JPS62219590A - Integrated element of photo semiconductor and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an integrated element of photo semiconductor wherein a leak current between adjacent photo semiconductor elements is small, by forming an epitaxial layer of high resistivity possessing a wave guide structure between photo semiconductor elements. CONSTITUTION:A semiconductor laser 11 and a photo detector 12 are formed on an n-InP substrate 20, and a coupling waveguide part 13 composed of a high resistive epitaxial layer are formed between the semiconductor laser 11 and the photo detector 12. Therefore a signal voltage of about +2V applied to the semiconductor laser and a voltage of about -6V applied to the photo detector 12 are separated with each other, so that a leak current does not flow. As for the coupling waveguide part 13, is waveguide is constituted of an InP layer 22 of low reflectivity and an InGaAsP layer 23 of high reflectivity so that the laser light emitted from the semiconductor laser is coupled to the photo detector 12 with low loss.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical semiconductor integrated device used in optical communications and optical information processing, and a method for manufacturing the same.

(Prior Art) Optical semiconductor integrated devices, in which multiple optical semiconductor elements are formed on a semiconductor substrate, can improve the performance of a single optical semiconductor element,
It is also expected to be a device that can achieve functions that cannot be achieved with a single optical semiconductor device. Optical semiconductor devices used here include semiconductor lasers, photodetectors, optical modulators, optical switches, and the like, and by appropriately combining these optical semiconductor devices, an optical semiconductor integrated device is formed.

=)\ In such an optical semiconductor integrated device, different voltages are frequently applied to adjacent optical semiconductor devices. For example, Iga et al.
1 of Electronics Letters published in 1980. (5
Volume 342 (Electronics 1etter
S, vol. 16.1, 980, 342), the optical semiconductor integrated device integrates a semiconductor laser and a photodetector for monitoring.
2V) is applied, and a negative voltage (approximately -6V) is applied to the photodetector. In this case, as described in this paper, it is necessary to prevent leakage current from flowing between the elements. In this reported example, grooves were formed to separate the elements from each other, spatially isolating each element and preventing leakage current from flowing. In this example, the groove is dug until it reaches the substrate, and the end face on the side of the groove from which the laser beam is emitted is completely exposed in the air. In addition, Melt and other optical semiconductor integrated devices (IEE Journal)
Of Quantum Electronics 1979 Volume 15 7
Page 2: Mert et al., IEEE Journal
al of Quantum Electronics,
Vol. QE15.1979.72) also integrated a semiconductor laser and a monitoring photodetector, similar to the first conventional example described above. In this case, as in the first example, grooves were formed to separate the elements so that no leakage current would flow between the elements. However, this groove was stopped at a depth that reached the active layer of the semiconductor laser, and the waveguide layer below the active layer connected the two elements.

In addition, Furuya and others published optical semiconductor integrated devices (IEE Journal of Quantum Electronics, 1982, Vol. 18, p. 1783: Furuya
et al,, TEEE Journal of Qu
antum Electronics, Vol QE1
8, 1982.1783) used a structure having a waveguide structure made of a multilayer structure of polyimide and silicon oxide as a method for electrically separating and optically coupling two optical semiconductor elements. Polyimide and silicon oxide are dielectric materials that serve to electrically isolate elements. Furthermore, since a waveguide structure is formed, the elements are optically coupled with lower loss than the first and second conventional examples.

As described above, conventional methods for separating elements of optical semiconductor integrated devices include forming grooves to spatially separate them when the applied voltages (4i) are different, or separating them spatially between the grooves. An insulator was embedded inside the device to electrically isolate the elements from each other to prevent leakage current from flowing.

(Problem to be Solved by the Invention) However, when the elements are separated using a method like the first conventional example described above, the light that should be guided between the elements is transmitted between the grooves. Since the light propagates through the air without a waveguide structure, it diverges and cannot be efficiently coupled to an adjacent optical semiconductor element, causing a large increase in loss. The second conventional example described above has the following features in order to eliminate such drawbacks of the first conventional example:
An attempt was made to create both an active layer and a waveguide layer to reduce coupling loss and prevent leakage current. However, in this case, about 0.15
Since most of the applied voltage is applied to the pm-thick active layer, there is a very high risk that high voltage will be applied near the formed grooves, causing insulation failure and leakage current. In addition, in the third conventional example, since a waveguide structure is formed between the optical semiconductor elements, the elements are optically coupled with lower loss than in the first and second conventional examples. Since the refractive index of the optical semiconductor element is significantly different, reflection loss between the semiconductor and the dielectric becomes large, and when a semiconductor laser is used as the optical semiconductor element, these dielectrics are used in the active layer of the semiconductor laser. were in direct contact with each other, which could lead to a loss of reliability.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical semiconductor integrated device in which leakage current between adjacent optical semiconductor elements is small, loss in coupling these optical semiconductor elements is small, and reliability of the optical semiconductor elements is not impaired. Another object of the present invention is to provide a method for manufacturing such an optical semiconductor integrated device.

(Means for Solving the Problems) The present invention provides an optical semiconductor integrated device in which at least two optical semiconductor elements are formed on the same semiconductor substrate, in which a waveguide structure is formed between the optical semiconductor elements. It is characterized by being formed of a high-resistance epitaxial layer. Another invention provides a first step of epitaxially growing two or more layers constituting optical semiconductor elements in a planar shape on a semiconductor substrate with a flat surface;
A second step 1' for forming grooves between the optical semiconductor elements by selectively etching between the two or more optical semiconductor elements.
, a third layer selectively fills and grows the etched groove.
The third step further comprises transporting at least one transition metal of iron, chromium, and manganese as a chloride, transporting a group 3 element as a chloride, and transporting a group 3 element as a chloride; This is a method for manufacturing an optical semiconductor integrated device characterized by buried epitaxial growth using a vapor phase growth method in which elements are transported using hydrogen compounds.

(Function) According to the first invention, two or more devices including an optical semiconductor element -1-
In an optical semiconductor integrated device in which two semiconductor elements are formed on the same semiconductor substrate, the electrical resistance between adjacent optical semiconductor elements is It is very large, so the leakage current is small, and the waveguide that connects these optical semiconductor elements is made of semiconductor, so the reflection loss is small. Also, because it has a waveguide structure, it is possible to connect two optical semiconductor elements. The coupling loss of the laser beam connecting between the two is reduced.

Furthermore, since the semiconductor is in direct contact with the active layer of the semiconductor laser, which is one of the optical semiconductor elements, reliability is not impaired. In particular, when the semiconductor substrate is InP, the high-resistance epitaxial layer is InGaA, and the waveguide structure has a multilayer structure of an sP layer and an InP layer, the oscillation wavelength is in the range of 1 m to 1.65 pm. It is possible to guide the laser light emitted from the laser to other optical semiconductor elements with small loss, and it contains at least one type of transition metal impurity among iron, chromium, and manganese.
This epitaxial layer has very high resistivity, which reduces leakage current between adjacent optical semiconductor elements. According to the second invention, the buried epitaxial growth of the high resistance layer is
This is carried out using a vapor phase growth method in which group elements are transported using chlorides, group V elements are transported using hydrogen compounds, and transition metals are transported using chlorides.

Buried growth requires selective growth inside the groove, but for this purpose it is necessary to have strong dependence on crystal orientation. Growth methods with such characteristics are the vapor phase growth method, in which growth is performed under conditions relatively close to thermal equilibrium, and the liquid phase growth method. Since the molecular beam epitaxial growth method and the organic transition metal vapor phase epitaxy method grow in a non-equilibrium state, the dependence on crystal orientation is very small, and it is difficult to selectively grow only in such narrow groove portions. Furthermore, according to our experiments, growing a high-resistance epitaxial film by mixing at least one type of transition metal impurity among iron, manganese, and chromium, which is one of the characteristics of the present invention, is not possible. This was possible with vapor phase growth, but it was not easy with liquid phase growth. This is thought to be because the segregation coefficient of these mixed transition metals is very small, so that the amount of transition metal impurities necessary for making the semiconductor high in resistance is not mixed. In this way, according to the above vapor phase growth method, a high-resistance waveguide structure consisting of a multilayer structure of InGaAsP layers and InP layers mixed with at least one type of transition metal impurity among iron, thallium, and manganese is embedded. Can be epitaxially grown.

(Example) Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram illustrating a first embodiment of the present invention, and n
- A semiconductor laser 11 and a photodetector 12 are formed on an InP substrate 20. A coupling waveguide section 13 made of a high-resistance epitaxial layer, which is a feature of the present invention, optically couples the semiconductor laser 11 and the photodetector 12. Here, the semiconductor laser 11 is a distributed feedback semiconductor laser, and includes a p-InP cladding layer 16, In, GaA
sP active layer 17, InGaAsP waveguide layer 1°8, n
-InP cladding layer 19 is laminated on n-InP substrate 20-. Then, the striped semiconductor laser positive electrode 1-5 is arranged so that the current flows concentratedly in the center.
It is sandwiched between dielectric films 14. The photodetector 12 is p
A photodetector using an n-junction, with a p-InP cladding layer 2
5. An InGaAsP absorption layer 26, an InGaAsP waveguide layer 27, and an n-InP cladding layer 28 are laminated on the n-TnP substrate 2. In order for this photodetector to work efficiently, the striped negative electrode 29 of the photodetector is sandwiched between dielectric films 30. These two elements have a common electrode 21 on the substrate side. A coupling waveguide section 13 for electrically separating these two elements and optically coupling them is formed at the second part of the figure 7 groove, and a high-resistance In
It is made up of a P layer 22, a high resistance 1nGaAsP waveguide layer 23, and a high resistance InP layer 24.

In this embodiment, since the coupling waveguide section 13 is formed of a high-resistance epitaxial layer, a signal voltage of about +2V applied to the semiconductor laser and a voltage of about +2V applied to the photodetector 12 are combined.
Since the voltages of V are separated from each other, almost no leakage current flows. The coupling waveguide section 13 is made of In, which has a low refractive index.
P layer 22 and InGaAsP waveguide layer 23 with high refractive index
Since the waveguide is formed by , the laser beam emitted from the semiconductor laser 1 is coupled to the photodetector 12 with low loss.

The parameters of each element in this example were as follows. The semiconductor laser 1 has an oscillation wavelength of 1.55 pm, and the thickness of each layer is 2p for the p-InP cladding layer 16.
m, InGaAsP active layer 17 is 0.15 pm, InG
The aAsP waveguide layer 18 has a thickness of 0.15 pm, the n-InP cladding layer 19 has a thickness of 41"m, and the semiconductor laser positive electrode 15 is made of gold-zinc, and its stripe width is 311m.
For the dielectric film 14, acid-:\anabolic silicon was used. The thickness of each layer of the photodetector is p-In
P cladding layer 25 is 211m, InGaAsP absorption layer 2
6 is 0.3 pm, n-ten nP cladding layer 28 is 4 pm
The striped negative electrode 29 of this photodetector had a width of 3 pm and was made of gold-zinc. Gold-tin was used for the common electrode 21. For the dielectric film 30, silicon oxide was used.

A coupling waveguide section 13 that electrically separates these two elements and optically couples them is formed at the bottom of a V-shaped groove consisting of 311 planes between the semiconductor laser 11 and the photodetector. , iron doped with 10110l6 resistivity about 105
High resistance InP layer 22 of Ω1cm, high resistance TnGaAs
It was formed of a multilayer epitaxial layer having a waveguide structure consisting of a P waveguide layer 23 and a high resistance rnP layer 24.

Although the parameters of each element in the bipod embodiment were selected as described above, it is clear that these are not limiting to the present invention.

-, IZ embodiment also corresponds to the embodiment of the second invention of the present invention.

Next, a second embodiment of the present invention is shown in FIG. This embodiment uses an external modulator 4 that can modulate the semiconductor laser 11 at high speed.
0 is an optical semiconductor integrated element T integrated on the same semiconductor substrate 20'' together with a semiconductor laser.

There are two types of optical modulators: those that change the amplification factor and absorption loss by applying a current in the forward direction, and those that change the absorption loss by applying a voltage in the opposite direction. The optical modulator used here is the latter type, and this type of modulator is capable of faster modulation. In FIG. 2, a semiconductor laser 11 and an optical modulator 40 are formed on an n-InP substrate 20. A coupling waveguide section 13 made of a high-resistance epitaxial layer, which is a feature of the present invention, optically couples the semiconductor laser 11 and the optical modulator 40. Here, the semiconductor laser 11 is a distributed feedback semiconductor laser similar to the first embodiment,
p-TnP cladding layer 16, InGaAsP active layer 17
, an InGaAsP waveguide layer 18, and an n-InP cladding layer 19 are laminated on an n-InP substrate 2O-J-, and a striped semiconductor laser positive electrode 15 is attached to a dielectric film 14 so that current flows in a concentrated manner. sandwiched between. Further, the optical modulator 40 includes a p-InP cladding layer 25
, InGaAsP absorption layer 26, n-InP cladding layer 2
8 is stacked on an n-InP substrate 20,
In order for this optical modulator 40 to work efficiently, the negative electrode 29 of the optical modulator also has a stripe shape, and the dielectric film 30
sandwiched between. These two elements have a common electrode 21 on the substrate side. The modulated laser beam 41 is emitted from the opposite end of the optical modulator.

The coupling waveguide section 13 that electrically separates these two elements and optically couples them includes a high-resistance InP layer 22, a high-resistance InGaAsP waveguide layer 23, and a high-resistance InGaAsP waveguide layer 23, as in the first embodiment. The resistance InP layer 24 has a structure formed in the second half of the V-shaped groove so as to have a waveguide structure.

In this embodiment, the coupling waveguide section 13 is formed of a high-resistance epitaxial layer, and a signal voltage of about +2V applied to the semiconductor laser and -6V applied to the optical modulator 40 are applied to the semiconductor laser.
voltages are separated from each other. Therefore, almost no leakage current flows. Since the coupled waveguide section 13 is formed of an InP layer 22 with a low refractive index and an InGaAsP waveguide layer 23 with a high refractive index, the laser beam emitted from the semiconductor laser 11 is optically transmitted with low loss. Coupled to modulator 40.

The parameters of each element in this example were as follows. The semiconductor laser 11 is the same as in the first embodiment. The thickness of each layer of the optical modulator is p-1nP cladding layer 25
is 2pm, and the TnQaAsP absorption layer 26 is 0.3111T.
The thickness of the 1, n-4nP cladding layer 28 was 4 pm, the width of the sliver type negative electrode 29 of this optical modulator was 31] m, and gold-zinc was used. For the dielectric film 30, silicon oxide was used. A coupling waveguide section 13 that electrically separates these two elements and optically couples them is formed at the bottom of the V-shaped groove between the semiconductor laser 11 and the photodetector, and is made of high-resistance InP. It had a waveguide structure including a layer 22, a high resistance InGaAsP waveguide layer 23, and a high resistance InP layer 24.

Although the parameters of each element in the above embodiments were selected as described above, it is clear that these values are not limiting for the present invention.

Next, a third embodiment of the present invention will be described. This example is a method of manufacturing the optical semiconductor integrated device of the first and second examples described above. When forming an optical semiconductor integrated device consisting of a semiconductor laser and a photodetector in the first embodiment on an InP semiconductor substrate, the layers that will become the semiconductor laser and the photodetector are formed into a flat plate on an InP semiconductor substrate with a flat surface. a first step of epitaxial growth, a second step of selectively etching between the two optical semiconductor elements to form a groove between the two optical semiconductor elements, and a third step of selectively filling and growing the etched groove. Consisting of The first step and the second step are the same as conventional ones, and the first step uses a vapor phase growth method that transports group 3 elements with chlorides and transports group 5 elements with hydrogen compounds. there was. Growth temperature is 690°C
The layered structure described in the first example was obtained. In the second step, V-shaped grooves were formed using a bromethanol etching solution using silicon oxide as a mask. The third step, which is a feature of the present invention, is to transport group 3 elements as chlorides, transport group 5 elements as hydrogen compounds, and remove at least one type of transition metal impurity among iron, chromium, and manganese as chlorides. The I
A waveguide structure consisting of a multilayer structure of nGaAsP layers and InP layers is buried and epitaxially grown. This step was performed in a vapor phase growth apparatus shown in FIG.

-j The left part of the cardiac reaction tube is divided into two chambers, the second chamber 5.
In room 7, InGaAsP is grown, and in room 58 below, InGaAsP is grown.
Grow P. When growing a multilayer structure, the In, P substrate 54 is moved between an upper chamber 57 and a lower chamber 58 by a substrate moving mechanism 55. When growing a high resistance InP layer, I
The nP substrate 54 is placed in the lower chamber 58, and hydrogen chloride and hydrogen are fed from the gas inlet 64 to the mixed melt 53 of iron and indium heated to about 800°C in the furnace 51 to react with indium chloride and iron chloride. and transported in chloride. Furthermore, phosphine, which transports group 5 elements, is fed through a narrow inlet 63. These gases are mixed, and a high-resistance InP layer is selectively grown in the groove portion of the InP substrate 54, which is heated to 600° C. and has grooves formed therein. High resistance InGaAsP
When growing a layer, the InP substrate 54 is placed in the upper chamber 57, and hydrogen chloride and hydrogen are fed through the gas inlet 62 to the iron and indium mixed melt 53 heated to about 800°C in the furnace 51. React with indium chloride and iron chloride and transport as chloride. Furthermore, hydrogen chloride and hydrogen are sent to the gallium melt 52 from the gas inlet 60, and gallium chloride is transported. Furthermore, phosphine and arsine, which transport group 5 elements, are fed through a narrow inlet 61. These gases are mixed, and a high-resistance InGaAsP layer is selectively grown in the groove portion of the InP substrate 54 in which the groove is formed. The reacted gas exits through the gas outlet 65.

According to the embodiment described in the Biped Embodiment, iron is selectively deposited on the figure 7 groove consisting of 311 sides with a width of 20 microns.
A multi-layer epitaxial layer was obtained, which was a waveguide structure of a high-resistance InP layer 22, a high-resistance InGaAsP waveguide layer 23, and a high-resistance InP layer 24 doped with 011-0l6 and having a resistivity of about 105 Ω·cm.

Although iron was used as the impurity transition metal in the two-leg example, high resistance can also be achieved by using chromium or manganese. Although the growth conditions for the third example were selected as described above, these values may be changed as appropriate.

Also, materials other than InP-based, such as GaAs-based, may also contain Fe,
When Cr and Mn are included, a high resistance layer can be obtained.

(Effects of the Invention) -1 = As explained above, according to the present invention, an optical semiconductor integrated device can be obtained in which the leakage current between adjacent optical semiconductor elements is small and the loss in coupling these optical semiconductor elements is small. It was done. Furthermore, an optical semiconductor integrated device was obtained without impairing the reliability of the optical semiconductor device. According to the present invention, optical semiconductor devices can be integrated in large numbers because optical loss is reduced, and leakage current between devices can be reduced, so devices can be arranged close together.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a first embodiment of the first invention of the present invention, in which 11-m-semiconductor laser, 12-m-photodetector, 13-
11-coupled waveguide section, 14-m-dielectric film, 15-m-semiconductor + electrode, 16--p-InP cladding layer, 17--InGaAs
P active layer, 18--4nGaAsP waveguide layer, 19--n-InP cladding layer, 2O--n-In
P substrate, 21-m=common electrode, 22-1-1 high resistance InP layer, 23-m-high resistance TnGaAsP waveguide layer,
24--high resistance InP layer, 25--p-Tn, P cladding layer, 26--InGaAsP absorption layer, 27--InGaAsP waveguide layer, 28--n-InP cladding layer, 29--photodetector-- 11-m-semiconductor laser, 13-1-coupled waveguide. Part, 4
0-m-light modulator, 14-m-dielectric film, 15-
m-semiconductor + electrode, 1.6--p-InP cladding layer, 17--InGaA
sP active layer, 18--- InGaAsP waveguide layer, 1
9--n-InP cladding layer, 2O--n-InP
Substrate, 21-m=common electrode, 22-m-high resistance n, P layer, 23-m-high resistance 1nGaAsP waveguide layer,
24--high resistance InP layer, 25--p-InP cladding layer, 26-- InGaAsP modulation absorption layer, 28-
- n-InP cladding layer, 29- one photodetector electrode, 30- one dielectric film, 41- one laser beam, and FIG. 3 is a diagram for explaining the second aspect of the present invention in detail. Yes, 50-m-reaction tube, 51-11 furnace, 52-m-gallium melt,

Claims (2)

[Claims] (1) In an optical semiconductor integrated device in which at least two or more optical semiconductor elements are formed on the same semiconductor substrate,
An optical semiconductor integrated device characterized in that a space between the optical semiconductor devices is formed of a high-resistance epitaxial layer having a waveguide structure. (2) A first step of epitaxially growing layers constituting two or more optical semiconductor elements in a planar shape on a semiconductor substrate with a flat surface, and selective etching between the two or more optical semiconductor elements. In the method for manufacturing an optical semiconductor integrated device, the method includes a second step of forming grooves between the optical semiconductor elements by etching, and a third step of selectively filling and growing the etched grooves. , manganese, and is characterized by buried epitaxial growth using a vapor phase growth method in which at least one transition metal of manganese is transported as a chloride, a group 3 element is transported as a chloride, and a group 5 element is transported as a hydrogen compound. A method for manufacturing an optical semiconductor integrated device.