WO2020062662A1

WO2020062662A1 - Electro-absorption modulation integrated laser chip and manufacture method therefor

Info

Publication number: WO2020062662A1
Application number: PCT/CN2018/123313
Authority: WO
Inventors: 万枫; 熊永华; 曾笔鉴; 余洁
Original assignee: 武汉电信器件有限公司
Priority date: 2018-09-30
Filing date: 2018-12-25
Publication date: 2020-04-02
Also published as: CN109256675A

Abstract

An electro-absorption modulation integrated laser chip and a manufacturing method therefor. The chip comprises: an output waveguide region, an EAM region (100), an isolation region, and a DFB region (200) provided in sequence. The isolation region is used for isolating the EAM region (100) and the DFB region (200), a lower layer of the isolation region is a passive waveguide layer (301), and an upper layer is an undoped InP layer (302), so as to reduce a photon-generated carrier in the isolation region under a working condition. The lower layer of the isolation region of the electro-absorption modulation integrated laser chip is the passive waveguide layer (301), and the upper layer is the undoped InP layer (302); the structure is able to reduce the photon-generated carrier in the isolation region under the working condition; even there is no photon-generated carrier in the isolation region, the problem of excessively fast bandwidth attenuation under a high bias voltage can be solved.

Description

Electrical absorption modulation integrated laser chip and manufacturing method thereof

Technical field

Embodiments of the present invention relate to the field of optoelectronic devices, and in particular, to an electroabsorption modulation integrated laser chip and a manufacturing method thereof.

Background technique

With the explosive growth of the Internet's demand for data transmission, optoelectronic modules need to continuously reduce the cost of their core optoelectronic chips, reduce their size, and increase their transmission throughput.

In a time division multiplexed network, an electro-absorption modulation integrated laser (EML) chip is a good choice. It has the advantages of small size and low cost. With the development of research, high-speed EML chip modules can provide data with a bit error rate of 40 ps / nm in a transmission distance of 2 kilometers.

In the optical communication network, the dispersion of the optical fiber limits the distance of data transmission. The distance is approximately inversely proportional to the square of the data rate. The 啁啾 parameter in the 25G EML module is a key indicator to ensure the quality of data transmission. There are two ways for the industry to optimize the chirp parameter. One is to redesign the structure of the quantum wells in the active area of the chip. Each method is different. The second is to reduce the 啁啾 parameter by biasing the EAM terminal. As the bias at the EAM terminal increases, the 啁啾 parameter of the chip decreases or even becomes negative. The negative effect of this method is the optical power output by the EML chip. It also decreases with increasing bias. However, it was found in experiments that when the EAM is biased more, the bandwidth of a 25G EML chip using a butt jointed structure will suddenly decrease at 10 Gbit / s during measurement, affecting the optical transmission characteristics.

Summary of the Invention

In order to solve the problems existing in the prior art, embodiments of the present invention provide an electro-absorption modulation integrated laser chip and a manufacturing method thereof.

According to a first aspect, an embodiment of the present invention provides an electro-absorption modulation integrated laser chip, including:

Set the output waveguide area, EAM part, isolation area and DFB part in turn;

The isolation region is used to isolate the EAM portion and the DFB portion, and a lower layer thereof is a passive waveguide layer and an upper layer is an undoped InP layer, so as to reduce photo-generated carriers in the isolation region in an operating state.

In a second aspect, an embodiment of the present invention provides a laser, including the electro-absorption modulation integrated laser chip according to the first aspect of the embodiment of the present invention.

According to a third aspect, an embodiment of the present invention provides a method for manufacturing an electro-absorption modulation integrated laser chip according to the first aspect, including:

S1, a DFB active layer is grown on the n-type In-P substrate;

S2, growing a grating layer on the DFB active layer, and fabricating a grating on the grating layer by using an electron beam etching technique;

S3, using a dry etching technique to etch a ridge waveguide at one end of the grating layer to form a DFB portion;

S4. An EAM active layer is grown on the other end of the DFB active layer and the grating layer by using a docking growth technology to form an EAM portion.

S5, a p-type In-P cladding layer is grown on the entire wafer;

S6. Using a dry etching technique, starting from the p-type In-P cladding layer, an output waveguide region and an isolation region are etched on both sides of the EAM active layer, and the output waveguide region is located in the Outside the EAM active layer, the isolation region is located between the EAM active layer and the ridge waveguide;

S7. A passive waveguide layer and an undoped In-P layer are respectively grown in the isolation region by using a docking technology.

The electroabsorption modulation integrated laser chip and the manufacturing method thereof provided by the embodiments of the present invention. The lower layer of the isolation region of the electroabsorption modulation integrated laser chip is a passive waveguide layer and the upper layer is an undoped InP layer. This structure can reduce the working state. The photo-generated carriers in the isolation region, or even the absence of photo-generated carriers in the isolation region, can solve the problem of excessive bandwidth attenuation under high bias.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly explain the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without paying creative labor.

FIG. 1 is a schematic diagram of a prior art EML chip structure;

2 is a schematic structural diagram of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention;

3 is a schematic flowchart of a manufacturing method of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention;

4 is a first schematic diagram of a chip manufacturing process of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention;

5 is a second schematic diagram of a chip manufacturing process of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention;

6 is a third schematic diagram of a chip manufacturing process of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention;

7 is a fourth schematic diagram of a chip manufacturing process of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention;

FIG. 8 is a fifth schematic diagram of a chip manufacturing process of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention; FIG.

FIG. 9 is a sixth schematic diagram of a chip manufacturing process of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention; FIG.

10 is a schematic top view of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention;

11 is a schematic cross-sectional structure diagram of a ridge waveguide of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention;

FIG. 12 is a schematic diagram showing a comparison of the bandwidth of an electroabsorption modulation integrated laser chip and a prior art electroabsorption modulation integrated laser chip under different EAM bias voltages according to an embodiment of the present invention.

Reference sign description

1. DFB active layer, 2. Grating layer,

3. EAM active layer, p-type In-P cladding,

5. Passive waveguide layer, 6. Un-doped In-P layer,

7. InGaAs active contact layer, 8. BCB layer,

9, metal electrode layer, 0, n-type In-P substrate,

100, EAM part, 200, DFB part,

300, isolation area, 400, output waveguide area,

301. A passive waveguide layer, 302, an undoped InP layer,

401, a passive waveguide layer, 402, an undoped InP layer,

500, MQW layer.

detailed description

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are the present invention. Part of the invention is invented, but not all. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Figure 1 is a schematic diagram of the structure of a prior art EML chip. An electro-absorption modulation integrated laser EML chip is composed of two parts, one is an EAM with an absorption layer, and the other is a DFB with an active layer.相连接。 Phase connection. The docking technology is a commonly used technology in the manufacturing process of EML chips. Its advantage is that it can optimize the quantum well structure of DFB and EAM separately to achieve better optical transmission efficiency. The structure of the isolation region is the same as that of the EAM quantum well, as shown in Figure 1.

In the working state, in the EML chip, EAM plus reverse bias voltage and DFB plus forward bias voltage, so a voltage gradient is generated in the isolation region, and this voltage gradient causes the photogenerated carriers to be redistributed in the isolation region. There are many studies on the escape time of photo-generated carriers, the most widely known of which is that the smaller the bias voltage, the longer the escape time of photo-generated carriers, typically over 100 ps. Generally, photo-generated carriers with a longer escape time will reduce the bandwidth under certain conditions of chip operation. The specific parameters affected may be that the accumulation of carriers increases the capacitance and reduces the isolation resistance.

FIG. 2 is a schematic structural diagram of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention. The electro-absorption modulation integrated laser chip shown in FIG. 2 includes:

The output waveguide area (consisting of 401 and 402), the EAM part 100, the isolation area (consisting of 301 and 302), and the DFB part 200 are sequentially arranged;

The isolation region is used to isolate the EAM portion 100 and the DFB portion 200, and a lower layer thereof is a passive waveguide layer 301 and an upper layer is an undoped InP layer 302, so as to reduce a light load in the isolation region in an operating state. Streamer.

Please refer to FIG. 2. The EML chip according to the embodiment of the present invention further includes a multi-quantum well MQW layer 500. The MQW located in the EAM part 100 is called EAM-MQW, and the MQW located in the DFB part 200 is called DFB-MQW.

Among them, the output waveguide region (consisting of 401 and 402), the EAM part 100, the isolation region (consisting of 301 and 302), and the DFB part 200 are located on the MQW layer and are sequentially connected on the MQW layer.

Since the photo-generated carriers with a longer escape time will reduce the bandwidth under a specific condition of the chip operation, the specific parameters affected may be that the accumulation of carriers increases the capacitance and reduces the isolation resistance. The lower layer of the isolation region of the electro-absorption modulation integrated laser chip of the embodiment of the present invention is a passive waveguide layer and the upper layer is an undoped InP layer. This structure can reduce the conductive effect of the isolation region and even make the isolation region non-conductive, thereby eliminating The electro-optical conversion effect of the isolation region in the prior art is reduced. Therefore, the embodiment of the present invention can reduce the photo-generated carriers in the isolation region under the working state, even make the photo-generated carriers not in the isolation region, and can solve the bandwidth attenuation under high bias. Too fast problem.

Based on the above embodiment, the lower layer of the output waveguide region is a passive waveguide layer 401, and the upper layer is an undoped InP layer 402, so that the electro-absorption modulation integrated laser chip is convenient for cleavage and improves optical coupling efficiency.

Please refer to FIG. 2. In the embodiment of the present invention, the structure of the output wavelength region is improved. The output waveguide region is composed of a lower passive waveguide layer 401 and an upper undoped InP layer 402. The combination of active waveguides and passive waveguides is used. Can be beneficial to the cleavage of the chip and improve the optical coupling efficiency.

Specifically, the length of the output waveguide region ranges from 48 to 52um, the length of the EAM portion ranges from 105 to 115um, the length of the isolation region ranges from 48 to 52um, and the length of the DFB portion ranges from 315 to 325um.

Preferably, the length of the output waveguide region is 50um, the length of the EAM portion is 110um, the length of the isolation region is 50um, and the length of the DFB portion is 320um.

The electro-absorption modulation integrated laser chip of the embodiment of the present invention uses a passive waveguide and a non-doped InP cladding layer as an isolation region, which can reduce photo-generated carriers in the isolation region under working conditions, and even make no photo-generated carriers in the isolation region. The carrier can solve the problem of excessive bandwidth attenuation under high bias.

An embodiment of the present invention further provides a laser, including the electroabsorption modulation integrated laser chip according to the embodiment of the present invention and any one of the embodiments.

It should be noted that any device including the electro-absorption modulation integrated laser chip of the embodiment of the present invention belongs to the protection scope of the embodiment of the present invention.

FIG. 3 is a schematic flowchart of a manufacturing method of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention. The manufacturing method shown in FIG. 3 includes:

S1, a DFB active layer is grown on the n-type In-P substrate;

S5, a p-type In-P cladding layer is grown on the entire wafer;

Please refer to FIG. 3, as a complete chip manufacturing process, the manufacturing method further includes:

S8, a layer of InGaAs active contact layer is grown on the entire wafer; S9, a double trench is etched on the InGaAs active contact layer by wet method, and BCB is filled in the double trench to reduce parasitic capacitance ; S10, making metal electrode layers in the EAM part and the DFB part, respectively.

According to the method described above, the fabricated electro-absorption modulation integrated laser chip has an isolation region composed of a passive waveguide layer and an undoped In-P layer, which can reduce photo-generated carriers in the isolation region in the working state, and even make it in the isolation region. Without photo-generated carriers, it can solve the problem of excessive bandwidth attenuation at high bias.

Among them, S7 further includes: using a docking technology to grow a passive waveguide layer and an undoped In-P layer in the output waveguide region 400, respectively.

Therefore, in the embodiment of the present invention, the output waveguide region is also composed of a passive waveguide layer and an undoped In-P layer, which can facilitate cleavage of the chip and improve optical coupling efficiency.

Specifically, the ridge waveguide has a width ranging from 16 to 20um and a length ranging from 315 to 325um. Preferably, the ridge waveguide has a width of 18um and a length of 320um.

Specifically, the length of the output waveguide region ranges from 48 to 52um, the length of the EAM portion ranges from 105 to 115um, the length of the isolation region ranges from 48 to 52um, and the length of the DFB portion ranges from 315 to 325um. Preferably, the length of the output waveguide region is 50um, the length of the EAM portion is 110um, the length of the isolation region is 50um, and the length of the DFB portion is 320um.

FIG. 4 is a first schematic diagram of a chip manufacturing process of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention, FIG. 5 is a second schematic diagram of a chip manufacturing process of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention, and FIG. The third schematic diagram of the chip manufacturing process of the absorption modulation integrated laser chip. FIG. 7 is the fourth schematic diagram of the chip manufacturing process of the electrical absorption modulation integrated laser chip according to the embodiment of the present invention. The fifth schematic diagram of the process, and FIG. 9 is the sixth schematic diagram of the chip manufacturing process of the electroabsorption modulation integrated laser chip according to the embodiment of the present invention. The manufacturing process of the EML chip according to the embodiment of the present invention is as follows:

Please refer to FIG. 4. In the embodiment of the present invention, a DFB active layer 1 is grown on an n-type In-P substrate 0, and a grating layer 2 is grown on the DFB active layer 1. The electron beam etching technology is used. A grating is made on the grating layer 2.

Referring to FIG. 5, a ridge waveguide is etched at one end of the grating layer 2 by using a dry etching technique to form a DFB portion 100; and a docking growth technique is used to etch the DFB active layer 1 and the grating layer 2. An EAM active layer 3 is grown on the other end after the etching to form an EAM portion 200;

Referring to FIG. 6, a p-type In-P cladding layer 4 is grown on the entire wafer.

Referring to FIG. 7, using a dry etching technique, starting from the p-type In-P cladding layer 4, the output waveguide region 400 and the isolation region 300 are etched on both sides of the EAM active layer 3, respectively. The output waveguide region 400 is located outside the EAM active layer 3, and the isolation region 300 is located between the EAM active layer 3 and the ridge waveguide;

Referring to FIG. 8, a passive waveguide layer 5 and an undoped In-P layer 6 are respectively grown in the isolation region 300 by using a docking technology; a passive waveguide layer 5 and Doped In-P layer 6.

Referring to FIG. 9, an InGaAs active contact layer 7 is grown on the entire wafer.

FIG. 10 is a schematic top view of an electroabsorption modulation integrated laser chip according to an embodiment of the present invention. Referring to FIG. 10, a double groove is etched on the InGaAs active contact layer 7 by a wet method, and BCB is filled in the double groove. A BCB layer 8 is formed to reduce parasitic capacitance; and finally, metal electrode layers 9 are formed in the EAM part and the DFB part, respectively.

FIG. 11 is a schematic cross-sectional structure diagram of a ridge waveguide of an electro-absorption modulation integrated laser chip according to an embodiment of the present invention, and FIG. 12 is an electro-absorption modulation integrated laser chip according to an embodiment of the present invention and a prior art electro-absorption modulation integrated laser chip at different EAM bias voltages The bandwidth comparison diagram below.

Please refer to Figure 11, BCB material can effectively reduce parasitic capacitance at the EAM terminal. After the chip is powered up, the bandwidth under different EAM bias voltages is measured and compared with the chip of the previous structure. The results are shown in Figure 12. It can be seen in Figure 12 that under the condition that the modulator EAM plus a lower bias voltage, the bandwidth of the EML chip of the two structures is not much different, and the bandwidth is basically above 25G. When the bias voltage Vb is greater than -1V, There is a significant difference in the bandwidth of EML chips. When the optical power of the old structure is attenuated to 3dB, the bandwidth is already attenuated to 10G, and the EML chip of the new structure is not attenuated. Experiments have proved that the new structure of the EML chip can solve the problem of excessive bandwidth attenuation under high bias.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than limiting them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still Modifications to the technical solutions described in the foregoing embodiments, or equivalent replacements of some of the technical features thereof; and these modifications or replacements do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

An electro-absorption modulation integrated laser chip is characterized in that it includes:

Set the output waveguide area, EAM part, isolation area and DFB part in turn;

The isolation region is used to isolate the EAM portion and the DFB portion, and a lower layer thereof is a passive waveguide layer and an upper layer is an undoped InP layer, so as to reduce photo-generated carriers in the isolation region in an operating state.
The electroabsorption modulation integrated laser chip according to claim 1, wherein a lower layer of the output waveguide region is a passive waveguide layer and an upper layer is an undoped InP layer, so that the electroabsorption modulation integrated laser chip is convenient Cleavage and improve optical coupling efficiency.
The electroabsorption modulation integrated laser chip according to claim 1 or 2, wherein:

The length of the output waveguide region is 48-52um, the length of the EAM part is 105-115um, the length of the isolation region is 48-52um, and the length of the DFB part is 315-325um.
The electroabsorption modulation integrated laser chip according to claim 3, wherein:

The length of the output waveguide region is 50um, the length of the EAM portion is 110um, the length of the isolation region is 50um, and the length of the DFB portion is 320um.
A laser, comprising the electro-absorption modulation integrated laser chip according to any one of claims 1-4.
The method for manufacturing an electro-absorption modulation integrated laser chip according to any one of claims 1-4, comprising:

S1, a DFB active layer is grown on the n-type In-P substrate;

S2. A grating layer is grown on the DFB active layer, and a grating is fabricated on the grating layer by using an electron beam etching technique;

S3, using a dry etching technique to etch a ridge waveguide at one end of the grating layer to form a DFB portion;

S4. An EAM active layer is grown on the other end of the DFB active layer and the grating layer by using a docking growth technology to form an EAM portion.

S5, a p-type In-P cladding layer is grown on the entire wafer;

S6. Using a dry etching technique, starting from the p-type In-P cladding layer, an output waveguide region and an isolation region are etched on both sides of the EAM active layer, and the output waveguide region is located in the Outside the EAM active layer, the isolation region is located between the EAM active layer and the ridge waveguide;

S7. A passive waveguide layer and an undoped In-P layer are respectively grown in the isolation region by using a docking technology.
The manufacturing method according to claim 6, wherein the S7 further comprises: using a docking technique to grow a passive waveguide layer and an undoped In-P layer in the output waveguide region, respectively.
The manufacturing method according to claim 6 or 7, wherein the ridge waveguide has a width ranging from 16 to 20um and a length ranging from 315 to 325um.
The manufacturing method according to claim 8, wherein the ridge waveguide has a width of 18um and a length of 320um.
The manufacturing method according to claim 6 or 7, wherein:

The length of the output waveguide region is 48-52um, the length of the EAM part is 105-115um, the length of the isolation region is 48-52um, and the length of the DFB part is 315-325um.