor light emitting device described in 1.Also good.
[0079]
  If a removal step is provided in the active region where carriers are injected, non-radiative recombination may occur due to oxidation or the like, which may reduce luminous efficiency.the aboveAfter the step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas as shown in FIG. Ga as part_xIn_{1- x}P_yAssuming that an As (0 <x ≦ 1, 0 <y ≦ 1) layer is grown, Ga_xIn_{1- x}P_ySince it is possible to form an active region using a narrow gap material (for example, GaAs) in a region closer to the active layer than As (0 <x ≦ 1, 0 <y ≦ 1), there is a concern about the reduction in the luminous efficiency. No surface emitting semiconductor laser with low threshold current operation and good temperature characteristics, which can eliminate the effect on device performance due to non-radiative recombination centers in the area where Al-based residue removal process has been performed An element can be obtained.
[0080]
  Also,A Ga region between the semiconductor region and the active layer containing nitrogen that performs the step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas._xIn_1-xP_yThe As (0 <x ≦ 1, 0 <y ≦ 1) layer is provided, and the region where the step of removing with the etching gas is performed is a resonator portion.1Formed by using the method for manufacturing a semiconductor light emitting device described in 1.May be.
[0081]
The process of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber with an etching gas may be performed between the lower reflecting mirror containing Al and the active layer containing nitrogen. It can be inside the vessel. However, if a removal step is provided in the active region where carriers are injected, non-radiative recombination may occur due to oxidation or the like, which may reduce the light emission efficiency. However, the growth is interrupted in the resonator portion, and the Al remaining in the growth chamber remains. After the step of removing the raw material, Al reactant, Al compound, or Al with an etching gas, and before growing the active layer, GaInP, GaPAs, or a GaInPAs layer is grown. An active region can be formed using a narrow gap material (for example, GaAs) in a region closer to the active layer than the GaPAs or GaInPAs layer. No worries, eliminating the effect on device performance due to non-radiative recombination centers in the area where the Al-based residue removal process has been performed Can operate a low threshold current, it is possible to temperature characteristics get a good surface emitting semiconductor laser device.
[0082]
According to the semiconductor light emitting device of this configuration, between the Al region remaining in the growth chamber, the Al reactant, the Al compound, or the semiconductor region subjected to the step of removing Al with an etching gas and the active layer containing nitrogen Since a GaInP, GaPAs, or GaInPAs layer is formed on the semiconductor region, damage that occurs during the process of removing with an etching gas or oxygen uptake due to growth interruption occurs in a semiconductor region in which a non-radiative recombination center is formed. Since there is a semiconductor layer having a band gap larger than the band gap between the active layer and the active layer, the number of carriers injected into the semiconductor region in which the non-radiative recombination centers are formed can be reduced, and the reduction in luminous efficiency can be suppressed. did it. In the case of a semiconductor laser, the threshold current can be made sufficiently low.
[0083]
  Also,Optical transmission modulethe aboveUsing a surface emitting semiconductor laser element as a light sourceMay be.
  By using a surface emitting semiconductor laser element having a low resistance, a low driving voltage, a low threshold current operation, and good temperature characteristics, a low-cost optical transmission module that does not require a cooling element can be realized. it can.
[0084]
  Also,Optical transceiver modulethe aboveA surface emitting semiconductor laser element, an optical fiber, and a receiving diode are provided, the surface emitting semiconductor laser element is used as a light source, laser light from the surface emitting semiconductor laser element is incident on the optical fiber, and a laser beam is emitted from the optical fiber. The light is received by the receiving diode.May be.
  By using a surface emitting semiconductor laser element having a low resistance, a low driving voltage, a low threshold current operation, and good temperature characteristics, a low-cost optical transceiver module that does not require a cooling element can be realized. it can.
[0085]
  Also,The optical communication systemthe aboveOptical transmission module orthe aboveUsing optical transceiver moduleMay be.
  Low-cost optical fiber communication system, optical interconnection system, etc. that do not require a cooling element by using a surface emitting semiconductor laser element with low resistance, low drive voltage, low threshold current operation, and good temperature characteristics as described above An optical communication system can be realized.
[0086]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0087]
(First embodiment)
A GaInNAs surface-emitting type semiconductor laser device according to the first embodiment of the present invention will be described. FIG. 9 is a diagram showing the structure of the GaInNAs surface emitting semiconductor laser device in the first embodiment (and the second embodiment).
[0088]
As shown in FIG. 9, the surface-emitting type semiconductor laser device in this example is formed on an n-GaAs substrate 201 having a plane orientation (100) of 2 inches in size and ¼ of the oscillation wavelength in each medium. N-Al with double thickness_xGa_1-xAn n-semiconductor distributed Bragg reflector (lower semiconductor distributed Bragg reflector: also simply referred to as a lower reflector) 202 having a periodic structure in which 35 cycles of As (x = 0.9) and n-GaAs are alternately stacked is formed (see FIG. The details are omitted in FIG. On top of this, undoped lower GaAs spacer layer 203, three layers of Ga_xIn_1-xN_yAs_1-yA multiple quantum well active layer 204 including an (x, y) well layer and a GaAs barrier layer and an undoped upper GaAs spacer layer 205 are formed.
[0089]
A p-semiconductor distributed Bragg reflector (upper semiconductor distributed Bragg reflector: also simply referred to as an upper reflector) 206 is formed thereon. The upper reflecting mirror 206 is a 3λ / 4-thick low refractive index layer (λ / 4-15 nm C-doped p-Al layer) in which AlAs serving as a selective oxidation layer is sandwiched between AlGaAs._xGa_1-xAs (x = 0.9), C-doped p-AlAs selectively oxidized layer 30 nm, 2λ / 4-15 nm C-doped p-Al_xGa_1-xAs (x = 0.9)) and λ / 4 thickness GaAs (1 period), and C-doped p-Al_xGa_1-xPeriodic structure in which As (x = 0.9) and p-GaAs are alternately stacked at a thickness that is ¼ times the oscillation wavelength in each medium. For example, it is composed of 25 periods (details omitted in the figure). ).
[0090]
The uppermost GaAs layer of the upper reflecting mirror 206 also serves as a contact layer 207 that contacts the electrode. The In composition x of the well layer in the active layer was 37%, and the nitrogen composition was 0.5%. The thickness of the well layer was 7 nm. It had about 2.5% compressive strain (high strain) with respect to the GaAs substrate 201.
[0091]
The raw materials for the GaInNAs active layer by MOCVD are TMG (trimethylgallium), TMI (trimethylindium), AsH.₃(Arsine), and DMHy (dimethylhydrazine) was used as a raw material for nitrogen. Carrier gas is H₂Was used. DMHy decomposes at a low temperature and is suitable for low temperature growth of 600 ° C. or less, and is a preferable raw material when growing a quantum well layer having a large strain required for low temperature growth. When the strain is large as in the active layer of the GaInNAs surface-emitting type semiconductor laser device of this example, low temperature growth that is non-equilibrium is preferable. In this example, the GaInNAs layer was grown at 540 ° C.
[0092]
In this example, in order to suppress oxygen uptake into the active layer and prevent the light emission efficiency from being lowered, the growth was interrupted during the growth of the lower GaAs spacer layer 203, and Al-based residues were excluded using DMHy gas. When DMHy is supplied using a DMHy cylinder, it can be removed by reaction with the Al-based residue remaining on the reaction chamber side wall, heating body, jig holding the substrate, etc., so that oxygen can be taken into the active layer. I was able to suppress it. This step may be performed after the growth of the semiconductor layer containing Al and before the growth of the active layer containing nitrogen.
[0093]
A mesa having a predetermined size was formed by exposing at least the side surface of the p-AlAs selective oxidation layer 208, and AlAs that appeared on the side surface was oxidized from the side surface with water vapor to form an AlxOy current narrowing portion 209. Then, the etched portion is buried and planarized with polyimide 210, the polyimide on the upper reflecting mirror 206 having the p contact portion and the light emitting portion is removed, and the p-side electrode 211 other than the light emitting portion on the p contact layer 207 is removed. The n-side electrode 212 was formed on the back surface.
[0094]
The oscillation wavelength of the manufactured surface emitting semiconductor laser element was about 1.3 μm. Since GaInNAs was used for the active layer, a long wavelength surface emitting semiconductor laser device could be formed on the GaAs substrate. Since the compound containing Al remaining in the apparatus was excluded by using an etching gas so that the active layer containing nitrogen was not taken into the film together with oxygen during the growth of the active layer containing nitrogen, oxygen was mixed into the active layer together with Al. Was able to be suppressed. As a result, a GaInNAs surface-emitting type semiconductor laser device that has high luminous efficiency and oscillates at a low threshold value can be manufactured by the MOCVD method advantageous for mass production.
[0095]
Further, the threshold current was low because the current was narrowed by selective oxidation of the selective oxidation layer mainly composed of Al and As. According to the current narrowing structure using the current narrowing layer composed of the Al oxide film that selectively oxidizes the selective oxidation layer, the current narrowing layer is formed close to the active layer, so that the current spread can be suppressed and the minute area that does not touch the atmosphere It is possible to confine carriers efficiently. Furthermore, the refractive index is reduced by oxidizing to an Al oxide film, and light can be efficiently confined in a minute region in which carriers are confined by the effect of the convex lens, which is extremely efficient and the threshold current is reduced. The In addition, the manufacturing cost can be reduced because the current narrowing structure can be easily formed.
[0096]
The MBE method is mainly used for semiconductor layers containing nitrogen and other group V such as GaInNAs. However, since the growth is in principle in a high vacuum, the amount of raw material supply cannot be increased. Increasing it has the disadvantage of placing a burden on the exhaust system. Although a high vacuum exhaust system exhaust pump is required, the throughput is poor because the exhaust system is burdened and easily broken to remove residual raw materials in the MBE chamber.
[0097]
A surface-emitting type semiconductor laser device is configured by sandwiching an active region including at least one active layer that generates laser light between semiconductor multilayer reflectors. While the thickness of the crystal growth layer of the edge-emitting laser is about 3 μm, for example, a 1.3 μm wavelength band-emitting semiconductor laser element requires a thickness exceeding 10 μm, but the MBE method requires a high vacuum. However, the growth rate is about 1 μm / h, and a growth interruption time for changing the raw material supply amount is not provided in order to grow a thickness of 10 μm. It takes at least 10 hours.
[0098]
The thickness of the active region is usually very small compared to the whole (10% or less), and most of them are layers constituting the multilayer mirror. The semiconductor multilayer mirror is formed by alternately laminating a low refractive index layer and a high refractive index layer (for example, 20 to 40) with a thickness (1/4) of the oscillation wavelength in each medium (λ / 4 thickness). Pair) is formed.
[0099]
In a surface emitting semiconductor laser device on a GaAs substrate, an AlGaAs material is used to change the Al composition to form a low refractive index layer (Al composition large) and a high refractive index layer (Al composition small). However, in actuality, the resistance increases particularly due to the hetero-barrier of each layer on the p side. Therefore, an interlayer having an Al composition between the low refractive index layer and the high refractive index layer is inserted between the multilayer reflectors. The resistance is reduced.
[0100]
As described above, the surface emitting semiconductor laser device has to grow semiconductor layers having different compositions exceeding 100 layers, and also provides an intermediate layer between the low refractive index layer and the high refractive index layer of the multilayer reflector. It is an element that needs to control the raw material supply amount instantaneously. However, in the MBE method, the supply amount is controlled by changing the temperature of the raw material cell, and the composition cannot be controlled flexibly. Therefore, it is difficult to reduce the resistance of the semiconductor multilayer mirror grown by the MBE method, and the operating voltage is high.
[0101]
On the other hand, the MOCVD method can control the composition instantly by simply controlling the flow rate of the source gas, does not require a high vacuum like the MBE method, and can increase the growth rate to 3 μm / h or more for easy throughput. The growth method is extremely suitable for mass production.
[0102]
As described above, according to the present embodiment, a 1.3 μm band surface emitting semiconductor laser device with low power consumption and low cost can be realized.
[0103]
(Second embodiment)
A GaInNAs surface-emitting type semiconductor laser device according to a second embodiment of the present invention will be described. The difference from the first embodiment is that the growth of the GaAs lower spacer layer 203 is interrupted during the growth of the oxygen source (O) in order to remove the Al source, Al reactant, Al compound, or Al remaining in the growth chamber.₂).
[0104]
The oscillation wavelength of the manufactured surface emitting semiconductor laser element was about 1.3 μm. Since GaInNAs was used for the active layer, a long wavelength surface emitting semiconductor laser device could be formed on the GaAs substrate.
[0105]
In order to prevent the compound containing Al remaining in the device from being taken into the film together with oxygen during the growth of the active layer containing nitrogen, the growth is interrupted between the layer containing Al and the active layer containing nitrogen. Etching gas oxygen (O₂), Al was taken in along with the oxygen at the interface where the growth was interrupted, but the compound containing Al remaining in the reaction chamber was excluded before the active layer growth, and oxygen was mixed with the Al in the active layer. I was able to suppress it. As a result, a GaInNAs surface-emitting type semiconductor laser device that has high luminous efficiency and oscillates at a low threshold value can be manufactured by the MOCVD method advantageous for mass production.
[0106]
(Third embodiment)
A GaInNAs surface-emitting type semiconductor laser device according to a third embodiment of the present invention will be described. FIG. 10 is a diagram showing the structure of a GaInNAs surface emitting semiconductor laser element in the third embodiment.
[0107]
The difference from the first embodiment is that in the process of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber, DMHy is supplied during the growth of the GaAs lower spacer layer 203 to form the GaInNAs layer. It has grown. This GaInNAs layer has a condition that the band gap energy is larger than that of the GaInNAs active layer.
[0108]
The oscillation wavelength of the manufactured surface emitting semiconductor laser element was about 1.3 μm. Since GaInNAs was used for the active layer, a long wavelength surface emitting semiconductor laser device could be formed on the GaAs substrate. Since the GaInNAs layer was grown by supplying DMHy as an etching gas so that the compound containing Al remaining in the apparatus was not taken into the film together with oxygen during the growth of the active layer containing nitrogen, the removal process was performed. Al was incorporated into the GaInNAs layer together with oxygen, but the compound containing Al remaining in the reaction chamber was excluded before the growth of the active layer, and it was possible to prevent oxygen from being mixed into the active layer together with Al. The GaInNAs layer subjected to this removal step can be said to be a dummy layer of the active layer. As a result, a GaInNAs surface-emitting type semiconductor laser device that has high luminous efficiency and oscillates at a low threshold value can be manufactured by the MOCVD method advantageous for mass production.
[0109]
(Fourth embodiment)
A GaInNAs surface-emitting type semiconductor laser device according to a fourth embodiment of the present invention will be described. FIG. 11 is a diagram showing the structure of a GaInNAs surface emitting semiconductor laser element in the fourth embodiment.
[0110]
The difference from the first embodiment is that the step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber is performed in the lower reflector region. The low refractive index layer constituting the lower reflecting mirror is almost composed of AlGaAs, but the layer closest to the active layer is Ga._xIn_{1 - x}P_yAs (x = 0.5, y = 1), the growth was interrupted in the middle of the GaAs layer, which is a high refractive index layer below, and DMHy was supplied.
[0111]
The oscillation wavelength of the manufactured surface emitting semiconductor laser element was about 1.3 μm. Since GaInNAs was used for the active layer, a long wavelength surface emitting semiconductor laser device could be formed on the GaAs substrate.
[0112]
Etching gas between the semiconductor layer containing Al and the active layer containing nitrogen so that the compound containing Al remaining in the apparatus is not taken into the film together with oxygen during the growth of the active layer containing nitrogen. Since DMHy was supplied, the compound containing Al remaining in the reaction chamber was excluded before the growth of the active layer, and it was possible to prevent oxygen from being mixed into the active layer together with Al. However, this interface may be damaged by an etching gas or the like to cause a defect. Nitrogen, oxygen, and Al may be incorporated. These may form non-radiative recombination centers.
[0113]
However, in this example, since a GaInPAs layer having a wide band gap is inserted between the interface where the growth is interrupted and the GaInNAs active layer, carriers can be suppressed from being injected into the growth interrupting interface. It is possible to prevent a decrease in light emission efficiency due to the light emission recombination center.
As a result, a GaInNAs surface-emitting type semiconductor laser device that has high luminous efficiency and oscillates at a low threshold value can be manufactured by the MOCVD method advantageous for mass production.
[0114]
(Fifth embodiment)
A GaInNAs surface-emitting type semiconductor laser device according to a fifth embodiment of the present invention will be described. FIG. 12 is a diagram showing the structure of a GaInNAs surface emitting semiconductor laser element in the fifth embodiment.
[0115]
The difference from the fourth embodiment is that the step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber is a Ga layer constituting the low refractive index layer constituting the lower reflector._xIn_{1 - x}P_yThis is because DMHy was supplied during the growth of the GaInP layer in the As (x = 0.5, y = 1) layer to grow the GaInNP layer.
[0116]
The oscillation wavelength of the manufactured surface emitting semiconductor laser element was about 1.3 μm. Since GaInNAs was used for the active layer, a long wavelength surface emitting semiconductor laser device could be formed on the GaAs substrate. The GaInNP layer was grown by supplying DMHy as an etching gas so that the compound containing Al remaining in the apparatus was not taken into the film together with oxygen during the growth of the active layer containing nitrogen. At the same time, Al was incorporated, but the compound containing Al remaining in the reaction chamber was excluded before the growth of the active layer, and it was possible to prevent oxygen from being mixed into the active layer together with Al.
[0117]
Further, since there is a GaInP layer having a wide band gap between the GaInNP layer and the GaInNAs active layer, the GaInNP layer that incorporates oxygen serving as a non-radiative recombination center is not an active region into which carriers are injected. The decrease in luminous efficiency due to the non-radiative recombination center can be prevented.
As a result, a GaInNAs surface-emitting type semiconductor laser device that has high luminous efficiency and oscillates at a low threshold value can be manufactured by the MOCVD method advantageous for mass production.
Although the GaInNP layer is formed in the middle of the GaInP layer, all the low refractive index layers of the lower reflecting mirror may be used as the GaInNP layer.
[0118]
(Sixth embodiment)
FIG. 13 is a diagram showing a sixth embodiment of the present invention, and is a schematic diagram of an optical transmission module combining a surface-emitting type semiconductor laser device and a fiber according to the fourth embodiment. In this embodiment, laser light from a 1.3 μm band GaInNAs surface emitting semiconductor laser element 301 is input to a silica-based optical fiber 302 and transmitted.
[0119]
It is possible to increase the transmission speed by arranging a plurality of surface emitting semiconductor laser elements having different oscillation wavelengths in an array in one or two dimensions and performing wavelength multiplexing transmission. It is also possible to increase the transmission speed by arranging surface emitting semiconductor laser elements in a one-dimensional or two-dimensional array, and combining optical fiber bundles composed of a plurality of corresponding optical fibers.
[0120]
Furthermore, when the surface-emitting type semiconductor laser device according to the present invention is used in an optical communication system, a low-cost and highly reliable optical transmission module can be realized, and a low-cost highly reliable optical communication system using the same can be realized. In addition, since the surface emitting semiconductor laser element using GaInNAs has a good temperature characteristic and a low threshold value, a system that generates little heat and can be used without cooling to a high temperature can be realized.
[0121]
(Seventh embodiment)
FIG. 14 is a diagram showing a seventh embodiment of the present invention, and is a schematic diagram of an optical transceiver module that is a combination of a surface emitting semiconductor laser element, a receiving photodiode, and an optical fiber according to a fifth embodiment. .
[0122]
When the surface-emitting type semiconductor laser device according to the present invention is used in an optical communication system, the surface-emitting type semiconductor laser device is low-cost, so that a surface-emitting type semiconductor laser device for transmission (1.3 μm band) is used as shown in FIG. A low-cost and highly reliable optical communication system using an optical transmission module in which a GaInNAs surface emitting semiconductor laser element) 305, a receiving photodiode 306, and an optical fiber 307 are combined can be realized.
[0123]
Further, in the case of the surface emitting semiconductor laser device using GaInNAs according to the present invention, the temperature characteristics are good, the operating voltage is low, and the threshold value is low, so there is little heat generation and no cooling to high temperature. A lower cost system can be realized.
[0124]
Furthermore, when a fluorine-doped POF (plastic fiber) that has a low loss in a long wavelength band such as 1.3 μm and a surface emitting laser using GaInNAs as an active layer are combined, the cost of the fiber is reduced and the diameter of the fiber is reduced. Since it is large and can be easily coupled with a fiber and the mounting cost can be reduced, a very low-cost module can be realized.
[0125]
(Eighth embodiment)
A GaInNAs surface-emitting type semiconductor laser device according to an eighth embodiment of the present invention will be described. FIG. 16 shows the structure of the GaInNAs surface-emitting type semiconductor laser device in this example.
[0126]
The difference from Example 1 is that the step of removing the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber forms a GaPAs layer in the resonator portion, and the growth is interrupted in the middle. The gas is supplied to the reaction chamber to exclude Al-based residues. More specifically, in this embodiment, the lower reflecting mirror is formed on the uppermost AlGaAs low refractive index layer. A GaAs layer may be formed between the AlGaAs low refractive index layer and the GaPAs layer, and an Al-based residue may be excluded in the middle of the GaAs layer.
[0127]
The oscillation wavelength of the manufactured surface emitting semiconductor laser element was about 1.3 μm. Since GaInNAs was used for the active layer, a long wavelength surface emitting semiconductor laser device could be formed on the GaAs substrate. Etching gas between the semiconductor layer containing Al and the active layer containing nitrogen so that the compound containing Al remaining in the device is not taken into the film together with oxygen during the growth of the active layer containing nitrogen. Since DMHy was supplied, the compound containing Al remaining in the reaction chamber was excluded before the growth of the active layer, and it was possible to prevent oxygen from being mixed into the active layer together with Al. However, there is a possibility that an oxide film is formed at this interface due to the growth interruption and a defect is generated. This may form a non-radiative recombination center.
[0128]
However, in this embodiment, since a GaPAs layer having a wider band gap than the GaAs spacer layer is inserted between the interface where the growth is interrupted and the GaInNAs active layer, it is possible to reliably prevent carriers from being injected into the growth interrupting interface. Therefore, it is possible to prevent a decrease in luminous efficiency due to the non-radiative recombination center at the growth interrupting interface. The GaPAs layer has a tensile strain with respect to the GaAs substrate. In the case where the active layer has a high compressive strain composition as in this embodiment, the tensile strain composition is preferable because it has an effect of compensating the strain of the active layer and can suppress lattice relaxation of the active layer. In this embodiment, the GaPAs layer is used, but a GaInP or GaInPAs layer may be used.
As a result, a GaInNAs surface-emitting type semiconductor laser device that has high luminous efficiency and oscillates at a low threshold value can be manufactured by the MOCVD method advantageous for mass production.
[0129]
The optical communication system using the surface emitting semiconductor laser device according to the present invention can be used not only for long-distance communication using an optical fiber, but also for transmission between devices such as a LAN (Local Area Network) and the like, and Can be used for short-distance communication as an optical interconnection such as data transmission between boards, between LSIs in a board, between elements in an LSI, and the like.
[0130]
In recent years, the processing performance of LSIs and the like has improved, but the transmission speed of the portion connecting them will become a bottleneck in the future. When the signal connection in the system is changed from the conventional electrical connection to the optical interconnect, for example, the optical transmission module or the optical transmission / reception module according to the present invention is used between the boards of the computer system, between the LSIs in the board, between the elements in the LSI, etc. Connection, an ultra-high-speed computer system becomes possible.
[0131]
Further, when a plurality of computer systems or the like are connected using the optical transmission module or the optical transmission / reception module according to the present invention, an ultra-high speed network system can be constructed. In particular, the surface-emitting type semiconductor laser element is suitable for a parallel transmission type optical communication system because the power consumption can be reduced by orders of magnitude compared to the edge-emitting type laser and the two-dimensional array can be easily formed.
[0132]
As described above, according to the GaInNAs-based material which is a semiconductor layer containing nitrogen, the Al (Ga) As / (Al) GaAs-based material having a proven record in a 0.85 μm band-emitting semiconductor laser device using a GaAs substrate. A semiconductor multilayer distributed Bragg reflector and a current narrowing structure by selective oxidation of AlAs can be applied. By manufacturing a surface emitting semiconductor laser device by the manufacturing method according to the present invention, the crystal quality of the GaInNAs active layer can be improved, Since the film reflector has a low resistance and the crystal quality and controllability of the multilayer structure as a surface emitting semiconductor laser device can be improved, a long wavelength surface emitting type such as a 1.3 μm band with a high level of practical use Semiconductor laser elements can be realized, and when these elements are used, low-cost optical fiber communication systems and optical interconnection systems that do not require cooling elements An optical communication system such as a system can be realized.
[0133]
【The invention's effect】
  According to the present invention, a method for manufacturing a semiconductor light emitting device using an active layer containing nitrogen such as GaInNAs having a high quality and a practical level is provided.Therealizable.
[0134]
  For more details,
(1) According to the method for manufacturing a semiconductor light emitting device of the first aspect, the growth of the semiconductor layer containing AlofAfter that, before the growth of the active layer containing nitrogen, gas that can be removed by reacting with the Al-based residue remaining on the reaction chamber side wall, the heating body, the jig holding the substrate, etc. Since it was supplied, oxygen uptake into the active layer could be suppressed, and a semiconductor light emitting device with high luminous efficiency could be formed.
[0135]
  Also,After the growth of the semiconductor layer containing Al and before the growth of the active layer containing nitrogen, using an organic nitrogen compound material cylinder such as DMHy as an etching gas, the Al material remaining in the growth chamber was supplied. , Or reacts with Al reactant, Al compound, or Al, and can react with Al-based residue remaining on the reaction chamber side wall, heating body, jig holding the substrate, etc., and can be removed. Incorporation of oxygen into the layer could be suppressed. As a result, a semiconductor light emitting device with high luminous efficiency could be formed.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a general MOCVD apparatus.
FIG. 2 is a diagram showing a room temperature photoluminescence spectrum from an active layer having a GaInNAs / GaAs double quantum well structure composed of a GaInNAs quantum well layer and a GaAs barrier layer, which are semiconductor layers containing nitrogen, manufactured by an MOCVD apparatus. is there.
FIG. 3 is a diagram showing a sample structure of a semiconductor light emitting device.
FIG. 4 shows an example of the semiconductor light emitting device shown in FIG. 3 in which an epitaxial growth apparatus (device having a cladding layer made of AlGaAs, an intermediate layer made of GaAs, and an active layer made of a GaInNAs / GaAs double quantum well structure) It is the figure which showed the depth direction distribution of nitrogen and oxygen concentration when forming using MOCVD.
FIG. 5 is a diagram showing the measurement conditions of FIG.
6 is a diagram showing a depth direction distribution of Al concentration of the same sample as FIG. 4; FIG.
7 is a diagram showing the measurement conditions of FIG. 6. FIG.
FIG. 8 is a diagram showing a result of evaluating a threshold current density by fabricating a broad stripe laser using AlGaAs as a cladding layer (a layer containing Al) and using a GaInNAs double quantum well structure (a layer containing nitrogen) as an active layer. is there.
FIG. 9 is a diagram showing the structure of a GaInNAs surface emitting semiconductor laser element in the first and second examples.
FIG. 10 is a diagram showing a structure of a GaInNAs surface emitting semiconductor laser element in a third embodiment.
FIG. 11 is a diagram showing the structure of a GaInNAs surface-emitting type semiconductor laser device in a fourth example.
FIG. 12 is a view showing a structure of a GaInNAs surface emitting semiconductor laser element in a fifth embodiment.
FIG. 13 is a diagram showing a sixth embodiment of the present invention.
FIG. 14 is a diagram showing a seventh embodiment of the present invention.
FIG. 15 is a graph showing the nitrogen composition dependence of the threshold current density experimentally determined by the inventors.
FIG. 16 is a diagram showing an eighth embodiment of the present invention.
[Explanation of symbols]
A: Raw material gas supply unit, A1: Group III gas line, A2: Group V gas line, B: Heating body, C: Exhaust unit,
11: Substrate loading / unloading port, 12: Growth chamber (reaction chamber), 13: Hydrogen purifier, 14: Bubbler, 15: AsH₃Gas cylinder, 15 ': dopant gas cylinder, 16: valve,
101: GaAs substrate, 102: lower cladding layer, 103: intermediate layer 103, 104: active layer, 105: upper cladding layer,
a1, b1: main line, a2, b2: vent line, dummy lines # 1 to # 4: dummy line,
201: n-GaAs substrate, 202: n-semiconductor distributed Bragg reflector (lower semiconductor distributed Bragg reflector: also simply referred to as lower reflector), 203: lower GaAs spacer layer, 204: multiple quantum well active layer, 205: upper GaAs spacer layer, 206: p-semiconductor distributed Bragg reflector (upper semiconductor distributed Bragg reflector: also simply referred to as upper reflector), 207: contact layer, 208: p-AlAs selectively oxidized layer, 209: AlxOy current narrowing part 210: polyimide, 211: p-side electrode, 212: n-side electrode, 213: GaInNAs layer, 214: GaInNP layer,
301, 305: semiconductor laser element, 302, 307: optical fiber, 306: receiving photodiode.

Claims (1)

In a method for manufacturing a semiconductor light emitting device, in which a semiconductor layer containing Al is provided between a substrate and an active layer made of a GaInNAs-based material containing nitrogen,
The semiconductor layer containing Al and the active layer containing nitrogen are grown using an organometallic Al raw material and a nitrogen compound raw material, respectively,
During the growth of the semiconductor layer provided between the Al-containing semiconductor layer and the nitrogen-containing active layer, the Al raw material, Al reactant, Al compound, or Al remaining in the growth chamber is removed from the organic nitrogen compound gas. A method for manufacturing a semiconductor light-emitting element, comprising a step of removing by supply to a growth chamber .

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