JP2000216101A - Crystal growth method of compound semiconductor mixed crystal and compound semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compound semiconductor mixed crystal which is enhanced in crystal quality preventing the coaggulation of component elements, fluctuation in composition, and phase separation from occurring owing to nonmiscibility by a method wherein the growth of a compound semiconductor mixed crystal possessed of a nonmiscible region composition in a thermal equilibrium state is interrupted, and a compound semiconductor layer which is of the same component elements and possessed of a miscible region composition is grown. SOLUTION: In a process where a compound semiconductor mixed crystal 3a possessed of nonmiscible region composition in a thermal equilibrium state is grown, the growth of the compound semiconductor mixed crystal 3a is interrupted, and a compound semiconductor thin film 3b which is of the same component elements with the compound semiconductor mixed crystal 3a and possessed of a miscible region composition in a thermal equilibrium state is grown. The growth of the compound semiconductor mixed crystal 3a is interrupted, by which coaggulation of component elements, fluctuation in composition, and phase separation are prevented from occurring due to nonmiscibility. The compound semiconductor thin film 3b is inserted, by which the grown compound semiconductor mixed crystal 3a is restrained from affecting the compound semiconductor mixed crystal 3a that is successively grown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a compound semiconductor mixed crystal, and more particularly to a method for growing a compound semiconductor mixed crystal having a composition in an immiscible region in a thermal equilibrium state, and a compound semiconductor grown by the method. The present invention relates to a compound semiconductor device comprising a mixed crystal.

[0002]

2. Description of the Related Art Conventionally, a group III-V or II-V
The compound semiconductor mixed crystal of Group I, especially the compound semiconductor mixed crystal of quaternary or more, can control the band gap and the lattice constant independently by appropriately selecting the composition, and operates in an arbitrary wavelength range. It is highly useful as a material for opto-electro devices. However, some materials have an immiscible region over a wide range of the mixed crystal composition, so that there is a problem that high quality crystals suitable for practical use cannot be obtained.

For example, as Group V elements, N and V
III-V compound semiconductor mixed crystal containing a group III element at the same time,
Since the nitrogen composition dependence of the band gap has a large bowing, N-free III-V group compound semiconductors have N
Is characterized by the fact that the band gap is reduced together with the lattice constant. Thereby, GaAs
(Or GaP) is expected to be an optoelectronic material that is lattice-matched to a substrate and operates in a longer wavelength range than before, but the ionic radii of N and Group V elements other than N are significantly different, and immiscibility is low. At present, high-quality crystals cannot be obtained due to increased immiscibility with an increase in the N composition, and the present situation is that the application to practical optoelectronic devices has not been achieved.

In particular, a GaInNAs-based semiconductor has a lattice matching composition with GaAs of 1.3 μm, 1.5 μm, and 1.5 μm.
AlGaAs having a band gap applicable as an active layer of a 5 μm band optical fiber communication laser.
Since a large conduction band band offset can be obtained by combining with an InGaP-based or InGaP-based semiconductor, it is expected to be a material for realizing a communication semiconductor laser with significantly improved temperature characteristics as compared with the conventional one (for example, applied physics). 65 (1996) 148).

A semiconductor laser using the GaInNAs layer as an active layer is disclosed, for example, in Japanese Journal Applied
Physics 37 (1998) p. 1380 or IEEE Photonics Tec
hnology Letters 10 (1998) N
It is manufactured by using a gas source molecular beam epitaxy (GSMBE) method using a radical as an N material, and has a thickness of 1.3 μm.
Room-temperature continuous oscillation in the oscillation wavelength range up to m has been confirmed.

However, the oscillation threshold value is about 24 mA at an oscillation wavelength of 1.2 μm, but shows a high value of 108 mA at an oscillation wavelength of 1.3 μm with a larger N composition. As the N composition increases, it becomes difficult to obtain high quality crystals.

As another example, Electronics Letters 33
(1997) p. 1386, metalorganic vapor phase epitaxy (MOVP) using dimethylhydrazine as N raw material.
A semiconductor laser having a GaInNAs layer as an active layer was manufactured by the method E), and pulse oscillation at room temperature was confirmed at an oscillation wavelength of 1.3 μm. However, the oscillation threshold value was similarly as high as 2.3 A, and the GaInNAs layer was observed. Is low in crystallinity. As described above, in order to obtain a high-quality crystal of GaInNAs having an immiscible region composition, as a growth method, a growth method capable of low-temperature growth without being in a thermal equilibrium state, such as the MBE method or the MOVPE method, is used. ,
In a region where the N composition is small and relatively immiscible, relatively high quality crystals are obtained. However, when the N composition is increased and the immiscibility is increased, it is difficult to obtain high quality crystals. There was a problem.

[0008]

As described above, MBE,
Even when a growth method capable of low-temperature growth that is not in a thermal equilibrium state, such as the MOVPE method, is used, the crystal growth of a compound semiconductor mixed crystal having a composition of an immiscible region in the thermal equilibrium state is caused by its immiscibility. There was a problem that high quality crystals could not be obtained.

Further, since high quality crystals cannot be obtained,
The compound semiconductor device using such a compound semiconductor mixed crystal has a problem that sufficient element characteristics cannot be obtained.

[0010] Conventionally, as a method for obtaining such a high-quality compound semiconductor mixed crystal having immiscibility, Japanese Patent Application Laid-Open No. Hei 7-263744 discloses a III-V group containing N and a V group other than N. As a method of growing a compound semiconductor mixed crystal, a first monoatomic layer in which group III atoms as its constituent elements and a group V atom other than N are laminated one by one, and a group III atom and N atom in one atomic layer According to a method of growing a compound semiconductor mixed crystal having a desired composition in a pseudo manner by using a superlattice in which a second monoatomic layer is laminated (prior art 1), or a method disclosed in JP-A-63-179513, A method of forming a compound semiconductor mixed crystal by forming a binary compound superlattice having substantially the same lattice constant as a compound semiconductor mixed crystal and then disordering the superlattice by heat treatment or ion implantation. (Prior art 2) has been proposed.

However, the prior art 1 is substantially equal to N
III-V compounds containing no N and I in which N is a V element
This is a method of growing a group III-V compound semiconductor mixed crystal containing N having a desired composition by a superlattice structure of a group II-V compound at a monoatomic layer level. Group III-V compounds as Group V elements have lattice constants that are significantly different from each other, and when growing their superlattice structures, crystals such as misfit dislocations caused by lattice mismatch at the hetero-growth interface. Defects are easy to occur,
There is a problem that it is difficult to obtain a high quality crystal.

Further, the prior art 2 grows a superlattice structure of a binary compound having substantially equal lattice constants,
Although the problem of generation of crystal defects due to lattice mismatch as in the prior art 1 does not occur, its application range is limited to a compound semiconductor mixed crystal material in which a binary compound composed of constituent elements can have substantially the same lattice constant. In addition, there is a problem that the composition of the obtained compound semiconductor mixed crystal is limited to the composition obtained by changing the mixing ratio of the binary compound (layer thickness ratio of the superlattice).

For example, a group III-V compound semiconductor containing N and a group V other than N, such as GaInNAs, is a binary compound (GaAs (lattice constant 0.565
3 nm), InAs (0.6058 nm), GaN
(0.45 nm) and InN (0.495 nm) have significantly different lattice constants, and there is no suitable combination of binary compounds to which the prior art 2 can be applied. Also,
InGaAsSb is a binary compound (I
nAs (lattice constant 0.6058 nm) and GaSb (0.6094 nm) have substantially the same lattice constant,
The composition range that can be produced by the superlattice is InGaAs.
The region is limited to a very limited region where the In / Ga composition ratio and the As / Sb composition ratio of the Sb mixed crystal are equal.

The problems of the prior arts 1 and 2 are attributable to the fact that a compound semiconductor mixed crystal formed as a mixture of binary compound semiconductors having greatly different lattice constants exhibits immiscibility. It can be said that this is an essential problem due to the characteristics of the immiscible compound semiconductor mixed crystal. Further, this problem is caused by the fact that, in a III-V compound semiconductor containing N and a V group other than N, a III-V compound containing no N and a III-V compound containing N as a V element are largely different from each other. This is more pronounced because they have different lattice constants.

Further, the prior art 1 includes a step of growing a superlattice structure composed of a monoatomic layer,
All of these include complicated steps, such as a step of disordering the superlattice structure composed of the original compound, and have the problem of low productivity.

The present invention has been made to solve the above problems.

[0017]

A first aspect of the present invention is a method for growing a compound semiconductor mixed crystal having a composition of an immiscible region in a thermal equilibrium state. By interrupting the crystal growth of the compound semiconductor mixed crystal, comprising the constituent elements of the compound semiconductor mixed crystal, having a composition of the mixing region in a thermal equilibrium state, by comprising a step of crystal growth of a compound semiconductor thin film,
The above object is achieved.

According to the first aspect of the present invention, the compound semiconductor mixed crystal having the composition of the immiscible region is interrupted during the step of growing the compound semiconductor mixed crystal having the composition of the immiscible region in the thermal equilibrium state. Aggregation of constituent elements, fluctuation of composition, phase separation, etc. due to its immiscibility, or reduction in surface flatness due to them, or suspension of growth at a stage where crystal defect growth can be recovered. Can be.

Further, during the interruption of the growth of the compound semiconductor mixed crystal layer having the composition of the immiscible region, the compound semiconductor thin film comprising the compound element of the compound semiconductor mixed crystal and having the composition of the mixed region is crystal-grown. In addition to recovering the crystallinity and surface flatness of the crystal surface, by coating the surface with a compound semiconductor thin film having the composition of the mixed region, the compound semiconductor that has already grown can be grown when the compound semiconductor mixed crystal layer is subsequently grown. Without being affected by the mixed crystal layer, the aggregation of the constituent elements due to immiscibility, the fluctuation of the composition, the occurrence of phase separation, etc., or the decrease in surface flatness and the growth of crystal defects due to them are again caused. The growth of high quality crystals can be sustained until they occur.

The composition of the compound semiconductor layer may basically have the composition of the miscible region, and an optimum composition may be determined based on the lattice matching with the compound semiconductor mixed crystal or the matching of the hetero interface. You can choose.

By interrupting the growth of the compound semiconductor mixed crystal having the composition of the immiscible region during the crystal growth process and repeating the crystal growth of the compound semiconductor thin film having the composition of the immiscible region during the interruption of the growth, Thus, a high-quality compound semiconductor mixed crystal layer having an arbitrary layer thickness can be obtained.

A second aspect of the present invention is a method for growing a group III-V compound semiconductor mixed crystal containing N and a group V element other than N, wherein the step of growing the compound semiconductor mixed crystal comprises:
Suspending the crystal growth of the compound semiconductor mixed crystal, comprising the constituent elements of the compound semiconductor mixed crystal, not including N, II
The above object is achieved by including the step of growing a crystal of an IV group compound semiconductor thin film.

According to a second aspect of the present invention, during the step of growing a group III-V compound semiconductor mixed crystal containing N and a group V element other than N, the growth is interrupted, so that the N and V
III-V compound semiconductor mixed crystals containing group elements cause agglomeration of constituent elements, composition fluctuations, phase separation, etc., due to their immiscibility, or decrease in surface flatness, crystal defects due to them Growth can be halted at a stage where it can be restored.

Further, II containing N and a group V element other than N
While the growth of the group IV compound semiconductor mixed crystal layer is interrupted, I is composed of the constituent elements of the compound semiconductor mixed crystal and does not include N.
By the step of growing a group II-V compound semiconductor thin film, the crystallinity and surface flatness of the crystal surface can be recovered, and the compound semiconductor mixed crystal can be continuously formed by coating the surface with a compound semiconductor layer containing no N. When the layer is grown, it is not affected by the already grown compound semiconductor mixed crystal layer, but again causes aggregation of constituent elements due to immiscibility, fluctuation of composition, phase separation, or the like. The growth of high quality crystals can be continued until the surface flatness decreases and crystal defects multiply.

Further, the composition of the compound semiconductor layer not containing N may be such that it does not contain N and has the composition of the mixing region.
The optimum composition can be selected based on the lattice matching with the compound semiconductor mixed crystal or the matching at the hetero interface.

The above III containing N and group V elements other than N
Arbitrary layer thickness can be obtained by repeating the step of interrupting the growth during the crystal growth process of the group V compound semiconductor mixed crystal and not including N during the growth interruption, and growing the crystal of the group III-V compound semiconductor thin film. It is possible to obtain a compound semiconductor mixed crystal layer having a high quality.

A third aspect of the present invention relates to a method for growing a group III-V compound semiconductor mixed crystal containing N and a group V element other than N, wherein the step of growing the compound semiconductor mixed crystal comprises:
A step of detecting a change in the surface state of the compound semiconductor mixed crystal and interrupting the crystal growth, and a step of growing a group III-V compound semiconductor thin film made of a constituent element of the compound semiconductor mixed crystal and not containing N. By including, the above-mentioned object is achieved.

According to the third aspect, by observing the change in the surface state of the compound semiconductor mixed crystal, the immiscibility is reduced due to the immiscibility.
Aggregation of constituent elements, fluctuations in composition, occurrence of phase separation, etc., or a decrease in surface flatness due to them, growth of crystal defects are detected, and the growth of the compound semiconductor mixed crystal layer is detected as follows.
The growth can be reliably stopped at a recoverable stage by the step of crystal growing a group III-V compound semiconductor thin film that does not include N.

According to a fourth aspect of the present invention, in the method for growing a compound semiconductor mixed crystal according to any one of the first to third aspects, the compound semiconductor thin film is obtained by selecting two from the raw materials forming the compound semiconductor mixed crystal. By being the original compound, the above object is achieved.

By making the compound semiconductor thin film a binary compound, in the step of growing the crystal of the compound semiconductor thin film, the surface crystallinity can be effectively reduced without causing the composition modulation due to the influence of the underlying compound semiconductor mixed crystal layer. Can be recovered, and the effects of claims 1 to 3 can be obtained more effectively. For example, when the growth is performed by the MBE method, only the shutter of a part of the raw material cell is closed, The growth of the compound semiconductor mixed crystal can be easily interrupted.

According to a fifth aspect of the present invention, there is provided the method of growing a compound semiconductor mixed crystal according to any one of the first to fourth aspects, wherein the compound semiconductor thin film has a layer thickness of two or more molecular layers. Is achieved.

When the thickness of the compound semiconductor thin film is two or more molecular layers, the effects of claims 1 to 4 can be more effectively obtained.

According to a sixth aspect of the present invention, in the method of growing a compound semiconductor mixed crystal according to any one of the third to fifth aspects, the growth is interrupted before phase separation of the compound semiconductor mixed crystal occurs. The goal can be achieved.

By suspending the growth of the compound semiconductor mixed crystal before the occurrence of phase separation, the growth can be continued without lowering the crystallinity of the compound semiconductor mixed crystal. The effects of 3 to 5 can be obtained more effectively.

A seventh aspect of the present invention is a compound semiconductor device comprising at least one compound semiconductor layer made of a compound semiconductor mixed crystal having a composition of an immiscible region in a thermal equilibrium state. The above object is achieved by performing the crystal growth by the compound semiconductor mixed crystal crystal growth method according to any one of the above (1) to (6).

A high-performance compound semiconductor device is obtained by forming a compound semiconductor device using a high-quality compound semiconductor mixed crystal obtained by the method for growing a compound semiconductor mixed crystal according to any one of claims 1 to 6. be able to.

According to a eighth aspect of the present invention, the compound semiconductor device according to the seventh aspect is a light emitting element, wherein at least the light emitting layer is made of a III-V compound semiconductor mixed crystal containing N and a group V element other than N. Thereby, the above object can be achieved.

A compound semiconductor device in which at least the light-emitting layer is made of a III-V compound semiconductor mixed crystal containing N and a group V element other than N, obtained by the method for growing a compound semiconductor mixed crystal according to any one of claims 1 to 7. By configuring a compound semiconductor device using the obtained high-quality compound semiconductor mixed crystal, a high-performance compound semiconductor device can be obtained.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments.

(Embodiment 1) As Embodiment 1 of the present invention, a gas source molecular beam epitaxy (GSM) using N radicals as an N source and a solid material as another material is used.
BE) method, a GaInNAs / well layer having a GaInNAs layer having a lattice matching composition with a GaAs substrate as a well layer.
A case where an AlGaAs single quantum well (SQW) structure is formed will be described.

The GaInNAs / AlGa prepared in FIG.
1 shows the structure of As-SQW. GaAs (100) jus
On a t-substrate (1), a lower cladding layer (2) made of Al _0.3 Ga _0.7 As having a thickness of 1 μm, and a GaIn layer having a thickness of 10 nm.
NAs quantum well layer (3), 0.2 μm thick Al _0.3 G
a Upper cladding layer (4) made of _0.7 As, thickness 0.1
A μm GaAs cap layer (5) is sequentially laminated.

In creating the SQW structure shown in FIG.
Regarding the SMBE raw material, Al, Ga and In were irradiated with a metal raw material using a Knudsen cell to irradiate a molecular beam to the substrate, and with respect to the As raw material, solid As was used and the substrate was irradiated with an As ₂ beam using a cracking cell. As the N radical, N ₂ gas decomposed by RF plasma was used.

Further, regarding the substrate temperature and the raw material molecular beam intensity,
The AlGaAs cladding layers (2, 4) and the GaAs cap layer (5) are set at a substrate temperature of 600 ° C., a growth rate of 1 μm / h, and a beam intensity ratio (V / III ratio) of 2 to 3. Grow. Also, GaInNA
When the s quantum well layer (3) is grown, the substrate temperature is set to 500
° C, and the molecular beam intensity is set so that the growth rate of In, Ga, and As is 1 µm / h and their V / III ratio is 1.5 to 2, and the desired N
An N radical beam whose intensity was set so as to obtain a composition was added. The group III composition was controlled by the In / Ga beam ratio.

The specific preparation procedure will be described below. First, G
Al _0.3 Ga at a substrate temperature of 600 ° C. on an aAs substrate (1)
After growing the lower cladding layer (2) made of _0.7 As,
The substrate temperature was set to 500 ° C., the In composition was 10.4%, and N
A 10 nm-thick GaInNAs quantum well layer (3) having a composition of 3.3% was grown. This GaInNAs quantum well layer (3) has an In composition of 12.5% and an N composition of 4.0.
% Of the GaInNAs layer, the growth was interrupted at the time of stacking 10 molecular layers (ML), a growth layer made of 3ML GaAs was stacked, and further, a 10ML GaInNAs layer was further stacked.
The growth of the s layer and the GaAs layer of 3 ML is repeated in the same manner, and three layers of G having a thickness of 10 ML as shown in FIG.
aInNAs layer (In composition 12.5%, N composition 4.0
%) (3a) was grown as a multilayer structure consisting of two GaAs layers (3b) having a layer thickness of 3ML. GaInN
Since the thickness of the GaAs layer (3b) inserted between the As layers (3a) is as small as 3 ML, the multilayer structure substantially has
GaIn corresponding to 10.4% of n composition and 3.3% of N composition
It can be regarded as a mixed crystal of NAs. Moreover, after setting again 600 ° C. The substrate temperature, on the GaInNAs quantum well layer (3), an upper cladding layer (4) made of Al _0.3 Ga _{0 .7} As, sequentially stacked GaAs cap layer (5), The structure of GaInNAs / AlGaAs-SQW of FIG. 1 was obtained.

The thus grown GaInNAs /
The AlGaAs SQW structure has a wavelength of 1.5 at room temperature.
It showed strong photoluminescence (PL) emission of μm. This PL emission intensity is 2 compared to a sample of the same structure in which a GaInNAs well layer having an In composition of 10.4% and an N composition of 3.3% is continuously grown by GSMBE.
In this embodiment, a GaInNAs mixed crystal of much higher quality than in the prior art was obtained.

(Embodiment 2) Next, as Embodiment 2 of the present invention, the GaInN
The As / AlGaAs-SQW structure is replaced by the GaInNA
The case where the composition of the s quantum well layer (3) is changed is shown, and it is shown that the same effect as in the first embodiment can be obtained even in a GaInNAs mixed crystal having a different N composition.

In this embodiment, the growth conditions of the GSMBE, the thickness of the GaInNAs layer (3a) until the growth is interrupted, and the thickness of the G layer inserted between the GaInNAs layers (3a).
The thickness of the aAs layer (3b) and the total thickness of the quantum well layer including the both are the same as in the first embodiment.
The emission wavelength was adjusted by changing the In composition and the N composition of the As layer (3a).

FIG. 3 shows each SQW created in this way.
The PL emission intensity of the structural sample at room temperature was
This is shown as the dependency on the N composition of the NAs quantum well layer (3). FIG. 3 also shows GaInNAs as a comparative example.
The PL emission intensity of a sample in which the quantum well layer (3) is formed as a continuous growth film having the same composition is also shown.
In the figure, the black circles indicate the results of the sample according to the present embodiment, and the white circles indicate the results of the sample according to the comparative example (in the figure, the third black circle from the right indicates the first embodiment).

As is clear from the figure, in the sample formed by continuous growth, the PL emission sharply decreases as the N composition increases, but in the sample prepared according to the present embodiment, the PL emission intensity due to the increase in the N composition increases. Is much smaller, shows stronger PL emission than a sample prepared by continuous growth, and shows a GaInNAs having a much higher crystal quality than the conventional one by the crystal growth method of the present invention over a wide range of N composition. A mixed crystal was obtained.

(Embodiment 3) As Embodiment 3 of the present invention, similarly to Embodiment 1, the GaInNAs /
The case where the AlGaAs-SQW structure is formed by changing the thickness of the GaAs layer inserted between the GaInNAs layers when growing the GaInNAs quantum well layer (3) will be described.

In this embodiment, the composition of the GaInNAs layer (3a) constituting the GaInNAs quantum well layer (3) and the layer thickness up to the interruption of the growth are the same as those in the first embodiment, and between the GaInNAs layer (3a). The growth was performed by changing the thickness of the GaAs layer (3b) to be inserted. GaAs layer (3
By changing the layer thickness of b), finally obtained Ga
Although the effective layer thickness and composition of the InNAs quantum well layer (3) are slightly changed, a study was made to the extent that the amount of change did not matter.

FIG. 4 shows each SQW created in this way.
The PL emission intensity at room temperature of the structural sample is shown as the dependence on the thickness of the GaAs layer (3b) to be inserted (in the figure, the third sample from the right shows the first embodiment).

In the figure, the result when the layer thickness of the GaAs layer (3b) is 0 indicates the case where the GaInNAs quantum well layer (3) is grown by continuous growth. As shown in the figure, the GaAs layer (3b) has a thickness of 1 ML, and a sufficient effect cannot be obtained. This is because at 1ML, Ga
That the surface of the InNAs layer (3a) cannot be completely covered,
Alternatively, it is considered that this is because the influence of the atomic arrangement of the GaInNAs layer (3a) under the GaAs layer (3b) at the stage when the growth of the GaInNAs layer (3a) is started again. When the thickness of the GaAs layer (3b) is 2 ML or more, even if the underlying GaInNAs layer (3a) has a surface step (step) at the atomic layer level, it can be completely covered. Yes, and 2
The ML GaAs layer (3b) forms the underlying GaInNA
The influence of the atomic arrangement of the s layer (3a) can be completely cut off, and the GaInNAs layer (3
a) can be grown without being affected by the underlying GaInNAs layer (3a).

The thickness of the GaAs layer to be inserted is such that the multilayer structure composed of the finally formed GaInNAs layer and the GaAs layer has substantially the average composition of both.
It is preferable that the thickness be less than or equal to a layer that can be regarded as a mixed crystal of aInNAs. Specifically, the thickness of the GaAs layer to be inserted is preferably about 10 ML.

(Embodiment 4) As Embodiment 3 of the present invention, a GaInNAs mixed layer is formed on a GaAs substrate by GSMBE as in Embodiment 1 while observing the surface state by high-speed electron diffraction (RHEED) during growth. Grow crystals,
The case where the growth of the GaInNAs layer is interrupted and the growth layer made of GaAs is inserted according to the change in the RHEED pattern will be described. In the present embodiment, GaIn
The composition of the NAs layer is In7.
1% and N2.5%.

FIG. 5 shows changes in the half width of the RHEED diffraction spot with the growth of the electron beam incident from the [01-1] direction. The growth of the GaInNAs layer is interrupted, and Ga
In the case of continuous growth without insertion of an As layer, the half-width of the diffraction spot shows a streak-like diffraction pattern in the range of several ML after the start of growth, as shown in FIG.
Although the half width is constant, the half width tends to increase from a growth thickness of about 10 ML, and the diffraction pattern changes in a spot shape. When the growth was further continued, a ring-shaped diffraction pattern indicating the growth of polycrystalline nitride (GaN, InN or InGaN) was obtained at the same time.

On the other hand, when the growth is started and the increase in the half-width of the diffraction spot is detected, the growth is interrupted and G
When the aAs layer was grown, as shown in FIG. 5B, the half-width of the diffraction spot was recovered along with the growth of the GaAs layer. From this state, when the growth of the GaInNAs layer is continued again, the same behavior as when the GaInNAs layer is grown first is exhibited, and the half-value width is the same as when the growth is interrupted and the growth is continued without inserting the GaAs layer. And no change in the diffraction pattern from a streak shape to a spot shape was observed.

On the other hand, the growth of the GaInNAs layer
If the HEED pattern is not interrupted until it becomes a spot-like stage, as shown in FIG. 5C, by increasing the thickness of the GaAs layer, the half width of the diffraction spot can be recovered.
Alternatively, no recovery of the diffraction pattern to a streak state was observed, and no good crystal was obtained.

As described above, while monitoring the crystal state of the surface of the GaInNAs growth layer, the growth is interrupted before the deterioration of the crystal due to the immiscibility occurs, and the GaAs layer, which is a stable binary compound, is inserted. As a result, a higher quality GaInNAs layer could be grown as compared with continuous growth.

The layer thickness at which crystal degradation due to immiscibility occurs depends on the growth conditions, the mixed crystal composition of GaInNAs, and the like. A method of judging the timing and inserting a recovery layer having an appropriate thickness is effective for effectively implementing the crystal growth method of the present invention.

In this embodiment, RHEED is used as a means for observing the crystal state of the growth surface, but the surface state may be observed by a surface light absorption method or a dynamic ellipsometry method. This method can also be used for growth by MOVPE method, which cannot perform RHEED observation due to high growth pressure.

(Embodiment 5) As Embodiment 5 of the present invention, GaI is obtained by the same GSMBE method as in Embodiment 1.
An example in which a semiconductor laser using nNAs-SQW as an active layer is manufactured will be described.

In FIG. 6, such GaInNAs
A semiconductor laser having an active layer having a -SQW structure is shown in a schematic sectional view. In this semiconductor laser, an n-type GaAs (100) substrate (1) is
0.5 μm thick buffer layer (6) made of As, n
1 μm thick n-type cladding layer (7) made of type Al _0.3 Ga _0.7 As, 0.15 μm thick n-type guiding layer (8) made of n-type GaAs, undoped Ga _0.929 In _0.071 N
SQW layer (9) made of _0.025 As _0.975 , p-type GaAs
A p-type guide layer (10) having a thickness of 0.15 μm and
0.5 μm thick p-type cladding layer (11) made of type Al _0.3 Ga _0.7 As, 0.1 μm thick made of p-type GaAs
m contact layers (12) were sequentially grown by GSMBE. In growing each layer, the same conditions as in the first embodiment were used for the substrate temperature and the molecular beam intensity.

After the respective semiconductor layers are grown in this manner, a part of the p-type Al _0.3 Ga _0.7 As clad layer (11) and a part of the p-type GaAs contact layer (12) are formed into a mesa stripe by wet etching. After etching and removal, an insulating layer (13) made of polyimide was formed so as to be embedded in the etched and removed portions of the p-type cladding layer (11) and the p-type contact layer (12). further,
An upper electrode (14) and a lower electrode (15) were formed to produce a ridge stripe type semiconductor laser.

This semiconductor laser has a λ / 2−
With the HR (90%) coating, continuous oscillation at room temperature was confirmed at an oscillation wavelength of 1.3 μm, and the oscillation threshold was 15 mA and the efficiency was 0.35 W / A. Also,
The characteristic temperature in the range from room temperature to 85 ° C. was 170K. Further, a reliability test was performed by driving the device at 85 ° C. and 10 mW. As a result, a life of 10,000 hours or more (a time when the drive current increases by 20% from the initial current)
Was confirmed.

As described above, by using the growth method according to the present invention, a high-performance semiconductor laser for optical communication having a high characteristic temperature, a low oscillation threshold, and high reliability was obtained.

In the above-described Embodiments 1 to 5, in growing GaInNAs, the GSMBE method using N radicals as an N source, or another crystal growth method, for example, an N source such as NH ₃ or a hydrazine-based compound may be used. The GSMBE method using a compound gas as a raw material may be used.
Needless to say, the same effect can be obtained by using the MOVPE method.

In the above embodiment, the GaAs
The growth of the layer was based on the method of alternately supplying and growing a Ga beam and an As beam. However, when a GaInNAs layer having a desired thickness was grown, supply of In and N radicals was stopped, and
By performing aGaAs growth and controlling the GaAs growth time, it is also possible to insert a GaAs layer having a desired thickness during the growth of GaInNAs. However, from the viewpoint of securing the flatness of the growth surface and strictly controlling the layer thickness, the growth by the alternate supply method is preferable.

In the above-described Embodiments 1 to 5, as a material of the compound semiconductor layer inserted between the GaInNAs layers, a compound composed of the constituent elements of the GaInNAs layer maintains the consistency of the heterointerface and has a pseudo-structure. Ga
It is preferable in obtaining an InNAs mixed crystal, and specifically, Ga
Binary compounds such as As and InAs, or InGaAs having a miscible region composition are preferred. Among them, GaAs, InAs, etc.
Since the original compound has a single composition, the surface crystallinity can be effectively recovered at the hetero-growth interface on the GaInNAs layer without being affected by the influence of the underlayer. In addition, when InGaAs is used, the growth of the GaInNAs layer can be interrupted and the growth of the InGaAs layer can be repeated only by controlling the supply of N.
The growth process can be simplified. Also, In
Has a high surface diffusion rate, and can effectively flatten the surface step generated on the GaInNAs growth surface.

(Embodiment 6) As Embodiment 6 of the present invention, AlGa is formed by the GSMBE method using NH ₃ as an N source.
An example of manufacturing a semiconductor laser using InNAs-SQW as an active layer will be described.

The semiconductor laser manufactured in this embodiment is the same as the semiconductor laser shown in FIG. 6 manufactured in Embodiment 5, except that the SQW quantum well layer (9) has a compression strain of 2% Al _0.10 Ga _0.58 In _0.32 N _0.019. As _0.981 −
Similar structure except that it is formed from SQW, the composition of the guide layers (8, 10) is Al _0.15 Ga _0.85 As, and the composition of the cladding layers (7, 11) is Al _0.40 Ga _0.60 As. Consists of

In the GSMBE method used in the present embodiment, NH ₃ was used as an N source, and all other raw materials were solid raw materials. The growth conditions of the GaAs and AlGaAs layers are the same as those of the first embodiment. In the growth of AlGaInNAs, the substrate temperature is set to 600 ° C., the growth rate is set to 0.5 μm / h, and the NH _{3 is} grown.
The V / III ratio of the raw material beam except for the above was adjusted to 2-3, and the NH ₃ gas beam intensity was adjusted so as to obtain a desired N composition.

In this embodiment, Al added to the quantum well layer is for improving the decomposition efficiency of the growth surface of the NH ₃ source beam, and by adding 10% of Al as a group III composition, It becomes possible to improve the amount of N taken in by 1000 times or more as compared with the case where Al is not added.

Under the above GSMBE growth conditions, AlGa
After growing the InNAs layer, the growth of the AlGaInNAs layer is interrupted before crystal deterioration due to immiscibility occurs, and further, the crystallinity and surface flatness are restored, and the AlGaInNAs layer is recovered.
The growth of the AlGaAs layer for covering the layer surface was repeated to grow an AlGaInNAs quantum well layer having a multilayer structure of the AlGaInNAs layer and the AlGaAs layer. AlGa constituting AlGaInNAs quantum well layer
The composition, thickness and number of layers of the InNAs layer and the AlGaAs layer are Al _0.09 Ga _0.52 In _0.39 N _0.023 As, respectively.
_0.977 , 7ML, 4 layers, Al _0.15 Ga _0.85 As, 2M
By forming three layers, Al _0.10 Ga _0.58 In _0.32 N _0.019 As having a layer thickness of 9.6 nm corresponding to an oscillation wavelength of 1.3 μm.
_{A 0.981} quantum well layer was obtained.

The final fabrication of the semiconductor laser device was performed in the same manner as in the fifth embodiment. As a result, the λ / 2-H
With the R (90%) coating applied, continuous oscillation at room temperature was observed at an oscillation wavelength of 1.3 μm. The oscillation threshold was 13 mA, and the efficiency was 0.40 W / A. Also,
The characteristic temperature in the range from room temperature to 85 ° C. was 170K. Further, a reliability test was performed by driving the device at 85 ° C. and 10 mW. As a result, a life of 10,000 hours or more (a time when the drive current increases by 20% from the initial current)
Was confirmed.

As described above, by using the growth method according to the present invention, a semiconductor laser using AlGaInNAs, which is one of the group III-V compound semiconductors containing N and V other than N, as a quantum well layer was manufactured. Also in this case, a high-performance semiconductor laser for optical communication having a high characteristic temperature, a low oscillation threshold, and high reliability could be obtained.

(Embodiment 7) As Embodiment 7 of the present invention, a ZnSTe mixed crystal prepared by using the compound semiconductor mixed crystal growing method of the present invention is applied to a current blocking layer.
An example in which an I-VI compound semiconductor blue laser is manufactured will be described.

The ZnSTe mixed crystal prepared in this embodiment is
When the S composition is 65%, lattice matching is possible with GaAs, and the band gap is smaller than that of ZnSe. Therefore, the S composition is suitable as a current blocking layer when producing a loss guide structure laser using ZnSe as an active layer. Although it is a material, the composition of an immiscible region under normal crystal growth conditions reflects a large difference in the bonding radius between S and Te, and there is a problem that it is difficult to obtain a high-quality crystal.

FIG. 7 is a schematic sectional view of a II-VI group semiconductor laser using a ZnSTe layer as a current blocking layer. In this semiconductor laser, n-type GaAs
(100) A 0.1 μm thick buffer layer (16) made of n-type ZnSe on a substrate (1), n-type ZnM having a band gap of 3.1 eV and a GaAs lattice matching composition
1.5 μm-thick n-type cladding layer (1
7), a thickness of 0.15 μ made of n-type ZnS _0.07 Se _0.93
m n-type guide layer (18), SQW layer (19) made of undoped ZnSe with a thickness of 8.0 nm, p-type ZnS _0.07
0.15 μm thick p-type guide layer made of Se _0.93 (2
0), a thickness of 1.0 μm made of p-type ZnMgSSe having a band gap of 3.1 eV and a GaAs lattice matching composition
m p-type cladding layer (21), p-type ZnSe / ZnTe
0.2 μm thick contact layer made of a multilayer film (22)
Were sequentially grown by the MBE method.

After the respective semiconductor layers are grown in this manner, a stripe-shaped dielectric layer is formed on the p-type ZnSe / ZnTe multilayer contact layer (22), and the dielectric layer is used as a mask. A part of the p-type ZnMgSSe cladding layer (21) and a part of the p-type ZnSe / ZnTe multilayer film contact layer (22) were removed by wet etching to form a mesa stripe structure. In addition, MOMB
According to the E method, a current blocking layer (2
3) is replaced with a p-type cladding layer (21) and a p-type contact layer (2).
It was formed so as to be embedded in the portion removed by etching in 2). In forming this ZnSTe current block layer (23), after growing a ZnSSe layer having an S composition of 65% by 0.1 μm, the growth is interrupted and the ZnSe layer is reduced to 0.01 μm.
The step of growing was repeated. After the formation of the current blocking layer, the aforementioned dielectric mask is removed, and the upper electrode (1) is removed.
4) A lower electrode (15) was formed to produce a ridge stripe type semiconductor laser.

The II-VI semiconductor laser fabricated in this manner enables the formation of a current blocking layer made of high-quality ZnSTe with a uniform, low defect density and an oscillation wavelength of 4 nm.
A high performance blue semiconductor laser of 60 nm was obtained.

(Embodiment 8) As Embodiment 8 of the present invention, GaAs formed using the crystal growth method of the present invention is used.
Ga operating at an oscillation wavelength of 1.3 μm using Sb as an active layer
An example in which a surface-emitting laser formed on an As substrate is manufactured will be described.

FIG. 8 is a schematic sectional view showing a surface emitting semiconductor laser having such a GaAsSb active layer.

This surface emitting laser is made of n-type GaAs (10
0) n-type semiconductor multilayer mirror (24) on substrate (1),
n-type Al _0.2 Ga _0.8 As clad layer (25), GaAs
Sb / GaAs strained quantum well active layer (26), p-type Al
_{A 0.2} Ga _0.8 As cladding layer (27) and a p-type GaAs contact layer (28) are sequentially formed by a molecular beam epitaxy (MBE) method using a solid source of each constituent element as a molecular beam source. Further, a p-type GaAs contact layer (2
8) On top, a multilayer mirror (29) made of amorphous Si and SiO ₂ is formed by electron beam evaporation. The multilayer film reflecting mirror (29) is removed by dry etching leaving a central portion in a cylindrical shape. In the vicinity of the active layer, a high resistance region (30) for current confinement is formed by irradiating a portion where the multilayer mirror (29) is not formed with protons. Also, n-type GaAs
On the back surface of the substrate (1), a lower electrode (14) is provided as a positive electrode,
p-type GaAs contact layer (28) multilayer reflector (2
An upper electrode (15) is formed as a negative electrode in a portion where 9) is not laminated.

In fabricating this surface emitting laser, MBE
The growth conditions were set such that the growth temperature of each layer was 600 ° C., and the molecular beam ratio was 2 such that the V / III ratio excluding Sb was 2.
The Sb composition in GaAsSb was controlled by the intensity of the Sb beam added to the Ga and As beams. Among the layers formed by MBE, the n-type semiconductor multilayer mirror (24) has a layer thickness of n-type GaAs corresponding to １ ／ optical distance of the oscillation wavelength.
It was formed of a multilayer film of s and n-type AlAs. The active layer portion is 2.5% sandwiched between GaAs barrier layers having a thickness of 10 nm.
GaAs _0.68 Sb _0.32 with a thickness of 8 nm having a compressive strain of
It comprises a GaAsSb / GaAs strained quantum well active layer (26) composed of a well layer. Active layer part thickness 8
The GaAs _0.68 Sb _0.32 well layers nm, GaAs _0.65 S
b After growing the _0.35 layer by 13 ML, the growth was interrupted and 2 ML
After growing a GaAs layer of 13 ML,
An s _0.65 Sb _0.35 layer was grown and formed by the crystal growth method of the present invention.

The upper multilayer reflector (29) is １ ／ of the oscillation wavelength like the n-type semiconductor multilayer reflector (24).
Amorphous Si and SiO ₂ with a layer thickness corresponding to the optical distance
Formed by the multilayer film.

In the surface emitting laser using GaAsSb as an active layer manufactured as described above, GaAsSb of high quality was obtained by the crystal growth method of the present invention, and a GaAsSb quantum well layer was manufactured by a conventional growth method. As compared with the case of performing the above, the oscillation threshold value is reduced, the efficiency is improved, and the element life is improved.

In the present embodiment, GaAs is contained in the GaAsSb layer.
Although a GaAsSb layer having a desired composition is grown by inserting the s layer, the composition of the heterointerface between the GaAsSb layer and the GaAs layer can be changed stepwise. G which grew
Since there is a lattice mismatch of 2.5% between aAsSb and GaAs, it is more preferable to change the hetero interface stepwise so as to alleviate the influence of lattice distortion at the hetero interface.

Embodiments 1 to 8 show examples of growing compound semiconductor mixed crystals having compositions in immiscible regions or manufacturing compound semiconductor devices containing these compound semiconductor mixed crystals according to the present invention. . As their immiscible compound semiconductor mixed crystals, as compound semiconductors containing N and a V group other than N, GaInNAs or AlGaIn
Examples of growth of NAs have been described, but GaInNP, GaInN
The crystal growth method of the present invention can be similarly applied to a mixed crystal of a III-V compound semiconductor containing P or Sb as a group V element other than N, such as Sb. Other III-V compound semiconductor mixed crystals or II-VI
GaAsSb or ZnS as mixed crystal of group III compound semiconductor
Although the growth example of Te is shown, the compound semiconductor mixed crystal having the composition in the immiscible region is not limited to these growth examples.
It goes without saying that the crystal growth method of the present invention can be similarly applied.

Note that the crystal growth method of the present invention uses the MBE
It is needless to say that the present invention can be applied to any case by using a crystal growth technique suitable for crystal growth of a compound semiconductor, such as the GSMBE method, the GSMBE method, and the MOVPE method.

[0091]

As described above, according to the present invention, the growth of a compound semiconductor mixed crystal having a composition of an immiscible region in a thermal equilibrium state is interrupted in accordance with the growing crystal state. By inserting a compound semiconductor layer having a composition of a miscible region consisting of the constituent elements described above, during the growth of the compound semiconductor mixed crystal, agglomeration of constituent elements due to immiscibility, fluctuation of the composition, phase separation, etc. Occurs or
It is possible to suppress the decrease in surface flatness and the growth of crystal defects due to these, and it is possible to obtain high-quality crystals. Furthermore, a compound semiconductor device using a compound semiconductor mixed crystal grown by this crystal growth method makes it possible to create a high-performance optoelectronic device.

[Brief description of the drawings]

FIG. 1 is a diagram showing Ga prepared in Embodiment 1 of the present invention.
It is sectional drawing which shows the structure of an InNAs / AlGaAs-SQW sample.

FIG. 2 is a view showing Ga formed in Embodiment 1 according to the present invention;
It is sectional drawing which shows the structure of the quantum well part of an InNAs / AlGaAs-SQW sample.

FIG. 3 is a view showing Ga formed in Embodiment 2 according to the present invention.
It is a figure which shows N concentration dependence of PL luminescence intensity of InNAs / AlGaAs-SQW sample.

FIG. 4 is a view showing Ga prepared in Embodiment 3 of the present invention.
FIG. 4 is a diagram showing the dependence of the PL emission intensity of the InNAs / AlGaAs-SQW sample on the thickness of the GaAs layer inserted in the GaInNAs layer.

FIG. 5 shows Ga grown in Embodiment 4 according to the present invention.
FIG. 7 is a diagram illustrating a change in RHEED half-width during growth of an InNAs film.

FIG. 6 is a cross-sectional view illustrating a structure of a semiconductor laser manufactured according to a fifth embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a structure of a semiconductor laser manufactured according to a seventh embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a structure of a surface emitting laser manufactured in Embodiment 8 according to the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 GaAs substrate 2 AlGaAs lower cladding layer 3 GaInNAs-SQW layer 3 a GaInNAs layer 3 b GaAs layer 4 AlGaAs upper cladding layer 5 GaAs cap layer 6 n-type GaAs buffer layer 7 n-type AlGaAs cladding layer 8 n-type GaAsN-GaAs GaAsQ layer Layer 10 p-type GaAs guide layer 11 p-type AlGaAs cladding layer 12 p-type GaAs contact layer 13 insulating layer 14 lower electrode 15 upper electrode 16 n-type ZnSe buffer layer 17 n-type ZnMgSSe cladding layer 18 n-type ZnSSe guide layer 19 ZnSeSQW layer 20 p-type ZnSSe guide layer 21 p-type ZnMgSSe cladding layer 22 p-type ZnSe / ZnTe multilayer structure contact layer 23 ZnSTe current blocking layer 24 n-type semiconductor multilayer mirror 25 n-type Al _0.2 Ga _0.8 As clad layer 26 GaAsSb / GaAs strained quantum well active layer 27 p-type Al _0.2 Ga _0.8 As clad layer 28 p-type GaAs contact layer 29 multilayer mirror 30 high resistance region

Continued on the front page F-term (reference) 5F041 AA40 CA05 CA34 CA35 CA41 CA43 CA66 5F045 AA05 AA16 AB09 AB10 AC12 AC15 AC19 AD09 AD10 AF04 BB08 BB12 CA10 DA53 DA55 DA63 DA65 DA67 5F103 AA04 BB04 BB07 DD05 DD30 GG01 JJ03 LL01 JJ RR01 RR06

Claims (8)

[Claims] 1. A method for growing a compound semiconductor mixed crystal having a composition of an immiscible region in a thermal equilibrium state, wherein the crystal growth of the compound semiconductor mixed crystal is interrupted during the step of growing the compound semiconductor mixed crystal. A method of growing a compound semiconductor thin film, comprising a compound element of the compound semiconductor mixed crystal and having a composition of a mixing region in a thermal equilibrium state. 2. I containing nitrogen (N) and a group V element other than N
A II-V compound semiconductor mixed crystal crystal growth method, wherein during the step of crystal growing the compound semiconductor mixed crystal, the crystal growth of the compound semiconductor mixed crystal is interrupted, and from the constituent elements of the compound semiconductor mixed crystal. And N-free, III-V
A method of growing a compound semiconductor mixed crystal, comprising the step of growing a group III compound semiconductor thin film. 3. III-V containing N and a group V element other than N
A crystal growth method for a group compound semiconductor mixed crystal, wherein during the step of growing the compound semiconductor mixed crystal, a step of detecting a change in the surface state of the compound semiconductor mixed crystal to interrupt the crystal growth; A method for growing a crystal of a compound semiconductor mixed crystal, comprising: a step of growing a group III-V compound semiconductor thin film comprising a constituent element of a semiconductor mixed crystal and containing no N. 4. The compound semiconductor mixed crystal according to claim 1, wherein the compound semiconductor thin film is a binary compound selected from two of the raw materials forming the compound semiconductor mixed crystal. Crystal growth method. 5. The method for growing a compound semiconductor mixed crystal according to claim 1, wherein the compound semiconductor thin film has a layer thickness of two or more molecular layers. 6. The method according to claim 3, wherein the step of interrupting the crystal growth of the compound semiconductor mixed crystal is performed before phase separation of the compound semiconductor mixed crystal occurs. The crystal growth method of the compound semiconductor mixed crystal according to the above. 7. A compound semiconductor device comprising at least one compound semiconductor layer made of a compound semiconductor mixed crystal having a composition of an immiscible region in a thermal equilibrium state, wherein the compound semiconductor layer comprises A compound semiconductor device formed by crystal growth by the compound semiconductor mixed crystal crystal growth method according to any one of the above. 8. The compound semiconductor device according to claim 7, wherein the compound semiconductor device is a light-emitting element, and at least a light-emitting layer is made of a III-V compound semiconductor mixed crystal containing N and a group V element other than N. The compound semiconductor device according to claim 1.