JP4154907B2 - Semiconductor optical device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a III-V compound semiconductor film, a semiconductor optical device, and a method for forming a semiconductor film.
[0002]
[Prior art]
The optical communication module includes a semiconductor laser element. This semiconductor laser element includes an InP substrate, an InP semiconductor layer, and a GaInAsP semiconductor layer. In the optical communication module, in order to stabilize the oscillation wavelength of the laser light with respect to temperature change, the semiconductor laser light element is disposed on the Peltier element.
[0003]
[Problems to be solved by the invention]
It is known that a semiconductor laser element using a GaInAsP semiconductor as an active layer has a relatively large temperature change when the temperature changes. This is because the temperature coefficient of the band gap of the GaInAsP semiconductor is large.
[0004]
The inventors have studied a GaInNAs semiconductor as a candidate for a semiconductor material that is superior in temperature characteristics of a semiconductor laser device than a GaInAsP semiconductor. Although the solidity of nitrogen in the base material GaInAs semiconductor is small, the inventors' research has shown that as a quaternary semiconductor containing nitrogen, Ga_0.65In_0.35N_0.1As_0.9The composition of a semiconductor has been realized. The inventors have also produced semiconductor laser elements. However, the inventors believe that further research is necessary to use GaInNAs semiconductors as practical semiconductor materials. That is, what is needed is to provide a semiconductor material with good crystallinity.
[0005]
Accordingly, an object of the present invention is to provide a ternary III-V compound semiconductor film having good crystallinity, a semiconductor optical device including the semiconductor film, and a method for forming a III-V compound semiconductor film. .
[0006]
[Means for Solving the Problems]
  A semiconductor optical device according to the present invention includes a GaAs substrate, a first p-type semiconductor layer provided on the GaAs substrate, a first n-type semiconductor layer provided on the GaAs substrate, and the first A first active layer provided between the p-type semiconductor layer and the first n-type semiconductor layer, wherein the first active layer comprises:It is provided to have a PL peak wavelength in a wavelength region exceeding 1.25 micrometers.It is a III-V group compound semiconductor layer made of GaInNPAs and provided on the GaAs substrate. In the III-V group compound semiconductor layer, the mixed crystal ratio (InP / InN) of InP and InN is0.1 or more4 or less,Above III -InAs in group V compound semiconductor layers _X NP _3-X In the cluster (X = 1 to 3), one or more As atoms are substituted with P atoms.
  A semiconductor optical device according to the present invention includes a GaAs substrate, a first p-type semiconductor layer provided on the GaAs substrate, a first n-type semiconductor layer provided on the GaAs substrate, A first active layer provided between the first p-type semiconductor layer and the first n-type semiconductor layer, wherein the first active layer comprises:It is provided to have a PL peak wavelength in a wavelength region exceeding 1.25 micrometers.A group III-V compound semiconductor layer made of GaInNPAs and another group III-V compound semiconductor layer containing gallium as a group III element and arsenic as a group V element, and the group III-V compound semiconductor layer is a well The other group III-V compound semiconductor layer is a barrier layer, and in the group III-V compound semiconductor layer, the mixed crystal ratio (InP / InN) of InP and InN is0.1 or more4 or less,Above III -InAs in group V compound semiconductor layers _X NP _3-X In the cluster (X = 1 to 3), one or more As atoms are substituted with P atoms.The III-V compound semiconductor layer and the another III-V compound semiconductor layer constitute a quantum well structure.
  Furthermore, the semiconductor optical device according to the present invention includes a second p-type semiconductor layer provided on the GaAs substrate, a second n-type semiconductor layer provided on the GaAs substrate, and the second p-type semiconductor layer. A second active layer provided between the type semiconductor layer and the second n-type semiconductor layer, wherein the second active layer comprises: III Gallium and indium as group elements and arsenic, phosphorus and nitrogen as group V elements provided on the GaAs substrate III -V group compound semiconductor layer, the first active layer is provided for one of the semiconductor light emitting device and the semiconductor modulation device, and the second active layer is formed of the semiconductor light emitting device and the semiconductor modulation device. Provided for the other, the first and second active layers are optically coupled to each other.
  Furthermore, the semiconductor optical device according to the present invention is:In the III-V group compound semiconductor layer of the second active layer, the mixed crystal ratio (InP / InN) of InP and InN is0.1 or moreLess than 4Yes, said III -InAs in group V compound semiconductor layers _X NP _3-X In the cluster (X = 1 to 3), one or more As atoms are substituted with P atoms.be able to.
[0007]
  One aspect of the present invention relates to a method for forming a semiconductor film. This method ( a ) Placing the substrate in a metal organic vapor phase growth apparatus; ( b ) Supplying a gallium source material, an indium source material, an arsenic source material, a nitrogen source material, and a phosphorus source material to a metal organic chemical vapor deposition apparatus; III And -V group compound semiconductor film forming step. III -V group compound semiconductor film III The group elements include gallium and indium, and the group V elements include arsenic, phosphorus, and nitrogen.
  By forming a ternary group III-V compound semiconductor film containing gallium and indium as group III elements and arsenic, phosphorus and nitrogen as group V elements in an organic metal growth apparatus, nitrogen having a relatively small atomic radius can be obtained. Phosphorus having a relatively large atomic radius can be added to the base material GaInAs semiconductor film. The inventor has discovered that metalorganic vapor phase epitaxy is advantageous for adding both phosphorus and nitrogen to the parent semiconductor.
[0008]
In this method, the gallium source material includes triethylgallium, the indium source material includes trimethylindium, the arsenic source material includes tertiary butylarsine, the phosphorus source material includes tertiary butylphosphine, and the nitrogen source material includes dimethylhydrazine. Can be included. These raw materials can be used for forming a semiconductor film containing both phosphorus and nitrogen in addition to gallium, indium and arsenic.
[0009]
In this method, the substrate can be a GaAs substrate and / or a silicon substrate. A quinary III-V group compound semiconductor can be formed on these substrates.
[0010]
In this method, the mixed crystal ratio of InP and InN is preferably larger than 0 in the III-V group compound semiconductor film. The mixed crystal ratio of InP and InN is preferably greater than 0 and 4 or less.
[0011]
Bonds of In and P and bonds of In and N can be provided in the group III-V compound semiconductor film. The interatomic distance between In and P is larger than the interatomic distance between Ga and As, and the interatomic distance between In and N is smaller than the interatomic distance between Ga and As. With the mixed crystal combining InP and InN, the average interatomic distance in this combined mixed crystal can be made closer to the interatomic distance between Ga and As.
[0012]
In this method, the III-V compound semiconductor film includes indium atoms bonded to a single nitrogen atom and one or more phosphorus atoms. A bond between In and P and a bond between In and N can be provided to the group III-V compound semiconductor film. The interatomic distance between In and P is larger than the interatomic distance between Ga and As, and the interatomic distance between In and N is smaller than the interatomic distance between Ga and As. Therefore, by replacing the As atom with one or more P atoms in the cluster composed of indium atom, arsenic atom and nitrogen atom, the average interatomic distance of another type of cluster generated by this substitution is changed between the atoms of Ga and As. It can be close to the distance.
[0013]
Another aspect of the present invention is a III-V compound semiconductor film provided on a substrate containing gallium and indium as group III elements and arsenic, phosphorus and nitrogen as group V elements. In this III-V compound semiconductor film, the mixed crystal ratio of InP and InN is larger than zero. Due to the mixed crystal of InP semiconductor and InN semiconductor, the average interatomic distance in this mixed crystal is close to the interatomic distance between Ga and As. Thereby, the crystallinity of the III-V compound semiconductor film is improved.
[0014]
Alternatively, in the group III-V compound semiconductor film, the mixed crystal ratio of InP and InN is greater than 0 and 4 or less.
[0015]
Alternatively, the III-V compound semiconductor film includes an indium atom bonded to a single nitrogen atom and one or more phosphorus atoms. In the group III-V compound semiconductor film, the average interatomic distance of clusters generated by substituting As atoms with one or more P atoms in a cluster composed of In atoms, As atoms, and nitrogen atoms is Ga and As. Close to the interatomic distance.
[0016]
The III-V compound semiconductor film can be provided on a substrate that is at least one of a GaAs substrate and a silicon substrate. A quinary III-V group compound semiconductor can be formed on these substrates.
[0017]
Yet another aspect of the present invention is a semiconductor optical device. The semiconductor optical device includes a substrate, a first p-type group III-V compound semiconductor layer, a first n-type group III-V compound semiconductor layer, and a first active layer. The first p-type III-V compound semiconductor layer is provided on the substrate. The first n-type group III-V compound semiconductor layer is provided on the substrate. This active layer is provided between the first p-type group III-V compound semiconductor layer and the first n-type group III-V compound semiconductor layer. The first active layer includes gallium and indium as group III elements, and includes a group III-V compound semiconductor layer provided on the substrate including arsenic, phosphorus, and nitrogen as group V elements.
[0018]
In the group III-V compound semiconductor layer of this semiconductor optical device, the mixed crystal ratio of InP semiconductor and InN semiconductor is larger than zero. The average interatomic distance of the mixed crystal obtained by combining the InP semiconductor and the InN semiconductor can be made closer to the interatomic distance between Ga and As. Thereby, the crystallinity of the III-V compound semiconductor film is improved. The mixed crystal ratio of the InP semiconductor and the InN semiconductor can be greater than 0 and 4 or less.
[0019]
Alternatively, the III-V compound semiconductor layer includes an indium atom bonded to a single nitrogen atom and one or more phosphorus atoms. In the group III-V compound semiconductor layer, the average interatomic distance of clusters generated by substituting As atoms with one or more P atoms in a cluster composed of In atoms, As atoms, and nitrogen atoms is expressed as Ga and As. It can be close to the interatomic distance.
[0020]
The III-V compound semiconductor optical device can include at least one of a semiconductor light emitting device and a semiconductor modulation device.
[0021]
In this semiconductor optical device, the active layer can further include another group III-V compound semiconductor layer. Each of the other group III-V compound semiconductor layers includes gallium as a group III element and arsenic as a group V element. The group III-V compound semiconductor layer and the plurality of other group III-V compound semiconductor layers constitute a quantum well structure. Since the ternary III-V group compound semiconductor is used, the crystallinity of the semiconductor layer constituting the quantum well structure can be improved. Examples of the quantum well structure include an SQW structure and an MQW structure.
[0022]
In this semiconductor optical device, the substrate can be at least one of a GaAs substrate and a silicon substrate. On these substrates, the above ternary III-V compound semiconductor can be formed.
[0023]
The semiconductor optical device can further include a second p-type semiconductor layer, a second n-type semiconductor layer, and a second active layer. The second p-type semiconductor layer is provided on the substrate. The second n-type semiconductor layer is provided on the substrate. The second active layer is provided between the second p-type semiconductor layer and the second n-type semiconductor layer. The second active layer includes a III-V group compound semiconductor layer. This group III-V compound semiconductor layer is provided on the substrate, and contains gallium and indium as group III elements and arsenic, phosphorus and nitrogen as group V elements. The first active layer is provided for one of the semiconductor light emitting element and the semiconductor modulation element, and the second active layer is provided for the other of the semiconductor light emitting element and the semiconductor modulation element. The first and second active layers are optically coupled to each other.
[0024]
Examples of the semiconductor light emitting element include a DFB semiconductor laser element and a Fabry-Perot semiconductor laser element. An example of the semiconductor modulation element is an electroabsorption modulation element.
[0025]
In this semiconductor optical device, if the mixed crystal ratio of InP and InN is larger than 0 and the mixed crystal ratio of InP and InN is 4 or less in the III-V group compound semiconductor layer of the second active layer, preferable. Alternatively, the group III-V compound semiconductor layer of the second active layer includes indium atoms bonded to nitrogen atoms and phosphorus atoms.
[0026]
Yet another aspect of the present invention is a method of manufacturing a semiconductor optical device. The method includes (c) a step of placing a substrate on a metal organic vapor phase epitaxy apparatus, (d) a step of forming a first conductivity type III-V compound semiconductor layer on the substrate, (e) a gallium source material, An indium source material, an arsenic source material, a nitrogen source material, and a phosphorus source material are supplied to a metal organic vapor phase growth apparatus, and gallium and indium are included as group III elements, and arsenic, phosphorus, and nitrogen are included as group III elements. Forming a group V compound semiconductor layer on the substrate; and (f) forming a second conductivity type III-V group compound semiconductor layer on the substrate. The III-V compound semiconductor layer is provided between the first conductivity type III-V compound semiconductor layer and the second conductivity type III-V compound semiconductor layer.
[0027]
Since the group III-V compound semiconductor layer is composed of a group III-V semiconductor containing gallium and indium as group III elements and arsenic, phosphorus and nitrogen as group V elements, an active layer with good crystallinity is obtained. Can do. Since the III-V compound semiconductor layer is provided between the first conductivity type III-V group compound semiconductor layer and the second conductivity type III-V group compound semiconductor layer, the electrons and holes are The second conductivity type III-V compound semiconductor layer is provided to the III-V compound semiconductor layer.
[0028]
In the method of manufacturing a semiconductor optical device, (g) another III-V compound semiconductor layer containing gallium as a group III element and arsenic as a group V element is formed on a substrate in a metal organic vapor phase growth apparatus. And (h) at least one of a step of forming a group III-V compound semiconductor layer on the substrate and a step of forming another group III-V compound semiconductor layer on the substrate. And a step of performing another III-V compound semiconductor layer so as to constitute a quantum well structure. A quantum well structure including a ternary III-V compound semiconductor can be realized. As the quantum well structure, an SQW structure and an MQW structure can be realized.
[0029]
In a method of manufacturing a semiconductor optical device, the gallium source material includes triethylgallium, the indium source material includes trimethylindium, the arsenic source material includes tertiary butylarsine, the phosphorus source material includes tertiary butylphosphine, nitrogen The source material can include at least one of dimethylhydrazine and ammonia. These materials can be used to add both phosphorus and nitrogen to the matrix GaInAs semiconductor.
[0030]
In the method of manufacturing a semiconductor optical device, the substrate can be at least one of a GaAs substrate and a silicon substrate. A quinary III-V group compound semiconductor can be formed on these substrates.
[0031]
The semiconductor optical device can include at least one of a semiconductor light emitting element and a semiconductor modulation element. In the semiconductor optical device, the semiconductor modulation element is optically coupled to the semiconductor light emitting element.
[0032]
In the method of manufacturing a semiconductor device, in the III-V compound semiconductor film, the mixed crystal ratio of the InP semiconductor and the InN semiconductor is preferably larger than 0, and more preferably 4 or smaller. Alternatively, in the III-V group compound semiconductor film, the molar ratio (P / N) of phosphorus to nitrogen is preferably greater than 0, and more preferably 4 or less.
[0033]
Thus, by combining InP and InN mixed crystals, the average interatomic distance of mixed crystals obtained from this combination can be made closer to the interatomic distance between Ga and As.
[0034]
In the method for manufacturing a semiconductor device, the III-V compound semiconductor film preferably includes an indium atom bonded to a single nitrogen atom and one or more phosphorus atoms. By replacing the As atom with one or a plurality of P atoms in a cluster composed of In atom, As atom and nitrogen atom, the average interatomic distance of the cluster generated by this substitution is made closer to the interatomic distance between Ga and As. be able to.
[0035]
The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, several embodiments of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.
[0037]
(First embodiment)
FIG. 1 is a schematic diagram showing a metal organic vapor phase growth apparatus for growing a ternary III-V group compound semiconductor film according to the present embodiment. The metal organic chemical vapor deposition apparatus 1 includes a decompression chamber 2, a decompression pump 4, a gas mixer 6, and a gas box 8. The decompression chamber 2 includes a stage 10 provided so that the substrate W can be mounted, a rotating mechanism 12 for rotating the stage 10, and a quartz tube 14 that guides a process gas onto the substrate W mounted on the stage 10. And have. A heater 10 a for adjusting the stage temperature is provided in the stage 10. The quartz tube 14 has one end 14a and the other end 14b. The one end 14a is connected to the gas mixer 6 via a supply line 16 for supplying process gas. The other end 14b is connected to a decompression pump 4 that exhausts reaction products and source gas. The gas mixer 6 is connected to the gas box 8 via a gas line 18. Gas box 8 is H₂A gas source 20, a group V gas source unit 22, a group III gas source unit 24, a dopant gas source unit 26, and mass flow controllers (MFCs) 28a to 28j are provided. H₂The gas source 20 is connected to the gas input 22a of the group V gas source unit 22, the gas input 24a of the group III gas source unit 24, and the gas input 26a of the dopant gas source unit 26, respectively. The gas output 22b of the group V gas source unit 22, the gas output 24b of the group III gas source unit 24, and the gas output 26b of the dopant gas source unit 26 are connected to the gas mixer 6, respectively.
[0038]
The group V gas source unit 22 includes a container 30a for storing dimethylhydrazine (DMHy), a container 30b for storing tertiarybutylarsine (TBAs), and a container 30c for storing tertiarybutylphosphine (TBP). Explaining the container 30a exemplarily, the container 30a is H.₂An input tube 30d and an output tube 30e are provided so that DMHy gas can be generated by bubbling the gas. The input pipe 30d is connected to the gas input 22a through a valve 30g. An MFC 28a is provided between the valve 30g and the gas input 22a. The output pipe 30e is connected to the gas mixer 6 through a valve 30f. A valve 30 h is provided between the gas input 22 a and the gas mixer 6. An MFC 28b is provided between the valve 30h and the gas input 22a.
[0039]
The group III gas source unit 24 includes a container 32a for storing tetraethylgallium (TEGa) and a container 32b for storing tetramethylindium (TMIn). If the container 32a is described as an example, the container 32a is H.₂It has an input tube 32c and an output tube 32d provided so that TEGa gas can be generated by bubbling the gas. The input pipe 32c is connected to the gas input 24a via the valve 32f. An MFC 28c is provided between the valve 32f and the gas input 24a. The output pipe 32f is connected to the gas mixer 6 through a valve 32e. A valve 32g is provided between the gas input 24a and the gas mixer 6. An MFC 28d is provided between the valve 32g and the gas input 24a.
[0040]
The dopant gas source unit 26 includes a container 34a for storing diethyl zinc (DEZn) and a container 34b for storing tetraethyl silicon (TeESi). When DEZn is used, Zn can be added as a p-type dopant. When TeESi is used, Si can be added as an n-type dopant. If the container 34a is described as an example, the container 34a is H.₂It has an input pipe 34c and an output pipe 34d provided so that DEZn gas can be generated by bubbling the gas. The input pipe 34c is connected to the gas input 26a through a valve 34f. An MFC 28e is provided between the valve 34f and the gas input 26a. The output pipe 34d is connected to the gas mixer 6 through a valve 34e. A valve 34g is provided between the gas input 26a and the gas mixer 6. An MFC 28f is provided between the valve 34g and the gas input 26a.
[0041]
Next, a III-V compound semiconductor multilayer film is grown on the substrate W using the metal organic vapor phase growth apparatus 1. FIG. 2 is a view showing a semiconductor device having a semiconductor multilayer film grown using the metal organic vapor phase growth apparatus shown in FIG. The semiconductor device 35 includes a substrate 36, an undoped GaAs layer 37, an undoped GaInNAsP layer 38, and an undoped GaAs layer 39. The undoped GaAs layer 37, the undoped GaInNAsP layer 38, and the undoped GaAs layer 39 are formed on the GaAs semiconductor substrate 36. The inventors have produced several samples having a structure as shown in FIG. The inventor has also produced a semiconductor device including an undoped GaInNAs layer instead of the undoped GaInNAsP layer 38 for reference. The film thickness of each layer is
Substrate 36: 350 micrometers
Layer 37: 0.2 micrometers
Layer 38: 0.01 micrometer
Layer 39: 0.1 micrometer
It is.
[0042]
As the substrate 36, a 2-inch size (100) plane GaAs semiconductor substrate is used. The growth temperature is 500 ° C., the growth pressure is 10132.5 Pa (76 Torr), the supply amount of DMHy is constant, [DMHy molar ratio] / ([TBAs molar ratio] + [DMHy molar ratio]) = 0. 978. The supply amount of TBP is changed within the range of 0.26 sccm to 0.26 sccm. After film formation, each sample was heat-treated at 665 ° C. for 10 minutes. The In composition is 28 percent and the N composition is less than 1 percent.
[0043]
The inventors have performed photoluminescence (PL) measurement of these samples. FIG. 3 is a drawing showing a photoluminescence spectrum (hereinafter referred to as a PL spectrum) at room temperature (25 ° C.). The characteristic curve C1 shows the PL spectrum of the undoped GaInNAs semiconductor, and the characteristic curve C2 shows the PL spectrum of the undoped GaInNAsP semiconductor with the mixed crystal ratio (InP / InN) = 0.1. When the two characteristic curves are compared, (a) the characteristic curve C2 has less tailing on both sides of the peak, and (b) the half width of the characteristic curve C2 is smaller than the half width of the characteristic curve C1. This comparison shows that the half width of the PL spectrum is small when phosphorus (P) is added to the GaInNAs semiconductor. Therefore, if the mixed crystal ratio (InP / InN)> 0, the crystallinity of the semiconductor layer is improved.
[0044]
FIG. 4 shows the PL spectrum peak intensity (arbitrary unit) and phosphorus (P) concentration (unit: atoms / cm).^ThreeIt is a graph which shows the relationship between these. In this graph, the measurement data P1 indicates the peak intensity of the PL spectrum of the GaInNAs semiconductor, and the measurement data P2 indicates the GaInNAsP semiconductor in the sample prepared under the TBP flow rate of 0.26 sccm (standard centimeter cubic per minute). The peak intensity of the PL spectrum is shown, and the measurement data P3 shows the peak intensity of the PL spectrum of the GaInNAsP semiconductor in the sample manufactured under the condition of a TBP flow rate of 1.3 sccm. Therefore, if the mixed crystal ratio (InP / InN)> 0, the crystallinity of the semiconductor layer is improved. Further, if the mixed crystal ratio (InP / InN) ≧ 0.1, the PL spectrum intensity superior to the experimental result is achieved.
[0045]
FIG. 5 is a graph showing the relationship between the PL spectrum peak intensity (arbitrary unit) and the peak wavelength (unit: nm). The characteristic line L1 shows the peak intensity of the PL spectrum of the GaInNAs semiconductor, and the characteristic line L2 shows the PL spectrum peak intensity of the GaInNAsP semiconductor of various compositions under the mixed crystal ratio (InP / InN) = 0.1. ing. Comparing both characteristic lines, the PL spectral peak intensity (characteristic line L2) of the GaInNAsP semiconductor is larger than the PL spectral peak intensity (characteristic line L1) of the GaInNAs semiconductor in a crystal composition having a peak wavelength exceeding 1.25 micrometers. That is, by adding phosphorus (P) to a GaInNAs semiconductor, crystallinity in a wavelength region (long wavelength region) exceeding 1.25 micrometers is improved.
[0046]
(Second embodiment)
FIG. 6 is a drawing showing a semiconductor device having a semiconductor multilayer film grown using the metal organic vapor phase growth apparatus shown in FIG. The semiconductor device 40 includes a semiconductor substrate 42, a buffer layer 44, a first cladding layer 46, a first light guide layer 48, an active layer 50, a second light guide layer 52, and a second cladding. A layer 54 and a cap layer 56 are provided.
[0047]
FIG. 7 is a flowchart showing a method of forming a multilayer semiconductor film included in the semiconductor device shown in FIG. The flowchart 120 includes the following steps. In the placement step S122, an n-type GaAs substrate is placed in the quartz tube 14 of the metal organic vapor phase growth apparatus 1. In step S124 of forming the buffer layer 44, the Ga source valve, the As source valve, and the Si source valve are opened to form an n-type GaAs semiconductor film on the GaAs substrate. In step S126 of forming the n-type GaInP semiconductor film 46, the Ga source valve, the In source valve, the P source valve, and the Si source valve are opened to form the n type GaInP semiconductor film on the GaAs buffer layer 44. . In step S128 of forming the first light guide layer, the Ga source valve and the As source valve are opened, and an undoped GaAs semiconductor film is formed on the n-type GaInP semiconductor film 46. In step S130 of forming the active layer 48, the Ga source valve, the As source valve, the In source valve, the P source valve, and the N source valve are opened to form an undoped GaInNAsP semiconductor film on the undoped GaAs semiconductor film. . In step S132 of forming the second light guide layer 52, the Ga source valve and the As source valve are opened to form an undoped GaAs semiconductor film on the active layer. In step S134 of forming the p-type GaInP semiconductor film, the Ga source valve, the In source valve, the P source valve, and the Zn source valve are opened, and the p-type GaInP semiconductor film is formed on the second light guide layer 52. Form. In step S136 of forming the cap layer, the Ga source valve, the As source valve, and the Zn source valve are opened to form the p-type GaAs semiconductor film 56 on the p-type GaInP semiconductor film. The semiconductor film is epitaxially grown on a GaAs substrate. If the lattice irregularity is in the range of about ± 2%, crystal growth is possible.
[0048]
In this experiment, a GaAs substrate was used as the semiconductor substrate, but a silicon substrate can also be used. The inventors formed a semiconductor multilayer film under the following three conditions using the metal organic vapor phase growth apparatus 1.
First experiment
Substrate: GaAs
((100) plane, electron concentration n = 2 × 10¹⁸cm^-3)
Buffer layer: GaAs
(200 nm, electron concentration n = 1.5 × 10¹⁸cm^-3)
First cladding layer: GaInP
(200 nm, electron concentration n = 7 × 10¹⁷cm^-3)
First light guide layer: GaAs
(140 nm, undoped)
Active layer: Ga_0.65In_0.35NAsP
(10nm, undoped)
Second light guide layer: GaAs
(140 nm, undoped)
Second cladding layer: GaInP
(500 nm, hole concentration p = 7 × 10¹⁷cm^-3)
Cap layer: GaAs
(100 nm, hole concentration p = 3 × 10¹⁸cm^-3).
Second experiment
Active layer: Ga_0.65In_0.35NP
(10nm, undoped)
Other semiconductor films are the same as those in the first experiment.
Third experiment
Active layer: Ga_0.65In_0.35NAs
(10nm, undoped)
Other semiconductor films are the same as those in the first experiment.
[0049]
The details of the film forming conditions will be described._0.65In_0.35The stage temperature is set to 530 ° C. when growing NAsP. When growing other semiconductor films, the temperature is set higher than the stage temperature, for example, 575 ° C. The pressure P in the growth furnace is set to 10132.5 Pa (76 Torr).
[0050]
Ga_0.65In_0.35When forming a NAsP semiconductor film, for example, the following flow ratio is used:
[TMIn molar ratio] / ([TMIn molar ratio] + [TMGa molar ratio]) = 0.35
[TBAs molar ratio] / ([TMIn molar ratio] + [TMGa molar ratio]) = 5
[DMHy molar ratio] / ([TBAs molar ratio] + [DMHy molar ratio]) = 0.97
[TBP molar ratio] / ([TBP molar ratio] + [TBAs molar ratio]) = 0.41
The growth rate is about 1 micrometer / hour.
[0051]
The inventors measured the characteristics of the obtained multilayer film. As a result, the inventors added both phosphorus (P) and nitrogen (N) to GaInAs, compared to the characteristics of GaInNAs._0.65In_0.35It has been found that the crystallinity of NAsP is good.
[0052]
The inventors have grown GaInNAsP using metal organic vapor phase epitaxy. According to the metal organic vapor phase epitaxy method, it is easier to control the amount of source gas than the MBE method. For example, as a phosphorus source, PH_ThreeAnd TBP can be used. For example, the nitrogen source is NH_ThreeAnd DMHy can be used. Since the vapor pressure of elemental phosphorus is high, it is not easy to control the supply amount of the phosphorus raw material in the MBE method. When the metal organic vapor phase epitaxy apparatus is used, the supply amount of both the phosphorus source and the nitrogen source can be related as the flow rate ratio of the source gas. Therefore, the amount of phosphorus source and nitrogen source supplied can be controlled by using metal organic vapor phase epitaxy.
[0053]
The inventors investigate that the crystallinity of the quaternary III-V compound semiconductor is better than the crystallinity of the quaternary III-V compound semiconductor. For further discussion, some practical assumptions are made that reflect practical semiconductor optical devices and experimental deposition conditions.
[0054]
(1) In the crystal, the number of nitrogen atoms is very small compared to the number of In atoms. With practical optical semiconductor devices in mind, Ga_1-XIn_XN_YAs_1-YZP_ZIn the semiconductor, In is X = 0.35 by composition ratio, and N is larger than Y = 0 and not larger than 0.05.
[0055]
(2) This Ga_1-XIn_XN_YAs_1-YZP_ZIn a semiconductor, a bond in which indium and nitrogen are directly bonded (In—N bond) is more stable than a bond between nitrogen and another group III element.
[0056]
(3) The atomic radius of the nitrogen atom is very small compared to the atomic radius of other elements. On the other hand, the atomic radius of In atoms is larger than the atomic radius of other elements. Therefore, in a GaInNAs semiconductor, in a micro picture, a large strain is locally generated in a region where nitrogen atoms are present. Since the bond distance between nitrogen and the group III atom (In) is small, this local strain acts to disturb the crystal lattice and causes crystal defects.
[0057]
Under these assumptions, the interatomic distances of the GaAs crystal, InP crystal, and InN crystal are obtained.
GaAs crystal: 0.245 nanometers (2.45 angstroms)
InN crystal: 0.215 nanometers (2.15 angstroms)
InP crystal: 0.254 nanometers (2.54 angstroms)
It becomes the value.
[0058]
Ga_1-XIn_XN_YAs_1-YZP_ZIn a semiconductor, elements present in large amounts in a crystal are Ga, In, and As. Ga_1-XIn_XN_YAs_1-YThe semiconductor film includes a large number of Ga—As bonds, but a very small number of In—N bonds. This Ga_1-XIn_XN_YAs_1-YWhen a small amount of P is added to the crystal, an In-P bond is generated. The interatomic distance of the In—P bond is larger than the interatomic distance of the Ga—As bond. Therefore, the In—P bond cancels a part of the local distortion caused by the In—N bond and reduces the distortion.
[0059]
FIG. 8 is a drawing schematically showing the bond between the group III element In and the group V elements As and N and the bond between the group III element Ga and the group V element As. Referring to FIG. 8, InAs_ThreeN cluster 60, InAs₂NP cluster 62, InAsNP₂Cluster 64, InNP_ThreeCluster 66, GaAs_ThreeCluster 68, InP_FourA cluster 69 is shown. In these clusters, as the As atoms are replaced by P atoms, the size of the clusters decreases in order.
[0060]
Using the index of the average interatomic distance of constituent atoms to estimate the change in cluster size,
GaAs_ThreeCluster: 0.245 nanometers (2.45 angstroms) InAs_FourCluster: 0.260 nanometers (2.60 angstroms) InAs_ThreeN cluster: 0.249 nanometer (2.49 angstrom) InAs₂NP cluster: 0.247 nanometers (2.47 angstroms) InAsNP₂Cluster: 0.246 nanometers (2.46 angstroms) InNP_ThreeCluster: 0.244 nanometers (2.44 angstroms) InP_FourCluster: 0.254 nanometers (2.54 angstroms).
[0061]
That is, InAs_XNP_3-XAs one or more As atoms are replaced by P atoms in the cluster, the average interatomic distance of the cluster containing the substituted atoms becomes GaAs._ThreeIt approaches the average interatomic distance in the cluster. From FIG. 8, it is visually understood that the local distortion caused by nitrogen is reduced by adding P as a constituent element. In addition, since the phosphorus element is a constituent element of the group III-V compound semiconductor and is not a p-type or n-type impurity, the electrical property is not affected. Further, since the amount of phosphorus atoms added is small, the band structure of the host crystal is not greatly affected.
[0062]
FIG. 9 shows InAs_XNP_3-X(X = 1-3) It is drawing which shows the relationship between the binding energy of the nitrogen atom in a cluster, and the number of P atoms in this cluster. The characteristic curve shown in FIG. 9 indicates that the binding energy between nitrogen and indium increases as the number of arsenic atoms substituted with phosphorus atoms increases. An increase in binding energy means that the bond between nitrogen and indium becomes stronger. That is, in a III-V group compound semiconductor film containing gallium and indium as group III elements and arsenic, phosphorus and nitrogen as group V elements, if the mixed crystal ratio of InP and InN is larger than 0, the InP semiconductor and InN semiconductor The average interatomic distance of the cluster obtained by the combination of the mixed crystals with can be made closer to the interatomic distance between Ga and As. Thereby, the crystallinity of the III-V compound semiconductor film is improved. In the group III-V compound semiconductor film, if the mixed crystal ratio of InP and InN is 3 or less, the bond between nitrogen and indium can be strengthened. If the mixed crystal ratio of InP and InN is 4 or less, the crystal distortion can be reduced to such an extent that no crystal defect occurs. If the mixed crystal ratio is about 4 or less, the phosphor concentration dependency of the emission wavelength is sufficiently small. When the mixed crystal ratio is 5 or more, the phosphorous concentration dependency of the emission wavelength increases, and the emission wavelength shifts to a short wavelength region. InP_FourThe cluster also acts to compensate for crystal distortion in the GaInNAsP semiconductor.
[0063]
Further, the III-V compound semiconductor film includes a single nitrogen atom and an indium atom bonded to one or more phosphorus atoms. In the group III-V compound semiconductor film, the average interatomic distance of clusters generated by substituting As atoms with one or a plurality of P atoms in a cluster composed of In atoms, As atoms, and nitrogen atoms is expressed as Ga and As. It can be close to the interatomic distance. The bond between indium and nitrogen is InNP._ThreeStrongest in the cluster. The optimum value of the composition ratio of nitrogen and phosphorus is 1: 3. Therefore, a preferable range of the composition ratio (molar ratio) of nitrogen and phosphorus is greater than 0 and 4 or less. If the composition ratio of nitrogen and phosphorus is 4 or less, crystal distortion can be reduced to such an extent that crystal defects do not occur.
[0064]
As can be understood from the above description, it has been shown that forming a mixed crystal of InP and InN in combination with nitrogen and phosphorus is effective in reducing crystal distortion. The results of the PL spectra shown in FIGS. 3 to 5 indicate that the addition of phosphorus (P) is useful for improving crystallinity even when the mixed crystal ratio InP / InN is as small as about 0.1. In addition, the results of investigations by the inventors indicate that crystal distortion is reduced even in a region where the mixed crystal ratio is larger.
[0065]
(Third embodiment)
The inventors believe that the group III-V compound semiconductor film realized in the first embodiment can be used for a semiconductor optical device to be described subsequently.
[0066]
FIG. 10 is a drawing showing a semiconductor optical integrated device including a DFB type semiconductor laser device. The semiconductor optical integrated device 70 includes a light emitting element portion 70a, an element separation portion 70b, and a modulation element portion 70c arranged along a predetermined axis. The element isolation part 70b is provided between the light emitting element part 70a and the modulation element part 70c. The light emitting element unit 70a has a structure of a DFB type semiconductor laser element. The modulation element unit 70c is optically coupled to the light emitting element unit 70a via the element separation unit 70b and has a structure of an EA type modulation element. The modulation element unit 70c modulates light from the light emitting element unit 70a in response to the drive signal.
[0067]
The light emitting element portion 70a includes an n-type III-V group semiconductor layer 74a, a first light guide layer 76a, a GaInNAsP active layer 78a, a second light guide layer 80a, and a p-type III-V group semiconductor layer 82a. And a p-type III-V group semiconductor layer 84 and a p-type III-V group semiconductor contact layer 86a. These semiconductor layers are sequentially provided on the substrate 72. The light emitting element unit 70 a includes an anode electrode 88 a provided on the p-type III-V group semiconductor contact layer 86 a and a cathode electrode 90 provided on the back surface of the substrate 72. In the light emitting element portion 70a, the refractive indexes of the n-type III-V semiconductor layer 74a and the p-type III-V semiconductor layer 82a are the same as those of the first light guide layer 76a, the active layer 78a, and the second light guide layer 80a. Less than the refractive index. Each of the photoluminescence wavelengths of the first and second light guide layers 76a and 80a is shorter than the photoluminescence wavelength of the active layer 78a. In the light emitting element portion 70a, a diffraction grating 92 is provided between the light guide layer and the clad layer (in this embodiment, between the second light guide layer 80a and the p-type III-V group semiconductor layer 82a).
[0068]
The modulation element unit 70c includes an n-type III-V group semiconductor layer 74b, a first light guide layer 76b, a GaInNAsP active layer 78b, a second light guide layer 80b, and a p-type III-V group semiconductor layer 82b. And a p-type group III-V semiconductor layer 84 and a p-type group III-V semiconductor contact layer 86b. These semiconductor layers are provided on the substrate 72. The modulation element portion 70 c includes an anode electrode 88 b provided on the p-type III-V group semiconductor contact layer 86 b and a cathode electrode 90 provided on the back surface of the substrate 72. The cathode electrode 90 is shared by the light emitting element part 70a and the modulation element part 70b. In the modulation element portion 70c, the refractive indexes of the n-type III-V group semiconductor layer 74b and the p-type III-V group semiconductor layer 82b are the same as those of the first light guide layer 76b, the active layer 78b, and the second light guide layer 80b. Less than the refractive index. Each of the photoluminescence wavelengths of the first and second light guide layers 76b and 80b is shorter than the photoluminescence wavelength of the active layer 78b.
[0069]
FIG. 11 is a drawing showing a semiconductor optical integrated device including a Fabry-Perot type semiconductor laser device. The semiconductor optical integrated device 100 includes a light emitting element unit 100a, an element isolation unit 100b, and a modulation element unit 100c arranged along a predetermined axis. The element isolation part 100b is provided between the light emitting element part 100a and the modulation element part 100c. The light emitting element portion 100a has a structure of a Fabry-Perot type semiconductor laser element. The modulation element unit 100c is optically coupled to the light emitting element unit 100a via the element separation unit 100b and has a structure of an EA type modulation element.
[0070]
The light emitting element portion 100a includes an n-type III-V group semiconductor layer 104a, a first light guide layer 106a, a GaInNAsP active layer 108a, a second light guide layer 110a, a p-type III-V group semiconductor layer 112a, and a p-type III. A -V group semiconductor layer 114 and a p-type III-V group semiconductor contact layer 116a are provided. These semiconductor layers are provided on the substrate 102. The light emitting element portion 100 a includes an anode electrode 118 a provided on the p-type III-V group semiconductor contact layer 106 a and a cathode electrode 120 provided on the back surface of the substrate 102. In the light emitting element portion 100a, the refractive indexes of the n-type III-V group semiconductor layer 104a and the p-type III-V group semiconductor layer 112a are the same as those of the first light guide layer 106a, the active layer 108a, and the second light guide layer 110a. Less than the refractive index. Each of the photoluminescence wavelengths of the first and second light guide layers 106a and 110a is shorter than the photoluminescence wavelength of the active layer 108a.
[0071]
The modulation element unit 100c includes an n-type III-V group semiconductor layer 104b, a first light guide layer 106b, a GaInNAsP active layer 108b, a second light guide layer 110b, a p-type III-V group semiconductor layer 112b, and a p-type III. A -V group semiconductor layer 114 and a p-type III-V group semiconductor contact layer 116b are provided. These semiconductor layers are provided on the substrate 102. The modulation element section 100 c includes an anode electrode 118 b provided on the p-type III-V group semiconductor contact layer 116 b and a cathode electrode 120 provided on the back surface of the substrate 102. The cathode electrode 120 is provided in common to the light emitting element unit 100a and the modulation element unit 100c. In the modulation element unit 100c, the refractive indexes of the n-type III-V group semiconductor layer 104b and the p-type III-V group semiconductor layer 112b are the same as those of the first light guide layer 106b, the active layer 108b, and the second light guide layer 110b. Less than the refractive index. Each of the photoluminescence wavelengths of the first and second light guide layers 106b and 110b is shorter than the photoluminescence wavelength of the active layer 108b.
[0072]
In the semiconductor optical integrated device of FIGS. 10 and 11, the material composition of the light emitting element portion and the modulation element portion is such that the photoluminescence wavelength of the active layer of the light emitting element portion is longer than the photoluminescence wavelength of the modulation element portion. It has been decided. Further, no contact layer is provided in the separation element portion. Therefore, the separation element portion is useful for increasing the separation resistance between the light emitting element portion and the modulation element portion.
[0073]
Although FIG. 10 and FIG. 11 show the optical integrated device, the GaInNAsP semiconductor layer can also be used for semiconductor optical devices such as a single semiconductor laser device and a single semiconductor modulation device.
[0074]
The semiconductor optical integrated device shown in FIGS. 10 and 11 can be manufactured by using the metal organic vapor phase growth apparatus 1 shown in FIG. The light emitting element portion and the modulation element portion of this semiconductor optical integrated device have a structure similar to that of the semiconductor device shown in FIG. Therefore, the structure of the light emitting element portion and the modulation element portion can be obtained by changing the recipe indicating the film forming conditions as desired.
[0075]
FIG. 12A shows the structure of a semiconductor optical integrated device. FIG. 12B is a diagram showing a band diagram obtained by the layer structure of the semiconductor optical integrated device. The band diagram shows Ec representing the edge of the conduction band and Ev representing the edge of the valence band. As shown in FIG. 12B, the active layer of the semiconductor optical integrated device 122 has a quantum well structure. The active layer 124 is provided between the n-type cladding layer 130 and the p-type cladding layer 132. A light guide layer 126 is provided between the active layer 124 and the n-type cladding layer 130. A light guide layer 128 is provided between the active layer 124 and the p-type cladding layer 132. The active layer 124 includes several well layers 124 a and several barrier layers 124. Each barrier layer 124 is located between the well layers 124a. In the present embodiment, the well layer 124a is made of a GaInNAsP semiconductor, and the barrier layer 124b is made of a GaAs semiconductor.
[0076]
By using a GaInNAsP layer for the well layer and a GaAs layer for the barrier layer, the uniformity of composition and film thickness can be improved in the quantum well structure. Therefore, the fluctuation of the periodicity of the quantum well structure can be reduced. Also, the flatness of the interface between the barrier layer and the well layer is improved. If the GaInNAsP film is applied to a semiconductor light emitting device, the temperature change of the oscillation wavelength is reduced. If the GaInNAsP film is applied to a semiconductor modulation element, the extinction ratio is improved.
[0077]
While the principles of the invention have been illustrated and described in the preferred embodiment, those skilled in the art will recognize that the invention can be modified in arrangement and detail without departing from such principles. For example, the source gas for growing the semiconductor film is not limited to those described in the embodiment, and trimethyl gallium as the group III source, trimethyl arsenic, arsine (AsH) as the group V source._Three) And hydrazine can be used. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.
[0078]
【The invention's effect】
As described above, a ternary III-V compound semiconductor film having good crystallinity, a semiconductor optical device including this semiconductor film, and a method for forming a III-V compound semiconductor film have been provided.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a metal organic vapor phase growth apparatus for growing a ternary III-V compound semiconductor film according to the present embodiment.
2 is a drawing showing a semiconductor device having a semiconductor multilayer film grown using the metal organic vapor phase epitaxy apparatus shown in FIG. 1. FIG.
FIG. 3 is a graph showing a photoluminescence spectrum.
FIG. 4 is a graph showing the relationship between PL spectrum peak intensity and phosphorus concentration.
FIG. 5 is a graph showing the relationship between PL spectrum peak intensity and peak wavelength.
6 is a drawing showing a semiconductor device having a semiconductor multilayer film grown by using the metal organic vapor phase growth apparatus shown in FIG. 1; FIG.
FIG. 7 is a flowchart showing a method for forming a multilayer semiconductor film included in the semiconductor device shown in FIG. 6;
FIG. 8 is a drawing schematically showing the bond between the group III element In and the group V elements As and N, and the bond between the group III element Ga and the group V element As.
FIG. 9 shows InAs_XNP_3-X(X = 1-3) It is drawing which shows the relationship between the binding energy of the nitrogen atom in a cluster, and the number of P atoms in this cluster.
FIG. 10 is a drawing showing a semiconductor optical integrated device including a DFB semiconductor laser device.
FIG. 11 is a drawing showing a semiconductor optical integrated device including a Fabry-Perot semiconductor laser device.
FIG. 12 (a) is a drawing showing a layer structure of a semiconductor optical integrated device. FIG. 12B is a diagram showing a band diagram obtained by the layer structure of the semiconductor optical integrated device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Organometallic vapor phase growth apparatus, 35, 40 ... Semiconductor device, 36 ... Substrate, 37 ... Undoped GaAs layer, 38 ... Undoped GaInNAsP layer, 39 ... Undoped GaAs layer, 42 ... Semiconductor substrate, 44 ... Buffer layer, 46 ... First clad layer 48 ... first light guide layer 50 ... active layer 52 ... second light guide layer 54 ... second clad layer 56 ... cap layer 70 ... semiconductor optical integrated device 70a ... Light-emitting element part, 70b ... Element separation part, 70c ... Modulation element part, 100 ... Semiconductor optical integrated element, 100a ... Light-emitting element part, 100b ... Element separation part, 100c ... Modulation element part

Claims (4)

A GaAs substrate;
A first p-type semiconductor layer provided on the GaAs substrate;
A first n-type semiconductor layer provided on the GaAs substrate;
A first active layer provided between the first p-type semiconductor layer and the first n-type semiconductor layer;
The first active layer is a group III-V compound semiconductor layer provided on the GaAs substrate made of quinary GaInNPAs and provided with a PL peak wavelength in a wavelength region exceeding 1.25 micrometers .
The mixed crystal ratio of InP and InN in group III-V compound semiconductor layer (InP / InN) is 0.1 to 4, InAs _X NP _3-X clusters of the III -V compound semiconductor layer (X = 1 to 3) A semiconductor optical device in which one or more As atoms are substituted with P atoms . A GaAs substrate;
A first p-type semiconductor layer provided on the GaAs substrate;
A first n-type semiconductor layer provided on the GaAs substrate;
A first active layer provided between the first p-type semiconductor layer and the first n-type semiconductor layer;
The first active layer includes a III-V group compound semiconductor layer made of quinary GaInNPAs and having a PL peak wavelength in a wavelength region exceeding 1.25 micrometers , and includes gallium as a group III element and V Another III-V compound semiconductor layer containing arsenic as a group element,
The group III-V compound semiconductor layer is a well layer, and the other group III-V compound semiconductor layer is a barrier layer.
In the group III-V compound semiconductor layer, the mixed crystal ratio of InP and InN (InP / InN) is 0.1 to 4, InAs _X NP _3-X clusters of the III -V compound semiconductor layer ( In X = 1 to 3), one or more As atoms are substituted with P atoms,
The said III-V group compound semiconductor layer and said another III-V group compound semiconductor layer are semiconductor optical elements which comprise a quantum well structure. A second p-type semiconductor layer provided on the GaAs substrate;
A second n-type semiconductor layer provided on the GaAs substrate;
A second active layer provided between the second p-type semiconductor layer and the second n-type semiconductor layer;
The second active layer includes a ternary III-V compound semiconductor layer provided on the GaAs substrate including gallium and indium as group III elements and arsenic, phosphorus and nitrogen as group V elements,
The first active layer is provided for one of a semiconductor light emitting device and a semiconductor modulation device,
The second active layer is provided for the other of the semiconductor light emitting device and the semiconductor modulation device,
The semiconductor optical device according to claim 1, wherein the first and second active layers are optically coupled to each other. In the group III-V compound semiconductor layer of the second active layer, the mixed crystal ratio of InP and InN (InP / InN) is 0.1 to 4, the said second active layer III - 4. The semiconductor optical device according to claim 3, wherein in the InAs _X NP _3-X cluster (X = 1 to 3) of the group V compound semiconductor layer, one or a plurality of As atoms are substituted with P atoms .

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