JP6729982B2 - Semiconductor optical integrated device - Google Patents

Description

The present application relates to a semiconductor optical integrated device in which semiconductor optical devices are integrated.

In an access system, which is an optical communication system between a relay station and a user, a direct modulation semiconductor laser transmitter (DML: Directly Modulated Laser) suitable for low-speed modulation has been often used in the past. When performing the above high-speed communication, an electro-absorption semiconductor optical modulator (EAM: Electro-absorption Modulator) suitable for high-speed modulation and a distributed feedback semiconductor laser (DFB-LD: Distributed Feedback Laser Diode, for simplicity, An EML (Electro-absorption Modulator integrated Laser), which is a semiconductor optical integrated device in which an LD (also referred to as LD) is integrated, is suitable. In the access system, the signal light intensity is attenuated because the optical signal is branched to a plurality of users. Therefore, there is a problem to increase the output of the semiconductor laser transmitter before branching.

Since the external modulator EAM is accompanied by insertion loss, it is necessary to increase the drive current of the LD and increase the optical output in order to increase the output of the EML. However, there are problems that there is a limit to increase the light output of the LD, that the power consumption of the LD and the temperature control element increases, and that the extinction characteristic of the EAM deteriorates as the light input to the EAM increases. Therefore, it is not easy to increase the output. In order to solve this problem, in Patent Document 1, a semiconductor optical integrated device in which a semiconductor optical amplifier (SOA: Semiconductor Optical Amplifier) is monolithically integrated on the same substrate on the EAM emission side of the device in which LD and EAM are integrated is used to achieve high output. Is being promoted. Further, since the LD and the SOA are configured to be fed by one terminal, the same feeding method as that for the element having the structure in which the SOA is not integrated is maintained. Therefore, the influence on the driving circuit of the semiconductor laser transmitter due to the element change is maintained. Can be made smaller.

In the SOA driven by a constant current, when the input light is multiplied, the carrier density in the active layer is consumed by the recombination and reduced, and the gain fluctuates. The carrier density fluctuation becomes more significant on the SOA emission side where the light intensity increases and as the SOA becomes longer. In this way, carrier density fluctuations occur according to the intensity of the modulated signal light incident on the SOA and its waveform pattern, and waveform fluctuations, that is, pattern effects, occur through gain fluctuations. The pattern effect becomes more remarkable as the modulation speed of the signal light increases, and in the case of the semiconductor laser transmitter in which the SOA is integrated, it has an influence when the modulation speed is 10 Gb/s or more. The response speed of the SOA is the carrier density recovery speed of the active layer and is influenced by the drive current of the SOA.

JP, 2013-258336, A US Patent Application Publication No. 2004/0042069

As described in Patent Document 1, in a semiconductor optical integrated device in which LD, EAM, and SOA are integrated in this order, when LD and SOA are connected and driven at the same terminal, LD and SOA have a common drive voltage. Is applied, and the total drive current is divided by an internal resistance ratio proportional to the ratio of the lengths of LD and SOA to be supplied. The current value required at this time is the sum of the current values supplied to the LD and the SOA. For example, in order to obtain a sufficient light output in the case of a general element where the LD and SOA have the same length, a current of about 100 mA flows to both LD and SOA when the printing voltage is about 1.5V. A total current of about 200mA is required. However, generally, in a small driver IC for driving an element in a semiconductor optical integrated element, a voltage of 3 V or more can be supplied, but the supply current is limited.

Series connection is effective for reducing the supply current, and Patent Document 2 discloses a technique of connecting an LD and an SOA in series to drive them. However, the configuration of Patent Document 2 is a configuration in which the LD and the SOA are mounted on the submount substrate, and cannot be directly applied to the configuration in which the LD and the SOA are monolithically integrated on the semiconductor substrate. ..

The present application discloses a technique for solving the above problems, and in a semiconductor optical integrated device in which optical devices are integrated on a semiconductor substrate, series connection of optical devices can be realized, and drive current from a power supply It is an object to provide a small number of high-power semiconductor optical integrated devices.

In all of the semiconductor optical integrated devices disclosed in the present application, there are provided a semiconductor amplifier and a plurality of semiconductor lasers configured such that holes are injected from the p-side cladding layer and electrons are injected into the active layer from the n-side cladding layer. In the semiconductor optical integrated device monolithically integrated on one surface of the same semiconductor substrate, the semiconductor substrate is a conductive semiconductor substrate, and the n-side cladding layer of the semiconductor amplifier and each of the n-side cladding layers of the plurality of semiconductor lasers. Is an electrical insulating layer formed between the semiconductor substrate and the respective n-side cladding layers of the plurality of semiconductor lasers, and the n-side cladding layer of the semiconductor amplifier and the respective n-side cladding layers of the plurality of semiconductor lasers. An n-side contact layer electrically insulated by an electrically insulating layer formed between the n-side clad layers of the plurality of semiconductor lasers is provided on each n-side of the plurality of semiconductor lasers. The semiconductor laser is provided between the clad layer and the electrical insulating layer, and is configured to electrically connect the n-side contact layer and the p-side clad layer of the semiconductor amplifier. And are electrically connected in series.

According to a semiconductor optical integrated device in which optical devices are integrated on a semiconductor substrate disclosed in the present application, it is possible to realize a series connection of optical devices and to provide a high output semiconductor optical integrated device with a small drive current from a power supply. There is an effect that can be.

FIG. 3 is a conceptual diagram showing a configuration of a main part of the semiconductor optical integrated device according to the first embodiment. FIG. 3 is an equivalent circuit diagram for explaining electrical connection of the semiconductor optical integrated device according to the first embodiment. 3A and 3B are views for explaining step 1 and step 2 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. 4A and 4B are views for explaining step 3 and step 4 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. 5A and 5B are views for explaining step 5 and step 6 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. 6A and 6B are views for explaining step 7 and step 8 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. 7A and 7B are views for explaining step 9 and step 10 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. 8A and 8B are views for explaining step 11 and step 12 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. 9A and 9B are views for explaining step 13 and step 14 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. 10A and 10B are diagrams for explaining step 15 and step 16 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. 11A and 11B are views for explaining step 17 and step 18 of the manufacturing process of the semiconductor optical integrated device according to the first embodiment, respectively. FIG. 9 is a conceptual diagram showing a configuration of a main part of a semiconductor optical integrated device according to a second embodiment. 13A and 13B are diagrams for explaining step 21 and step 22 of the manufacturing process of the semiconductor optical integrated device according to the second embodiment, respectively. 14A and 14B are views for explaining step 23 and step 24 of the manufacturing process of the semiconductor optical integrated device according to the second embodiment, respectively. 15A and 15B are views for explaining step 25 and step 26 of the manufacturing process of the semiconductor optical integrated device according to the second embodiment, respectively. 16A and 16B are diagrams for explaining step 27 and step 28 of the manufacturing process of the semiconductor optical integrated device according to the second embodiment, respectively. FIG. 9 is a conceptual diagram showing a configuration of a main part of a semiconductor optical integrated device according to a third embodiment. 18A and 18B are views for explaining step 31 and step 32 of the manufacturing process of the semiconductor optical integrated device according to the third embodiment, respectively. 19A and 19B are diagrams for explaining step 33 and step 34 of the manufacturing process of the semiconductor optical integrated device according to the third embodiment, respectively. FIG. 16 is a conceptual diagram showing another configuration of the main parts of the semiconductor optical integrated device according to the third embodiment. FIG. 16 is a conceptual diagram showing a configuration of a main part of a semiconductor optical integrated device according to a fourth embodiment. FIG. 16 is a conceptual diagram showing another configuration of the main part of the semiconductor optical integrated device according to the fourth embodiment. FIG. 16 is a block diagram showing a schematic configuration of a semiconductor optical integrated device according to a fifth embodiment. FIG. 24 is an equivalent circuit diagram for explaining electrical connection of the configuration of FIG. 23 of the semiconductor optical integrated device according to the fifth embodiment. 23 is a block diagram showing another schematic configuration of the semiconductor optical integrated device according to the fifth embodiment. FIG. FIG. 27 is an equivalent circuit diagram for explaining electrical connection of the configuration of FIG. 25 of the semiconductor optical integrated device according to the fifth embodiment. FIG. 27 is an equivalent circuit diagram for explaining another electrical connection of the configuration of FIG. 25 of the semiconductor optical integrated device according to the fifth embodiment.

FIG. 1 is a conceptual diagram showing a configuration of a main part of a semiconductor optical integrated device according to the first embodiment. In this semiconductor optical integrated device, a semiconductor laser (LD) 101, an electroabsorption type semiconductor optical modulator (also simply referred to as a modulator or EAM) 102, and a semiconductor optical amplifier (SOA) 103 are the same semiconductor substrate (n-InP). It is integrated on the substrate 1. As the dimensions of each element, for example, the semiconductor laser length is 300 μm, the semiconductor optical amplifier length is 150 μm, and the modulator length is 200 μm.

The semiconductor laser 101 has, as main components, an n-InP clad layer 51 as an n-side clad layer, an active layer 8, and a p-side clad layer, which are sequentially formed on an n-InP substrate 1 which is a conductive semiconductor substrate. The p-InP clad layer 9 of FIG. The modulator 102 is composed of an n-InP clad layer 51, a modulator absorption layer 10, and a p-InP clad layer 9 which are sequentially formed on the n-InP substrate 1. The semiconductor optical amplifier 103 is basically similar to the semiconductor laser 101 in that it is formed on the n-InP substrate 1 in order, and has an n-InP cladding layer 53 as an n-side cladding layer, an active layer 8, and a p-side cladding layer. The p-InP clad layer 9 of FIG. In addition, in the semiconductor optical integrated device according to the first embodiment, the n-InP substrate 1 in the semiconductor optical amplifier 103 portion and the n-InP clad layer 53 are electrically insulated from each other by an electrical insulating layer. An Fe-doped semi-insulating InP layer 3 is provided, and a conductive n-InGaAsP contact layer 43 is provided as an n-side contact layer between the Fe-doped semi-insulating InP layer 3 and the n-InP cladding layer 53. There is. Further, between the n-InP clad layer 51 in the semiconductor laser 101 part and the modulator 102 part and the n-InP clad layer 53 in the semiconductor optical amplifier 103 part, an Fe-doped semi-insulating InP layer 19 as an electric insulating layer is provided. The n-side cladding layer 51 of the semiconductor laser 101 and the n-side cladding layer 53 of the semiconductor optical amplifier 103 are electrically insulated from each other. Note that the insulating material applicable to the semiconductor optical integrated device disclosed in the present application is not an insulating material such as quartz or ceramic but a semiconductor material, and is a material for flowing an electric current among the materials constituting the element. It is called "semi-insulating" because it is a material having a sufficiently high resistivity so that it can be considered that no current flows. Since the p-side clad layer 9 can obtain a separation resistance that is about three orders of magnitude higher than that on the n-side simply by engraving the isolation portion between the elements by etching, it is particularly a semi-insulating material and is used as the modulator 102 and the semiconductor optical amplifier. It is not necessary to embed between 103 and between the semiconductor laser 101 and the modulator 102.

Further, on the p-side clad layer 9 in the semiconductor laser 101 portion, on the p-side contact electrode 261 and on the p-side clad layer 9 in the modulator 102 portion so that electrical connection with the outside or between elements can be made. A p-side contact electrode 262 is formed on the p-side clad layer 9 in the semiconductor optical amplifier 103. An n-side contact electrode 25 is formed on the lower surface of the n-InP substrate 1. The n-InGaAsP contact layer 43, which is an n-side contact layer provided below the n-side clad layer 53 of the semiconductor optical amplifier 103, is lateral to the n-side clad layer 53 (lateral direction perpendicular to the optical axis of the laser). The n-side contact electrode 253 is provided on the upper surface of the projected n-side contact layer 43.

In the semiconductor laser 101 and the semiconductor optical amplifier 103, holes are injected from the p-side clad layer and electrons are injected into the active layer from the n-side clad layer by passing a current from the p-side clad layer to the n-side clad layer. As a result, light is generated when holes and electrons recombine in the active layer. In this semiconductor optical integrated device, the light emitted from the semiconductor laser 101 is input to the modulator 102. In the modulator 102, the absorption amount of light changes due to an electric field applied in the opposite direction to an MQW (Multi Quantum Well) that is the modulator absorption layer 10. If light is transmitted to the modulator 102 when no voltage is applied, and light is absorbed and does not transmit when an electric field is applied, the light output can be modulated. The light transmitted through the modulator 102 is input to the semiconductor optical amplifier 103. In the semiconductor optical amplifier 103, light is amplified and output according to the current value injected into the semiconductor optical amplifier 103.

The electrical connection of the semiconductor optical integrated device of FIG. 1 will be described. Between the p-side contact electrode 263 of the semiconductor optical amplifier 103 and the n-side contact electrode 25 provided on the lower surface of the n-InP substrate 1, a DC voltage is applied from an external DC power supply (not shown). It The n-side contact electrode 253 of the semiconductor optical amplifier 103 and the p-side contact electrode 261 of the semiconductor laser 101 are connected by a conductor such as a wire 27. With this connection, as shown in the equivalent circuit of FIG. 2, the semiconductor laser 101 and the semiconductor optical amplifier 103 are connected in series, and currents of the same current value flow in the semiconductor laser 101 and the semiconductor optical amplifier 103. A signal voltage for modulation is applied to the p-side contact electrode 262 of the modulator 102.

In a conventional semiconductor optical integrated device in which a semiconductor laser and a semiconductor optical amplifier are integrated on a semiconductor substrate, the electrode on the n side is common as shown in Patent Document 1, and therefore, the semiconductor laser and the semiconductor laser are integrated. The semiconductor optical amplifiers could not be electrically connected in series. On the other hand, in the semiconductor optical integrated device according to the first embodiment, regarding the n-side cladding layer, the n-side cladding layer 51 of the semiconductor laser 101 part and the n-side cladding layer 53 of the semiconductor optical amplifier 103 part are electrically connected. The n-side clad layer 53 and the n-side contact electrode 25 of the semiconductor optical amplifier 103 are electrically insulated. Further, an n-side contact layer 43 for electrically connecting to the n-side clad layer 53 of the semiconductor optical amplifier 103 part is provided, the n-side contact layer 43 is laterally extended, and an n-side contact electrode 253 is provided on the upper surface thereof. .. With this configuration, the p-side clad layer of the semiconductor laser 101 and the n-side clad layer 53 of the semiconductor optical amplifier 103 can be electrically connected, and the semiconductor laser 101 and the semiconductor optical amplifier 103 are electrically connected in series. It was possible to connect.

Next, a method of manufacturing the semiconductor optical integrated device according to the first embodiment will be described. 3A and 3B to FIGS. 11A and 11B are views for explaining the manufacturing process. However, the detailed structure and manufacturing process of the semiconductor optical integrated device applied to the present application are not limited to the following.

As shown in FIG. 3A, a semiconductor laser 101 and a modulator 102 are covered with an insulating film 2 having a width of several tens of μm on an n-InP substrate 1 which is a conductive semiconductor substrate, and the n-InP substrate 1 is etched by several μm. (Step 1). Thereafter, as shown in FIG. 3B, the Fe-doped semi-insulating InP layer 3 and the n-InGaAsP contact layer 4 are selectively grown (step 2). The insulating film 2 is removed, and as shown in FIG. 4A, the n-InP clad layer 5, the n-InGaAsP diffraction grating layer 6, and the n-InP clad layer 5 are grown on the entire surface (step 3). Next, as shown in FIG. 4B, an insulating film 2 is formed between the modulator 102 and the semiconductor optical amplifier 103 with an opening of several tens of μm and a width of several tens of μm, and the n-InGaAsP contact layer 4 is exposed. Are removed by etching (step 4). After the etching, the n-InP clad layer 5, the n-InGaAsP diffraction grating layer 6, and the n-InP clad layer 5 in the semiconductor optical amplifier 103 portion are completed as the n-side clad layer 53 at this stage. Further, the n-InP clad layer 5, the n-InGaAsP diffraction grating layer 6, and the n-InP clad layer 5 in the semiconductor laser 101 portion are formed at a stage where the n-InGaAsP diffraction grating layer 6 becomes a diffraction grating in step 7 described later. The n-side clad layer 51 is completed.

Further, as shown in FIG. 5A, the n-InGaAsP contact layer 4 is removed by etching except the semiconductor optical amplifier 103, and the other portions are all removed by etching to form the n-InGaAsP contact layer 4 as an n-side contact layer 43 ( Step 5). Thereafter, as shown in FIG. 5B, the Fe-doped semi-insulating InP layer 20 is grown using the insulating film 2 as a mask (step 6). Thereafter, the insulating film 2 is removed, and the n-InGaAsP diffraction grating layer 6 of the diffraction grating portion 7 of the semiconductor laser 101 is etched at a cycle of 200 nm to form a diffraction grating of the semiconductor laser as shown in FIG. 6A (step 7). Thereafter, as shown in FIG. 6B, the active layer 8 and the p-InP clad layer 9 are formed (step 8).

Next, as shown in FIG. 7A, the insulating film 2 is formed with a width of several tens of μm so as to open an opening in the modulator 102, and the p-InP clad layer 9 and the active layer 8 are etched (step 9). ). Thereafter, as shown in FIG. 7B, the modulator absorption layer 10 and the p-InP cladding layer 9 are selectively grown on the entire surface (step 10). Then, the insulating film 2 is removed, the insulating film 2 is formed again as shown in FIG. 8A, and a pattern for processing the waveguide is formed (step 11). The insulating film 2 at this stage has a width of about 1 μm in the semiconductor laser 101 and the semiconductor optical amplifier 103, which form a buried waveguide in which both sides of the waveguide are embedded with a semiconductor, and the both sides of the waveguide are not covered with the semiconductor. The portion of the modulator 102 that forms the waveguide is formed with a width of about several tens of μm. After that, etching is performed so as to stop in the middle of the Fe-doped semi-insulating InP layer 20. Thereafter, using the insulating film 2 as a mask, buried growth is performed with the p-InP buried layer 11, the n-InP buried layer 12, and the p-InP buried layer 11 as shown in FIG. 8B (step 12).

After that, the insulating film 2 is removed, and the p-InP cladding layer 9 and the p-InGaAs contact layer 13 are grown on the entire surface as shown in FIG. 9A (step 13). As shown in FIG. 9B, the semiconductor laser 101 and the semiconductor optical amplifier 103 that form a buried waveguide in which both sides of the waveguide are embedded with a semiconductor have a width of several tens of μm, and both sides of the waveguide are not covered with the semiconductor. The portion of the modulator 102 forming the waveguide forms a mesa with a width of about 1 μm. Etching is performed so that the depth of the mesa stops in the middle of the Fe-doped semi-insulating InP layer 20 (step 14).

As shown in FIG. 10A, etching is performed until the n-InGaAsP contact layer 43 is exposed in the portion of the semiconductor optical amplifier 103 where the n-side contact electrode 253 is formed (step 15). Thereafter, as shown in FIG. 10B, the p-InGaAs contact layer 13 between the semiconductor laser 101 and the modulator 102 and between the modulator 102 and the semiconductor optical amplifier 103 is etched to electrically insulate them. Secure (step 16). Next, as shown in FIG. 11A, an insulating film 15 is formed on the entire surface, and the p-InGaAs contact layer 13 of the semiconductor laser 101, the modulator 102, and the semiconductor optical amplifier 103, and the n-InGaAsP contact of the semiconductor optical amplifier 103 are formed. An opening is formed on layer 43 (step 17). Finally, as shown in FIG. 11B, the electrode 17 and the gold plating 18 are formed (step 18 ), whereby the electrode 17 and the gold plating 18 in each opening are formed as each contact electrode and the p of the semiconductor laser 101 is formed. The electrical connection between the side contact electrode 261 and the n-side contact electrode 253 of the semiconductor optical amplifier 103 is completed. In this example, the anode of the semiconductor laser 101, that is, the p-side contact electrode 261 on the p-InGaAs contact layer 13 of the semiconductor laser, and the cathode of the semiconductor optical amplifier 103, that is, the n-side contact electrode 253 on the n-InGaAsP contact layer 43. Are connected to the electrode 17 by gold plating 18. Not limited to this, as shown in the conceptual diagram of FIG. 1, the p-side contact electrode 261 of the semiconductor laser 101 and the n-side contact electrode 253 of the semiconductor optical amplifier may be connected by the wire 27. Finally, the entire wafer is polished to a thickness of about 100 μm, and the n-side contact electrode 25 is formed on the back surface of the wafer, that is, the surface of the semiconductor substrate 1 opposite to the surface on which the elements are formed.

As described above, in the semiconductor optical integrated device according to the first embodiment, the conductive semiconductor substrate 1 is used, and the Fe-doped semi-conductive layer is used as the electrical insulating layer between the n-side cladding layer 53 of the semiconductor optical amplifier 103 and the semiconductor substrate 1. The insulating InP layer 3 was provided, and the n-side clad layer between the semiconductor optical amplifier 103 and the modulator 102 was also replaced with the Fe-doped semi-insulating InP layer 19 which was an electrical insulating layer. With this configuration, the semiconductor optical amplifier 103 is electrically insulated from the conductive semiconductor substrate 1 and the semiconductor laser 101. Furthermore, the n-side contact layer 43 is provided between the n-side clad layer 53 of the semiconductor optical amplifier 103 and the Fe-doped semi-insulating InP layer 3 to supply power from the conductive semiconductor substrate 1 to the n-side clad layer 53. Instead, it is possible to supply power to the n-side cladding layer 53 through the n-side contact electrode 253 and the n-side contact layer 43. With this configuration, the semiconductor laser 101 and the semiconductor optical amplifier 103 formed on the same semiconductor substrate 1 can be connected in series, and the current from the DC power supply can be reduced. According to this configuration, serial connection can be realized without increasing the number of drive terminals as compared with the conventional case.

According to the semiconductor optical integrated device of the first embodiment, since the semiconductor laser 101 and the semiconductor optical amplifier 103 are connected in series, the current from the DC power supply can be reduced. Moreover, since the electrode structure of the integrated semiconductor laser and modulator is the same as the conventional structure, the negative side can be connected to the n-side contact electrode 25 on the back surface of the semiconductor substrate 1 as in the conventional case, and the same driving as in the conventional case can be performed. Method is possible.

Embodiment 2.
FIG. 12 is a conceptual diagram showing a configuration of a main part of the semiconductor optical integrated device according to the second embodiment. The difference from the configuration of FIG. 1 is that the n-side clad layer between the modulator 102 and the semiconductor optical amplifier 103 is not the Fe-doped semi-insulating InP layer 19 but a Zn diffusion region 24 made p-type by impurity diffusion. Is that Thus, the modulator 102 and the semiconductor optical amplifier 103 may be made of a material that can be electrically insulated, and various semi-insulating semiconductor materials can be used.

A method of manufacturing the semiconductor optical integrated device of FIG. 12 will be described with reference to FIGS. 13A and 13B to FIGS. 16A and 16B, focusing on parts different from the manufacturing method described in the first embodiment. First, as shown in FIG. 13A, an Fe-doped semi-insulating InP layer 3, an n-InGaAsP contact layer 4, and an n-InP clad layer 5 are formed on an n-InP substrate 1 which is a conductive semiconductor substrate (step 21). .. Next, as shown in FIG. 13B, an oxide film (ZnO) 23 containing Zn, which is a p-type dopant, is formed between the modulator 102 and the semiconductor optical amplifier 103, and thermally annealed so that Zn is Fe-doped semi-insulating. Thermal diffusion is performed until the conductive InP layer 3 is reached (step 22). The region where Zn is diffused is the electrically insulating layer 24. Then, the oxide film (ZnO) 23 containing Zn is removed, and the n-InP cladding layer 5, the n-InGaAsP diffraction grating layer 6, and the n-InP cladding layer 5 are grown on the entire surface as shown in FIG. 14A ( Step 23). Next, as shown in FIG. 14B, the n-InGaAsP diffraction grating layer 6 in the diffraction grating portion 7 of the semiconductor laser 101 is etched at a cycle of 200 nm to form a semiconductor laser diffraction grating (step 24). After that, the active layer 8 and the p-InP clad layer 9 are formed as shown in FIG. 15A (step 25), and the insulating film 2 is opened at the modulator 102 as shown in FIG. 15B. The p-InP clad layer 9 and the active layer 8 are formed with a width of several tens of μm (step 26). Thereafter, as shown in FIG. 16A, the modulator absorption layer 10 and the p-InP cladding layer 9 are selectively grown on the entire surface (step 27). After that, the insulating film 2 is removed, the insulating film 2 is formed again as shown in FIG. 16B, and a pattern for processing the waveguide is formed. Modulation for forming a waveguide having a shape in which a semiconductor laser 101 and a semiconductor optical amplifier 103, both sides of which are buried with a semiconductor, have an insulating film width of about 1 μm so that both sides of the waveguide are not covered with a semiconductor. The insulating film 2 is formed in the portion of the container 102 with a width of about several tens of μm (step 28). After that, etching is performed to reach the Zn diffusion region 24, which is an electrically insulating layer, but does not reach the n-InGaAsP contact layer 4. Subsequent steps of the step 12 described in the first embodiment after the step of performing buried growth on both sides of the ridge are the same as the steps described in the first embodiment.

The major difference from the state after the process of step 11 of the first embodiment is that the n-side cladding layer between the modulator 102 and the semiconductor optical amplifier 103 is not the Fe-doped semi-insulating InP layer 19 but the impurity diffusion. That is, it is a Zn diffusion region 24 which is a p-type electric insulating layer.

As described above, in the semiconductor optical integrated device according to the second embodiment, the conductive semiconductor substrate 1 is used, and the Fe-doped electrically insulating layer, which is an electrically insulating layer, is provided between the n-side cladding layer 53 of the semiconductor optical amplifier 103 and the semiconductor substrate 1. The semi-insulating InP layer 3 was provided, and the n-side clad layer between the semiconductor optical amplifier 103 and the modulator 102 was replaced with a Zn diffusion region 24 which was an electric insulating layer made p-type by impurity diffusion. With this configuration, the semiconductor optical amplifier 103 is electrically insulated from the conductive semiconductor substrate 1 and the semiconductor laser 101. Furthermore, the n-side contact layer 43 is provided between the n-side clad layer 53 of the semiconductor optical amplifier 103 and the Fe-doped semi-insulating InP layer 3 to supply power from the conductive semiconductor substrate 1 to the n-side clad layer 53. Instead, it is possible to supply power to the n-side cladding layer 53 through the n-side contact electrode 253 and the n-side contact layer 43. With this configuration, the semiconductor laser 101 and the semiconductor optical amplifier 103 formed on the same semiconductor substrate 1 can be connected in series, and the current from the DC power supply can be reduced. According to this configuration, serial connection can be realized without increasing the number of drive terminals as compared with the conventional case.

According to the semiconductor optical integrated device of the second embodiment, as in the first embodiment, the semiconductor laser 101 and the semiconductor optical amplifier 103 are connected in series, so that the current from the DC power supply can be reduced. Moreover, since the electrode structure of the integrated semiconductor laser and modulator is the same as the conventional structure, the negative side can be connected to the n-side contact electrode 25 on the back surface of the semiconductor substrate 1 as in the conventional case, and the same driving as in the conventional case can be performed. Method is possible.

It should be noted that in both the first and second embodiments, as shown in FIG. 21 of the fourth embodiment, which will be described later, between the n-side cladding layer 51 of the semiconductor laser 101 and the conductive semiconductor substrate 1. An Fe-doped semi-insulating InP layer 3 is provided as an electrical insulating layer to electrically separate the semiconductor laser 101 side from the semiconductor substrate 1, and the n-side cladding layer 51 on the semiconductor optical amplifier 103 side and the conductive semiconductor substrate 1. An insulating layer such as the Fe-doped semi-insulating InP layer 3 may not be provided between them, and the electrically conductive state may be established. In this case, the semiconductor laser 101 and the semiconductor optical amplifier 103 can be connected in series by providing the n-side contact layer between the n-side cladding layer 51 and the Fe-doped semi-insulating InP layer 3. Needless to say.

Embodiment 3.
FIG. 17 is a conceptual diagram showing the configuration of the main part of the semiconductor optical integrated device according to the third embodiment. In this structure, the basic structure of the device is realized on a semi-insulating semiconductor substrate 104. The n-InGaAsP contact layer, which is the n-side contact layer provided on the semi-insulating semiconductor substrate 104, is separated into the n-side contact layer 41 and the n-side contact layer 43 between the modulator 102 and the semiconductor optical amplifier 103. It is configured. Further, by replacing the n-side clad layer between the modulator 102 and the semiconductor optical amplifier 103 with the Fe-doped semi-insulating InP layer 19, the cathode portion of the semiconductor optical amplifier 103 is electrically connected to the semiconductor laser 101 and the modulator 102. Insulated. Other configurations are the same as those in FIG. Since the cathode is taken from the n-side contact electrode 251 on the n-side contact layer 41 of the semiconductor laser 101 and the modulator 102 and the n-side contact electrode 253 on the n-side contact layer 43 of the semiconductor optical amplifier 103, the number of power supply terminals is increased. Is one more than that formed on the conductive semiconductor substrate 1 of FIG.

The electrical connection of the semiconductor optical integrated device of FIG. 17 will be described. A DC voltage is applied between a p-side contact electrode 263 of the semiconductor optical amplifier 103 and an n-side contact electrode 251 of the semiconductor laser 101 from a DC power supply (not shown) provided outside. The n-side contact electrode 253 of the semiconductor optical amplifier 103 and the p-side contact electrode 261 of the semiconductor laser 101 are connected by a conductor such as a wire 27. With this connection, as in the semiconductor optical integrated device according to the first embodiment of FIG. 1, the semiconductor laser 101 and the semiconductor optical amplifier 103 are connected in series as shown in the equivalent circuit of FIG. 2, and the semiconductor laser 101 and the semiconductor optical amplifier are connected. A current having the same current value flows through 103.

Of the method of manufacturing the semiconductor optical integrated device having the configuration of FIG. 17, only the part different from the manufacturing method described in the first embodiment will be described. As shown in FIG. 18A, the n-InGaAsP contact layer 4, the n-InP cladding layer 5, the n-InGaAsP diffraction grating layer 6, and the n-InP cladding layer 5 are grown on the entire surface of the semi-insulating semiconductor substrate 104 (step 31). Next, as shown in FIG. 18B, the insulating film 2 is formed to have a width of several tens of μm by forming an opening of several tens of μm between the modulator 102 and the semiconductor optical amplifier 103, and the n-InGaAsP contact layer 4 is etched. Remove (step 32). Thereafter, as shown in FIG. 19A, the n-InGaAsP contact layer 4 between the modulator 102 and the semiconductor optical amplifier 103 is etched to be separated into an n-side contact layer 41 and an n-side contact layer 43 (step 33). The semiconductor laser 101 and the modulator 102 are electrically insulated from the semiconductor optical amplifier 103 on the n side. Next, as shown in FIG. 19B, the Fe-doped semi-insulating InP layer 20 is grown using the insulating film 2 as a mask. Subsequent processes are almost the same as the processes after step 7 for forming the diffraction grating in FIG. 6A described in the first embodiment. However, since the semi-insulating semiconductor substrate 104 is used, the difference is that the n-side contact electrode 251 of the semiconductor laser must be provided on the n-side contact layer 41.

FIG. 20 is a conceptual diagram showing another structure of the main part of the semiconductor optical integrated device according to the third embodiment. The configuration of the semiconductor optical integrated device in FIG. 20 is similar to the configuration in FIG. 17 in that the basic structure of the device is realized on a semi-insulating semiconductor substrate 104. 17 is different from the semiconductor optical integrated device shown in FIG. 17 in that a part of the n-side cladding layer between the modulator 102 and the semiconductor optical amplifier 103 is replaced with a p-type InP layer 24, or a p-type InP layer 24 is formed by impurity diffusion to produce an electric property. This is the point that the structure is electrically insulated.

Thus, either the n-side clad layer between the modulator 102 and the semiconductor optical amplifier 103 is replaced with the Fe-doped semi-insulating InP layer 19 or the p-type Zn diffusion region 24 is formed by impurity diffusion. But it is possible. For the Fe-doped semi-insulating InP layer 19, refer to the process described in the first embodiment, and for the Zn-diffused region 24 that is p-typed by impurity diffusion, refer to the process described in the second embodiment. Can be created.

As described above, in the semiconductor optical integrated device according to the third embodiment, the semi-insulating semiconductor substrate 104 is used, and between the n-side cladding layer 51 of the semiconductor laser 101 and the n-side cladding layer 53 of the semiconductor optical amplifier 103. Is insulated from the n-side cladding layer 51 of the semiconductor laser 101 by insulating the Fe-doped semi-insulating InP layer 3 or an electrically insulating layer of a semi-insulating semiconductor material such as a Zn diffused region 24 made p-type by impurity diffusion. The semiconductor optical amplifier 103 is electrically insulated from the n-side cladding layer 53. Further, an n-side contact layer 41 is provided between the n-side cladding layer 51 of the semiconductor laser 101 and the semi-insulating semiconductor substrate 104, and an n-side contact layer 41 is provided between the n-side cladding layer 53 of the semiconductor optical amplifier 103 and the semi-insulating semiconductor substrate 104. The side contact layers 43 were provided, and the respective n-side contact layers were laterally bulged out to enable electrical connection to the respective n-side cladding layers. With this configuration, the semiconductor laser 101 and the semiconductor optical amplifier 103 formed on the same semiconductor substrate 104 can be connected in series.

Similar to the first and second embodiments, the semiconductor laser 101 and the semiconductor optical amplifier 103 are connected in series, so that the current from the DC power supply can be reduced.

Fourth Embodiment
FIG. 21 is a conceptual diagram showing the configuration of the main part of the semiconductor optical integrated device according to the fourth embodiment. The fourth embodiment is a semiconductor optical integrated device in which a plurality of semiconductor lasers 101 and at least one semiconductor optical amplifier 103 are monolithically integrated on the same semiconductor substrate. For simplicity, FIG. 21 shows a configuration example in which two semiconductor lasers 101 are integrated in parallel, the outputs of the two semiconductor lasers 101 are multiplexed by the optical multiplexer 105, and the combined outputs are input to the semiconductor optical amplifier 103. In the configuration example of FIG. 21, the n-type InP substrate 1, which is a conductive semiconductor substrate, is used as the semiconductor substrate, as in the first or second embodiment.

As in FIG. 1, the n-side clad layer between the semiconductor laser 101 and the optical multiplexer 105 is replaced with the Fe-doped semi-insulating InP layer 19, and the n-side clad layer 51 of the semiconductor laser 101 and the semiconductor substrate 1 are The space between them is insulated by the Fe-doped semi-insulating InP layer 3. As a result, the semiconductor laser 101 and the semiconductor optical amplifier 103 are electrically separated at the n-side cladding layer. The n-side contact layer 41 for electrically connecting to the n-side cladding layers 53 of the two semiconductor lasers 101 is provided as the n-side contact layer 41 common to both semiconductor lasers 101. An n-side contact electrode 251 is provided on the n-side contact layer 41. The p-side contact electrode 261 of the semiconductor laser 101 is used as an element anode, and the n-side contact electrode 251 of the semiconductor laser 101 and the p-side contact electrode 263 of the semiconductor optical amplifier 103 are electrically connected by the wire 27. The structure for connection is not limited to the structure in which the wire 27 is provided, but a structure for connection with metal on the chip can be used.

As in the second embodiment, that is, the semiconductor optical integrated device shown in FIG. 12, a part of the n-side contact layer between the semiconductor laser 101 and the optical multiplexer 105 is replaced with a p-type InP layer, or p-type is formed by impurity diffusion. It is also possible to use a structure in which it is electrically insulated.

The conductive semiconductor substrate 1 is used, and the Fe-doped semi-insulating InP layer 3 is provided as an electrical insulating layer between the n-side clad layer 53 of the semiconductor laser 101 and the semiconductor substrate 1 so that the semiconductor laser 101 and the photosynthesizer 105 are connected to each other. The n-side cladding layer is also replaced with an electrically insulating layer such as the Fe-doped semi-insulating InP layer 19 or the p-type InP layer 24 so that the semiconductor laser 101 is electrically insulated from the conductive semiconductor substrate 1. With this configuration, by electrically connecting the p-side clad layer 9 of the semiconductor optical amplifier 103 and the n-side clad layer 51 of the semiconductor laser 101, the semiconductor laser 101 and the semiconductor laser 101 formed on the same semiconductor substrate 1 are connected. The amplifier 103 can be connected in series, and the drive current from the DC power supply can be reduced. Since a semi-insulating substrate is not used, the number of drive terminals does not increase compared to the conventional case.

According to the semiconductor optical integrated device having the configuration of FIG. 21, the drive current can be reduced. Further, since the semiconductor laser 101 and the semiconductor optical amplifier 103 are connected in series, only one drive terminal is required on the upper surface of the substrate.

FIG. 22 is a conceptual diagram showing another structure of the main part of the semiconductor optical integrated device according to the fourth embodiment. The semiconductor optical integrated device shown in FIG. 22 has almost the same basic structure as the semiconductor optical integrated device shown in FIG. 21, and a plurality of semiconductor lasers 101 and at least one semiconductor optical amplifier 103 are described in the third embodiment. Similarly to the above, the semiconductor optical integrated device is monolithically integrated on the same semi-insulating semiconductor substrate 104. Similar to the third embodiment, the n-side contact layer 41 is provided between the n-side cladding layer 51 of the semiconductor laser 101 and the semi-insulating semiconductor substrate 104, the n-side cladding layer 53 of the semiconductor optical amplifier 103 and the semi-insulating semiconductor substrate. An n-side contact layer 43 was provided between the n-side contact layers 104, and each n-side contact layer was laterally overhanged so that each n-side clad layer could be electrically connected. The n-side contact layer 41 is provided commonly to the plurality of semiconductor lasers 101. With this configuration as well, a semiconductor formed on the same semi-insulating semiconductor substrate 104 by electrically connecting the p-side cladding layer 9 of the semiconductor optical amplifier 103 and the n-side cladding layer 51 of the semiconductor laser 101. The laser 101 and the semiconductor optical amplifier 103 can be connected in series, and the drive current can be reduced. However, since the semi-insulating substrate is used, the number of terminals is increased as compared with the configuration of FIG.

Embodiment 5.
FIG. 23 is a block diagram showing a schematic configuration of the semiconductor optical integrated device according to the fifth embodiment. In the semiconductor optical integrated device according to the fourth embodiment, that is, in the configuration shown in FIGS. 21 and 22, two semiconductor lasers 101 are described, but the number of semiconductor lasers is not limited to two. FIG. 23 is a block diagram of a semiconductor optical integrated device in which a plurality of semiconductor lasers 101 are multiplexed by an optical multiplexer 105 on a semiconductor substrate and input to a semiconductor optical amplifier 103. FIG. 24 is an electrically equivalent circuit when a plurality of semiconductor lasers 101 and semiconductor optical amplifiers 103 are connected in series in the configuration of FIG. In order to selectively drive any one of the plurality of different semiconductor lasers 101, for example, the plurality of semiconductor lasers 101 having different wavelengths of lasers to be output, the cathode side of the semiconductor laser 101 and the semiconductor optical amplifier 103 can be driven. The cathode side is electrically insulated, and the cathode of the semiconductor laser 101 and the anode of the semiconductor optical amplifier 103 are electrically connected.

FIG. 25 is a block diagram of an integrated device in which a plurality of semiconductor lasers 101 are combined on the same semiconductor substrate by an optical multiplexer 105A and an optical combiner 105B, and are input to the semiconductor optical amplifier 103A and the semiconductor optical amplifier 103B. .. FIG. 26 is an equivalent circuit when two semiconductor optical amplifiers 103A and 103B are connected in series, and a serial body of these semiconductor optical amplifiers 103A and 103B and the semiconductor laser 101 are connected in series. 27 is an equivalent circuit when two semiconductor optical amplifiers 103A and 103B are connected in parallel, and a parallel body of these semiconductor optical amplifiers 103A and 103B and the semiconductor laser 101 are connected in series. 24, 26 and 27, the cathode side of the semiconductor laser 101 and the cathodes of the semiconductor optical amplifier 103A and the semiconductor optical amplifier 103B are formed by any of the insulating structures described in the first to fourth embodiments. 26 is electrically insulated, and in the case of FIG. 26, the cathode side of the semiconductor optical amplifier 103A and the cathode side of the semiconductor optical amplifier 103B are also electrically insulated.

By referring to the insulating structures of the first to fourth embodiments, it is understood that a configuration in which a plurality of semiconductor optical amplifiers are connected in series can be used as shown in FIG. Similarly, it is understood that it is possible to adopt a configuration in which a plurality of semiconductor lasers are connected in series.

In summary, the semiconductor optical integrated device disclosed in the present application is configured such that holes are injected from the p-side cladding layer and electrons are injected into the active layer from the n-side cladding layer. In a semiconductor optical integrated device in which a semiconductor optical device is monolithically integrated on the same semiconductor substrate, the n-side clad layer of the first semiconductor optical device and the n-side clad layer of the second semiconductor optical device are electrically An n-side contact layer that is insulated and is electrically connected to the n-side clad layer of at least one of the first semiconductor optical device and the second semiconductor optical device is provided between the n-side clad layer and the semiconductor substrate. And a p-side clad layer of a semiconductor optical device different from the semiconductor optical device provided with the n-side contact layer and electrically connected to each other. Since the optical element and the second semiconductor optical element are electrically connected in series, the current capacity of the DC power supply can be reduced. Each of the first semiconductor optical device and the second semiconductor optical device is a semiconductor laser as long as holes are injected from the p-side cladding layer and electrons are injected into the active layer from the n-side cladding layer. Alternatively, it may be a semiconductor optical amplifier.

Although various exemplary embodiments and examples are described in this application, various features, aspects, and functions described in one or more embodiments may be The present invention is not limited to the application, and can be applied to the embodiments alone or in various combinations. Therefore, innumerable variations not illustrated are envisioned within the scope of the technology disclosed herein. For example, it is assumed that at least one component is modified, added or omitted, and at least one component is extracted and combined with the components of other embodiments.

1 semiconductor substrate (n-InP substrate), 3 electrical insulating layer (Fe-doped semi-insulating InP layer), 51, 53 n-side clad layer (n-InP clad layer), 8 active layer, 9 p-side clad layer (p -InP clad layer), 19 electric insulating layer (Fe-doped semi-insulating InP layer), 24 electric insulating layer (Zn diffusion region), 25 n-side contact electrode, 261, 262, 263 p-side contact electrode, 101 semiconductor laser, 103 Semiconductor optical amplifier

Claims (5)

In both cases, a semiconductor amplifier and a plurality of semiconductor lasers configured to inject holes from the p-side cladding layer and electrons from the n-side cladding layer into the active layer are monolithically formed on one surface of the same semiconductor substrate. In the integrated semiconductor optical integrated device,
The semiconductor substrate is a conductive semiconductor substrate, and the n-side cladding layer of the semiconductor amplifier and the n-side cladding layers of the plurality of semiconductor lasers are the n-sides of the semiconductor substrate and the plurality of semiconductor lasers. Electrical insulation by an electrical insulation layer formed between the cladding layer and the n-side cladding layer of the semiconductor amplifier and each of the plurality of semiconductor lasers And an n-side contact layer for electrically connecting to each of the n-side cladding layers of the plurality of semiconductor lasers is provided between each of the n-side cladding layers of the plurality of semiconductor lasers and the electrical insulating layer. Is provided,
The n-side contact layer and the p-side clad layer of the semiconductor amplifier are electrically connected to each other, and the semiconductor amplifier and each semiconductor laser of the plurality of semiconductor lasers are electrically connected in series. A semiconductor optical integrated device characterized in that The other surface of the semiconductor substrate is provided with an n-side contact electrode connected to the negative side of DC, and the p-side contact electrode connected to the positive side of DC is provided in each of the p-side cladding layers of the plurality of semiconductor lasers. The semiconductor optical integrated device according to claim 1, wherein the semiconductor optical integrated device is provided. In both cases, a semiconductor amplifier and a plurality of semiconductor lasers configured to inject holes from the p-side cladding layer and electrons from the n-side cladding layer into the active layer are monolithically formed on one surface of the same semiconductor substrate. In the integrated semiconductor optical integrated device,
The n-side cladding layer of the semiconductor amplifier and the n-side cladding layers of the plurality of semiconductor lasers are electrically connected between the n-side cladding layer of the semiconductor amplifier and the n-side cladding layers of the plurality of semiconductor lasers. An n-side contact for forming an insulating layer and being electrically insulated by the semiconductor substrate being a semi-insulating semiconductor substrate and electrically connecting to each n-side cladding layer of the plurality of semiconductor lasers. A layer is provided between each of the n-side cladding layers of the plurality of semiconductor lasers and the semiconductor substrate,
The n-side contact layer and the p-side clad layer of the semiconductor amplifier are electrically connected to each other, and the semiconductor amplifier and each semiconductor laser of the plurality of semiconductor lasers are electrically connected in series. A semiconductor optical integrated device characterized in that 4. The semiconductor light according to claim 1, wherein the n-side contact layer extends laterally from an n-side cladding layer of one of the plurality of semiconductor lasers. Integrated device. 5. An optical multiplexer, which combines the outputs of the plurality of semiconductor lasers and inputs the combined outputs to the semiconductor amplifier, is provided between the semiconductor amplifier and the plurality of semiconductor lasers. The semiconductor optical integrated device according to any one of items.

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