JP3443803B2 - Semiconductor structure and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor structure having a semiconductor carrier confinement layer composed of a strained quantum well having an island structure composed of a plurality of islands, which is a new low-dimensional carrier confinement structure, and a resultant formation thereof. The present invention relates to a semiconductor structure, which can be used for improving device characteristics in the field of semiconductor optoelectronic devices.

[0002]

2. Description of the Related Art In a semiconductor heterostructure, when its size is equal to or smaller than the de Broglie wavelength of carriers (electrons, holes) in a semiconductor crystal, and is several tens of nm or less, an effect different from that of a normal bulk crystal, That is, it is pointed out that the quantum confinement effect can be obtained. As a result, the density of states of carriers becomes 1 in a stepwise manner in a two-dimensional quantum well.
In the one-dimensional quantum wire structure, it is localized like spikes, and in the zero-dimensional quantum box structure, it is completely discrete.

In the bulk-structured semiconductor shown in the perspective view of FIG. 22 (a), the density of states of carriers gradually increases as the energy increases, as shown in FIG. 22 (b). However, in the semiconductor having the quantum well structure shown in the perspective view of FIG.
As shown in FIG. 2 (d), as the energy rises, it rises stepwise, and in the semiconductor having the quantum wire structure shown in the perspective view of FIG.
As shown in (f), as the energy rises, it exists in a spike shape and does not rise uniformly. And FIG.
In the semiconductor having the quantum box structure shown in (g), the density of states of carriers is in a completely localized state, as shown in FIG.

In fact, due to the progress of the crystal growth technique, a good quality thin film as a quantum well or a multi-quantum well structure in which these are stacked is produced, and the emission spectrum having a half-value width narrower than that of a bulk crystal is reflected, reflecting the state density Has been obtained.
Then, peculiar physical properties such as the generation of excitons at room temperature have been observed. Further, by utilizing this peculiar quantum effect, a large improvement in characteristics of semiconductor lasers and useful devices such as semiconductor optical modulators and optical switches have been developed. Due to the useful properties of these quantum well structures, the fabrication of quantum wire structures and quantum box structures in which the density of states is further localized and their physical properties are being actively researched.

As a method of manufacturing a semiconductor low-dimensional structure such as the above-described quantum wires and quantum boxes, a two-dimensional quantum well film is used.
A method of forming a fine pattern by using an electron beam exposure method and processing by an etching method, a method of directly forming a pattern by a focused ion beam, and the like are known. In all of these, semiconductor epitaxial growth is used to control the composition in the thickness direction to form an ultrathin film, and then size control in the in-plane lateral direction is performed by processing such as lithography and etching. Therefore, the dimensions of the lateral structure are
Limited by processing accuracy.

On the other hand, the confinement region of the carrier is
Metal Organic Vapor Deposition (Metal Organic Va
Attempts have also been made to make it by using growth techniques such as por phase epitaxy (MOVPE) and molecular beam epitaxy (MBE). By utilizing the chemical nature of crystal growth to grow a thin film on a substrate crystal that has been subjected to a certain process, a crystal having a stable three-dimensional structure with facets can be produced depending on the growth conditions and growth method.

Here, if two or more kinds of crystals are continuously grown under different conditions, a particular crystal can be confined three-dimensionally by another crystal. The feature of this method is that since the region where the carrier exists is not directly processed, the processing damage and pollution to the region are small. When the growth technique is used, the semiconductor surface is covered in a pattern with an insulating film such as SiO ₂ and a thin wire or box structure is grown in the opening.

In addition, a method of forming a facet on a crystal plane having a V-groove shape and forming a fine line structure at the bottom of the V-groove, and a step formed on a slightly inclined substrate. A method of forming a fine line structure in the vertical direction based on So far, as a quantum box structure aiming at realization of a 0-dimensional electron-hole system, SiO has been used.
GaAs by MOVPE selective growth using ₂ as a mask
A tetrahedral quantum box is being studied by forming an AlGaAs epitaxial film on a (111) B substrate.

[0009]

However, in the structure of these thin wires / boxes, it is necessary to form not only the film thickness direction but also a structure of several tens nm in the plane of the quantum well thin film one-dimensionally or two-dimensionally. Therefore, the quality of the crystal is likely to deteriorate as compared with the quantum well thin film. Therefore, there is a problem that it is difficult to realize a quantum wire / quantum box having optical characteristics equal to or higher than that of a quantum well.

When utilizing selective growth on a semiconductor substrate formed by using SiO ₂ as a selective mask as described above, A
There is a problem that the diffusion length of l is short, and the dependence on the selective mask when growing an AlGaAs epitaxial film is large, and it is difficult to form a fine box. That is, the density of the boxes of the quantum boxes to be manufactured is regulated by the processing of the selective mask, and it is necessary to remove the selective mask when forming a device (semiconductor device), and these are problems. .

Incidentally, for example, GaAs / AlGaAs is formed on a flat GaAs substrate by a semiconductor epitaxial method.
After growing and cleaving the periodic structure of, GaAs / AlGaA is formed on the cleaved (110) plane periodic structure.
There is a method of producing a multilayer quantum wire structure by growing an s structure. This is a high-concentration Al underlayer that is the cleaved surface.
Ga by using a natural oxide film on AlGaAs having a composition
As selective growth of As occurs, the underlying GaAs / AlGaA
It is possible to realize a multi-layer quantum wire structure with a multi-layer structure of GaAs / AlGaAs that reflects the periodic structure of s.
However, in this method, since the cleavage plane of the crystal is used, it is necessary to form an electrode in a narrow region, and there is a problem that it is difficult to manufacture an optical device.

On the other hand, as an example of forming a quantum structure only by vapor phase crystal growth on a semiconductor substrate having no underlying structure, a method of forming InP in an island shape on a GaAs substrate has been reported. Due to the large difference in lattice constant between GaAs and InP, InP is not formed as a film on the GaAs substrate but is formed into islands randomly aggregated. However, according to this method, as described above, there is a large variation in their sizes, and when a film is formed with a high density, InP has defects and a single crystal cannot be obtained due to lattice mismatch, so that it can be formed. There is a problem that the island-shaped InP has a low density and cannot be used as an optical device at a practical use level.

The present invention has been made in order to solve the above problems, and in order to obtain optical characteristics equivalent to or higher than those of a quantum well structure with a structure similar to a quantum box, carrier confinement is performed. The purpose is to enable formation of fine high-density island regions as a layer.

[0014]

The semiconductor structure of the present invention comprises a group III-V compound semiconductor and has a main surface of (n1
1) Substrate with B side (n = 2, 3, 4, 5, 6, 7)
And a semiconductor barrier layer formed on this substrate, and a semiconductor
Formed so as to be surrounded by the barrier layer and has strain
A semi-conductor with an island structure consisting of multiple separated islands
It is characterized by including a body carrier confinement layer and a semiconductor barrier layer formed on the semiconductor carrier confinement layer .

[0015]

The semiconductor structure of the present invention is III-
It is composed of a Group V compound semiconductor and has a main surface of (n11) B plane (n
= 2,3,4,5,6,7), a semiconductor barrier layer formed on the substrate, and a plurality of isolated islands formed so as to be surrounded by the semiconductor barrier layer and having a strain. A semiconductor carrier confinement layer having an island structure made of, a semiconductor barrier layer formed on the semiconductor carrier confinement layer, a semiconductor carrier barrier layer formed on the semiconductor barrier layer, and an optical guide layer. And

[0017]

The semiconductor structure manufacturing method of the present invention uses the vapor phase crystal growth method to form the (n11) B plane (n =
2, 3, 4, 5, 6, 7) as a main surface, a first step of forming a semiconductor barrier layer on a substrate made of a III-V group compound semiconductor, and subsequently a semiconductor by a vapor phase crystal growth method. The second step of forming a strained quantum well layer having a lattice mismatch on the barrier layer, and thereafter, the strained quantum well layer and the semiconductor barrier layer are mass-transported to separate the strained quantum well layer. A third step of suspending growth until a semiconductor carrier confinement layer having an island structure composed of a plurality of islands surrounded by a semiconductor barrier layer is formed, and subsequently, the semiconductor is formed by a vapor phase crystal growth method. A fourth step of forming a semiconductor barrier layer on the carrier confinement layer.

[0019]

(Function) (n11) B surface (n = 2, 3, 4, 5, 6,
Microscopically, the III-V group compound semiconductor having 7) as the main surface has a (100) plane in which smooth epitaxial growth is likely to occur and a (111) B plane in which growth hardly occurs on the V group stabilizing plane. The crystal orientation is configured .

Therefore, when the strained quantum well layer is formed by the vapor phase crystal growth method, the strained quantum well layer is aggregated in an island shape by mass transport to form an island structure composed of a plurality of islands. At the same time, the semiconductor barrier layer formed thereunder also performs mass transport, thereby forming a structure that surrounds the strained quantum well layer that has become an island. Then, these structures show a unique optical property that strong emission having a narrow half-value width, which is not found in the conventional quantum structure, is observed.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, the basic structure relating to the island region will be described with reference to the drawings. Figure 1
It is a perspective view which shows the basic structure of the semiconductor structure which has an island structure . In the figure, 11 is a semiconductor substrate, 12 is a semiconductor barrier layer formed on the semiconductor substrate, 13 is a carrier confinement layer formed so as to be sandwiched between the semiconductor barrier layers 12, and 14 is a carrier confinement layer 13. The strained quantum well thin film, 15 constitutes the carrier confinement layer 13,
It is a fine island whose thickness is relatively thicker than that of the strained quantum well film 14. The semiconductor quantum structure shown in FIG. 1 is a new low-dimensional semiconductor quantum structure in which a two-dimensional quantum well structure and a zero-dimensional quantum box structure coexist, and strong emission with a narrow half-value width not seen in conventional quantum structures. Shows a unique optical property that is observed.

FIG. 2 is a development of the semiconductor quantum structure of FIG. 1, in which a semiconductor barrier layer 22 is formed on a semiconductor substrate 21.
And a carrier confinement layer 23 formed so as to be sandwiched therebetween are shown in a multi-layer (three layers) state. In the state of FIG. 2, three layers of the strained quantum well film 24 and the island 25 that form the carrier confinement layer 23 are alternately formed.

[0023] Figure 1 described above, the structure of FIG. 2 is a basic structure, in order to improve these optical properties, usually in an appropriate buffer layer or different barrier layers used at the time quantum well film making, or cap Layers may be added. Although these are not essential to the structure of the present invention, they are important for the development of good optical properties, which is a remarkable effect of the present invention.

[0024] The inventors have studied so far, above
The semiconductor quantum well structure described above is realized by a combination of a specific semiconductor substrate, a semiconductor barrier layer, and a semiconductor carrier confinement layer. GaA whose main surface is the (n11) B plane (where n = 2, 3, 4, 5, 6, 7)
If a compound semiconductor made of III-V group such as s or InP is used as the substrate, good characteristics are exhibited. In the substrate composed of these compound semiconductors, the (n11) B plane is (100) plane where smooth epitaxial growth is likely to occur microscopically, and the (111) B plane where growth is extremely unlikely to occur on the V group stabilizing plane such as As. , The vapor-phase crystal growth on this surface shows a peculiar aspect.

For example, in the case of a GaAs (n11) B substrate, the semiconductor carrier confinement layer is strained In _z Ga _{1 -z} A.
When the semiconductor barrier layer is Al _y Ga _1-y As in s, or the semiconductor carrier confinement layer is strained GaAs _z Sb _1-z and the semiconductor barrier layer is Al _y Ga _1-y As, the above-mentioned peculiar aspect is confirmed. It was Also, for example, in the case of an InP (n11) B substrate, the semiconductor carrier confinement layer is strained In _z G
a _1-z As and the semiconductor barrier layer is In _x Al _y Ga _1-xy A
s, or the semiconductor carrier confinement layer is strained In _x G
a _1-x As _z Sb _1-z and the semiconductor barrier layer is In _y Al _1-y A
When s, a peculiar aspect was similarly confirmed.

FIG. 3 is a sectional view showing a method of manufacturing the above-mentioned semiconductor quantum structure. The following describes the basic method of manufacturing a semi-conductor quantum structure of this. First, as shown in FIG. 3A, as described above, the semiconductor buffer layer 32, the semiconductor barrier layer 33, the strained quantum well layer 34, the semiconductor on the high index plane substrate 31 having the (n11) B plane as the main surface. Barrier layer 35, carrier confinement layer 3 composed of strained quantum well thin film
6 are continuously formed.

Immediately after the growth of these layers, FIG.
As shown in (a), the carrier confinement layer 36 is in a strained quantum well film state. However, a suitable time for growth interruption your extract, as shown in FIG. 3 (b), some changes in the carrier confinement layer 36, a strained quantum well film 37 thinner in a relatively thickness, The carrier confinement layer 36a is composed of fine islands 38 having a relatively large film thickness dispersed therein.

Thereafter, as shown in FIG. 3C, the semiconductor barrier layer 39 and the semiconductor cap layer 310 are formed to have a flat surface structure. Here, the role of the strained quantum well layer 34 is not so essential, even in the absence, effects of which are sufficiently exhibited. However, the insertion of the strained quantum well layer 34 tends to make the sizes of the islands uniform when the semiconductor structure of the present invention described later is manufactured.

When an ordinary strain-free quantum well film is used for the semiconductor carrier confinement layer, such an island structure is not formed. Therefore, the strain energy of the strained quantum well film is involved in the formation of this structure. Is inferred. As described above, even with a strained quantum well film, and if the island by thickness and composition is obtained based on the structure that will be distributed in the quantum well in the thin film (thin film), the quantum well layer is completely Island In some cases, the structure becomes a separated quantum box. This is because the strain energy varies depending on the thickness and composition of the strained quantum well film to be formed.

The islands and structure dispersed on the quantum well film, no film of the quantum well, marked differences optically seen the island is completely separated structure. The emission spectrum of a completely separated island shows an emission intensity spectrum similar to that of a strained quantum well thin film grown on a normal (100) plane substrate, whereas the above-mentioned semiconductor quantum structure , A strong emission intensity and a narrow spectral half-width are exhibited as compared with the strained quantum well thin film grown on the (100) plane substrate. These excellent optical characteristics indicate that the above-mentioned semiconductor structure can be applied to a semiconductor laser and an optical nonlinear device.

The following will be described with reference to FIG examples of the aforementioned semiconductor structures. 4 (a) is a sectional view showing a configuration example of a semi-conductor structure. First, a method of manufacturing this semiconductor quantum structure will be described. In this example, the main surface is (31
1) On the GaAs substrate 41, which is the B side, depressurize MO
Using the VPE method, the temperature condition was 750 ° C., and the same MO
This semiconductor structure is formed in a VPE apparatus by continuously growing various materials by changing other gas conditions etc. without taking them out from the processing chamber.

First, GaAs is grown to a film thickness of 10 nm.
GaAs buffer layer 42 is formed. Then, Al
_After growing _0.5 Ga _0.5 As to form a lower barrier layer 43 having a film thickness of 30 nm, a strained quantum well layer 44 having a film thickness of 15 nm made of strained In _0.2 Ga _0.8 As and Al _0.5 Ga _0.5 A are formed.
The barrier layer 45 made of s and having a film thickness of 100 nm and the strain I
n _0.25 Ga _0.75 As is continuously and sequentially grown, and a growth interruption time of 2.5 minutes is set at this stage.

Here, the strained Al _0.5 Ga _0.5 As grown before the barrier layer 45 forms a film with the strained quantum well layer 44 because the barrier layer 45 is subsequently formed, but it is grown on the buffer layer 45. The strained In _0.25 Ga _0.75 As is composed of a strained quantum well thin film in which a part of the strained quantum well thin film is relatively thinned due to this growth interruption, and fine islands of relatively thicker film dispersed therein. The carrier confinement layer 46 is composed of After the growth was interrupted for 2.5 minutes, Al _0.5 Ga _0.5 As was then grown thereon to form a film having a thickness of 50.
nm planarization barrier layer 47 is formed, and GaAs is formed thereon.
Is grown to form a gap layer 48 having a film thickness of 10 nm,
The semiconductor quantum structure shown in the cross-sectional view of FIG. 4A was formed.

[0034] The semi-conductor quantum structure described above as Sample 1-a, while the purpose of comparison, in exactly the same procedure, the samples 1-b in which the main surface is a GaAs substrate is a (311) A plane
Then, a sample 1-c using a GaAs substrate whose main surface is the (100) plane was prepared. Further, in the sample 1-a, the main surface where the flattening barrier layer 47 and subsequent layers are not formed is (31
1) Sample 1-d formed on the GaAs substrate which is the B surface
And a sample 1-e formed on a GaAs substrate whose main surface is a (100) plane were prepared, and their structures were compared.
The structure was observed with a scanning electron microscope.

As a result of the observation, samples 1-a, 1-b, 1-
In c and 1-e, nothing was observed on the surface, and it was found that a flat surface was obtained. Here, sample 1-a
Has a carrier confinement layer 46 having an island region therein, but since a planarization barrier layer 47 and a gap layer 48 are formed on the carrier confinement layer 46, its surface is flat as shown in FIG. Has become.

On the other hand, in Sample 1-d, the state shown in the cross-sectional view of FIG. 4 (b) was obtained as shown in the electron micrograph showing the fine pattern formed on the substrate of FIG. I found out. This sample 1-d is shown in FIG.
As shown in (b), the carrier confinement layer 46 made of strained In _0.25 Ga _0.75 As has a thin film 49 having a thickness of 3 nm and islands 410 having a diameter of about 70 nm and a thickness of about 10 nm dispersed therein. Was becoming. In addition, this sample 1-d
Is prepared for observing the surface of the carrier confinement layer 46, and is the carrier confinement layer 4 of the sample 1-a.
6 is also in the same state.

As shown in FIGS. 4 (b) and 5, Ga
It can be seen that islands 410 are regularly formed on the surface of the carrier confinement layer 46, although no processing is performed on the As substrate 41. This is because the above-mentioned semiconductor quantum structure causes regular self-organization due to the surface state of the (311) B plane of the substrate and the surface energy due to the strain of the strained quantum well layer formed thereon. It is shown that.

FIG. 6 is a waveform diagram showing the emission spectra of the above-mentioned samples 1-a and 1-c at room temperature. In the figure, 61 is a waveform showing the emission spectrum of Sample 1-a, and 62 is a waveform showing the emission spectrum of Sample 1-c. As is clear from FIG. 6, the half width of the waveform 61 is about 8 nm when viewed in wavelength, that is, 10 meV, and the half width of the waveform 62 is 25.7 meV, and the half width of the waveform 61 is smaller. There is. Here, in FIG. 6, the peaks are expressed as being constant in order to compare the half widths of the respective waveforms, but the emission intensity of the sample 1-a is twice as large as that of the sample 1-c. Has become.

Then, as is clear from FIG. 6, the waveform 6
Towards the first peak wavelength is shifted to the shorter wavelength side than the peak wavelength of the waveform 62, the quantum confinement effect of the semi-conductor quantum structure of this has been observed. Even in a GaAs / AlAs-based quantum well, which is known to exhibit good emission characteristics, the half-value width of the spectrum is about 20 meV (Reference: Akira Okamoto, Optical Properties of Superlattice Structure, Chapter 3, p57, published by Corona Publishing Co., Showa). 63
In the past, it was not possible to observe such a narrow half width at room temperature in the InGaAs system.

Example 2. Hereinafter, another example will be described. Example This, in Example 1 above, continuously sequential growth interruption after distortion In _0.25 Ga _0.75 As be formed to 2 minutes after the barrier layer 45, following after the growth interruption Al _0.5 Ga _0.5 As
Was grown to form a flattening barrier layer having a film thickness of 50 nm. Then, in the example of this 2, this distortion In _0.25 of thickness 5nm subsequent to planarizing the barrier layer Ga _0.75 As growth and the growth interruption for 2 minutes, the film thickness of 50 nm Al _0.5 Ga _0.5
The growth of As was repeated twice, and then a cap layer made of GaAs was formed to form a semiconductor quantum structure having three carrier confinement layers as shown in FIG.

After subjecting the cross section of the semiconductor quantum structure of this three-layer structure to pretreatment such as stainless steel etching, it was observed with a scanning electron microscope. As a result, strain In _0.25 Ga _0.75 As was grown, and then growth was suspended. In the layer formed by (1) and (2), it was observed that islands having a diameter of about 50 nm and a thickness of about 9 nm were dispersed in a thin film having a thickness of about 2.5 nm, and three layers were formed. When the emission spectrum of this sample was observed at room temperature, it had a half-value width of 16.7 meV as shown in FIG.
Waveform 71 was obtained, and intense light emission was obtained. On the other hand, using a GaAs substrate whose main surface is the (100) plane,
In the other comparative sample produced in the same manner, a waveform 72 having a spectral half width of 35 meV was obtained, and its emission intensity was also small.

Hereinafter, islands having various diameters were formed by changing the substrate, the barrier layer, the quantum well layer, the growth temperature, and the number of laminations .
The results of Examples 3 to 17 are shown in Table 1.

[0043]

[Table 1] [] In the column of "barrier layer" in the table shows the strained quantum well layer formed below the barrier layer below the carrier confinement layer having an island structure.

As is apparent from Examples 1, 2 and Table 1 were pre-mentioned, (n11) B carrier confinement layer growth formation comprising a strained quantum well on the substrate surface, by performing the growth interruption, various it can be seen that can form a semi-conductor quantum structure of this in the system.

Then, for example , in Example 4, (21
1) On the B-plane GaAs substrate, fine islands with a diameter of about 60 nm were obtained, and the emission intensity was more than three times that when using the (100) -plane GaAs substrate, and the half-width of the emission spectrum was half maximum. Also, a narrow one of 12 meV was obtained. Also,
For example , also in Example 6, an emission spectrum having a half width as narrow as 14 meV was obtained. In addition , in Example 10, (2
11) A fine island with a diameter of about 60 nm was obtained on the B-plane InP substrate, and the full width at half maximum of the emission spectrum was as narrow as 15 meV, and the emission intensity was 3 in comparison with the case of using the (100) -plane InP substrate. More than doubled.

[0046] and, similarly, of Example 11 For example (31
1) Even on the B-plane InP substrate, an emission spectrum with a narrow full width at half maximum of 13 meV was obtained. As is clear from the above-mentioned example , when a carrier confinement layer composed of a barrier layer and a strained quantum well thin film is formed on a (n11) B-plane substrate, and then growth interruption is performed, the formed quantum carrier becomes a carrier confinement layer. A semiconductor structure is obtained in which fine islands having a relatively large film thickness are dispersed in the well film. Therefore, it is also effective for other various combinations of that is either bright et al.

By the way, in the upper clean 1-19, to form a carrier confinement layer made of strained quantum well film,
After that, by suspending the growth, fine islands having a relatively large film thickness are dispersed and formed in the formed quantum well film serving as the carrier confinement layer, but the present invention is not limited to this. . By holding the growth interruption for a predetermined time, the formed quantum well film serving as the carrier confinement layer may be completely separated into fine islands.

[0048] Hereinafter in the present invention, a semiconductor carrier confinement layer will be described with reference to the drawings Overview Once the configuration that has become an island structure. FIG. 8 is a perspective view showing the basic structure of the semiconductor structure of the present invention. This structure has a high-index plane substrate 81 having a plane inclined from a low-index plane such as a (100) plane or a (111) plane of a conventionally used compound semiconductor, and a semiconductor barrier layer 82 formed thereon. , This semiconductor barrier layer 8
It is composed of a carrier confinement layer 83 which is surrounded by 2 and becomes a disk-shaped island made of a semiconductor layer having a strain therein.

Conventionally, the semiconductor carrier confinement layer 83
As for, a dice-shaped product having almost the same height and width was used. That is, it is a quantum box. However, the present invention is different from the conventional quantum box in that, as shown in FIG. 8, as the semiconductor carrier confinement layer 83, a flat disk-shaped island spreading in the in-plane direction is used.

High index plane substrate 81 of the above compound semiconductor
As the substrate, a (n11) B substrate of GaAs or InP (here, n = 2, 3, 4, 5, 6, 7) is used. Microscopically, the crystal orientations of these are (100) plane, which facilitates smooth epitaxial growth, and V
It is composed of a (111) B plane in which growth does not occur remarkably on the group stabilizing plane. Therefore, the vapor phase crystal growth on this surface shows a peculiar aspect, and as a result, the semiconductor structure as shown in FIG. 8 is obtained.

The basic concept of the method for manufacturing this semiconductor structure will be described below. FIG. 9 is a sectional view for explaining the method for manufacturing this semiconductor structure. First, the semiconductor barrier layer 92 is formed on the high-index plane substrate 91, and the strained quantum well thin film 93 is formed thereon. Immediately after growth,
As shown in (a), the quantum well film 93 is not divided into islands.

[0052] However, our growth interruption of a suitable period of time ECTS,
The strained quantum well layer is crystallized in an island shape to form a carrier confinement layer 94 in a disk shape. And in FIG.
As shown in (b), the barrier layer 92 mass-transports and surrounds the island-shaped carrier confinement layer 94. After that, as shown in FIG. 9C, a semiconductor barrier layer 95 is further grown to obtain a flat surface.

Here, in the above description, one carrier confinement layer having an island structure is formed, but the present invention is not limited to this. As shown in FIG. 10, the carrier confinement layer having an island structure may be multi-layered. FIG. 10 is a sectional view showing a state where carrier confinement layers having an island structure are stacked in a direction perpendicular to the substrate surface as a semiconductor structure.
1 is a high index plane substrate, 102 is a disk-shaped carrier confinement layer, and 103 is a semiconductor barrier layer which surrounds the carrier confinement layer 102 by mass transport. Thus, by forming the carrier confinement layer 102 to have a laminated structure, a semiconductor structure having a high density can be obtained.

The method of manufacturing the semiconductor structure having this laminated structure will be briefly described below. First, as shown in FIG. 11A, the semiconductor barrier layer 112,
Carrier confinement layer 113 having a disk-shaped island structure
To form a first layer. The method for forming the carrier confinement layer 113 in this case is, as shown in FIGS. 9A to 9C, made by the same method as the carrier confinement layer described above, and the formed carrier confinement layer 113 is a semiconductor. The entire circumference is surrounded by the barrier layer 112.

Then, a strained quantum well thin film 114 is further formed thereon as shown in FIG. 11 (b), and growth interruption is given thereafter to form an island structure as shown in FIG. 11 (c). Then, a second carrier confinement layer 115 is formed, and thereafter, as shown in FIG. 11D, the barrier layer 1 is formed thereon.
Grow 16 By repeating these series of processes, a semiconductor structure laminated in multiple layers can be formed.

The above-described embodiments of the present invention will be described more specifically below. Example 1 . The semiconductor structure shown in FIGS. 8 and 9 is the basic structure of the present invention. Therefore, in order to actually use it as an optical device, it is necessary to improve the crystallinity and optical characteristics, and to provide an appropriate buffer layer, quantum well layer, or gap layer between the substrate and the island region or on the island region. There is.

FIG. 12 is a sectional view showing the structure of the semiconductor structure according to the first embodiment of the present invention. In the figure, 1
21 is a GaAs substrate whose main surface is the (311) B plane, 1
22 GaAs buffer layer formed on the GaAs substrate 121, a lower barrier layer made of _Al x _{Ga 1-x} As 123, 124 is GaAs and the lattice-mismatched In _y
A strained quantum well layer made of Ga _1-y As, a lower barrier layer made of Al _x Ga _1-x As formed on the quantum well layer 124, and a strained quantum well made of In _z Ga _1-z As. Carrier confinement layer 127 having a disk-shaped island structure obtained by forming
Is an upper barrier layer made of Al _x Ga _1-x As, 128
Is a cap layer made of GaAs.

[0058] Hereinafter, an implementation example of the invention, a method of manufacturing the semiconductor structure shown in FIG. 12. In this example, the MOVPE method is used on the GaAs substrate 121 whose main surface is the (311) B plane, the temperature condition is 750 ° C., and the same MOVPE apparatus is used without continuous removal from the processing chamber. The semiconductor structure is formed by growing various materials by changing other gas conditions.

First, GaAs is grown to form the GaAs buffer layer 122. Subsequently, Al _x Ga _1-x As is grown to form the lower barrier layer 123, and then In _y G
a _1-y As, Al _x Ga _1-x As and In _z Ga _1-z As
Of strained quantum wells are sequentially grown, and a growth interruption time of 2 minutes is set at this stage. Grown In _y Ga _1-y As
Is formed into a film with the strained quantum well layer 124. Due to this growth interruption, the strained quantum well made of In _z Ga _{1 -z} As is aggregated and crystallized in an island shape to form a desk-shaped carrier confinement layer 126. Become.

Then, In _y Ga _1-y As grown under the carrier confinement layer 126 mass-transports to cover the carrier confinement layer 126, and the lower barrier layer 12
It becomes 5. After the above-mentioned growth interruption for 2 minutes, Al _x Ga _1-x As is then grown on this to form the upper barrier layer 12.
7 is formed, GaAs is grown to form the gap layer 128, and a structure having a flat surface and including a semiconductor structure is formed.

Here, the size and distance of each carrier confinement layer 126 can be changed by the In concentration z. Note that this is A of the lower barrier layer 125.
It does not depend on the 1 concentration (0 to 60%). The larger the difference between the lattice constant of the lower layer and the lattice constant of the strained quantum well to be formed, the larger the strain energy, which influences the size of the desk shape and the distance interval. And the difference in lattice constant is
In this case, In _z Ga _{1 -z} A of the carrier confinement layer 126
It is determined by the composition ratio of In and Ga of s.

As a result, the size and distance of the carrier confinement layer 126 can be changed depending on the In concentration z. For example, the In concentration Ga of the growing In _z Ga _1-z As
The carrier confinement layer 126 has a disk-shaped diameter size of about 1 each.
The sizes are 50 nm, about 100 nm, and about 70 nm, and the size can be controlled.

Further, the size and the distance interval of the carrier confinement layer 126 can be changed by the initial growth film thickness of In _z Ga _1-z As. For example, the In concentration z is 3
When the thickness of the grown In _z Ga _1-z As is fixed at 0% and changed from 10 nm to 3 nm, the diameter size of the disk-shaped island of the carrier confinement layer 126 becomes 100.
nm to 50 nm. In the lattice-matched GaAs quantum well film, such a phenomenon of island formation does not occur, so it is understood that the above phenomenon is controlled by the strain energy of the strained InGaAs film.

Here, the strained quantum well film 12 to be formed below
The role of 4, not very essential, this is without, after the growth of the In z _Ga 1-z _As, you fluff waiting time of about 2 minutes, the above-mentioned islands can be formed. But In _y
When the strained quantum well layer 124 made of Ga _1-y As is provided, the disk dimensions of the carrier confinement layer 126 tend to be more uniform.

After forming the upper barrier layer 127 for planarization, growth of In _z Ga _{1 -z} As and 2
By repeating the growth interruption for a minute and the growth of the barrier layer for planarization, it is possible to manufacture a stacked semiconductor structure corresponding to the repetition. In the above example, G
The case of aAs (311) B substrate is shown.
The other surface (211) B surface, (411) B surface, (511) B surface, in which the surface and the (111) B surface are mixed in different ratios,
A semiconductor structure can be formed on the (611) B plane, the (711) B plane, and the like.

A system using a GaAs substrate, strained GaAs _z Sb _1-z as a semiconductor carrier confinement layer and Al _y Ga _1-y As as a barrier layer, strained In as a semiconductor carrier confinement layer on an InP substrate. _x Ga _1-x As
And a system using In _y Al _z Ga _{1 -yz} As as a barrier layer and strain I as a semiconductor confinement layer on the InP substrate.
The MOVPE method is used in the same manner even in a strained epitaxial film growth system of another material, such as a system using n _x Ga _1-x As _z Sb _1-z and In _y Al _1-y As as a semiconductor barrier layer. Thus, a similar semiconductor structure can be formed on a compound semiconductor single crystal substrate having a high index plane.

Of course, the size and density of the island-structured semiconductor carrier confinement layer to be formed differ depending on the above-mentioned material system. However, the use of a (n11) B-plane substrate, the use of a strained semiconductor layer as the semiconductor carrier confinement layer, and the mass transport of the strained semiconductor layer and the barrier layer during the growth interruption can be achieved by the present invention. Is a basic requirement of.

This semiconductor structure exhibits unique optical characteristics different from those of the conventionally manufactured quantum well box. That is, in the quantum box formed by conventional selective growth, the emission intensity at room temperature is weaker than that of the quantum well, and due to the size fluctuation during fabrication, etc., the luminescence light obtained by applying excitation light The width of the spectrum line of is considerably wide. The full width at half maximum of this spectrum line was usually 40 meV or more.

However, in the semiconductor structure of the present invention, the emission intensity is higher and the width of the spectrum line is significantly smaller than that of the quantum well formed on the (100) substrate under the same conditions, and the full width at half maximum of 20 eV or less is obtained. Show. Even in a GaAs / AlAs-based quantum well, which is known to exhibit good emission characteristics, the full width at half maximum of the spectrum line of the luminescence light is about 20 mmeV (Reference: Optical property of superlattice structure by S. Okamoto, No. 3 Chapter p57, published by Corona, 1988), I
In the nGaAs-based quantum box, such a narrow half width was not observed at room temperature.

As described above, as compared with the conventional processing method and the emission spectrum of the quantum wire or quantum box structure formed by selective growth,
The full width at half maximum of the spectrum line of the obtained emitted light is very narrow,
The strong emission intensity is due to the fact that the islands of each semiconductor island region are formed with extremely uniform and high density, and that the density of states is discretized due to the quantum confinement effect in the structure of the island region. It is a thing. These excellent optical characteristics show that the semiconductor structure of the present invention can be applied to a semiconductor laser and an optical nonlinear device such as an optical nonlinear switch.

Next, the state of the semiconductor structure of the present invention will be described in detail. First, as shown below, Sample 1-a (FIG. 13A) according to the present invention was prepared. First, a GaAs substrate 131 whose main surface is the (311) B plane
The GaAs buffer layer 132 was grown to a thickness of 10 nm by using the low pressure MOVPE method under the temperature condition of 750 degrees.

Subsequently, a lower barrier layer 133 made of Al _0.5 Ga _0.5 As is grown to a thickness of 30 nm, and then In
_A strained quantum well layer 134 made of _0.2 Ga _0.8 As was grown to 5 nm, and a barrier layer 135 made of Al _0.5 Ga _0.5 As was grown to 30 nm. continue,
5 strained quantum well layers made of In _0.3 Ga _0.7 As
13 is grown, the growth is suspended for 2 minutes, and then the planarization barrier layer 137 made of Al _0.5 Ga _0.5 As is grown to 30 nm and the cap layer 138 made of GaAs is grown to 10 nm. A semiconductor structure as shown in (a) was produced as Sample 1-a.

For comparison, a sample 1-b (not shown) was prepared in exactly the same procedure by using a GaAs substrate having a (311) A plane as the main surface in exactly the same procedure. Sample 1-c using a GaAs substrate with a (100) plane
(Not shown) was produced. Furthermore, a growth interruption was performed for 2 minutes in the same procedure, and thereafter, a sample in which the planarization barrier layer 137 and subsequent layers were not grown was taken as a GaAs substrate (Sample 1-d) whose main surface was a (311) B plane, The GaAs substrate (Sample 1-e) whose surface is the (311) A plane and whose main surface is (10)
A 0-plane GaAs substrate (Sample 1-f) was prepared and its structures were compared.

As a result of observing these samples with a scanning electron micrograph, flat surfaces were observed in Sample 1-a, Sample 1-b, and Sample 1-c. And sample 1-d
In, as shown in the sectional view of FIG. 13 (b), In _0.3 G
have layers grown a _{0 .7} As is a diameter of about 100nm island, around which is Al _0.5 Ga _0.5 As surrounds the layer grown structure was obtained.

On the other hand, in Sample 1-e, as shown in the sectional view of FIG. 13C and the photograph of the fine pattern formed on the substrate by the scanning electron microscope of FIG. 14A,
Period on the surface has a step shape that does not have all the so beautiful, so-called self-faceting has occurred, had not been on the island structure. Also, sample 1-f
Then, as shown in FIG. 13D, the quantum well had a completely flat surface.

In FIGS. 13A to 13D, the same reference numerals indicate the same parts. 139 is a GaAs substrate whose main surface is a (100) plane, and 140 is a film thickness of 5 n.
m strained quantum well layer of In _0.3 Ga _0.7 As, 14
1 is a GaAs substrate whose main surface is the (311) A plane, 14
Reference _numeral 2 is a strained quantum well layer formed by growing In _0.3 Ga _0.7 As to have a film thickness of 5 nm.

FIG. 14 (b) is a scanning electron micrograph of the fine pattern formed on the substrate, showing the surface condition of Sample 1-d. As shown in FIG. 14B, GaAs
The substrate 131 (FIG. 13) has not been processed,
After growing the strained quantum well layer on the barrier layer 135, 2
The island-shaped carrier confinement layer 136 formed by the growth interruption for a minute is regularly formed. this is,
It has been shown that the semiconductor structure of the present invention causes regular self-assembly due to the specific surface state of the (311) B plane and the surface energy due to the strain of the semiconductor layer (strain well layer) in which the strain is present. There is.

FIG. 15 shows the emission spectra of Sample 1-a and Sample 1-c at room temperature. In the figure, 15
1 is the emission spectrum of sample 1-a, 152 is sample 1-c
Is an emission spectrum of. Conventionally, the quantum wire or quantum box structure that could be fabricated was inferior in emission intensity to the flat quantum well structure. In the emission spectrum 151 of the sample 1-a, the emission of the sample 1-c, which is a quantum well whose main surface is formed on the (100) plane, although the island structure is similar to that of the quantum box. Spectrum 1
A luminescence intensity more than twice that of 52 was obtained.

The full width at half maximum (FWHM) of the spectrum line of the obtained emission spectrum 151 is 15 meV, which is about half the emission spectrum 152 from the quantum well having a flat structure. The emission spectrum 151 has the emission peak wavelength shifted to the short wavelength side with respect to the emission spectrum 152, and the quantum confinement effect is observed. Such excellent optical characteristics indicate that the semiconductor structure of the present invention can be applied to semiconductor lasers and optical nonlinear devices.

Comparative Example 1. In this comparative example 1, a structure similar to that of the example 1 was manufactured by a GaAs / AlGaAs system which is a lattice matching system. First,
Depressurized MO onto a GaAs substrate whose main surface is (311) B plane
VPE method, temperature condition of 750 ℃, GaAs
Was grown to a thickness of 10 nm.

Subsequently, a lower barrier layer made of Al _0.5 Ga _0.5 As was grown to a thickness of 30 nm, and then lattice-matched GaA was formed.
s quantum well layer was grown to 5 nm and then Al _0.5 Ga
_A barrier layer of _0.5 As was grown to 30 nm. Then, a GaAs quantum well layer was grown to a thickness of 5 nm, and then a sample with a growth interruption of 2 minutes was prepared. When this sample was observed with a scanning electron microscope, its surface had a completely flat structure and no island structure was observed.

Example 2. Hereinafter, a method for manufacturing a semiconductor structure according to the second embodiment of the present invention will be described. As shown in FIG. 16, on the GaAs substrate 161 whose main surface is the (311) B plane, the buffer layer 162 was formed by first growing GaAs using the low pressure MOVPE method under the temperature condition of 750 ° C. .

Subsequently, a lower barrier layer 163 made of Al _0.5 Ga _0.5 As was grown to a thickness of 30 nm, and then In _0.2 Ga was formed.
_The strained quantum well layer 164 made of _0.8 As is grown to a thickness of 5 nm, and then the barrier layer 16 made of Al _0.5 Ga _0.5 As is grown.
5 was grown. Then, a strained quantum well layer made of In _0.3 Ga _0.7 is grown, an island 166 is formed after a growth interruption of 2 minutes, and a planarization barrier layer 167 made of Al _0.5 Ga _0.5 As is formed to a thickness of 20 nm. I grew it.

Thereafter, growth of a strained quantum well layer made of In _0.3 Ga _0.7 , growth interruption for 2 minutes, and Al _0.5 Ga _0.5
The growth of the flattening barrier layer 167 made of As and having a film thickness of 20 nm was repeated twice, and then the cap layer 168 made of GaAs was formed to have a thickness of 10 nm. The cross section of the semiconductor structure formed as described above was observed by a scanning electron microscope after performing a stainless etching process or the like. As a result,
It was observed that a semiconductor structure having a three-layer structure composed of islands 166 having a diameter of about 50 nm was obtained.

The semiconductor structure according to the present invention is not limited to the above embodiment. Tables 2 and 3 below show the results of other examples in which semiconductor structures were manufactured with various material systems by changing the substrate, barrier layer, quantum well layer, growth temperature, and stacking number. is there.

[0086]

[Table 2]

[0087]

[Table 3]

[0088] As apparent from Examples 3 to 28 shown in Examples 1, 2 and Tables 2 and 3 were pre-mentioned, (n11) B
It is understood that a semiconductor structure can be formed in various systems by growing and forming a carrier confinement layer composed of a barrier layer and a strained quantum well on the surface of the substrate, and by interrupting the growth. Then, for example, in Example 3 , fine islands with a diameter of about 65 nm were obtained, and the emission intensity was more than twice as high as that of the quantum well structure produced using the (100) GaAs substrate. The half width of the spectrum line was as narrow as 18 meV.

Further, for example, in Example 7 , about 60 nm
A fine diameter island is obtained, and the emission intensity is (100) GaA.
Approximately twice as much as that of the quantum well structure fabricated using the s substrate, and the full width at half maximum of the emission spectrum line is 19 meV.
I got a narrow one. In addition, in Example 8 , the number of islands is 25.
The luminescence intensity was (10 nm).
0) It was slightly lower than that of the quantum well structure manufactured using the GaAs substrate.

On the other hand, in Example 16 , an emission spectrum line having a narrow half width of 20 meV was obtained, and in Example 23 ,
Similarly, an emission spectrum line with a narrow half-value width of 21 meV was obtained, and the emission intensity was three times or more as compared with that of the quantum well structure produced using the (100) GaAs substrate. Since the emission spectrum with a narrow half width as in the above example obtained at room temperature is usually observed only in a very good quantum well thin film, the semiconductor structure according to the present invention has a characteristic optical characteristic. You can see that From the above, the present invention is not limited to the above-mentioned embodiment,
It is either bright et al also useful against a variety of other combinations.

By the way, as a result of analyzing the island structure composed of a plurality of islands as described above by a transmission electron microscope and energy dispersive elemental analysis, strained InG aggregated in an island shape is obtained.
It has been found that In is contained in the upper part where the lower AlGaAs barrier layer is mass-transported on aAs to cover the island. AlGaAs, which is especially an island
In the surface portion of the microcrystal of InAlG containing a considerable amount of In.
It has the structure of aAs.

This is because In causes segregation in a series of processes of the self-organization phenomenon in which strained InGaAs becomes island-shaped. Therefore, the volume occupied by the InGaAs carrier confined portion in the quantum structure having the island structure is considerably reduced as compared with the state of the quantum well film before self-organization. Although the volume of the carrier confined portion of this island can be estimated from the surface density and the cross-sectional shape, it is considered to be reduced to about 30 to 5% depending on the production conditions.

Here, the film thickness of the island is not significantly increased from the film thickness of the initially grown quantum well. However, this is based on the result of evaluating the cross-sectional shape by stainless steel etching. Therefore, AlGaAs around the island
Since some In is mixed in the
The size of the island obtained by the stainless steel etching using the selective etching of AlGaAs and AlGaAs may be slightly larger than the actual carrier confined portion.

FIG. 17 compares the emission spectrum and the emission excitation spectrum of Example 3 in Table 2 with a quantum well formed on a GaAs substrate having a (100) main surface grown simultaneously under the same growth conditions. FIG.
Although the carrier confinement part has an island structure, the emission spectrum shows very sharp absorption by excitons, and its emission intensity is more than double that of a quantum well formed on a (100) GaAs substrate, The half width of the spectrum was as narrow as 18 meV. This narrow emission spectrum reflects the effect of excitons being confined to the fine regions of the island.

Further, as described above, considering that the volume of the carrier confining portion having the island structure is significantly lower than the volume of the quantum well state before becoming the island, (100 The fact that the emission intensity is increased as compared with the quantum well formed on the) plane indicates that the transition probability of the emission portion having an island structure is greatly increased. It can be concluded that this is due to the fact that the island portion vibrates and the strength is increased, and that the crystallinity of the island portion is very excellent and there are almost no non-light emitting processes.

In the optical semiconductor device according to the present invention in which the carrier confinement layer has an island structure, the excitation spectrum of the emitted light also shows a sharp shape, as shown in FIG. 17 (b). Since the excitation spectrum corresponds to the absorption spectrum, it shows that the exciton absorption of the island is very sharp and the intensity is high. From this, and from the prediction that the oscillator strength of the island is increasing, this structure has a useful feature for application to an optical modulator.

Example 29 . An embodiment in which the above-described invention is applied to an optical modulator will be described below. 18 is a sectional view showing the structure of an optical modulator according to Embodiment 29 of the present invention. On the main surface (31
1) A buffer layer 182 made of n-type GaAs and an n-type Al are formed on the substrate 181 made of n-type GaAs serving as the B surface by metalorganic vapor phase epitaxy (MOVPE).
Lower cladding layer 18 made of _0.25 Ga _0.75 As
A lower guide layer 184 made of 3, n-type Al _0.2 Ga _0.8 As is continuously grown.

Subsequently, an optical guide layer 185 made of Al _0.15 Ga _0.85 As as a semiconductor carrier barrier layer was grown, and a strained In _0.25 Ga _0.75 As quantum well film was grown to 5 n.
It grows to a thickness of m and continues to have Al _0.15 Ga if necessary.
Grow _0.85 As. After that, by providing a growth interruption time of 2.5 minutes, the strained In _0.25 Ga _0.75 As quantum well film is subjected to mass transport to form an island structure 186 composed of a plurality of agglomerated islands, around which Al _0.15 Ga is formed.
_The barrier layer 187 made of _0.85 As is covered.

The above process is repeated 4 times to obtain the island structure 186.
And a barrier layer 187 are stacked in five layers, and then an optical guide layer 188, which is an upper semiconductor carrier barrier layer made of Al _0.15 Ga _0.85 As, is grown thereon.
Subsequently, the guide layer 189, p-type Al _0.25 Ga _0.85 A
an upper clad layer 190 made of s, and finally P
^A contact layer 191 made of ^{+ type} GaAs is grown.

Next, the contact layer 191 and the cladding layer 190 are processed to have a width of 50 μm as shown in FIG.
A ridge 191a of about m is formed. This processing is shown in Figure 1.
A resist pattern patterned by photolithography is formed on the contact layer 191 in the state shown in FIG. 8, and the contact layer 191 and the clad layer 190 are etched using this as a mask to form a ridge 191a.

After forming the ridge 191a, the resist pattern is peeled off, an insulating film 192 made of silicon oxide or the like is formed on the entire surface by sputtering or the like, and the insulating film 192 above the ridge 191a corresponding to the electrode is removed (etched off). After that, Cr / Au or Ti / Pt / A
A p electrode 193 such as u is formed. After that, after thinning the substrate, an n electrode 194 such as AuGeNi is formed on the back surface. After that, ohmic sintering is performed and the length is 300μ.
Cleavage to m completes the modulator structure as shown in FIG.

The p-electrode 19 of the device manufactured as described above
3, a voltage is applied by bonding an Au wire to the n-electrode 194. Then, the dispersed light was made incident from one end face using an optical fiber, the light obtained from the other end face was received by the optical fiber, and the absorption spectrum was measured by the photocounting method. FIG. 20 is a characteristic diagram showing absorption spectra with and without applying a reverse bias between both electrodes.

As is clear from the figure, sharp exciton absorption was observed, and a large absorption shift of 20 meV was obtained by applying a reverse bias of 3V. Further, as a result of measuring an extinction ratio by applying an alternating current of 3 V using light having a wavelength of 915 nm, a large value of 30 dB was obtained. This is considered to reflect the characteristics of the semiconductor carrier confinement layer having an island structure in which exciton absorption is sharp and the absorption shift due to an electric field is large.

[0104] Incidentally, in FIGS. 1 and 2, strained quantum well thin film 14
Although an example in which the fine islands 15 having a relatively thicker film thickness are formed is shown above, the present invention is not limited to this. Figure 21
The island-formed strained quantum well film 23a shown in FIG.
21 may be formed, or an island may be formed like the strained quantum well film 23b shown in FIG. Note that, in FIG. 21, other reference numerals are the same as those in FIG.

[0105]

As described above, according to the present invention, a semiconductor barrier layer is formed on a semiconductor substrate having a high index plane by a vapor phase crystal growth method, and then a vapor phase layer is formed on the semiconductor barrier layer under predetermined conditions. A strained quantum well film having a lattice mismatch is formed to a predetermined thickness by the crystal growth method, and after growth of this strained quantum well film, growth is interrupted and mass transport is performed to form an island structure on the strained quantum well film. Thus, a semiconductor quantum structure having a strained quantum well film on which fine islands are formed with high uniformity and high density on a substrate that has not been subjected to any processing such as photolithography or etching. The structure can be obtained.

Further, a step of forming a semiconductor barrier layer by a vapor phase crystal growth method on a high index plane semiconductor substrate, and a step of forming a strained quantum well having a lattice mismatch by a vapor phase crystal growth method. After the growth of the strained quantum well layer, a step of mass transporting the strained quantum well layer and the lower barrier layer to form an island after growth interruption, and subsequently forming a semiconductor upper barrier layer on the island by vapor phase crystal growth method By using this step, it is possible to manufacture a semiconductor structure in which a fine semiconductor island structure is formed with high uniformity and high density on a substrate that has not been subjected to any processing such as photolithography or etching.

In the semiconductor quantum structure thus obtained, the island structure of the carrier confinement layer can be laminated in the film thickness direction by changing the material and the film thickness. A quantum structure is obtained. That is, since these semiconductor quantum structures realize a low-dimensional quantum structure that confines electrons and exhibit strong light emission, they can be applied to semiconductor lasers and semiconductor optical nonlinear devices that can be practically used.

[Brief description of drawings]

FIG. 1 is a perspective view showing a basic structure of a semiconductor quantum structure according to the present invention.

FIG. 2 is a cross-sectional view showing a state of a multilayer structure obtained by developing the semiconductor quantum structure of FIG.

3 is a cross-sectional view showing a method of manufacturing semi-conductor quantum structure.

4 is a sectional view showing the configuration of a semi-conductor quantum structure.

FIG. 5 is an electron micrograph showing a fine pattern formed on a substrate.

FIG. 6 is a waveform diagram showing emission spectra of Samples 1-a and 1-c at room temperature.

FIG. 7 is a waveform diagram showing an emission spectrum in a semiconductor quantum structure in which three carrier confinement layers are formed.

FIG. 8 is a perspective view showing a basic structure of a semiconductor structure of the present invention.

FIG. 9 is a cross-sectional view illustrating the method for manufacturing the semiconductor structure.

FIG. 10 is a cross-sectional view showing a state in which the semiconductor structure is multilayered.

FIG. 11 is a cross-sectional view for explaining the method of manufacturing a semiconductor structure having a laminated structure.

FIG. 12 is a sectional view showing the structure of a semiconductor structure according to Example 20 of the present invention.

FIG. 13 is a cross-sectional view for explaining the state of the semiconductor structure of the present invention.

FIG. 14 is a photograph of a fine pattern formed on a substrate by a scanning electron microscope in the semiconductor structure of the present invention.

FIG. 15 is an explanatory diagram showing an emission spectrum of a semiconductor structure according to the present invention and an ordinary quantum well structure.

16 is a sectional view showing a structure of a semiconductor structure as a multilayer in Example of the present invention.

FIG. 17 shows the emission spectrum and the emission excitation spectrum of Example 3 in Table 2 in comparison with a quantum well formed on a GaAs substrate having a (100) main surface grown simultaneously under the same growth conditions. It is a spectrum figure.

18 is a sectional view showing an optical modulator structure according to the embodiment of the present invention.

19 is a sectional view showing an optical modulator structure according to the embodiment of the present invention.

20 is a characteristic diagram showing absorption spectra when a reverse bias is applied between both electrodes of the optical modulator of FIG. 19 and when it is not applied.

FIG. 21 is a cross-sectional view showing a state of a multilayer structure showing another example of FIG.

FIG. 22 is an explanatory diagram showing configurations of a bulk structure, a quantum well structure, a quantum wire structure, and a quantum box structure, and respective state density spectra.

[Explanation of symbols]

11 Semiconductor substrate 12 Semiconductor barrier layer 13 Carrier confinement layer 14 Strained quantum well thin film 15 islands

Continuation of front page (56) Reference JP-A-5-62896 (JP, A) US Patent 5075742 (US, A) P. J. A. Thijis, J .; JM Binsma, L .; F. Tieme ijer, R.M. W. M. Slotweg, R.S. van Roijen, T .; v an Dong, "Sub-mA threshold operation of of λ = 1.5 μm straight in InGaAs multipl e quantum well las las ol s sr. No. 31, April, 1992, June, 1994. 26, pp.3217-3219, title missing there Toshiaki FUKUNAG A, Hisao NAKASHIM A, "Photoluminescen ce from AlGaAs-GaA s Single Quantum W ells with Growth I nterrupted Heteroi nterfaces Gr, JAPAN ESE JOURNAL OF APP LIED PHYSICS, 1986 year October, Vol.25, No.10 , Pp. L 856-L 858, title missing (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 29/06 H01L 29/66 H01L 21/20-21/205 H01L 33/00 H01S 5 / 34-5/343 Web of Science

Claims (12)

(57) [Claims] 1. A main table comprising a III-V group compound semiconductor
The surface is (n11) B surface (n = 2, 3, 4, 5, 6, 7)
A substrate, a semiconductor barrier layer formed on this substrate, and a semiconductor barrier layer formed so as to be surrounded by the semiconductor barrier layer,
Has an island structure consisting of multiple separated islands
A semiconductor structure comprising: a semiconductor carrier confinement layer having ; and a semiconductor barrier layer formed on the semiconductor carrier confinement layer. 2. The semiconductor structure of claim 1, wherein the substrate is GaAs and the semiconductor carrier confinement layer is strained.
In _z Ga _1-z As and the semiconductor barrier layer is Al _y Ga _1-y A
A semiconductor structure characterized by being s . 3. The semiconductor structure of claim 1, wherein the substrate is GaAs and the semiconductor carrier confinement layer is strained.
The semiconductor barrier layer is made of GaAs _z Sb _1-z and is made of Al _y Ga _1-y As.
Semiconductor structure, characterized in that it. 4. The method of claim 1 Symbol mounting of a semiconductor structure, the semiconductor carrier confinement layer and the substrate is of InP strain I
n _z Ga _{1 -z} As and the semiconductor barrier layer is In _x Al _y Ga
A semiconductor structure characterized by being _1-xy As. 5. The method of claim 1 Symbol mounting of a semiconductor structure, the semiconductor carrier confinement layer and the substrate is of InP strain I
n _x Ga _1-x As _z Sb _1-z and the semiconductor barrier layer is In _y
A semiconductor structure characterized by being Al _1-y As . 6. The semiconductor structure of claim 1 Symbol mounting a semiconductor carrier confinement layer and the substrate is of InP strain I
A semiconductor structure comprising n _z Ga _{1 -z} As and a semiconductor barrier layer of InP . 7. The method of claim 1 Symbol mounting of a semiconductor structure, the semiconductor carrier confinement layer and the substrate is of InP strain I
A semiconductor structure, characterized in that the semiconductor barrier layer is In _y Al _1-y As and is n _z Ga _1-z As . 8. A main table comprising a III-V compound semiconductor
The surface is (n11) B surface (n = 2, 3, 4, 5, 6, 7)
A substrate, a semiconductor barrier layer formed on this substrate, and a semiconductor barrier layer formed so as to be surrounded by the semiconductor barrier layer,
Has an island structure consisting of multiple separated islands
A semiconductor carrier confinement layer having the semiconductor carrier confinement layer and a semiconductor carrier confinement layer formed on the semiconductor carrier confinement layer.
Rear layer and semiconductor carrier barrier formed on this semiconductor barrier layer
A semiconductor structure comprising a layer and a light guide layer . 9. The semiconductor structure of claim 8 Symbol mounting said semiconductor carrier confinement layer has a plurality of stages stacked
The semiconductor structure characterized by that. 10. The semiconductor structure according to claim 8 or 9.
Where the substrate is GaAs and the carrier confinement layer is strained In _z
Ga _1-z As semiconductor carrier barrier layer and optical guide layer
Is Al _y Ga _1-y As . 11. A vapor phase crystal growth method is used to obtain (n11)
I having B surface (n = 2, 3, 4, 5, 6, 7) as a main surface
Semiconductor barrier on a substrate made of II-V group compound semiconductor
The first step of forming a layer, and the first step, followed by a vapor phase crystal growth method
Strained quantum well with lattice mismatch on semiconductor barrier layer
A second step of forming a layer, and the strained quantum well layer and the semiconductor after the second step.
Due to mass transport with the barrier layer, the strain
The quantum well layer separates, and this becomes the semiconductor barrier layer.
A semiconductor carrier with an island structure consisting of multiple islands surrounded
(3) The growth interruption until the confinement layer becomes the third
And the third step, followed by a vapor phase crystal growth method.
Forming a semiconductor barrier layer on the semiconductor carrier confinement layer
Semiconductor structure comprising a fourth step of
Manufacturing method . 12. A method of manufacturing a semiconductor structure of claim 1 1 Symbol placement, subsequent to the fourth step, the new by vapor phase crystal growth method
Fifth, forming strained quantum well layers with lattice mismatch
And the fifth step, the strained quantum well layer and the lower half
By mass transport with the conductor barrier layer ,
The strained quantum well layer separates and becomes the semiconductor barrier layer.
A semiconductor key having an island structure composed of a plurality of surrounded islands.
Stop the growth until it becomes a barrier confinement layer
6 and the sixth step, followed by a vapor phase crystal growth method.
Forming a semiconductor barrier layer on the semiconductor carrier confinement layer
Semiconductor structure comprising a seventh step of
Manufacturing method .