JP4284944B2 - Method for manufacturing gallium nitride based semiconductor laser device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a gallium nitride based semiconductor light emitting device, and more particularly to a method for manufacturing a gallium nitride based semiconductor light emitting device capable of increasing the indium composition in the light emitting layer without causing crystal degradation of an active layer. Is.
[0002]
[Prior art]
Nitride III-V compound semiconductors, typified by gallium nitride (GaN), are actively researched as materials for light-emitting elements that can emit light from the green to the blue visible region and the ultraviolet region. Has been.
In particular, a nitride semiconductor laser element using a nitride III-V compound semiconductor attracts attention as a light source for an optical disk device.
[0003]
Here, with reference to FIG. 4, a basic configuration of a nitride-based semiconductor laser device formed of a gallium nitride-based compound semiconductor will be described. FIG. 4 is a schematic cross-sectional view showing the basic configuration of the nitride-based semiconductor laser device.
The nitride-based semiconductor laser device 10 is a semiconductor laser device composed of a gallium nitride-based compound semiconductor. As shown in FIG. 4, the nitride-based semiconductor laser device 10 is sequentially stacked on the n-GaN substrate 12 and has a thickness of 3 μm. n-GaN buffer layer 14, n-Al having a thickness of 1.3 μm_0.08Ga_0.92N clad layer 16, n-GaN guide layer 18 having a thickness of 0.1 μm, MQW active layer 20, p-GaN guide layer 22 having a thickness of 0.1 μm, p-Al having a thickness of 0.5 μm_0.07Ga_0.93It has a laminated structure of an N clad layer 24 and a p-GaN contact layer 26 having a thickness of 0.1 μm.
[0004]
The MQW active layer 20 is n-In_0.02Ga_0.98N (50Å) / n-In_0.2Ga_0.8N (25Å) / n-In_0.02Ga_0.98It is configured as a barrier layer, a well layer, and a barrier layer made of N (50 Å).
The p-GaN contact layer 26 and p-Al_0.07Ga_0.93The upper layer of the N clad layer 24 is processed into a striped ridge 28.
Both sides of ridge 28 and p-Al_0.07Ga_0.93On the remaining layer of the N-cladding layer 24, SiO with an opening above the p-GaN contact layer 26₂A film 30 is provided as an insulating film.
A p-side electrode 32 is provided on the opened p-GaN contact layer 24, and an n-side electrode 34 is provided on the back surface of the n-GaN substrate 12.
[0005]
Here, with reference to FIG. 5, a conventional method for manufacturing the above-described nitride-based semiconductor laser device will be described. FIG. 5 is a graph showing the relationship between the growth process and the growth temperature when a conventional method is applied to grow a gallium nitride compound semiconductor layer.
As shown in FIG. 5, first, in the first growth step, hydrogen gas is used as a carrier gas, and NH is used as a nitrogen source._ThreeA gas is used to grow an n-GaN buffer layer 14 having a thickness of 3 μm and an n-Al film having a thickness of 1.3 μm on the n-GaN substrate 12 by MOCVD at a growth temperature of about 1000 ° C._0.08Ga_0.92An N clad layer 16 and an n-GaN guide layer 18 having a thickness of 0.1 μm are grown in this order.
Next, the process proceeds to the second growth step, the carrier gas is switched to nitrogen gas, and the growth temperature is lowered to about 700 ° C. as shown in FIG._0.02Ga_0.98N (50Å) / n-In_0.2Ga_0.8N (25Å) / n-In_0.02Ga_0.98N (50Å) MQW active layer 20 is grown.
[0006]
Next, the process proceeds to the third growth step, where the carrier gas is switched again to hydrogen, and as shown in FIG. 5, the growth temperature is raised again to 1000 ° C., the p-GaN guide layer 22 having a film thickness of 0.1 μm, P-Al with a thickness of 0.5 μm_0.07Ga_0.93An N cladding layer 24 and a 0.1 μm p-GaN contact layer 26 are grown in this order.
As described above, in the conventional method, NH is used as the nitrogen raw material._ThreeIs always used during the growth of gallium nitride compound semiconductor layers._ThreeContinue to supply.
[0007]
Next, the p-GaN contact layer 26 and p-Al_0.07Ga_0.93The ridge 28 is formed by etching the upper layer of the N clad layer 24. Subsequently, SiO₂A film 30 is formed on the entire surface of the substrate, and SiO on the p-GaN contact layer 26 is formed.₂The film 30 is opened, a p-side electrode 32 is formed on the p-GaN contact layer 26, the back surface of the n-GaN substrate 12 is polished and adjusted to a predetermined substrate thickness, and then the n-side electrode is formed on the back surface of the substrate. 34 is formed.
Thereby, the nitride semiconductor laser element 10 described above can be formed.
[0008]
Conventionally, when producing a nitride semiconductor laser element, as described above, ammonia (NH_ThreeIn many cases, a gallium nitride compound semiconductor is formed by an MOCVD method using the above.
By the way, NH used as nitrogen source_ThreeThe decomposition efficiency is about several percent even at about 1000 ° C., and rapidly decreases below 800 ° C. As a result, when the nitride semiconductor layer is grown at a growth temperature of 800 ° C. or less, nitrogen is insufficient, and the crystallinity of the nitride semiconductor layer is deteriorated. Therefore, NH_ThreeIn order to grow a gallium nitride compound semiconductor using as a nitrogen source, it is necessary to set the growth temperature to 800 ° C., preferably to a temperature exceeding 1000 ° C.
[0009]
The growth temperature at the time of growing a gallium nitride compound semiconductor by applying the MOCVD method differs depending on the composition of the gallium nitride compound semiconductor in addition to the restriction due to the decomposition temperature of the raw material.
In general, when a nitride semiconductor layer not containing In (indium) such as GaN or AlGaN mixed crystal is grown, in order to form a good nitride semiconductor layer by supplying sufficient nitrogen, A growth temperature of about ℃ is required.
On the other hand, when growing a nitride semiconductor layer containing In, such as GaInN mixed crystal, In is easily desorbed because the vapor pressure of In is high, and in order to suppress this, the temperature is made lower than the growth temperature of GaN or the like. It is necessary.
[0010]
[Problems to be solved by the invention]
By the way, in order to realize a nitride-based semiconductor laser device that emits blue or green laser light, which is highly demanded industrially, using a GaInN layer as a light emitting layer, an indium composition of a group III element of the GaInN layer is set. It is necessary to make it 20 atomic% to 50 atomic%.
For this purpose, the growth temperature must be about 700 ° C. to 800 ° C. in order to suppress the desorption of In, which has a high vapor pressure and is easily desorbed, during MOCVD growth of the GaInN layer.
[0011]
In a light emitting element such as a semiconductor laser element, a laminated structure called a double hetero structure is generally formed in which a light emitting layer is sandwiched by a clad layer having a smaller refractive index.
Therefore, in a nitride-based semiconductor laser device having a GaInN layer as a light emitting layer and an AlGaN layer or a GaN layer as a cladding layer, a GaInN layer as a light emitting layer is 700 ° C. on the AlGaN layer or GaN layer provided as the lower cladding layer. It is necessary to form an AlGaN layer or a GaN layer on the GaInN layer as the upper cladding layer after the growth at a growth temperature of 800 ° C. to 800 ° C.
[0012]
But NH_ThreeAs described above, a growth temperature of 1000 ° C. is required to grow an AlGaN layer or a GaN layer as an upper cladding layer using nitrogen as a raw material for nitrogen. However, when an AlGaN layer or a GaN layer is grown at 1000 ° C., a GaInN crystal Since the InN bond is weak, the GaInN layer, which is a light emitting layer, is deteriorated by heat during the growth of the AlGaN layer or the GaN layer, and the crystal structure is destroyed. As a result, there is a problem that the light emission efficiency is lowered. .
In particular, in order to obtain visible light such as blue to green, the indium composition of the light emitting layer needs to be 20 to 50%. With such a high In composition, however, the degree of deterioration of the GaInN layer due to the heat described above is more significant. It becomes even more prominent.
Therefore, in order to prevent the deterioration of the GaInN layer, when the AlGaN layer or the GaN layer provided on the GaInN layer is grown at 1000 ° C. or less, the crystallinity of the light emitting layer can be prevented from being deteriorated, but NH_ThreeDecomposition efficiency of AlGaN or the crystallinity of AlGaN or GaN deteriorates.
[0013]
As described above, according to the conventional method, it is difficult to manufacture a blue to green semiconductor laser element made of a gallium nitride compound having a light emitting layer having a high indium composition and good crystallinity. Up to now, the problem has been described by taking a semiconductor laser element as an example, but this is a problem applicable to all semiconductor light emitting elements including a light emitting diode.
Therefore, an object of the present invention is to provide a method of manufacturing a gallium nitride semiconductor light emitting device for blue to green light emission, which has a double hetero structure having a light emitting layer having a high indium composition and good crystallinity. is there.
[0014]
[Means for Solving the Problems]
The present inventor conducted the following experiment in order to examine deterioration of the MQW active layer due to heat.
First, a GaN layer having a thickness of 30 nm is grown on a sapphire substrate at a temperature of 500 ° C. by MOCVD, then a GaN layer having a thickness of 2 μm at a temperature of 1000 ° C., and n-In at a temperature of 700 ° C._0.02Ga_0.98N (50Å) / n-In_0.2Ga_0.8N (25Å) / n-In_0.02Ga_0.98An MQW active layer containing 20% N of N (50%) and a GaN layer having a thickness of 0.1 μm were grown sequentially by MOCVD at a temperature of 1000 ° C. to produce a GaN-based stacked structure.
Next, the laminated structure was taken out from the MOCVD furnace, and the laminated structure was divided into three to obtain samples 1, 2, and 3. Samples 1 and 2 were again annealed in the MOCVD furnace as follows, and sample 3 was not annealed.
[0015]
NH_ThreeN while supplying gas₂In the atmosphere, Sample 1 was annealed at 900 ° C. and Sample 2 was annealed at an annealing temperature of 1000 ° C. for 30 minutes. The annealing time of 30 minutes is used for the above-described nitride-based semiconductor laser device 10 to produce a p-GaN guide layer, p-Al guide layer on the MQW active layer._0.07Ga_0.93The time is the same as the time required for growing the N clad layer and the p-GaN contact layer.
Then, photoluminescence spectra of two types of annealed samples 1 and 2 and sample 3 that was not annealed were measured.
These three types of photoluminescence spectra are as shown in FIG.
[0016]
As shown in FIG. 6, it was confirmed that Sample 3 that was not subjected to the annealing treatment emitted light having a PL wavelength of 450 nm from the active layer.
However, from Sample 2 annealed at 1000 ° C., no significant emission at a PL wavelength of 450 nm could be observed. On the other hand, from the sample 1 annealed at 900 ° C., light emission at a PL wavelength of 450 nm was observed with a light intensity almost equal to that of the sample 3 not annealed.
[0017]
The above experimental results show that in Sample 2 annealed at 1000 ° C., the active layer deteriorates due to the heat at the time of annealing, and the light emitting function is significantly reduced.
On the other hand, when annealed at 900 ° C., the degree of degradation of the active layer is limited, indicating that the light emitting function is maintained.
[0018]
Therefore, the present inventor has developed a nitrogen-containing compound such as hydrazine having a high decomposition efficiency even at a relatively low temperature when growing at least a gallium nitride compound semiconductor layer on the light emitting layer by metal organic vapor phase epitaxy. The idea was to prevent deterioration of crystallinity due to heat of the light emitting layer by growing a gallium nitride compound semiconductor layer at 900 ° C. or lower as a raw material.
Then, the present inventor has confirmed that this idea is effective through experiments, and has come to invent the present invention.
[0019]
In order to achieve the above object, a nitride semiconductor laser device manufacturing method according to the present invention (hereinafter referred to as a first invention method) substantially contains indium on a substrate by MOCVD in sequence. Forming a stacked structure including a first gallium nitride compound semiconductor layer not containing, a second gallium nitride compound semiconductor layer containing indium, and a third gallium nitride compound semiconductor layer containing substantially no indium In a method for manufacturing a gallium nitride based semiconductor light emitting device having:
NH as nitrogen source_ThreeAnd growing a first gallium nitride compound semiconductor layer by MOCVD at a growth temperature exceeding 900 ° C .;
Next, NH as a nitrogen raw material_ThreeAnd growing a second gallium nitride compound semiconductor layer by MOCVD at a first growth temperature of 900 ° C. or lower,
Next, NH as a nitrogen raw material_ThreeA step of growing a third gallium nitride compound semiconductor layer by MOCVD at a growth temperature not lower than the first growth temperature and not higher than 900 ° C. using an organic nitrogen compound other than
It is characterized by having.
[0020]
In the first invention method, when the first gallium nitride compound semiconductor layer is grown by the MOCVD method, NH is used._ThreeBy using a gas as a nitrogen material and growing at a growth temperature exceeding 900 ° C., the first gallium nitride compound semiconductor layer having good crystallinity can be grown at a rapid growth rate.
When the second gallium nitride compound semiconductor layer is grown by MOCVD, NH_ThreeBy using a gas as a nitrogen source and growing at a first growth temperature of 900 ° C. or less, for example, 700 ° C., a second gallium nitride compound semiconductor layer having a high indium composition and good crystallinity is rapidly grown. Can grow at speed.
Further, when the third gallium nitride compound semiconductor layer is grown by the MOCVD method, hydrazine (N₂H_Four) Or an organic nitrogen compound such as a substituted hydrazine crystal, and the third gallium nitride compound semiconductor layer containing indium is grown by growing the third gallium nitride compound semiconductor layer at a growth temperature of 900 ° C. or lower. Prevents deterioration.
In other words, in the method of the present invention, the growth process conditions of the first and second gallium nitride compound semiconductor layers are substantially the same as those in the conventional method, but the growth temperature of the third gallium nitride compound semiconductor layer is set to be the same. By lowering, the crystal degradation of the second gallium nitride compound semiconductor layer is prevented.
[0021]
Another method for manufacturing a nitride-based semiconductor laser device according to the present invention (hereinafter referred to as a second inventive method) is the first gallium nitride substantially free of indium on a substrate by MOCVD. Gallium nitride semiconductor having a step of forming a stacked structure including a compound semiconductor layer, a second gallium nitride compound semiconductor layer containing indium, and a third gallium nitride compound semiconductor layer substantially free of indium In the method for manufacturing a light emitting device,
NH as nitrogen source_ThreeAnd growing a first gallium nitride compound semiconductor layer by MOCVD at a growth temperature exceeding 900 ° C .;
Subsequently, NH as a nitrogen raw material_ThreeA step of growing a second gallium nitride compound semiconductor layer and then a third gallium nitride compound semiconductor layer by MOCVD at a growth temperature of 900 ° C. or lower using an organic nitrogen compound other than
It is characterized by having.
[0022]
In the second invention method, when the first gallium nitride compound semiconductor layer is grown by the MOCVD method, NH is used._ThreeBy using a gas as a nitrogen raw material and growing at a growth temperature exceeding 900 ° C., the first gallium nitride compound semiconductor layer having good crystallinity can be grown at a rapid growth rate.
In addition, when the second and third gallium nitride compound semiconductor layers are grown by the MOCVD method, a hydrazine (N₂H_Four) Or an organic nitrogen compound such as a hydrazine substitute, and the second gallium nitride compound semiconductor layer and then the third gallium nitride compound semiconductor layer are grown at a growth temperature of 900 ° C. or lower to contain indium. Crystal degradation of the second gallium nitride compound semiconductor layer is prevented.
In the step of growing the second gallium nitride compound semiconductor layer and then the third gallium nitride compound semiconductor layer, a growth temperature when the second gallium nitride compound semiconductor layer is grown, and a third gallium nitride compound The growth temperature for growing the compound semiconductor layer may be the same or different from each other.
[0023]
In the first and second invention methods, the second gallium nitride-based compound semiconductor layer is an active layer having a multiple quantum well structure, and the well layer contains indium of 20 to 50 atomic% of the group III metal. When it is a containing layer, it can be applied optimally. That is, it is most suitable for manufacturing a gallium nitride based semiconductor light emitting device that emits green light from blue light of 450 nm to 520 nm.
[0024]
In the method of the present invention, the gallium nitride compound semiconductor is a nitride compound semiconductor containing Ga and N, for example, GaN, GaInN, AlGaN or the like.
[0025]
In the method of the present invention, an organic nitrogen compound is a term that is contrasted with an inorganic nitrogen compound, and is NH._ThreeExamples of organic nitrogen compounds other than hydrazine (N₂H_Four), Substituted hydrazine, amine nitrogen compounds, and the like.
NH as a nitrogen source_ThreeIn the process of growing a gallium nitride compound semiconductor layer using an organic nitrogen compound other than the above, NH is used as a nitrogen source._ThreeIn addition to organic nitrogen compounds other than_ThreeMay be used.
[0026]
The substituted hydrazine is a compound in which at least a part of hydrogen atoms constituting hydrazine is substituted with a methyl group, for example, monomethylhydrazine (CH_Three-NH-NH₂), 1,1-dimethylhydrazine (CH_Three-NH-NH-CH_Three) Etc.
Hydrazine and its substitutes are NH at the same decomposition efficiency._Threetaller than. For example, when growing a III-V compound semiconductor containing only nitrogen as a group V element, NH is used as a nitrogen source._ThreeWhen NH is used, NH_ThreeThe molar ratio (supply ratio) of the organic metal that is the raw material of the group III element is NH_Three/ Organic metal = 10,000 or so.
On the other hand, when hydrazine and its substitute are used as the nitrogen source, NH_ThreeAt the same growth temperature as in the case of using hydrazine, the supply amount of the nitrogen raw material can be reduced to about hydrazine and its substitution product / organometallic = 50.
The decreasing tendency of the supply amount of the nitrogen raw material becomes more prominent as the growth temperature is lowered. That is, even if the growth temperature is low, the nitrogen source species that contribute to the growth can be increased on the substrate, so that the nitrogen deficiency is improved and a gallium nitride compound semiconductor layer with good crystallinity can be grown. .
According to the method of the present invention, a double heterostructure can be grown without deteriorating the light emitting layer.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below specifically and in detail with reference to the accompanying drawings.
Embodiment 1
The present embodiment is an example of an embodiment in which the method for manufacturing a gallium nitride based semiconductor light emitting device according to the first invention method is applied to the manufacture of the gallium nitride based semiconductor laser device described above. FIG. 1 is a schematic diagram showing the configuration of an MOCVD apparatus when applying the methods of Embodiments 1 and 2, and FIG. 2 shows the growth of a gallium nitride compound semiconductor layer by applying the method of this embodiment. It is a graph which shows the relationship between this growth process and growth temperature.
[0028]
First, the configuration of an MOCVD apparatus for forming a gallium nitride compound semiconductor layer by applying the method of this embodiment will be described with reference to FIG.
As shown in FIG. 1, the MOCVD apparatus 40 includes a susceptor 42 that holds a substrate W therein and a heater 44 that is provided below the susceptor 42 and heats the substrate W via the susceptor 42. A tube 46, a source gas supply system 48 that supplies a source gas to the reaction tube 46, and an exhaust gas treatment device 50 that exhausts exhaust gas from the reaction tube 46 for processing.
[0029]
The gas supply system 48 is NH_ThreeIt has a gas cylinder 52, and NH is connected to the reaction tube 46 by the first gas supply tube 54._ThreeIt has a gas supply system, a mass flow controller (MFC) 56, and a bubbler 58 containing dimethylhydrazine.₂Or N₂, A system for supplying dimethylhydrazine as a nitrogen raw material to the reaction tube 46 via the first gas supply tube 54, a mass flow controller (MFC) 60, and a bubbler 62 containing a group III organic metal, and a carrier gas As H₂Or N₂And a system for supplying the group III organic metal to the reaction tube 46 through the second gas supply tube 64.
In addition, a bypass line and an on-off valve are provided at a necessary place of the piping.
[0030]
With the above configuration, NH_ThreeAlternatively, dimethylhydrazine is supplied to the reaction tube 46 through the first gas supply tube 54 together with a carrier gas such as hydrogen or nitrogen as a raw material for nitrogen, which is a group V element.
TMG (trimethylgallium), TMA (trimethylaluminum), and TMI (trimethylindium) are used as raw materials for group III elements gallium, aluminum, and indium, respectively, together with a carrier gas such as hydrogen or nitrogen, through a second gas supply pipe 64. It is supplied to the reaction tube 46.
When implanting n-type impurities, for example, SiH_FourSilicon ions are implanted using a gas. When p-type impurities are implanted, for example, bis = cyclopentamagnesium ((C_FiveH_Five)₂Mg ions are implanted using Mg) as a raw material.
Note that all gas supply amounts are controlled by a mass flow controller.
[0031]
Next, a method for growing a gallium nitride compound semiconductor layer constituting the nitride semiconductor laser element 10 by MOCVD using the above-described MOCVD apparatus 40 will be described.
First, as shown in FIG. 2, in the first growth step, hydrogen gas is used as a carrier gas, and NH is used as a nitrogen source._ThreeA gas is used and an MOCVD method is used to grow a growth temperature of about 1000 ° C. on the n-GaN substrate 12._0.08Ga_0.92An N clad layer 16 and an n-GaN guide layer 18 having a thickness of 0.1 μm are sequentially grown.
[0032]
Next, in the second growth step, the carrier gas is switched to nitrogen gas, and the growth temperature is lowered to 700 ° C. as shown in FIG._0.02Ga_0.98N (50Å) / n-In_0.2Ga_0.8N (25Å) / n-In_0.02Ga_0.98N (50Å) MQW active layer 20 is grown.
Next, in the third growth step, the carrier gas is again switched to hydrogen gas, and at the same time, NH_ThreeWhile stopping the gas supply and supplying dimethylhydrazine as a nitrogen raw material, as shown in FIG. 2, the growth temperature is raised to 800 ° C., the p-GaN guide layer 22 having a film thickness of 0.1 μm, and the film thickness of 0.5 μm. P-Al_0.07Ga_0.93An N clad layer 24 and a p-GaN contact layer 26 having a thickness of 0.1 μm are sequentially grown by MOCVD.
[0033]
After the p-GaN contact layer 26 is grown, the temperature is lowered to 400 ° C. while supplying dimethylhydrazine so that nitrogen is not desorbed from the film formation surface.
Thereafter, the stripe-shaped ridge 28 is formed through a photolithography process, an etching process, and the like, and the nitride-based semiconductor laser device 10 is manufactured in the same manner as in the prior art.
[0034]
In this embodiment, when a p-gallium nitride compound semiconductor layer is grown on the MQW active layer 18, NH_ThreeGas is supplied and dimethylhydrazine is supplied as a nitrogen raw material._ThreeNH as a nitrogen source without stopping gas supply_ThreeA mixed gas of gas and dimethylhydrazine may be supplied.
Also, the p-GaN guide layer 22, p-Al_0.07Ga_0.93The growth temperature of the N clad layer 24 and the p-GaN contact layer 26 does not need to be 800 ° C., and the growth temperature may be in the range of 700 ° C. to 900 ° C.
[0035]
In this embodiment, a GaN substrate is used as the substrate. However, a sapphire substrate or a SiC substrate may be used, and a gallium nitride compound semiconductor layer may be grown on the substrate via a low-temperature buffer layer.
[0036]
Embodiment 2
The present embodiment is an example of an embodiment in which the method for manufacturing a gallium nitride based semiconductor light emitting device according to the second invention method is applied to the manufacture of the gallium nitride based semiconductor laser device described above. FIG. 3 is a graph showing the relationship between the growth process and growth temperature of the gallium nitride compound semiconductor layer when the method of this embodiment is applied.
First, in the first growth step, hydrogen gas is used as a carrier gas and NH is used as a nitrogen source in the same manner as in the first embodiment._ThreeAs shown in FIG. 3, an n-GaN buffer layer 14 having a film thickness of 3 μm and an n-Al film having a film thickness of 1.3 μm are formed on the n-GaN substrate 12 at a growth temperature of about 1000 ° C._0.08Ga_0.92An N clad layer 16 and an n-GaN guide layer 18 having a thickness of 0.1 μm are sequentially grown.
[0037]
Next, in the second growth step, hydrogen gas is used as a carrier gas and NH is used as a nitrogen source._ThreeSwitching from gas to dimethyl hydrazine, the growth temperature was lowered to 700 ° C. as shown in FIG._0.02Ga_0.98N (50Å) / n-In_0.2Ga_0.8N (25Å) / n-In_0.02Ga_0.98N (50Å) MQW active layer 20 is grown.
Subsequently, in the third growth step, as shown in FIG. 3, while maintaining the growth temperature at 700 ° C., the p-GaN guide layer 22 having a thickness of 0.1 μm and the p-Al having a thickness of 0.5 μm._0.07Ga_0.93An N clad layer 24 and a p-GaN contact layer 26 having a thickness of 0.1 μm are sequentially grown.
[0038]
After the p-GaN contact layer 26 is grown, the temperature is lowered to 400 ° C. while supplying dimethylhydrazine so that nitrogen is not desorbed from the film formation surface.
Thereafter, the stripe-shaped ridge 28 is formed through a photolithography process, an etching process, and the like, and the nitride-based semiconductor laser device 10 is manufactured in the same manner as in the prior art.
In the method according to the present embodiment, it is not necessary to change the growth temperature between the first and second growth steps, so that productivity can be improved.
[0039]
【The invention's effect】
According to the first and second invention methods, after the second gallium nitride compound semiconductor layer containing indium is grown, the third gallium nitride compound semiconductor layer substantially free of indium is added to the second gallium nitride compound semiconductor layer. When forming a film on a gallium nitride compound semiconductor layer, hydrazine (N₂H_Four) Or a substitution product of hydrazine, and the third gallium nitride compound semiconductor layer is grown at a growth temperature of 900 ° C. or less, whereby thermal degradation of the second gallium nitride compound semiconductor layer can be prevented.
By manufacturing a gallium nitride semiconductor light emitting device having a large indium composition by using the method of the present invention, it is possible to realize a light emitting device that emits green light from blue light with stable light emission characteristics and improved light emission efficiency. it can.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of an MOCVD apparatus used when applying the methods of Embodiment Examples 1 and 2. FIG.
FIG. 2 is a graph showing a relationship between a growth process and a growth temperature of a gallium nitride compound semiconductor layer when the method of Embodiment 1 is applied.
FIG. 3 is a graph showing a relationship between a growth process and a growth temperature of a gallium nitride compound semiconductor layer when the method of the embodiment is applied.
FIG. 4 is a schematic cross-sectional view showing a basic configuration of a nitride-based semiconductor laser device.
FIG. 5 is a graph showing a relationship between a growth process and a growth temperature of a gallium nitride-based compound semiconductor layer when a conventional method is applied.
FIG. 6 is a graph showing photoluminescence spectra of three types of laminated structure samples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Nitride semiconductor laser element, 12 ... n-GaN substrate, 14 ... n-GaN buffer layer, 16 ... n-Al_0.08Ga_0.92N clad layer, 18 ... n-GaN guide layer, 20 ... MQW active layer, 22 ... p-GaN guide layer, 24 ... p-Al_0.07Ga_0.93N clad layer, 26... P-GaN contact layer, 28... Ridge, 30.₂Membrane, 32 ... p-side electrode, 34 ... n-side electrode, 40 ... MOCVD apparatus, 42 ... susceptor, 44 ... heater, 46 ... reaction tube, 48 ... source gas supply system, 50 ... Exhaust gas treatment equipment, 52 …… NH_ThreeGas cylinder 54... First gas supply pipe 56. Mass flow controller (MFC) 58. Bubbler 60. Mass flow controller (MFC) 62.

Claims (5)

Hydrogen gas as carrier gas, NH as nitrogen source _Three A step of sequentially growing an n-type GaN buffer layer, an n-type AlGaN cladding layer and an n-type GaN guide layer on an n-type GaN substrate at a growth temperature exceeding 900 ° C. by using a gas and MOCVD method;
After growing the n-type GaN buffer layer, the n-type AlGaN cladding layer, and the n-type GaN guide layer, the carrier gas is switched to nitrogen gas, the growth temperature is lowered to 700 to 800 ° C., and NH is used as a nitrogen source. _Three A step of growing an active layer having a multi-quantum well structure made of a gallium nitride-based compound semiconductor in which the well layer contains 20 atomic% or more and 50 atomic% or less of indium of a group III metal by using a gas and an MOCVD method;
After growing the active layer, the carrier gas is again switched to hydrogen gas, and at the same time, NH _Three Gas supply was stopped and hydrazine (N ₂ H _Four ) Or a hydrazine substitution product at a growth temperature not lower than 900 ° C. and not higher than the growth temperature of the active layer by MOCVD, a p-type GaN guide layer, a p-type AlGaN cladding layer, and a p-type are formed on the active layer. A step of sequentially growing a GaN contact layer;
After growing the p-type GaN contact layer, hydrazine (N ₂ H _Four ) Or a step of lowering the temperature to 400 ° C. while supplying a substituted hydrazine
A method for manufacturing a gallium nitride based semiconductor laser device comprising: Hydrogen gas as carrier gas, NH as nitrogen source _Three A step of sequentially growing an n-type GaN buffer layer, an n-type AlGaN cladding layer and an n-type GaN guide layer on an n-type GaN substrate at a growth temperature exceeding 900 ° C. by using a gas and MOCVD method;
After growing the n-type GaN buffer layer, the n-type AlGaN cladding layer, and the n-type GaN guide layer, hydrogen gas is used as a carrier gas, and hydrazine (N ₂ H _Four ) Or a hydrazine substitution product, the growth temperature is lowered to 700 to 800 ° C., and the well layer is made of a gallium nitride compound semiconductor containing indium of 20 to 50 atomic% of the group III metal by MOCVD. Growing an active layer having a multiple quantum well structure;
After the active layer is grown, hydrogen gas is used as a carrier gas, and hydrazine (N ₂ H _Four ) Or a hydrazine substitute, and a MOCVD method is used to grow a p-type GaN guide layer, a p-type AlGaN cladding layer, and a p-type GaN contact on the active layer at a growth temperature not lower than 900 ° C. Sequentially growing the layers;
After growing the p-type GaN contact layer, hydrazine (N ₂ H _Four ) Or a step of lowering the temperature to 400 ° C. while supplying a substituted hydrazine
A method for manufacturing a gallium nitride based semiconductor laser device comprising: In the step of growing the p-type GaN guide layer, the p-type AlGaN cladding layer, and the p-type GaN contact layer, hydrazine (N ₂ H _Four ) Or hydrazine substituents and simultaneously NH _Three The method for manufacturing a gallium nitride based semiconductor laser device according to claim 1 or 2, wherein: The n-type GaN buffer layer, the n-type AlGaN cladding layer and the n-type GaN guide layer are grown at 1000 ° C., the active layer is grown at 700 ° C., and the p-type GaN guide layer and the p-type AlGaN cladding layer are grown. The method for manufacturing a gallium nitride based semiconductor laser device according to claim 1, wherein the p-type GaN contact layer is grown at 800 ° C. The n-type GaN buffer layer, the n-type AlGaN cladding layer and the n-type GaN guide layer are grown at 1000 ° C., the active layer is grown at 700 ° C., and the p-type GaN guide layer and the p-type AlGaN cladding layer are grown. The method for manufacturing a gallium nitride based semiconductor laser device according to claim 2, wherein the p-type GaN contact layer is grown at 700 ° C.

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