阅读说明：本技术 化合物半导体外延片及其制造方法 (Compound semiconductor epitaxial wafer and method for manufacturing same ) 是由 篠原政幸 酒井健滋 高桥雅宣 于 2021-05-12 设计创作，主要内容包括：本发明提供一种以低成本改善了结晶性并提升了亮度的化合物半导体外延片及其制造方法。所述化合物半导体外延片在由GaM构成的单晶基板(M为P或As)和由GaA-((1-a))M-(a)构成的混晶率恒定层(其中,A为P或As,M和A不同；且0≤a≤1)之间,包含由GaA-((1-x))M-(x)(其中,0≤x≤1)构成的混晶率变化层,混晶率变化层具有由A的混晶率增加部和A的混晶率减少部构成的多个阶梯,多个阶梯各自的厚度为2～4μm,在混晶率变化层中形成有5～19个阶梯,在各个阶梯之间,A的混晶率从单晶基板向混晶率恒定层增加。(The invention provides a compound semiconductor epitaxial wafer with improved crystallinity and brightness at low cost and a manufacturing method thereof. The compound semiconductor epitaxial wafer is formed on a single crystal substrate (M is P or As) composed of GaM and a single crystal substrate composed of GaA (1‑a) M a The constant mixed crystal ratio layer (wherein A is P or As, M is different from A, and a is not less than 0 and not more than 1) comprises GaA (1‑x) M x (wherein x is 0. ltoreq. x.ltoreq.1) and a mixed crystal ratio of AA plurality of steps each having a thickness of 2 to 4 μm and each consisting of a rate increasing section and a mixed crystal rate decreasing section A, wherein 5 to 19 steps are formed in the mixed crystal rate changing layer, and the mixed crystal rate of A increases from the single crystal substrate to the mixed crystal rate constant layer between the steps.)

1. A compound semiconductor epitaxial wafer is prepared from single crystal substrate composed of GaM and GaA_(1-a)M_aBetween the layers with constant mixed crystal ratio, containing GaA_(1-x)M_xA mixed crystal ratio changing layer formed, wherein M is P or As, A is P or As, M is different from A, a is more than or equal to 0 and less than or equal to 1, x is more than or equal to 0 and less than or equal to 1, the compound semiconductor epitaxial wafer is characterized in that,

the mixed crystal ratio changing layer has a plurality of steps each of which is composed of a mixed crystal ratio increasing portion of A and a mixed crystal ratio decreasing portion of A,

the plurality of steps each having a thickness of 2 to 4 μm,

5 to 19 steps are formed in the mixed crystal ratio changing layer,

the mixed crystal ratio of a increases from the single crystal substrate to the mixed crystal ratio constant layer between the respective steps.

2. The compound semiconductor epitaxial wafer as claimed in claim 1, wherein,

the respective thicknesses of the steps are 2 to 3 μm, and 8 to 12 steps are formed in the mixed crystal ratio changing layer.

3. A method for manufacturing a compound semiconductor epitaxial wafer comprising a single crystal substrate of GaM and GaA_(1-a)M_aBetween the layers with constant mixed crystal ratio, containing GaA_(1-x)M_xA method for producing a compound semiconductor epitaxial wafer having a mixed crystal ratio changing layer, wherein M is P or As, A is P or As, M is different from A, a is 0. ltoreq. a.ltoreq.1, x is 0. ltoreq. x.ltoreq.1,

the manufacturing method is characterized in that:

epitaxially growing the mixed crystal ratio variable layer by using a group III gas for supplying Ga and a group V gas for supplying As or P,

performing the epitaxial growth by performing 5 to 19 cycles of sudden increase and decrease in the supply amount of the group V gas which is the raw material of the group A,

in this cycle, a plurality of steps each composed of the mixed crystal ratio increasing portion of A and the mixed crystal ratio decreasing portion of A are formed in the mixed crystal ratio changing layer,

the thickness of each of the plurality of steps is set to 2 to 4 μm,

and increasing the mixed crystal ratio of A from the single crystal substrate to the mixed crystal ratio constant layer between the steps.

4. The method of manufacturing a compound semiconductor epitaxial wafer according to claim 3, wherein the cycle of the sudden increase and the gradual decrease is set to 8 to 12 times, and the thickness of each step is set to 2 to 3 μm.

Technical Field

The present invention relates to a compound semiconductor epitaxial wafer and a method for manufacturing the same, and more particularly, to a compound semiconductor epitaxial wafer having a mixed crystal ratio changing layer and a method for manufacturing the same.

Background

A compound semiconductor epitaxial wafer is used for manufacturing orange or yellow light emitting diodes including red light emitting diodes, wherein a mixed crystal ratio constant layer is formed on a gallium phosphide GaP or gallium arsenide GaAs single crystal substrate, and the mixed crystal ratio constant layer is formed of gallium arsenide phosphide GaAs or gallium phosphide GaAs which is a III-V group compound semiconductor not constituting the single crystal substrate and meets constant mixed crystal ratio (1-a) and constant gallium phosphide GaAs GaP_(1-a)P_a(wherein a is a real number satisfying 0. ltoreq. a.ltoreq.1).

The emission wavelength of the light emitting diode depends on the mixed crystal ratio a, and for example, when the single crystal substrate is gallium phosphide GaP, a for yellow emission is 0.9, a for orange emission is 0.67, and a for red emission is 0.57.

In addition, when the substrate is composed of a single crystal substrate of a compound semiconductor such as GaP or GaAs, etc., and GaAs formed on the substrate_(1-a)P_aWhen the lattice mismatch of the constant crystal ratio layer is large, misfit dislocation occurs at the interface to relieve stress caused by the lattice mismatch. However, if the dislocations propagate to the constant-mixed-crystal-ratio layer in which the light-emitting region is formed, the dislocations cause a decrease in the light-emitting efficiency of the light-emitting diode.

Therefore, in order to suppress propagation of such misfit dislocation, the single crystal substrate and GaAs are used_(1-a)P_aBetween the layers with constant mixed crystal ratio, GaAs with gradually changed mixed crystal ratio (1-x) of GaAs and GaP_(1-x)P_xA mixed crystal ratio changing layer. As a method for forming the mixed crystal ratio changing layer, there are known: a method of gradually changing the composition of the raw material gas supplied to the growth environment of the mixed crystal ratio-changing layer and gradually changing the vapor phase growth temperature (patent document 1).

The temperature of the vapor phase growth is changed to improve GaAs_(1-x)P_xJunction of mixed crystal ratio changing layerAnd (4) crystallinity. The composition of the mixed crystal ratio changing layer is changed from that of the single crystal substrate to GaAs in accordance with epitaxial growth_(1-a)P_aWhen the composition of the constant mixed crystal ratio layer is to be increased, that is, when the mixed crystal ratio (1-x) of GaAs is to be increased, that is, when the GaAsP layer is epitaxially grown on the GaP substrate while increasing the composition ratio of As in the source gas, the vapor phase growth temperature must be gradually decreased, and when the mixed crystal ratio x of ga P is to be increased, that is, when the GaAsP layer is epitaxially grown on the GaAs substrate while increasing the composition ratio of P in the source gas, the vapor phase growth temperature must be gradually increased.

In addition to a method of forming a layer by gradually changing the mixed crystal ratio as conventionally known, a method of forming a layer by gradually changing the mixed crystal ratio in a mixed crystal ratio-changing layer, contrary to the conventional method, has been disclosed in which the mixed crystal ratio is rapidly changed when epitaxial growth of the mixed crystal ratio-changing layer is performed, and the layer is formed while relatively gently restoring the mixed crystal ratio immediately thereafter (patent document 2).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 49-11468

Patent document 2: japanese laid-open patent publication No. 9-199757

Disclosure of Invention

Technical problem to be solved by the invention

However, if the variation width in the variable layer of the mixed crystal ratio is large, the improvement of crystallinity in the constant layer of the mixed crystal ratio cannot be sufficiently performed, and finally, a crystal with misfit dislocations left is formed, resulting in a decrease in luminance.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a compound semiconductor epitaxial wafer having improved crystallinity and improved luminance at low cost, and a method for manufacturing the same.

Means for solving the problems

In order to achieve the above object, the present invention provides a compound semiconductor epitaxial wafer formed on a single crystal substrate (M is P or As) made of GaM and a compound semiconductor epitaxial wafer made of GaA_(1-a)M_aA mixed crystal ratio constant layer (wherein A is P or As, M and A are different; anda is more than or equal to 0 and less than or equal to 1), comprising_(1-x)M_x(wherein x is 0. ltoreq. x.ltoreq.1) and a mixed crystal ratio changing layer, wherein the compound semiconductor epitaxial wafer is characterized in that,

the mixed crystal ratio changing layer has a plurality of steps (step) composed of a mixed crystal ratio increasing part of A and a mixed crystal ratio decreasing part of A,

the plurality of steps each having a thickness of 2 to 4 μm,

5 to 19 steps are formed in the mixed crystal ratio changing layer,

the mixed crystal ratio of a increases from the single crystal substrate to the mixed crystal ratio constant layer between the respective steps.

In the compound semiconductor epitaxial wafer, the number of steps is increased, and the increase range of the mixed crystal ratio is reduced by 1, so that the crystallinity can be improved at low cost and the brightness can be improved.

In this case, the thickness of each of the steps is preferably 2 to 3 μm, and 8 to 12 steps are preferably formed in the mixed crystal ratio changing layer.

In this case, it is possible to more reliably improve the luminance and to further suppress the material cost.

Further, the present invention provides a method for producing a compound semiconductor epitaxial wafer, which comprises forming a single crystal substrate of GaM (M is P or As) and forming GaA_(1-a)M_aThe constant mixed crystal ratio layer (wherein A is P or As, M is different from A, and a is not less than 0 and not more than 1) comprises GaA_(1-x)M_x(wherein x is 0. ltoreq. x.ltoreq.1) in the mixed crystal ratio changing layer,

the manufacturing method is characterized in that:

epitaxially growing the mixed crystal ratio variable layer by using a group III gas for supplying Ga and a group V gas for supplying As or P,

in the epitaxial growth, 5 to 19 cycles (cycles) of sudden increase and decrease in the amount of the group V gas which is a raw material of the group A are performed,

in this cycle, a plurality of steps each composed of the mixed crystal ratio increasing portion of A and the mixed crystal ratio decreasing portion of A are formed in the mixed crystal ratio changing layer,

the thickness of each of the plurality of steps is set to 2 to 4 μm,

and increasing the mixed crystal ratio of A from the single crystal substrate to the mixed crystal ratio constant layer between the steps.

With this method for manufacturing a compound semiconductor epitaxial wafer, a compound semiconductor wafer having improved brightness can be manufactured in a relatively simple manner.

In this case, the period of the sudden increase and the gradual decrease is preferably set to 8 to 12 times, and the thickness of each step is preferably set to 2 to 3 μm.

In this way, the luminance can be more surely improved while substantially maintaining the material cost or productivity.

Effects of the invention

The compound semiconductor epitaxial wafer of the present invention is a compound semiconductor epitaxial wafer having improved crystallinity and improved luminance at low cost. In addition, according to the method for manufacturing a compound semiconductor epitaxial wafer of the present invention, a compound semiconductor wafer having improved brightness can be manufactured in a relatively simple manner.

Drawings

Fig. 1 is a schematic cross-sectional view of one example of a compound semiconductor epitaxial wafer of the present invention.

Fig. 2 is a diagram showing an example of the relationship between the layer thickness and the mixed crystal ratio (1-x) of GaAs, when the method for producing a compound semiconductor epitaxial wafer of the present invention is set to 5 steps.

FIG. 3 is a graph comparing the luminance in examples 1 to 4 and comparative examples 1 to 5.

Description of the reference numerals

1: a compound semiconductor epitaxial wafer; 2: an n-type GaP single crystal substrate; 3: an n-type GaP epitaxial layer; 4: n-type GaAs_(1-x)P_xA mixed crystal ratio changing layer; 5: n-type GaAs_(1-a)P_aA mixed crystal ratio constant layer; 6: n-type GaAs_(1-a)P_aA mixed crystal ratio constant layer (N-doped); 7: p-type GaAs_(1-a)P_aConstant mixed ratio layer (N-doped).

Detailed Description

As described above, the present invention aims to provide a compound semiconductor epitaxial wafer having improved crystallinity and improved luminance at low cost, and a method for manufacturing the same.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have found that a compound semiconductor epitaxial wafer having improved crystallinity and improved luminance can be produced at low cost, and have completed the present invention. The compound semiconductor epitaxial wafer is formed on a single crystal substrate (M is P or As) composed of GaM and a single crystal substrate composed of GaA_(1-a)M_aThe constant mixed crystal ratio layer (wherein A is P or As, M is different from A, and a is not less than 0 and not more than 1) comprises GaA_(1-x)M_x(wherein x is 0. ltoreq. x.ltoreq.1), wherein the mixed crystal ratio changing layer has a plurality of steps each consisting of a mixed crystal ratio increasing portion of A and a mixed crystal ratio decreasing portion of A, the plurality of steps each have a thickness of 2 to 4 μm, 5 to 19 steps are formed in the mixed crystal ratio changing layer, and the mixed crystal ratio of A increases from the single crystal substrate to the mixed crystal ratio constant layer between the steps.

The present invention will be described in detail below with reference to the drawings attached to the specification, but the present invention is not limited thereto.

Fig. 1 shows a schematic cross-sectional view of one example of a compound semiconductor epitaxial wafer of the present invention. The compound semiconductor epitaxial wafer 1 has an n-type gallium phosphide (GaP) single-crystal substrate 2 on which are formed in this order: an n-type GaP epitaxial layer 3; n-type phosphorus gallium arsenide (GaAs)_(1-x)P_x) A mixed crystal ratio changing layer 4 (wherein x is 0. ltoreq. x.ltoreq.l), in which mixed crystal ratio (1-x) of gallium arsenide (GaAs) as a III-V group compound semiconductor that does not constitute a substrate in the mixed crystal ratio changing layer 4 changes (increases or decreases) in the growth direction of the epitaxial layer; and n-type GaAs having a constant mixed crystal ratio (1-a) of GaAs_(1-a)P_aA mixed crystal ratio constant layer 5 (wherein 0. ltoreq. a. ltoreq.1), and N-type GaAs doped with nitrogen (N) and having a constant mixed crystal ratio (1-a) of GaAs_(1-a)P_aA mixed crystal ratio constant layer 6 on the GaAs layer_(1-a)P_aP-type GaAs obtained by doping and growing p-type impurities is formed on the constant mixed crystal ratio layer 6_(1-a)P_aA mixed crystal ratio constant layer (N-doped) 7.

The mixed crystal ratio changing layer 4 has a plurality of steps each composed of a mixed crystal ratio increasing portion of As and a mixed crystal ratio decreasing portion of As. This means that 1 step is formed with a pair of 1 increasing portion and 1 decreasing portion, and the step is plural. The reduced portion is in a range not to offset the increased amount of As, and the thickness of each step is 2 to 4 μm. In addition, 5 to 19 steps are formed in the mixed crystal ratio changing layer 4. Further, between the steps, the mixed crystal ratio of As is changed from GaP single crystal substrate to GaAs_(1-a)P_aThe mixed crystal ratio constant layer increases.

In this case, the thickness of each step is preferably 2 to 3 μm, and 8 to 12 steps are preferably formed in the mixed crystal ratio changing layer. In this way, the luminance can be improved more reliably while maintaining the material cost.

As described above, the compound semiconductor epitaxial wafer according to the present invention can provide a compound semiconductor epitaxial wafer having improved crystallinity and improved luminance at low cost.

After electrodes are mounted on the compound semiconductor epitaxial wafer 1, the compound semiconductor epitaxial wafer is cut into an appropriate size and packaged into a package (package) to obtain a light-emitting diode. The light-emitting diode is not particularly limited, and for example, an orange light-emitting diode having a central emission wavelength of 629nm can be produced.

In the case where the single crystal substrate 2 is GaP, the GaAs substrate can be used in the same manner.

That is, when a GaAs substrate is used, the following are formed on a GaAs single crystal substrate: a GaAs epitaxial layer; n-type GaAs_xP_(1-x)A mixed crystal ratio changing layer (wherein x is 0-l) in which the mixed crystal ratio (1-x) of GaP as a group III-V compound semiconductor not constituting a substrate changes (increases or decreases) in the growth direction of an epitaxial layer, and GaAs having a constant mixed crystal ratio (1-a) of GaP is formed in the order of n-type and p-type_aP_(1-a)A mixed crystal ratio constant layer (wherein, a is more than or equal to 0 and less than or equal to 1).

In the case of the GaAs substrate, the mixed crystal ratio changing layer has a plurality of steps each including a P mixed crystal ratio increasing portion and a P mixed crystal ratio decreasing portion. The reduction part is a range not offsetting the increased amount of P, and the respective thicknesses of the steps are2 to 4 μm. In addition, 5 to 19 steps are formed in the mixed crystal ratio changing layer. Further, the mixed crystal ratio of P is changed from GaAs single crystal substrate to GaAs between steps_aP_(1-a)The mixed crystal ratio constant layer increases.

In this case, as in the case of a GaP substrate, the thickness of each step is preferably 2 to 3 μm, and 8 to 12 steps are preferably formed in the mixed crystal ratio changing layer. In this way, the GaAs substrate can achieve a more reliable improvement in luminance while maintaining the material cost.

In addition, the invention also provides a manufacturing method of the compound semiconductor epitaxial wafer.

The method for producing a compound semiconductor epitaxial wafer of the present invention is a method for producing a compound semiconductor epitaxial wafer comprising a single crystal substrate made of GaM (M is P or As) and GaA_(1-a)M_aThe constant mixed crystal ratio layer (wherein A is P or As, M is different from A, and a is not less than 0 and not more than 1) comprises GaA_(1-x)M_x(wherein x is 0. ltoreq. x.ltoreq.1) in the mixed crystal ratio changing layer,

the manufacturing method is characterized in that:

a group III gas for supplying Ga and a group V gas for supplying As or P are used to epitaxially grow a mixed crystal ratio-changing layer, and a period of 5 to 19 times of sudden increase and gradual decrease in the supply amount of the group V gas, which is a raw material of A, is performed during the epitaxial growth, and a plurality of steps each composed of a mixed crystal ratio increasing portion of A and a mixed crystal ratio decreasing portion of A are formed in the mixed crystal ratio changing layer in the period, and the thickness of each of the plurality of steps is set to 2 to 4 [ mu ] m, and the mixed crystal ratio of A is increased from the single crystal substrate to the mixed crystal ratio-maintaining layer between the steps.

Next, a method for manufacturing a compound semiconductor epitaxial wafer according to the present invention will be described with reference to fig. 2. FIG. 2 shows making GaAs_(1-x)P_xThe change of each parameter of the mixed crystal ratio changing layer 4 during the vapor phase growth on the GaP substrate 2. The vertical axis of FIG. 2 shows the mixed crystal ratio (1-x) of GaAs. In addition, the horizontal axis represents the layer thickness of the epitaxial layer.

In the method for producing a compound semiconductor epitaxial wafer of the present invention, the III th compound semiconductor epitaxial wafer supplied with gallium (Ga) is usedA group V gas for supplying arsenic (As) or phosphorus (P) to the group V gas, and epitaxially growing a mixed crystal ratio variable layer. In the method for producing a compound semiconductor epitaxial wafer of the present invention, the Ga supply source, the As or P supply source is not particularly limited, and for example, high-purity Ga and hydrogen chloride (HCl) may be reacted with each other to form a Ga source supply gas (group III gas), and hydrogen arsenide (AsH) may be used₃) As the source of As, Phosphine (PH) can be used₃) As a P source. Further, H may be supplied₂And the like.

First, GaP epitaxial layer 3 is vapor-grown on GaP single crystal substrate 2 to d₁₀Is measured. Then, GaAs is reacted_(1-x)P_xThe mixed crystal ratio changing layer 4 is vapor-grown on the GaP epitaxial layer 3 to (d)₂₂-d₁₀) Thickness of (1), the GaAs_(1-x)P_xIn the mixed crystal ratio changing layer 4, the mixed crystal ratio (1-x) of GaAs changes in the growth direction of the epitaxial layer in the range of 0 to (1-a).

Although fig. 2 shows the case of the GaAs mixed crystal ratio increasing layer having 5 steps, the method for manufacturing the compound semiconductor epitaxial wafer of the present invention includes 5 to 19 periods (steps) of sudden increase and gradual decrease of the mixed crystal ratio, and preferably 8 to 12 periods (steps).

Further, in each period, a plurality of steps each consisting of an increasing portion and a decreasing portion of the mixed crystal ratio are formed, and the thickness of each step is set to 2 to 4 μm, preferably 2 to 3 μm.

GaAs_(1-x)P_xThe mixed crystal ratio changing layer 4 is formed by a mixed crystal ratio increasing part R which sharply increases the mixed crystal ratio (1-x) of GaAs along the growth direction of the epitaxial layer₁₁、R₁₂、R₁₃、R₁₄、R₁₅、R₁₆And a mixed crystal ratio reducing section S for gradually reducing the mixed crystal ratio (1-x) within a range of increasing amount of the mixed crystal ratio (1-x) without canceling out GaAs₁₁、S₁₂、S₁₃、S₁₄、S₁₅And a mixed crystal ratio adjusting part A₁₃And (4) forming.

The combination of the mixed crystal ratio increasing portion and the mixed crystal ratio decreasing portion (R)₁₁And S₁₁、R₁₂And S₁₂、R₁₃And S₁₃、R₁₄And S₁₄、R₁₅And S₁₅) The number of repetition of (2) is determined by the size of the predetermined mixed crystal ratio (1-a) and the increase rate and decrease rate of the mixed crystal ratio (1-x).

Further, a mixed crystal ratio adjusting part A is provided at the uppermost part of the mixed crystal ratio changing layer 4₁₃. The mixed crystal ratio adjusting part A₁₃The mixed crystal ratio of (2) is changed while keeping (1-x) at (1-a) when the mixed crystal ratio of gallium arsenide GaAs (1-x) in the mixed crystal ratio changing layer 4 reaches (1-a) by increasing and decreasing a predetermined number of times, but gradually increases (1-x) to (1-a) when the mixed crystal ratio is slightly smaller than (1-a). In the example shown in FIG. 2, the increase in the mixed crystal ratio is caused by the formation of the portion R₁₆The mixed crystal ratio (1-x) of GaAs in the mixed crystal ratio changing layer 4 reaches (1-a), and the mixed crystal ratio adjusting section A₁₃The mixed crystal ratio of gallium arsenide GaAs in (1) is changed while maintaining (1-x) to (1-a).

When the mixed crystal ratio changing layer 4 is epitaxially grown, the mixed crystal ratio increasing part R is formed₁₁～R₁₆In which misfit dislocation occurs, stress due to lattice mismatch distributed in the growth direction of the epitaxial layer can be effectively relaxed in each local region, and the mixed crystal ratio reducing portion S can be formed₁₁～S₁₅Because the crystal damaged by the occurrence of misfit dislocation is repaired, an epitaxial wafer with small warpage and good crystallinity can be produced. In addition, the crystal mixture ratio is increased at the R portion₁₁～R₁₆The mixed crystal ratio is sharply increased, and therefore the mixed crystal ratio changing layer 4 becomes thin, and a compound semiconductor epitaxial wafer can be efficiently produced.

Here, in GaAs_(1-x)P_xA mixed crystal ratio increasing part R in the mixed crystal ratio changing layer 4₁₁～R₁₆In order to sharply increase the mixed crystal ratio (1-x) of GaAs in the growth direction of the epitaxial layer, the composition of the gas raw material must be sharply changed.

In order to rapidly increase the mixed crystal ratio (1-x) of GaAs by changing the composition of the gas material, there are various methods such As rapidly increasing only the gas material of arsenic (As), rapidly increasing the gas material of As, and rapidly decreasing the gas material of phosphorus (P), but it is important to follow a constant condition in order to obtain good crystal quality with good reproducibility.

The inventors of the present application performed a series of experiments with respect to epitaxial layers having various mixed crystal ratios while changing the supply amount of the gas raw material and the vapor phase growth temperature, and observed the crystal state of the epitaxial layer. As a result, it was found that when 5 to 19, preferably 8 to 12, cycles of sharp increase and gradual decrease in the mixed crystal ratio are included, and a plurality of steps each composed of a mixed crystal ratio increasing portion of As and a mixed crystal ratio decreasing portion of As are formed in the mixed crystal ratio changing layer in each cycle, and the thickness of the steps is set to 2 to 4 μm, preferably 2 to 3 μm, good crystallinity of the epitaxial layer can be obtained.

After the mixed crystal ratio changing layer is thus formed, for example, hydrogen chloride (HCl), and arsine (AsH) are added₃) Phosphine (PH)₃) Is set to be constant while reducing hydrogen sulfide (H)₂S) gas, while growing the layer with a constant mixed crystal ratio.

Finally, a mixed ratio constant layer having the same mixed ratio as that of the composition constant layer and doped with nitrogen as a light emission center is vapor-grown, and a p-type layer doped with a p-type dopant such as zinc (Zn) is further formed, whereby a compound semiconductor epitaxial wafer for a light emitting diode can be manufactured.

After electrodes are mounted on the compound semiconductor epitaxial wafer, it is cut into an appropriate size and loaded into a package, thereby manufacturing a light emitting diode. The light-emitting diode is not particularly limited, and for example, an orange light-emitting diode having a central emission wavelength of 629nm can be produced.

In the case where the single crystal substrate 2 is GaP, the GaAs substrate can be used in the same manner.

That is, when a GaAs substrate is used, first, a GaAs epitaxial layer is vapor-phase-grown on a GaAs single crystal substrate. Then, with the above GaAs_(1-x)P_xIn the same manner as the mixed crystal ratio-changing layer, n-type GaAs in which the mixed crystal ratio (1-x) of GaP as a group III-V compound semiconductor does not constitute a substrate and is changed (increased or decreased) in the growth direction of the epitaxial layer is formed_xP_(1-x)A mixed crystal ratio changing layer (wherein x is 0-l), and forming GaAs with a constant mixed crystal ratio (1-a) of GaP in the order of n-type and p-type_aP_(1-a)Crystal mixing ratioA constant layer (wherein 0. ltoreq. a. ltoreq.1).

In the case of the GaAs substrate, the mixed crystal ratio changing layer has a plurality of steps each including a P mixed crystal ratio increasing portion and a P mixed crystal ratio decreasing portion. The decreasing portions are set to a range not to cancel the increasing amount of P, and the thickness of each step is set to 2 to 4 μm, thereby forming 5 to 19 steps in the mixed crystal ratio changing layer. In addition, the mixed crystal ratio of P is changed from GaAs single crystal substrate to GaAs between steps_aP_(1-a)The mixed crystal ratio constant layer increases.

In this case, the cycle of the sharp increase and the gradual decrease is preferably set to 8 to 12 times, and the thickness of each step is preferably set to 2 to 3 μm. If so, the luminance can be more surely improved and the material cost can be further reduced.

As described above, according to the method for manufacturing a compound semiconductor epitaxial wafer of the present invention, a compound semiconductor wafer having improved luminance can be manufactured relatively easily.

Examples

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

(example 1)

Is manufactured by the following method_(1-x)P_xThe mixed crystal ratio changing layer has a mixed crystal ratio (1-x) of GaAs varying from 0 to 0.33.

After the n-type GaP single crystal was sliced to a predetermined thickness, a GaP mirror wafer having a thickness of about 300 μm was obtained by chemical etching and mechanochemical polishing, and this wafer was used as a GaP single crystal substrate.

Furthermore, hydrogen (H) is used₂) Hydrogen sulfide (H) diluted to 50ppm with hydrogen₂S), high-purity arsine (AsH)₃) High purity Phosphine (PH)₃) And high-purity hydrogen chloride (HCl) as a gas for vapor phase growth.

Firstly, at 2870cm³A flow rate of hydrogen gas H per minute was introduced into a vapor phase growth furnace for atmospheric pressure in which a GaP single crystal substrate and a container containing high-purity gallium (Ga) were placed at predetermined positions₂By using hydrogen H as carrier gas₂Charging the vapor phase growth furnaceThe temperature was raised after the partial substitution, and the diameter of the GaP single crystal substrate was 50mm, and the off-angle at the crystal orientation (100) was 10 °.

After the temperature of the GaP single crystal substrate reached 845 deg.C, high purity HCl was introduced and reacted with high purity gallium disposed in a container to generate gallium chloride (GaCl), and H was introduced₂S and PH₃An n-type GaP epitaxial layer having a thickness of about 3 μm is grown on a GaP single crystal substrate. Then, by introducing AsH for 1 minute₃And pH₃The GaP epitaxial layer is epitaxially grown so that the mixed crystal ratio of GaP is decreased by 0.034 (i.e., the mixed crystal ratio of GaAs is increased by 0.034). Subsequently, the AsH is changed₃And pH₃The temperature was decreased, and growth was performed so that the mixed crystal ratio of GaP was increased by 0.005 in 16 minutes (i.e., the mixed crystal ratio of GaAs was decreased by 0.005). The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 2.51 μm, and this was repeated 10 times.

The flow rate was further changed to decrease the mixed crystal ratio of GaP by 0.034 in 1 minute, and then the flow rate was changed to decrease the mixed crystal ratio of GaP by 0.004 in 16 minutes. The mixed crystal ratio changing layer is formed in this manner. Then, adding HCl and AsH₃、PH₃While setting the flow rate of H constant₂The mixed crystal ratio constant layer was grown for 38 minutes while decreasing the S gas.

Finally, an n-type mixed crystal ratio constant layer having the same mixed crystal ratio as that of the composition constant layer and doped with nitrogen as a light emission center was vapor-grown, and a p-type layer doped with zinc (Zn) was further formed by vapor-phase growth, thereby obtaining a compound semiconductor epitaxial wafer for a light-emitting diode. After electrodes were mounted on the compound semiconductor epitaxial wafer, the wafer was cut into an appropriate size and packaged, thereby producing an orange light-emitting diode having a central emission wavelength of 629 nm.

(example 2)

By mixing AsH₃And pH₃Each of the layers was introduced for 1 minute, and epitaxial growth was performed on the GaP epitaxial layer to reduce the mixed crystal ratio of GaP by 0.059. Subsequently, the AsH is changed₃And pH₃To lower the temperatureThe mixed crystal ratio of GaP was increased by 0.005 every 25 minutes. The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 3.92 μm, and this was repeated 5 times. An epitaxial wafer for a light-emitting diode was produced under the same conditions as in example 1, except that growth was performed by changing the flow rate further so that the mixed crystal ratio of GaP was decreased by 0.059 in 1 minute, and then the flow rate was changed so that the mixed crystal ratio of GaP was decreased by 0.004 in 25 minutes to form a mixed crystal ratio-changed layer.

(example 3)

By mixing AsH₃And pH₃Each of the layers was introduced for 1 minute, and epitaxial growth was performed on the GaP epitaxial layer to reduce the mixed crystal ratio of GaP by 0.034. Subsequently, the AsH is changed₃And pH₃The temperature was decreased, and the mixed crystal ratio of GaP was increased by 0.005 every 25 minutes. The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 3.92 μm, and this was repeated 10 times. An epitaxial wafer for a light-emitting diode was produced under the same conditions as in example 1, except that the flow rate was changed further to grow the mixed crystal ratio of GaP to be decreased by 0.034 in 1 minute, and then the flow rate was changed to grow the mixed crystal ratio of GaP to be decreased by 0.004 in 25 minutes to form a mixed crystal ratio-changed layer.

(example 4)

By mixing AsH₃And pH₃The mixed crystal ratio of GaP was reduced by 0.021 by conducting epitaxial growth on the GaP epitaxial layer after each introduction for 1 minute. Subsequently, the AsH is changed₃And pH₃The temperature was decreased, and the mixed crystal ratio of GaP was increased by 0.005 in 16 minutes. The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 2.51 μm, and this was repeated 19 times. An epitaxial wafer for a light-emitting diode was produced under the same conditions as in example 1, except that the flow rate was changed further to grow the mixed crystal ratio of GaP to be decreased by 0.021 for 1 minute, and then the flow rate was changed to grow the mixed crystal ratio of GaP to be decreased by 0.004 for 16 minutes to form a mixed crystal ratio-changed layer.

Comparative example 1

By mixing AsH₃And pH₃Each of the layers was introduced for 1 minute, and epitaxial growth was performed on the GaP epitaxial layer to reduce the mixed crystal ratio of GaP by 0.112. Subsequently, the AsH is changed₃And pH₃The temperature was decreased, and the mixed crystal ratio of GaP was increased by 0.005 every 25 minutes. The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 3.92 μm, and this was repeated 2 times. An epitaxial wafer for a light-emitting diode was produced under the same conditions as in example 1, except that the flow rate was changed further to grow the mixed crystal ratio of GaP to be decreased by 0.112 in 1 minute, and then the flow rate was changed to grow the mixed crystal ratio of GaP to be decreased by 0.004 in 25 minutes to form a mixed crystal ratio-changed layer.

Comparative example 2

By mixing AsH₃And pH₃Each of the layers was introduced for 1 minute, and epitaxial growth was performed on the GaP epitaxial layer to reduce the mixed crystal ratio of GaP by 0.059. Subsequently, the AsH is changed₃And pH₃The temperature was decreased, and the mixed crystal ratio of GaP was increased by 0.005 every 12 minutes. The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 1.88 μm, and this was repeated 5 times. An epitaxial wafer for a light-emitting diode was produced under the same conditions as in example 1, except that growth was performed by changing the flow rate further so that the mixed crystal ratio of GaP was decreased by 0.059 in 1 minute, and then the flow rate was changed so that the mixed crystal ratio of GaP was decreased by 0.004 in 12 minutes to form a mixed crystal ratio-changed layer.

Comparative example 3

By mixing AsH₃And pH₃Each of the layers was introduced for 1 minute, and epitaxial growth was performed on the GaP epitaxial layer to reduce the mixed crystal ratio of GaP by 0.069. Subsequently, the AsH is changed₃And pH₃The temperature was decreased, and the mixed crystal ratio of GaP was increased by 0.005 every 12 minutes. The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 1.88 μm, and this was repeated 4 times. Except that the growth was carried out by further changing the flow rate so that the mixed crystal ratio of GaP was reduced by 0.069 in 1 minute, and then the flow rate was changed so that the mixed crystal ratio of GaP was reduced by 12 minutesAn epitaxial wafer for a light-emitting diode was produced under the same conditions as in example 1 except that the mixed crystal ratio changing layer was grown so as to form 0.004.

Comparative example 4

By mixing AsH₃And pH₃Each of the layers was introduced for 1 minute, and epitaxial growth was performed on the GaP epitaxial layer to reduce the mixed crystal ratio of GaP by 0.034. Subsequently, the AsH is changed₃And pH₃The temperature was decreased, and the mixed crystal ratio of GaP was increased by 0.005 every 6 minutes. The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 0.94 μm, and this was repeated 10 times. An epitaxial wafer for a light-emitting diode was produced under the same conditions as in example 1, except that the flow rate was changed further to grow the mixed crystal ratio of GaP to be decreased by 0.034 in 1 minute, and then the flow rate was changed to grow the mixed crystal ratio of GaP to be decreased by 0.004 in 6 minutes to form a mixed crystal ratio-changed layer.

Comparative example 5

By mixing AsH₃And pH₃Each of the layers was introduced for 1 minute, and epitaxial growth was performed on the GaP epitaxial layer, thereby decreasing the mixed crystal ratio of GaP by 0.02. Subsequently, the AsH is changed₃And pH₃The temperature was decreased, and the mixed crystal ratio of GaP was increased by 0.005 in 16 minutes. The thickness of the epitaxial layer (thickness of 1 step) obtained by the decrease and increase of the mixed crystal ratio was 2.51 μm, and this was repeated 21 times. An epitaxial wafer for a light-emitting diode was produced under the same conditions as in example 1, except that the flow rate was changed further to grow the mixed crystal ratio of GaP to be decreased by 0.02 in 1 minute, and then the flow rate was changed to grow the mixed crystal ratio of GaP to be decreased by 0.004 in 16 minutes to form a mixed crystal ratio-changed layer.

Table 1 shows a comparison of the mixed crystal ratio change layers of the compound semiconductor epitaxial wafers of examples 1 to 4 and comparative examples 1 to 5. In addition, the GL thickness (μm) of table 1 is defined as follows.

Thickness of 1 step x total number of steps GL

Fig. 3 shows the results of comparing the luminance of the light emitting diodes of examples 1 to 4 and comparative examples 1 to 5.

[ Table 1]

	Example 1	Example 2	Example 3	Example 4	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4	Comparative example 5
										Thickness of 1 step [ mu ] m]	2.51	3.92	3.92	2.51	3.92	1.88	1.88	0.94	2.51
Total number of steps	10	5	10	|19	2	5	4	10	21
										GL thickness [ mu ] m]	25.1	19.6	39.2	47.7	7.84	9.40	7.53	9.40	52.7
Luminance [ mcd ]]	5.17	5.05	5.27	5.33	4.72	4.67	4.55	3.11	5.33
										Cost of	O	O	O	O	O	O	O	O	×

As can be seen from table 1 and fig. 3: in comparative examples 1 to 4, the luminance was lower than 5mcd, and the luminance was reduced. In addition, although the brightness of comparative example 5 was about the same as that of example 4, the material cost was higher than that of example because the mixed crystal ratio changing layer was thick.

On the other hand, it is found that in examples 1 to 4, which are examples of the compound semiconductor epitaxial wafer of the present invention, the luminance was 5mcd or more, which is higher than that in comparative examples 1 to 4. Therefore, it is found that the compound semiconductor epitaxial wafer of the present invention is a compound semiconductor epitaxial wafer having improved crystallinity and improved luminance at low cost, and that such a compound semiconductor epitaxial wafer can be produced.

In addition, although the present examples and comparative examples were performed using GaP as the substrate, the same effect is exhibited when P of the mixed crystal ratio changing layer is changed by using GaAs as the substrate.

The present invention is not limited to the above embodiments. The above embodiments are merely exemplary, and any embodiments having substantially the same configuration and having substantially the same effects as the technical idea described in the claims of the present invention are included in the scope of the present invention.