JPH01186693A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain growth layers having different band gap energies by performing epitaxial growth once, by forming an epitaxial layer containing an ultra thin film 500Angstrom or less thick on a semiconductor substrate having a plurality of regions where mesa-stripes having different widths are formed. CONSTITUTION:The first and second mesa-stripe regions 11 and 11' having different widths are formed on a semiconductor substrate 1. Then, the first and second quantum well layers 15a and 15b which contain an ultra thin film layer (500Angstrom or less thick) consisting of an epitaxial growth layer and have different band gaps as well are formed on the mesa-stripe regions 11 and 11'. Further, the first and second semiconductor regions 3 and 2 which contain quantum well layers 15a and 15b and are different each other are also formed on the mesa-stripe regions 11 and 11'. Thus, growth layers having different band gap energies may be formed on the same plane at a plurality of regions located on the substrate 1 by performing an epitaxial growth once.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is a component necessary for the optical communication field and the optical information processing field.
The present invention relates to semiconductor devices, such as optical integrated circuits and multi-wavelength laser arrays, in which a light emitting section, a light receiving section, an optical waveguide, etc. are integrated on the same substrate, and the manufacturing method necessary for manufacturing the same.

BACKGROUND OF THE INVENTION In the field of optical communications, light emitting elements, light receiving elements, and light control elements are essential components. Optical integrated circuits that integrate these elements on the same substrate form the basic structure of optical repeaters, optical switches, etc., and their performance greatly increases.

This is very advantageous from the standpoint of improving reliability. Furthermore, optical multiplex communications, which have become popular in recent years, require light sources (semiconductor lasers) with different oscillation wavelengths, and multi-wavelength laser arrays integrated on the same substrate are becoming important. Furthermore, in the field of optical information processing, the appearance of optical integrated circuits with such a configuration is eagerly awaited for optical pickups of optical discs, compact discs, and the like.

Although the structure of these integrated elements differs depending on the application, they basically have the cross-sectional structure shown in FIG. 8. Here I
This shows the case using nP/TnGaAg P thread material. 1 is an n-InP substrate, 2 is an optical waveguide region, 3 is a light emitting region, and 4 is a light receiving region. 6 to 7 are each InGaA
In the sP layer, 5 is an optical waveguide layer, 6 is an active layer, and 7 is a light receiving layer. Further, 8 is a P-InP layer, and each region (2 to 4) is electrically isolated by an isolation groove 9. Optical waveguide layer 6. active layer 6
．． The light-receiving layer 7 is formed on the same optical axis, and the band gap of the InGaAsP mixed crystal constituting each layer is larger than that of the optical waveguide layer, and the band gap of the light-receiving layer is larger than that of the active layer. Must be smaller than the gap. With such a configuration, the light emitting section 2
The emitted light waves 21 and 22 are incident on the light receiving layer 7° and the optical waveguide layer 6 with high coupling efficiency to obtain an optical integrated circuit having multiple functions such as monitoring optical power, modulating light waves, controlling switches, etc. Can be done. Compared to the case where each region is configured as a hybrid with single elements, it is possible to improve performance and reliability without requiring complicated optical alignment, and it is possible to significantly reduce the size of the element. .

Problems to be Solved by the Invention However, in order to obtain epitaxial layers (6 to 7) with different band gaps on the same plane as shown in FIG. 8, each layer must generally be an InGaAsP layer with a different composition. Epitaxial growth is required. For example, in this case, first, the first multilayer epitaxial growth is performed with the light emitting part 3 excepted and masked with an insulating film, then the second multilayer epitaxial growth is performed with the light receiving part 4 removed and masked.
Furthermore, it does not require epitaxial growth for a total of three times, such as masking off the light control area and performing the third growth, but also involves multiple steps such as insulating film deposition and photolithography. Additionally, a very complex manufacturing process is required. Furthermore, when epitaxial growth is performed on a masked substrate, abnormal growth in the boundary region becomes a problem, and the coupling efficiency of light waves between each region 2 to 4 cannot be increased, which impairs the benefits of integration. Become.

On the other hand, in recent years, optical multiplex communication has been actively researched and developed in the field of optical communication. Therefore, there has been a demand for semiconductor lasers with different oscillation wavelengths, and research and development of multi-wavelength laser arrays integrated on the same substrate has also become active. Wavelength multiplexing semiconductor lasers that have been developed in the past are roughly divided into a hybrid type shown in FIG. 9 and a monolithic type shown in FIG. 10. The configuration shown in Figure 9 has 3
Semiconductor laser 32, 33°3 with two different oscillation wavelengths
This is a wavelength multiplexed laser mounted with 4. A drawback of this element is that it is necessary to align the emission directions of each element, which puts a considerable burden on assembly and mounting.

Furthermore, since it is necessary to make the characteristics of each element uniform, there is a problem that the yield is low. On the other hand, in the structure of the monolithic wavelength multiplexed laser shown in FIG. 10, each of the semiconductor lasers 36, 37, and 38 has active layers having different forbidden band widths on the same substrate 1. Therefore, compared to a hybrid type, complicated optical alignment is not required, and improved performance and reliability can be expected. However, since it is necessary to grow crystals for each active layer, the process is complicated and its fabrication is extremely difficult. Not only is it complicated, but it also has problems in that it is difficult to improve performance, reliability, etc.

An object of the present invention is to obtain a multi-wavelength laser or a composite optical integrated circuit using a manufacturing method that is advantageous in terms of process.

Means for Solving the Problems The present invention aims to solve the above-mentioned problems by forming a first . forming a second mesa stripe region; On the second mesa stripe, first and second quantum well layers including an ultra-thin film layer of SOO Å or less, such as an epitaxial growth layer, and having different band gaps are formed;
Said 1st. the first mesa stripe on the second mesa stripe. A different first quantum well layer comprising a second quantum well layer. A semiconductor device characterized in that a second semiconductor region is formed, in which at least one layer of thickness S is formed by epitaxial growth on a semiconductor substrate in which mesa stripes with different widths are formed in a plurality of regions.
This is a method for manufacturing a semiconductor device including a step of forming a quantum well layer including an ultra-thin film layer of OO Å or less.

Operation By using the above-mentioned method, growth layers with different band gap energies can be formed on the same plane in multiple regions on the substrate by - times of epitaxial growth, and optical integrated circuits can be manufactured very easily. It is possible to easily realize optical integrated circuits that have high performance and high reliability due to good light wave coupling without abnormal growth between regions, and wavelength multiplexed lasers with different oscillation wavelengths in each region. EXAMPLE Below, the embodiment of the present invention is the same as the conventional example (InGaAsP
/InP-based materials will be described as an example.

First, FIG. 1 shows a first embodiment of the present invention, which is an external modulator type laser in which an optical waveguide, a semiconductor laser, and an optical waveguide are integrated. This consists of a light emitting section 3 made up of a semiconductor laser and an optical modulation section 2 made up of an optical waveguide. Here, on the n-InP substrate 1, a mesa stripe 11 with a width W is formed in the light emitting part 3, and a mesa stripe 11' with a width W2 in the light modulation part 2. can be easily formed by patterning a mask such as 5i02, etching with a He, 5/H, PO4 etchant, and then removing the mask. Here, the height H of the step of the mesa stripe 11.11' is approximately 2 μm. InGaA is grown on this InP substrate 1 by, for example, liquid phase epitaxial growth method (hereinafter referred to as LPX method).
A multiple quantum well structure (MQW) consisting of an sP well layer 16b and an InP barrier layer 16& is formed, and further a P-InP cladding layer (2 μm in film thickness) is formed.

FIG. 2 is a cross-sectional structural diagram of a growth boat showing an outline of a method for producing a multiple quantum well layer by the LPK method. The n-InP substrate 1 shown in FIG. 1 on which mesa stripes are formed is fitted into a slider 52 of a growth boat.

Here, in the initial state, the substrate 1 is in the position (FIG. 2(a)). Next, slide the slider 2 to the right 57 and place the substrate 1 into the melt 5 stored in the melt holder 63.
6, 58', contact with InGaAsP melt 65 without stopping (Fig. 2(a)), and InP melt 6
Stop at point B on the right side of ' (Figure 2 (C)).

Furthermore, slide the slider 62 in the opposite direction to the hem point 68 to bring the substrate 1 into contact with each melt (56, 56', !55) (Fig. 2 (d)), and return to the state shown in Fig. 2 (&). .

By repeating this operation, Figure 1(b), (0
), InP substrate 1 with mesa stripe is coated with InP.
GaA! A multiple quantum well layer (MQW layer) 15 consisting of an IP well layer 151L and an InP barrier layer 15b is obtained.In the case of a single quantum well layer, only one direction slide from e) to (C) in Fig. 2 is obtained. 1(b) and 1(0) are the cross-sections of the light emitting section 5-mm' and the light modulating section BB' in FIG. 1(&), respectively.

Here, 1 is an n-InP substrate, 16 is an InGamus sP/
InPMQW layer (15a InP barrier layer, 1s b
(InGaAgP well layer), 8 is a P-InP layer, 11.
11' is a mesa stripe.

It has been found that when epitaxial growth is performed on such a mesa structure using the LPK method, the film thickness on the mesa stripe is thinner than when grown on a normal flat area, and that it largely depends on the width of the stripe 11, 11'.

In Figure 3. The relationship between the film thickness and stripe width of the 8Gao2 SO, 46PO, and 54 well layers is shown. The growth was carried out by slide growth at a growth temperature of 590°C, a slide speed of 30/S, and a substrate width of 10 m.The width of the melt hole of the growth boat was 7 m. Further, the level difference in the mesa is 1 μm.

As shown in Figure 3, I formed on the mesa stripe.
The thickness of the nGaAsP well layer 15b largely depends on the width of the mesa stripe. The film thickness (width OO) on the flat part is about 200 evaporations, but as the stripe width becomes narrower, the film thickness decreases, and when it becomes less than 3 μm, it does not grow at all. This is because the effective supersaturation degree of the melt on the stripe decreases due to the concentration of solute in the melt on the stepped portion of the mesa.

In this way, the thickness of the epitaxial layer can be controlled by changing the stripe width within the range of 3 to 30 μm.

On the other hand, FIG. 4 shows the relationship between the InGaASP well layer thickness and bandgap wavelength. In the case of a normal epitaxial layer with a thickness of 500 Å or more, the band gap wavelength hardly changes with changes in film thickness, but when a quantum well layer of 500 Å or less is formed, the band gap wavelength decreases due to the quantum size effect. Assuming that the stripe width of the light emitting section 3 is 30 μm and the stripe width W2 of the light modulating section is e7zm, the film thickness of the well layer 16b is equal to that of the light emitting section, as understood from FIGS. 1 and 3. 3, there are 200 people, while in the optical modulation section 2, there are 50 people.On the other hand, the bandgap wavelength of the MQW layer 15 at this time is 1.3 μm in the former, but 1.23 μm in the latter. There is a difference of about 70 nm from the light emitting section 3.Therefore, the light wave with a wavelength of 1.3 .mu.m emitted from the light emitting section 3 is hardly absorbed by the optical waveguide layer in the optical modulating section 2, and can be guided with low loss.

Furthermore, since the active layer 6 of the light emitting section 3 and the optical waveguide layer 6 of the light modulating section 20 formed in this way are the same epitaxial layer and are on the same optical axis, it is possible to obtain a high value of light wave coupling efficiency of 80% or more. There is no need to worry about instability due to axis misalignment.

Furthermore, by forming a diffraction grating in the light emitting section 3 to configure a distributed feedback laser, it is possible to obtain high quality laser light that does not require a cleavage plane. Furthermore, p -InP between both regions
By separately etching the layer 8, it is possible to independently apply an electric field or inject a current to the optical modulation section 2, and it is possible to perform optical modulation using the absorption coefficient and refractive index change due to the electro-optical effect, carrier injection effect, and quantum Stark effect, etc. Light control can be performed.

As described above, with the optical integrated circuit and the manufacturing method thereof according to the present invention, a high performance and highly functional optical integrated circuit can be obtained in a very simple manner.

In the first embodiment, InG2LA! is formed by two mesa stripe regions having different widths. ! P/I
Although the n P external modulator structure is shown, the same applies to the case where the light receiving area is included on the same substrate. In this case, a mesa region having a third stripe width is formed as a light receiving region,
By making the width of the mesa stripe larger than that of the light emitting region or the optical waveguide region, the bandgap can be made smaller in this region than in other regions, and light from the light emitting region and the optical waveguide region can be efficiently received. . Further, the process is exactly the same when the mesa stripe is formed not on the InP substrate but on an already grown epitaxial layer.

Furthermore, a mesa stripe region can be formed by forming two grooves (double channels).

Next, a multi-wavelength laser as a second embodiment of the present invention will be explained using the same (InGaAsP/InP-based semiconductor material).

FIG. 6 shows a three-wave multiplexed semiconductor laser as a second embodiment of the present invention. 01o is an n-type InP substrate, 11° 12, 13
The stripe widths are 6 μm and 15 μm, respectively.

It is a 3011m mesa stripe. 14 is n-type InP
15 is a multi-quantum well layer which is an active layer, and 16 is a p-type I layer.
The nP layer 17 is a p-type InGaAgP contact layer. The height of mesa stripe 11, 12, 13 is approximately 2μ
It is m. The fabrication of this semiconductor laser begins with n-type InP
After patterning a mask such as 8102 on the substrate, HCI
/ After etching with H3PO4-based etchant, the mask is removed to form a mesa. A mesa can also be obtained by forming a double channel. On the InP substrate having this mesa, for example, n is grown by liquid phase growth method.
The thickness of the type InP layer 14 is 1.3 μm after s μm growth.
band InGaAsP quantum well layer and 1.06μm band InG
A multi-quantum well layer consisting of an aAsP barrier layer is grown, and then a condylar p-type InP layer 16 and a p-type InG layer are successively grown.
aASP Near: Grow y tact layer. When epitaxial growth is performed on this mesa structure using the liquid phase growth method, the film thickness on the mesa stripes becomes thinner than that on a normal flat part, and also depends largely on the width of each stripe. As shown in Figure 3, 1.3 μm band I
The relationship between the thickness of the nGaAsP well layer and the stripe width is shown. Here, as in the first embodiment, the growth was performed using the slide growth method in which the substrate is grown while sliding, and the growth temperature was 5.
90'C, slide speed 309/! The width of the 160° substrate is 10. The length of the melt hole in the F1a1+ growth boat is 7. Further, the height of the mesa is 2 μm.

Here, when comparing the emission wavelengths of mesa parts 11 and 13, the film thickness of the well layer of mesa part 11 is 200 as shown in Fig. 3, while that of mesa part 13 is 60, as shown in Fig. 4. A large wavelength difference of about 701 m can be obtained. In a normal epitaxial layer with a thickness of 600 Å or more, the change in forbidden band wavelength is small with respect to the film thickness, but a large change can be obtained by forming a quantum well layer with a thickness of 600 Å or less. A semiconductor laser as shown in FIG. 6 is manufactured using the structure shown in FIG. 6 as described above. 18 is an n-type electrode, 19 is a p-type electrode, 2o
is an electrical isolation groove between each element. With such an element configuration, a three-wave multiplexed semiconductor laser centered on a wavelength of 1.3711 m can be obtained.

Furthermore, if a buried structure is adopted by the second epitaxial growth, the characteristics of the laser can be further improved. It goes without saying that the present invention is also effective for other compound semiconductor materials such as LM5ZGaAs. Furthermore, while epitaxial growth has been explained using liquid phase growth, it goes without saying that metal organic vapor phase growth and molecular beam epitaxy are also possible in principle by optimizing the growth conditions.

On the other hand, Fig. 7(a) shows the MQ formed on the mesa stripe.
This is a 31M cross-sectional photograph of the W layer (3500x magnification). same(
b) and (0) are enlarged photographs (magnification: 17,000 times) of the MQW layer 16 in the X and Y parts on the flat part 40 and the mesa stripe 11 with a width of 6 μm, respectively. .

From this figure, the well layer thickness in the MQW layer 16 is ~4
00 people, while the latter is ~100 people, and it is recognized that the film thickness is greatly different and the band gap energy is greatly different between the two.

In addition to the effects of the invention, the semiconductor device and method for manufacturing the same according to the present invention have the following advantages:
It is characterized by forming an epitaxial layer including at least one ultra-thin film layer of 500 Å or less by epitaxial growth on a semiconductor substrate having a plurality of regions in which mesa stripes with different widths are formed, -
With multiple epitaxial growth steps, growth layers with different band gap energies can be obtained in multiple regions on the substrate. In addition, by making each area a light-receiving, two-emitting, and optical waveguide area, good light wave coupling between each area is achieved, resulting in an optical integrated circuit with high performance and high reliability, and each area can be used as a semiconductor laser. As a result, it is possible to obtain a multi-wavelength laser with greatly different oscillation wavelengths, and its usefulness is great.

[Brief explanation of the drawing]

FIG. 1 (IL) is a plan view of an optical integrated circuit according to a first embodiment of the present invention, FIG. 2(&) to (d) are schematic process sectional views of the method for manufacturing a quantum well structure according to the present invention, and FIG. 3 is a diagram showing the mesa stripe width (W) and InGaAS in the example.
P A diagram showing the relationship between the well layer thickness, FIG. 4 is a diagram showing the relationship between the well layer thickness and the bandgap wavelength, and FIG.
Figure 6 is a cross-sectional view of the three-wave multiplexed laser, Figure 7 (IL)
, (b), (0) are 31M cross-sectional photographs of the MQW crystal layer on the mesa stripe taken with an electron microscope, Figure 8 is a structural cross-sectional view of a typical conventional optical integrated circuit, and Figure 9 is a cross-sectional view of a conventional hybrid type. FIG. 1o is a structural sectional view of a conventional monolithic wavelength multiplexed semiconductor laser. 1... InP substrate, 2... Light modulation section,
3... Light emitting part, 6... Optical waveguide layer, 6.
...Active layer, 11-13...Mesa stripe, 16...MQW layer, 16...p
-InP layer, 20... Separation groove. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure (a) ←Light emitting part 3--Reikuichikou Henkei part 2- Figure 1 Figure 2 A I3 Figure 33 (pm Nomesa Strike ° Width Figure 4 In8aAsFH and P layer ax
(A) Fig. 5 Fig. 6 Fig. 20 Mep part Fig. 7 Ia No. / Fig. 8 Fig. 9 Fig. 10

Claims (7)

[Claims] (1) First and second mesa stripe regions having different widths are formed on a semiconductor substrate, and an ultra-thin film layer of 500 Å or less made of an epitaxial growth layer is formed on the first and second mesa stripe regions, and a band 1st with different gap
, a second quantum well layer is formed, and different first and second semiconductor regions including the first and second quantum well layers are formed on the first and second mesa stripes. semiconductor devices. (2) The semiconductor device according to claim 1, wherein the first and second regions are a light emitting region, a light receiving region, an optical waveguide region, or any two thereof. (3) The semiconductor device according to claim 1, wherein the quantum well layer is an active layer, and the first and second regions are light emitting regions having different emission wavelengths. (4) forming a quantum well layer including at least one ultra-thin film layer with a thickness of 500 Å or less by epitaxial growth on a semiconductor substrate on which first and second mesa stripes with different widths are formed; 1. A method of manufacturing a semiconductor device, comprising forming first and second regions each made of the quantum well layer and having different band gap energies on the first and second mesa stripes. (5) The method for manufacturing a semiconductor device according to claim 4, wherein the epitaxial growth method is a liquid phase method. (6) The method for manufacturing a semiconductor device according to claim 4, wherein the width of the mesa stripe is 3 μm or more. (7) The semiconductor substrate is InP and the ultra-thin film layer is InGaAsP
A method for manufacturing a semiconductor device according to claim 4, characterized in that: