JPH0262090A - Manufacture of optical semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an optical device having a new structure and by a new method of manufacture by controlling a growing speed or a film thickness by changing the rate between an area of an exposed portion of a substrate crystal and an area covered with a film difficult to grow. CONSTITUTION:Exposed grooves 3, 4 in a GaAs substrate layer each have a width of mum order, satisfying a relation the width B > the width A. A GaAs, AlGaAs superlattice layer is grown on the substrate by an organic metal vapor phase growing method for example. Because of the relation B>A, the superlattice layer is grown to be thicker at the portion of the groove 3 than at the portion of the groove 4. Further, a growing period of the superlattice is shorter along the groove 4 compared with the groove 3, i.e., longer as it goes narrower. Hereby, superlattice layers having different optical characteristics are simultaneously formed. Thus, layers having different refractive indexes and band gaps, etc., are well controllably and simultaneously formed along the different width grooves 3, 4. Hereby, an optical device having a new structure is yielded by a new method of manufacture.

Description

Detailed Description of the Invention 1. Name of the invention Method for manufacturing an optical semiconductor device 2. Claims (1) A film in which compound semiconductor crystals are difficult to grow is formed on a crystal substrate, and a part of the film is removing the crystal planes to expose a plurality of locations, simultaneously forming a plurality of compound semiconductor crystal layers on each of the plurality of exposed crystal planes using a vapor phase growth method, and determining the area of the exposed portion of the substrate at the plurality of exposed locations. and the area of the film that is difficult to crystallize, controlling the growth rate of the semiconductor crystal layer growing at the plurality of exposed locations,
A method for manufacturing an optical semiconductor device, comprising forming the semiconductor crystal layers having different thicknesses and different optical properties.

(2) A plurality of striped exposed portions having different widths are formed, active regions having different film thicknesses are formed at the plurality of locations, and a plurality of semiconductor lasers having different wavelengths are formed on the substrate. 3. Industrial Field of Application The present invention relates to a semiconductor laser in which a plurality of regions having different film thicknesses are formed on the same substrate by one crystal growth.

This invention relates to a method for manufacturing optical semiconductor devices such as light emitting diodes and optical waveguides.

2. Description of the Related Art As a method for forming layers with different thicknesses on the same substrate by one crystal growth, there is a liquid phase growth method used when manufacturing compound semiconductor devices such as semiconductor lasers. FIG. 6 shows the structure of a typical semiconductor laser. The laser manufacturing method will be explained first. 61 is an InP substrate, 62 is an InP buffer 7 layers,
53 is engineering nG4A! The iP active region 64 is a p-InP cladding layer, which is successively grown on the substrate by liquid phase growth. Concave stripes 6Q, 81 are formed on such a growth substrate.
and then p-InPs5. n-Indexes
, p-InP67 layers are grown to form a buried semiconductor laser at the bottom of the trench. At this time, in this liquid phase growth method using In as a solvent, the growth speed differs depending on the location and shape of the concave portions 6Q, al, and convex portions 58, 59, and I
This is due to the fact that there are five nP layers, but the surface is almost flat.

Problems to be Solved by the Invention Generally, in the liquid phase growth method, the growth speed of narrow concave portions is fast, and the growth speed of narrow convex portions is slow.

In this way, the liquid phase growth method allows the film thickness to be changed depending on the shape, but it is difficult to control it with high precision. on the other hand,
Film formation methods such as evaporation and sputtering allow film thickness control, but it is difficult to achieve shape effects. Therefore, liquid phase growth is currently mainly used to fabricate devices such as lasers, optical guides/wavelengths, and optical integrated circuits using compound semiconductors, but it lacks controllability of film thickness and is typically used to form quantum gate structures. As described above, this was an issue in achieving higher performance and integration.

Therefore, the present invention aims to improve the controllability of the thickness of thin single crystal films, improve the method for manufacturing compound semiconductor optical devices, mainly semiconductor lasers, and apply them to higher performance and optical integration.

Means for Solving the Problems The method for manufacturing an optical semiconductor device of the present invention includes forming a film on a crystal substrate in which compound semiconductor crystals are difficult to grow, and removing a part of the film to change the crystal planes at a plurality of locations. and simultaneously forming a plurality of compound semiconductor crystal layers on each of the plurality of exposed crystal planes using a vapor phase growth method, so that the area of the exposed portion of the substrate at the plurality of exposed locations and the area of the film that is difficult to crystallize are The growth rate of the semiconductor crystal layer growing at the plurality of exposed locations is controlled, and the semiconductor crystal layers having different film thicknesses and different optical characteristics are formed at the plurality of exposed locations.

In addition, active regions are formed in stripes having different widths at a plurality of locations, active regions having different thicknesses are formed at the plurality of locations, and a plurality of semiconductor lasers having different wavelengths are formed on the substrate. Furthermore, a plurality of striped exposed portions having different widths are connected in series,
The present invention also provides a method for forming an active region of a semiconductor laser, which is made of a single-layer or multilayer superlattice film having a quantum size effect in the exposed portion, by a vapor phase growth method. We also create monolithic integrated circuits of components.

Function The present invention allows vapor phase crystal growth methods such as organometallic vapor phase epitaxy and halide vapor phase epitaxy to be applied to areas where crystal growth is difficult, such as a 5102 film formed on a single crystal substrate, and to substrate crystals. We found that there is a large difference in the crystal growth rate depending on the area and width ratio of the exposed part, and we also found that, for example, thin crystal films of 0.1 μm or less can be grown with particularly good control. A new method for manufacturing optical devices has been discovered by combining the superlattice structure, which exhibits this effect, and can be used to create semiconductor lasers, lasers with optical waveguides, external cavity lasers, multi-wavelength lasers, etc.

In other words, in the crystal growth method of the present invention, when a part of the substrate crystal is covered with a film that is difficult to grow, the concentration of the crystal growth component elements in the gas phase increases, and the crystal growth occurs preferentially in the exposed portion of the substrate single crystal. The growth speed, that is, the film thickness, is controlled by changing the ratio of the exposed area of the substrate crystal to the area covered with a film that is difficult to grow. Furthermore, by applying it to the formation of a superlattice that is an ultra-thin film with a quantum mercury effect, it is possible to change the effective refractive index or effective band gap and obtain optical devices with new structures and manufacturing methods. can.

Embodiment A first embodiment of the present invention is shown in FIG. A perspective view and an enlarged cross-sectional structure are shown. In the figure, 1 is a substrate single crystal GaA
s,2 is an 8102 layer on which crystal growth is difficult to occur, and the width C is the same. Exposed groove 3 in substrate GaAS layer
, 4 each have a width on the order of μm, and have the relationship B)A. On such a substrate, for example, metal organic chemical vapor phase epitaxy (MO-C''/D method) C(CHs)xAj!
, (CH3)5Ga, MuSH4), GaAs
, grow a superlattice layer of A7IGaAs. Groove 3゜4
The superlattice layer is a GaAg30 film with a thickness of about tens to hundreds of layers.
．． 32, 34, 36, 40, 42, 44°46 and mu7!
GaAs 31, 33, 36, 41.43°45 are grown alternately. B) From the relationship in A, the superlattice layer grown in this way grows thicker in the groove 3 part than in the groove 40 part, and the growth period of the superlattice part is shorter in the groove 4, and in the groove 3 part. The longer the lattice layer is, that is, the narrower the width, the longer the lattice layer is, so that superlattice layers having different optical properties are simultaneously formed. Note that the crystal layer hardly grows on 5i022. In this way, it becomes possible to simultaneously form layers with different refractive indexes, band gaps, etc. in grooves with different widths with good controllability.

FIG. 2 shows a second embodiment. 5 on substrate GaAs 1
102 films 2A and 2B are formed, and grooves 3.4 are formed. The difference from the first embodiment is that the widths d of the grooves 3 and 4 are the same, but the widths e and f of the 5i02 films 2A and 2B forming the grooves are different. GaAs and MuJGa were deposited on such a substrate using the MO-1''/D method in the same manner as in the first embodiment.
When the As superlattice is grown, it grows thicker in the groove 3 where the width is 8102 wide, and it grows thinner in the groove 4 where the width is narrower 8102. Furthermore, even if the width of the striped grooves is the same, the period of the superlattice layer is longer in the grooves with a wider width.

1st. As shown in the second embodiment, the area where the crystal plane on the crystal plane is exposed or the area surrounding it 5102
The speed of crystal growth differs depending on the area ratio of the film that is difficult to grow crystals, and it is possible to simultaneously create regions with different growth film thicknesses on the same substrate with good controllability. This example is 5i02
Although nitride films such as 5ixN or other oxide dielectrics can be used, similar effects can be achieved. Furthermore, similar effects can be achieved not only with caAs but also with InP-based materials.

FIG. 3 shows a third embodiment. 1 is a GaAS substrate, and 2 is 5102. 5i022, the width of the cover and the shape of the growth stripe portion 3 are not linear, but the widths are different (partially different) to have a step in the plane. The portion 6 of the stripe 5i02 having different widths changes stepwise. G2LA! grown on such a GaAs substrate 1! ! When comparing groove 3 and groove 4 in the /mu1GILAS superlattice structure, as described in Examples 1 and 2, groove 3 grows thicker and groove 4 grows thinner. Furthermore, groove 3
The periodic length of the portion is longer than the periodic length of the groove 40 portion. Therefore, the band structure is different between the groove 3 part and the groove 4 part, and the effective band gap of the layer grown in the groove 40 part is larger than the effective band gap of the layer grown in the groove 3 part. This bandgap difference, that is, GaAs/A
The thickness and periodic length of the /GaAs multiplex structure can be controlled by the stripe width of 5i02, the groove width and the width of 51 on the same substrate.
This is possible by considering the area covered by 02 and the area of the groove.

FIG. 4 shows an external cavity type semiconductor laser using the fourth embodiment, that is, the third embodiment. FIG. 4(a) is a perspective view of this example of the groove structure, and FIG. 4(b) is a sectional view through the active region 6. GIL on GiLAs substrate 1
A multilayer structure including a quantum well structure of A8/AlGaAS is epitaxially grown. At this time, crystal growth is performed on the substrate by the MO-C'/D method using 5i02 masks having different stripe widths as shown in FIG. 5102
After removing the mask, an n-6caAs buried layer 7, 1)-AlGaAg buried layer 8 is grown again, and a p-GaAs electrode layer 9 is formed thereon. 10.1
1 is an electrode to the p and n layers. Active region 6 (6A,
A groove 12 is formed where the width of 6B') changes.

In the active region 6, the thickness and period of the caAs layer and the 711GaAS layer in the quantum well structure during growth are different as shown in FIG. 3, so that it is possible to have a difference in effective band gap. In this case, the effective bandgap of the region 6 is made smaller than that of the region 6B. now,! @
When a current is injected between 10 and 11, six areas emit light.

At this time, the center of the light wavelength spectrum μ that is emitted is smaller than the effective bandgap of the region 6B that becomes the optical waveguide section. Therefore, the absorption in the region 6B, which becomes the optical waveguide portion, can be extremely reduced compared to when the structures of the regions 6A and eB are made with the same composition. A resonator can be constructed by folding both ends, and a semiconductor laser having an external resonator structure is constructed. Conventionally, when constructing such a semiconductor laser, it is necessary to grow the light emitting region and the waveguide region separately, which have four different compositions, which not only increases the number of times of growth but also requires the growth of the light emitting active region and the optical waveguide region. It is extremely difficult to match the coupling portions of the two, making it difficult to create a laser with a low threshold and narrow spectral linewidth with good reproducibility.

By employing the method of the present invention, a monolithic external cavity semiconductor laser with good characteristics and a small number of growth cycles can be realized. Although this example has been explained using an embedded semiconductor laser with a cleaved plane resonator, it can be applied to any other laser structure, and the resonator can also be applied to a diffraction grating type distributed reflection type resonator. Needless to say.

Furthermore, in the integration of optical circuits, monolithic coupling of semiconductor lasers and optical waveguides will become a necessary elemental technology. It is effective to apply this embodiment to waveguide coupling between a semiconductor laser and other optical components (optical switch, directional coupler, light-receiving element nine-brancher), etc. For example, a diffraction grating is provided above the active region 6A to form a DFB type laser, and the region 6B
can be used as an optical waveguide to connect other parts.

FIG. 6 shows a sixth embodiment. FIG. 5 shows a perspective view of the structure of the semiconductor laser, a plan view of the substrate during growth of the second layer, and a cross section thereof. 1 is a GaAs substrate, 20.25 is an active region manufactured by the method shown in the first example and the second example, 21.22 is an AJGaAs buried layer, and 23 is a 5102 insulating film. , 24.26 is the electrode, 27
indicates a separation groove.

As shown in Figure 6('b), GILA! ! 1. Forming a layer 5i02 having grooves 3 and 4 of different widths on the substrate 1.
, GaAs buffer layer by MO-CVD method, Mu7! G.I.
LAS cladding layer.

GaAs/A]GaAs superlattice layer, p-type AlGaA3
Active regions 20 and 25 having different stripe widths are formed by sequentially forming cladding layers. The superlattice layer formed in the region 20.25 has a different thickness and period depending on the stripe width of the grooves 3 and 4 and the area of the groove 5i02, and thus has a different effective band gap. Next, take out the growth furnace and 5i02
was removed, the active area was shaped by etching, and the MO was removed again.
-N-type and p-type AlG using CVD method or liquid phase growth method! L.A.
I buried layers 21, 22 are formed, and 5102 insulating layers 23. Electrodes 24°26 and separation grooves 27 are formed, and region 2
A semiconductor laser having an active region of 0.26 mm is constructed.

Since the two lasers have different superlattice period lengths in their active regions, their respective oscillation wavelength spectra /L/ are different, and two wavelength lasers are constructed on the same substrate. Normally, when constructing a two-wavelength semiconductor laser, at least three crystal epitaxial processes are required, but with the method of the present invention, it is possible to construct a buried laser with two epitaxial growth steps. In this example, there are 2 wavelengths, but 3 wavelengths, 4 wavelengths,
It is possible to form a buried semiconductor laser with multiple wavelengths such as . . . by epitaxial growth only twice on the same substrate.

As an example of the present invention, a superlattice structure of A/GaAs and GaAS on a GaAs substrate was given, but
Needless to say, the present invention can be applied to IN-V group raw conductors such as GaAsP and A4Ga1nP on a GaAs substrate.

Moreover, it can be applied to all compound semiconductors such as 1l-Vl group.

In the examples, MO-CVD method was used, but GaC
Halide vapor phase epitaxy using I3, Icl5, and sH4 also has a similar selective growth effect.

Effects of the Invention As described above, according to the present invention: 1. Crystals having different band gaps and different refractive indexes can be formed at the same time in one growth.

2. Multi-wavelength lasers can be fabricated with one active region growth.

3. The external cavity laser can be made monolithic and highly efficient by growing the active region once.

4. It becomes possible to exhibit features such as the ability to easily combine a semiconductor laser and an optical component.

[Brief explanation of the drawing]

Figure 1! a) and (t)) are a perspective view and an enlarged cross-sectional view of an epitaxial crystal growth substrate in the method of one embodiment of the present invention, FIGS. 2(a) and (b) are cross-sectional views of an epitaxial crystal substrate, and FIG. (a) is a plan view of crystal substrates with different 5i02 bar stripe widths, and (b) is the same (
4(a) is a sectional view taken along the line X-x' of FIG. 4(0), FIG. 4(0) is a sectional view of the main part after growth, and FIGS. 4(a) and 4(b) are structural perspective views of the external cavity laser. 6(C) is a detailed sectional view, FIG. 6(A) is a perspective view of the semiconductor laser array, FIG. 6(1)) is a plan view of the substrate before growth in FIG. 6 is a cross-sectional structural view taken along the line Y-Y' in FIG. 6(b), and FIG. 6 is a cross-sectional view of a semiconductor laser having a conventional structure. 1...GaAl substrate, 2...5i02
．． 3.4... Groove, 30, 32, 34, 36, 4
0,42,44°46---GaA! i,
3ff, 33, 35, 41, 43°46...
...MlGamu S0 Name of agent Patent attorney Shigetaka Awano and 1 other person 30
．． 32.3 Saki 36,4θr 4144.46・-QαHaS3/, 33.36.4/, 4345-Aノ0工A
sFig.2 Fig.1 Fig.Fig.Fig.Otsu θ Do/

Claims (5)

[Claims] (1) A film in which compound semiconductor crystals are difficult to grow is formed on a crystal substrate, a part of the film is removed to expose a plurality of crystal planes, and a vapor phase growth method is applied to the plurality of exposed crystal planes. A plurality of compound semiconductor crystal layers are simultaneously formed thereon, and the growth rate of the semiconductor crystal layer is grown at the plurality of exposed parts based on the area of the substrate exposed part of the plurality of exposed parts and the area of the film that is difficult to crystallize. and at the multiple exposure locations,
A method for manufacturing an optical semiconductor device, comprising forming the semiconductor crystal layers having different film thicknesses and different optical properties. (2) A plurality of striped exposed portions having different widths are formed, active regions having different film thicknesses are formed at the plurality of locations, and a plurality of semiconductor lasers having different wavelengths are formed on the substrate. A method for manufacturing an optical semiconductor device according to claim 1. (3) A stripe-shaped exposed portion having a plurality of different widths is connected in series, and a semiconductor laser made of a single-layer or multilayer superlattice film having a quantum size effect is attached to the exposed portion. 2. The method of manufacturing an optical semiconductor device according to claim 1, wherein the active region is formed by a vapor phase growth method. (4) The compound semiconductor film on the substrate crystal that is difficult to grow is S
It is a compound of i and O or a compound of Si and N, and the vapor phase growth method of the compound semiconductor is an organometallic vapor phase epitaxy method or a halide vapor phase epitaxy method, as described in claim 1. A method for manufacturing an optical semiconductor device. (5) A coupling optical waveguide section between the semiconductor laser and other optical components is formed by the method described in claim 1, and a monolithic integrated circuit of a plurality of thin film optical components including the semiconductor laser is manufactured. A method for manufacturing an optical semiconductor device, characterized by: