CN112366518B - Distributed feedback laser and preparation method thereof - Google Patents
Distributed feedback laser and preparation method thereof Download PDFInfo
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- CN112366518B CN112366518B CN202011211156.6A CN202011211156A CN112366518B CN 112366518 B CN112366518 B CN 112366518B CN 202011211156 A CN202011211156 A CN 202011211156A CN 112366518 B CN112366518 B CN 112366518B
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- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
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- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
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- H—ELECTRICITY
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
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Abstract
The invention discloses a distributed feedback laser and a preparation method thereof, wherein the preparation method comprises the following steps: preparing an epitaxial structure of the distributed feedback laser, wherein the epitaxial structure comprises a grating layer; the epitaxial structure comprises a first surface and a second surface which are oppositely arranged; preparing a photoelectrochemical etching first electrode; preparing an absorption layer on the first surface and patterning the absorption layer to form a grating pattern in the absorption layer; performing photoelectrochemical corrosion on the epitaxial structure on one side of the first surface to form a grating pattern in the grating layer; etching a part of the epitaxial structure on one side of the first surface to form a ridge structure; preparing a first type of ohmic contact metal on the surface of the ridge structure, and preparing a second type of ohmic contact metal on one side of the second surface; and carrying out scribing, cleavage, coating and splitting processes on the epitaxial structure to form the distributed feedback laser. Solves the problems of interface pollution caused by the preparation of the internal grating in the prior art the process is complex and the working wavelength can not be changed because the period of the internal grating is fixed.
Description
Technical Field
The embodiment of the invention relates to the technical field of semiconductors, in particular to a distributed feedback laser and a preparation method thereof.
Background
The full width at half maximum of a Distributed Feedback Laser (DFB) output spectrum is very narrow, generally less than 1MHz; and the single-mode characteristic is good, the side mode suppression ratio is ultrahigh and is generally more than 40dB, so that the method has very important application in the fields of data transmission, optical fiber communication, laser radar, sensing mapping and the like, and is concerned by the industrial and academic fields at home and abroad.
The existing DFB laser has two types of gratings: the DFB laser with the surface grating structure adopts a one-time epitaxial growth technology, the grating structure is prepared on the surface of the laser through a micro-nano processing technology, and the coupling effect of the grating is weak due to the fact that the surface grating is far away from an active area, and single-mode stability of a device is poor. In addition, etching damage is generated when the surface grating is etched and prepared, the grating surface has many surface states such as dangling bonds, which affect the performance and reliability of the device.
In order to ensure higher coupling efficiency, the common DFB laser usually adopts a multiple epitaxial growth technology to prepare an internal grating, this method has the following disadvantages: (1) The interface of secondary epitaxial growth is easily polluted, the interface has very high impurities such as carbon, silicon, oxygen and the like, the impurities can form impurity energy levels in the semiconductor material, the impurity energy levels can generate non-radiative recombination to reduce the internal quantum efficiency of the device, the impurity energy levels can also serve as the capture center of a current carrier to influence the responsiveness of the device, and finally the performance and the reliability of the device can be seriously influenced. (2) The preparation process is very complex, the cost of multiple times of epitaxial growth is very high, resulting in higher device cost and limiting the application range of DFB lasers. (3) After the epitaxial growth is finished, the grating period in the epitaxial wafer is fixed, therefore, the operating wavelength of the device is fixed and cannot be changed, which increases the company stock and is not beneficial to mass production.
Disclosure of Invention
In view of this, embodiments of the present invention provide a distributed feedback laser and a method for manufacturing the same, so as to solve the technical problems in the prior art that interface pollution is caused by using a multi-time epitaxial growth technology to manufacture an internal grating, a manufacturing process is complicated, the application range of a DFB laser is limited due to high cost of multi-time epitaxial growth and device manufacturing, and the working wavelength of a device cannot be changed due to fixed period of the internal grating, which is not conducive to mass production.
In a first aspect, an embodiment of the present invention provides a method for manufacturing a distributed feedback laser, including:
preparing an epitaxial structure of a distributed feedback laser, wherein the epitaxial structure comprises a grating layer; the epitaxial structure comprises a first surface and a second surface which are oppositely arranged;
preparing a photoelectrochemical etching first electrode;
preparing an absorption layer on the first surface and patterning the absorption layer to form a grating pattern in the absorption layer;
performing photoelectrochemical etching on the epitaxial structure on one side of the first surface to form the grating pattern in the grating layer;
etching a part of the epitaxial structure on one side of the first surface to form a ridge structure;
preparing a first type of ohmic contact metal on the surface of the ridge structure, and preparing a second type of ohmic contact metal on one side of the second surface;
and carrying out processes of scribing, cleavage, coating and splitting on the epitaxial structure to form the distributed feedback laser.
Optionally, performing photoelectrochemical etching on the epitaxial structure on the first surface side to form the grating pattern in the grating layer, including:
arranging the epitaxial structure in a photoelectrochemical etching solution, wherein a photoelectrochemical etching second electrode is arranged in the photoelectrochemical etching solution;
providing a power supply, wherein the power supply is respectively electrically connected with the photoelectrochemical corrosion first electrode and the photoelectrochemical corrosion second electrode to form a loop;
providing a light source to illuminate the epitaxial structure on the first surface side to form the grating pattern in the grating layer.
Optionally, preparing an absorption layer on the first surface and patterning the absorption layer to form a grating pattern in the absorption layer, including:
depositing an absorption layer on one side of the first surface;
coating an adhesive on one side of the absorption layer away from the epitaxial structure;
spin-coating a photoresist on one side of the adhesive, which is far away from the epitaxial structure;
forming a grating pattern in the photoresist by adopting an electron beam exposure or holographic exposure mode;
and transferring the grating pattern into the absorption layer by reactive ion beam etching.
Optionally, after etching a portion of the epitaxial structure on one side of the first surface to form a ridge structure, the method further includes:
depositing an insulating layer on the first surface, wherein the insulating layer covers the ridge structure;
removing the insulating layer on the surface of the ridge structure by adopting photoetching and etching technologies;
preparing a first type of ohmic contact metal on the surface of the ridge structure, wherein the first type of ohmic contact metal comprises the following steps:
and preparing a second type ohmic contact metal on the surface of the ridge structure exposed by the insulating layer.
Optionally, the preparing an epitaxial structure of a distributed feedback laser includes:
providing a substrate;
preparing a buffer layer on one side of the substrate;
preparing a lower optical field limiting layer on one side of the buffer layer far away from the substrate;
preparing a lower waveguide layer on one side of the lower optical field limiting layer far away from the substrate;
preparing an active region on the side of the lower waveguide layer away from the substrate;
preparing an upper waveguide layer on one side of the active region far away from the substrate;
preparing the grating layer on one side of the lower waveguide layer far away from the substrate;
preparing an upper optical field limiting layer on one side of the grating layer far away from the substrate;
a contact layer is prepared on the side of the upper optical field limiting layer away from the substrate.
Optionally, preparing the photoelectrochemically etched first electrode includes:
preparing the photoelectrochemical etching first electrode at the edge area of the first surface;
or preparing the photoelectrochemical corrosion first electrode on the second surface;
before the second-type ohmic contact metal is prepared on the second surface side, further comprising:
thinning the substrate; when the photoelectrochemical etching first electrode is prepared on the second surface, the substrate is thinned, and the photoelectrochemical etching first electrode is removed.
Optionally, photon energy of emergent light of the light source is greater than forbidden bandwidths of the grating layer and the absorption layer, and is less than forbidden bandwidths of the contact layer and the upper optical field limiting layer.
Optionally, a forbidden bandwidth of the grating layer is greater than a forbidden bandwidth of the active region.
Optionally, the material of the absorption layer includes at least one of polysilicon, black silicon, germanium, black phosphorus, lead antimonide, lead sulfide, indium antimonide, and gallium antimonide.
In a second aspect, an embodiment of the present invention further provides a distributed feedback laser, which is prepared by using the preparation method provided in the first aspect.
According to the method for preparing the distributed feedback laser, the epitaxial structure of the distributed feedback laser is prepared through one-time epitaxial growth, interface pollution caused by multiple times of epitaxial growth is avoided, the grating structure on the surface of the laser epitaxial wafer is transferred into the grating layer of the laser through a photoelectrochemical corrosion method, and the DFB laser can be used for preparing the internal grating DFB laser with high coupling efficiency only through one-time epitaxial growth. The technical problems that the internal grating prepared by adopting a multi-time epitaxial growth technology in the prior art is easy to cause interface pollution, the process is complex, and the working wavelength cannot be changed due to the fixed period of the internal grating are solved, the internal grating epitaxial structure of the DFB laser required by the preparation of one-time epitaxial growth is realized, the interface pollution caused by secondary epitaxial preparation is avoided, and the performance and the reliability of the device are effectively improved; the preparation process of the device is simple, and the cost of the device is greatly reduced; meanwhile, the working wavelength of the device can be adjusted, so that the device is beneficial to scale production and has good market competitiveness.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments thereof, made with reference to the following drawings:
fig. 1 is a flowchart of a method for manufacturing a distributed feedback laser according to an embodiment of the present invention;
fig. 2 is a schematic surface view of a distributed feedback laser according to an embodiment of the present invention;
FIG. 3 isbase:Sub>A schematic cross-sectional view of the distributed feedback laser of FIG. 2 taken along the direction A-A';
FIG. 4 isbase:Sub>A schematic cross-sectional view taken along A-A' of FIG. 2 after the DFB grating pattern is prepared;
FIG. 5 isbase:Sub>A schematic cross-sectional view taken along A-A' of FIG. 2 after transfer of the DFB grating pattern to the absorbing layer;
FIG. 6 is a schematic diagram of an apparatus for producing a DFB laser by photoelectrochemical etching according to an embodiment of the present invention;
FIG. 7 isbase:Sub>A schematic cross-sectional view taken along A-A' of FIG. 2 after photo-electrochemical etching to form an internal grating;
fig. 8 is a schematic cross-sectional view of a distributed feedback laser along the direction B-B' in fig. 2 according to an embodiment of the present invention;
fig. 9 is a flowchart of a method for manufacturing a distributed feedback laser according to another embodiment of the present invention.
The following are the reference signs:
101 is a substrate, 102 is a buffer layer, 103 is a lower optical field limiting layer, 104 is a lower waveguide layer, 105 is an active region, 106 is an upper waveguide layer, 107 is a grating layer, 108 is an optical field limiting layer, 109 is an upper contact layer, 110 is an absorption layer, 111 is photoresist, 112 is an insulating dielectric film, 113 is a p-type ohmic contact electrode, 114 is a p-type thickened electrode, and 115 is an n-type ohmic contact electrode.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be fully described by the detailed description with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are a part of the embodiments of the present invention, not all embodiments, and all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without inventive efforts fall within the scope of the present invention.
Examples
The embodiment of the invention provides a preparation method of a distributed feedback laser. Fig. 1 isbase:Sub>A flowchart ofbase:Sub>A method for manufacturingbase:Sub>A distributed feedback laser according to an embodiment of the present invention, fig. 2 isbase:Sub>A schematic surface view of the distributed feedback laser according to the embodiment of the present invention, and fig. 3 isbase:Sub>A schematic cross-sectional view of the distributed feedback laser in fig. 2 alongbase:Sub>A directionbase:Sub>A-base:Sub>A', as shown in fig. 1, fig. 2, and fig. 3, the method for manufacturing the distributed feedback laser includes:
s101, preparing an epitaxial structure of the distributed feedback laser, wherein the epitaxial structure comprises a grating layer; the epitaxial structure includes a first surface and a second surface disposed opposite to each other.
Specifically, as shown in fig. 3, an epitaxial structure of a DFB laser is prepared on a substrate by a single epitaxial growth, where the epitaxial structure includes a grating layer 107 for further preparing an internal grating required by a specific operating wavelength, and according to the requirement of preparing the DFB laser, the epitaxial structure may further include a substrate 101, a buffer layer 102, a lower optical field confining layer 103, a lower waveguide layer 104, an active region 105, an upper waveguide layer 105, an optical field confining layer 108, and an upper contact layer 109, and includes a first surface and a second surface that are oppositely disposed, where the first surface is a surface of the contact layer 109 away from the optical field confining layer 108, and the second surface is a surface of the substrate 101 away from the buffer layer 102.
S102, preparing a photoelectrochemical corrosion first electrode.
Specifically, an epitaxial structure of the distributed feedback laser is cleaned, metal is coated or deposited on the epitaxial structure to enable the epitaxial structure to have conductivity, and the photoelectrochemical corrosion first electrode is prepared.
S103, preparing an absorption layer on the first surface and patterning the absorption layer to form a grating pattern in the absorption layer.
Specifically, fig. 4 isbase:Sub>A schematic cross-sectional view taken alongbase:Sub>A-base:Sub>A 'direction in fig. 2 after the DFB grating pattern is prepared, and fig. 5 isbase:Sub>A schematic cross-sectional view taken alongbase:Sub>A-base:Sub>A' direction in fig. 2 after the DFB grating pattern is transferred to the absorption layer. As shown in fig. 4 and 5, an absorption layer 110 and a photoresist 111 are prepared on a first surface of the epitaxial structure, a desired grating pattern is prepared on the photoresist 111 by means of electron beam exposure or holographic exposure, and then the pattern of the photoresist 111 is transferred into the absorption layer by means of reactive ion beam etching RIE, so that the grating pattern is formed in the absorption layer by the pattern of the photoresist. The absorption layer has the function of absorbing light energy, and the area irradiated by light is etched by light and the area which is not irradiated is left to form the required grating pattern.
And S104, performing photoelectrochemical corrosion on the epitaxial structure on one side of the first surface to form a grating pattern in the grating layer.
Specifically, fig. 6 isbase:Sub>A schematic diagram of an apparatus for preparingbase:Sub>A distributed feedback laser by photoelectrochemical etching according to an embodiment of the present invention, and fig. 7 isbase:Sub>A schematic cross-sectional view along the directionbase:Sub>A-base:Sub>A' shown in fig. 1 after an internal grating is prepared by photoelectrochemical etching. As shown in fig. 6 and 7, the epitaxial structure D is etched on the first surface side by means of photoelectrochemical etching, wherein the epitaxial structure D is etched as a first electrode in a photoelectrochemical etching circuit, the first surface side of the epitaxial structure is irradiated with light of a specific wavelength, the etching rate is controlled by controlling the power of the irradiated light and the current in the circuit, and the grating layer 107 irradiated with the light is etched to form a grating pattern under the irradiated light condition.
And S105, etching a part of the epitaxial structure on one side of the first surface to form a ridge structure.
Specifically, fig. 8 is a schematic cross-sectional view of the distributed feedback laser along the direction B-B' in fig. 2, after a grating pattern is formed in the grating layer 107, an etching solution (Buffered Oxide Etch, BOE) may be used to clean the surface of the epitaxial structure to remove the absorption layer 110, and then a photoresist 111 is used as a mask to form a ridge structure by using a reactive coupled plasma ICP etching, where the ridge structure includes a portion of the upper optical field limiting layer 108 and a portion of the contact layer 109, as shown in fig. 8.
S106, preparing first type ohmic contact metal on the surface of the ridge structure, and preparing second type ohmic contact metal on one side of the second surface.
Specifically, the first type ohmic contact metal may be a P-type ohmic contact metal, the second type ohmic contact metal may be an n-type ohmic contact metal, and the P-type ohmic contact metal is coated or deposited on the surface of the ridge structure and the n-type ohmic contact metal is coated or deposited on one side of the second surface, so that the distributed feedback laser may be further manufactured.
And S107, scribing, cleaving, coating and splitting the epitaxial structure to form the distributed feedback laser.
Specifically, scribing, cleaving, coating and splitting processes are carried out on epitaxial structures of first type ohmic contact metal and second type ohmic contact metal, and the distributed feedback laser with the specific working wavelength is prepared.
In summary, in the preparation method of the distributed feedback laser provided by the embodiment of the invention, the epitaxial structure of the distributed feedback laser is prepared by adopting one-time epitaxial growth, so that interface pollution caused by adopting multiple times of epitaxial growth is avoided, and the grating structure on the surface of the laser epitaxial wafer is transferred into the grating layer of the laser by a photoelectrochemical etching method, so that the DFB laser can be used for preparing the internal grating DFB laser with high coupling efficiency only by adopting one-time epitaxial growth. The technical problems that the internal grating is easy to interface pollution and the process is complex when the multi-time epitaxial growth technology is adopted for preparing the internal grating in the prior art are solved, the internal grating epitaxial structure of the DFB laser required by the preparation of one-time epitaxial growth is realized, the interface pollution caused by the preparation of the secondary epitaxial growth is avoided, and the performance and the reliability of the device are effectively improved; the preparation process of the device is simple, and the cost of the device is greatly reduced.
As one possible embodiment, as shown in fig. 4 and 5, a method for manufacturing a distributed feedback laser according to an embodiment of the present invention includes preparing an absorption layer on a first surface and patterning the absorption layer to form a grating pattern in the absorption layer, including:
step 31, depositing an absorption layer on the first surface side.
Specifically, the absorption layer 110 is deposited on one side of the first surface of the epitaxial structure, the absorption layer may be made of at least one of polysilicon, black silicon, germanium, black phosphorus, lead antimonide, lead sulfide, indium antimonide, gallium antimonide and other narrow band gap materials, has a function of absorbing irradiation light energy, and is photo-etched after light irradiation to leave a region which is not irradiated with light to form a desired grating pattern.
Step 32, applying an adhesive on the side of the absorption layer away from the epitaxial structure.
Specifically, an adhesive (not shown) is further applied to a side of the absorption layer 110 away from the epitaxial structure for fixing the photoresist.
Step 33 spin-coating a photoresist on the side of the adhesive away from the epitaxial structure.
Specifically, a photoresist 111 is further spin-coated on the side of the adhesive away from the epitaxial structure, for preparing the grating pattern.
And step 34, forming a grating pattern in the photoresist by adopting an electron beam exposure or holographic exposure mode.
Specifically, a desired grating pattern is formed in the photoresist 111 by further electron beam exposure or holographic exposure.
Step 35, transferring the grating pattern into the absorption layer by reactive ion beam etching.
Specifically, a grating pattern in the photoresist 111 is further transferred into the absorption layer 110 using reactive ion beam etching, the grating pattern required to form the internal grating is prepared.
As a possible embodiment, as shown in fig. 6 and 7, a method for manufacturing a distributed feedback laser according to an embodiment of the present invention includes performing a photoelectrochemical etching on an epitaxial structure on a first surface side to form a grating pattern in a grating layer, including:
and 41, arranging the epitaxial structure in a photoelectrochemical etching solution, wherein a photoelectrochemical etching second electrode is arranged in the photoelectrochemical etching solution.
Specifically, as shown in fig. 6, the epitaxial structure D is placed in an alkaline NaOH solution, or a solution satisfying photoelectrochemical etching, the epitaxial structure D is used as a first electrode, and metal platinum PT is used as a second electrode.
And step 42, providing a power supply, wherein the power supply is electrically connected with the photoelectrochemical corrosion first electrode and the photoelectrochemical corrosion second electrode respectively to form a loop.
Specifically, a direct current power supply DC can be selected to be respectively connected with the epitaxial structure and the metal platinum PT, so that the epitaxial structure and the metal platinum PT form an electrochemical corrosion electric loop in an alkaline NaOH solution.
Step 43, providing a light source to illuminate the epitaxial structure on the first surface side to form a grating pattern in the grating layer.
Specifically, as shown in fig. 6 and 7, a light source with a specific wavelength is provided to irradiate the first surface side of the epitaxial structure D, so as to form a combined manner of photoelectric irradiation and electrochemical etching, the power of the light irradiated by the light source S and the current in the DC circuit of the DC power supply are controlled to control the etching rate, the grating layer 107 irradiated by the light is etched into a porous structure or completely etched away, and an internal grating under the irradiation condition is formed, so that a desired grating pattern is formed in the grating layer 107.
The method adopts a photoelectrochemistry corrosion mode, can also provide light sources with various wavelengths, and obtains grating structures with different working wavelengths by changing the irradiation wavelength of the light source and etching, thereby solving the problem that the working wavelength can not be changed due to fixed period of the internal grating in the prior art, and realizing the purpose of adjusting the wavelength of the internal grating of the laser. The required internal grating is obtained through the epitaxial structure of the DFB laser grown by one-time epitaxy, so that interface pollution caused by secondary epitaxial preparation is avoided, the performance and reliability of the device are effectively improved, the effects of simplifying the preparation process of the device and reducing the cost of the device are achieved, the enterprise scale production is facilitated, and the market competitiveness is achieved.
As a possible embodiment, with reference to fig. 3 continuously, a method for manufacturing a distributed feedback laser according to an embodiment of the present invention is a method for manufacturing an epitaxial structure of a distributed feedback laser, including:
and step 11, providing a substrate.
Specifically, the substrate 101 is provided, and the substrate material may be any one or a combination of two or more of GaAs, inP, inGaAs, gaN, alN, siC, si, and SOI, which is selected according to the requirements of actually manufacturing the laser.
And step 12, preparing a buffer layer on one side of the substrate.
And step 13, preparing a lower optical field limiting layer on the side, far away from the substrate, of the buffer layer.
And 14, preparing a lower waveguide layer on the side, away from the substrate, of the lower optical field limiting layer.
And step 15, preparing an active region on one side of the lower waveguide layer far away from the substrate.
Step 16, preparing an upper waveguide layer on the side of the active region away from the substrate.
And step 17, preparing a grating layer on one side of the lower waveguide layer far away from the substrate.
And step 18, preparing an upper optical field limiting layer on the side, far away from the substrate, of the grating layer.
And step 19, preparing a contact layer on the side, far away from the substrate, of the upper optical field limiting layer.
Specifically, an epitaxial structure is prepared in a one-step growth mode along a direction away from one side of a substrate, a lower optical field limiting layer 103 is prepared on one side of a buffer layer 102 away from the substrate 101, a lower waveguide layer 104 is prepared on one side of the lower optical field limiting layer 103 away from the substrate 101, an active region 105 is prepared on one side of the lower waveguide layer 104 away from the substrate 101, an upper waveguide layer 106 is prepared on one side of the active region 105 away from the substrate 101, S101-7, a grating layer 107 is prepared on one side of the lower waveguide layer 106 away from the substrate 101, an optical field limiting layer 108 is prepared on one side of the grating layer 107 away from the substrate 101, and a contact layer 109 is prepared on one side of the upper optical field limiting layer 108 away from the substrate 101. The active region, the contact layer, the upper/lower optical field limiting layer, the upper/lower waveguide layer and the grating layer can be made of AlGaInAs, alGaInN and the like, and the buffer layer can be made of n-InP and the like.
Optionally, with reference to fig. 3, photon energy of emergent light of the light source is greater than forbidden bandwidths of the grating layer and the absorption layer, and is smaller than forbidden bandwidths of the contact layer and the upper optical field limiting layer.
Specifically, referring to fig. 3, the photon energy of the emergent light of the light source is selected to be greater than the forbidden bandwidths of the grating layer 107 and the absorption layer 110 and less than the forbidden bandwidths of the contact layer 109 and the upper optical field limiting layer, so that the photon energy of the incident light in the photoelectrochemical etching process is greater than the forbidden bandwidths of the grating layer 107 and the absorption layer 110, can be absorbed by the grating layer 107 and the absorption layer 110, and is less than the forbidden bandwidths of the contact layer 109 and the upper optical field limiting layer 108, so that the incident light can penetrate through the p-type contact layer 109 and the upper optical field limiting layer 108, and the built-in grating pattern is prepared.
Optionally, with continued reference to fig. 3, the forbidden bandwidth of the grating layer is greater than the forbidden bandwidth of the active region.
Specifically, referring to fig. 3, the active region 105 has a multi-quantum well structure, and the forbidden bandwidth of the grating layer 107 is further set to be larger than the forbidden bandwidth of the active region 105, so that the light energy emitted by the active layer 105 can pass through the grating layer 107 after the laser is manufactured.
As a possible embodiment, with continued reference to fig. 8, a method for manufacturing a distributed feedback laser according to an embodiment of the present invention is a method for manufacturing a photoelectrochemically etched first electrode, including:
step 21, preparing a photoelectrochemical corrosion first electrode on the edge area of the first surface; or preparing the photoelectrochemical corrosion first electrode on the second surface.
Specifically, as shown In fig. 8, when the photoelectrochemical etching first electrode is prepared, according to the requirements of actual production, the photoelectrochemical etching first electrode may be prepared on the edge area of the first surface of the epitaxial structure contact layer 109 away from the substrate 101 or on the second surface of the epitaxial structure substrate 101 away from the buffer layer 102, and may be prepared by a preparation method of coating or depositing metal In or AuGe, and the first electrode may be a p-type ohmic contact electrode 113, and then a p-type thickened electrode 114 is obtained by a coating or depositing method, so as to enhance the conductivity of the first electrode.
Step 22, before preparing the n-type ohmic contact metal on the second surface side, further comprising: thinning the substrate; when the photoelectrochemical corrosion first electrode is prepared on the second surface, the photoelectrochemical corrosion first electrode is removed while the substrate is thinned.
Specifically, after the first electrode is prepared, when the photoelectrochemical etching first electrode is prepared on the second surface of the epitaxial structure substrate 101 away from the buffer layer 102, the photoelectrochemical etching first electrode is removed while the substrate 101 is thinned, and the n-type ohmic contact metal 115 is further prepared on one side of the second surface of the epitaxial structure by coating or depositing metal.
As a possible embodiment, fig. 9 is a flowchart of a method for manufacturing a distributed feedback laser according to another embodiment of the present invention, as shown in fig. 9, the method for manufacturing a distributed feedback laser further includes:
s201, preparing an epitaxial structure of the distributed feedback laser, wherein the epitaxial structure comprises a grating layer; the epitaxial structure includes a first surface and a second surface disposed opposite to each other.
In particular, as shown in fig. 1.
S202, preparing a photoelectrochemical corrosion first electrode.
In particular, as shown in fig. 1.
S203, preparing an absorption layer on the first surface and patterning the absorption layer to form a grating pattern in the absorption layer.
Specifically, as shown in fig. 1.
And S204, performing photoelectrochemical corrosion on the epitaxial structure on one side of the first surface to form the grating pattern in the grating layer.
In particular, as shown in fig. 1.
S205, etching a part of the epitaxial structure on one side of the first surface to form a ridge structure.
In particular, as shown in fig. 1.
S206, an insulating layer is deposited on the first surface, and the insulating layer covers the ridge structure.
In particular, with continued reference to fig. 8 and 9, after etching a portion of the epitaxial structure on the first surface side of the epitaxial structure to form a ridge structure, depositing an insulating layer 112 on the first surface of the epitaxial structure to cover the ridge structure, wherein the insulating layer 112 is an insulating dielectric film, which may be SiO 2 、SiN x 、SiON、Al 2 O 3 、AlON、 SiAlON、TiO 2 、Ta 2 O 5 、ZrO 2 And polysilicon, or the like.
And S207, removing the insulating layer on the surface of the ridge structure by adopting photoetching and etching technologies.
Specifically, the insulating layer on the surface of the ridge structure is removed by adopting photoetching and etching technologies, so that the surface of the formed ridge structure is exposed.
And S208, preparing first type ohmic contact metal on the surface of the ridge structure exposed by the insulating layer, and preparing second type ohmic contact metal on one side of the second surface.
Specifically, with continued reference to fig. 8 and 9, a first type ohmic contact metal, preferably a P-type ohmic contact metal, and a second type ohmic contact metal, preferably an n-type ohmic contact metal, are prepared on the surface of the ridge structure exposed by the insulating layer 112, wherein the ohmic contact metal may be any one or a combination of two or more of Ni, ti, pd, pt, au, al, tiN, ITO, auGe, auGeNi, and IGZO, and optionally, the P-type ohmic contact metal may be Ni, ti, or Au.
And S209, scribing, cleaving, coating and splitting the epitaxial structure to form the distributed feedback laser.
Specifically, as shown in fig. 1, a distributed feedback laser having a desired grating pattern is prepared.
As a feasible embodiment, the embodiment of the present invention further provides a distributed feedback laser, which is prepared by the preparation method described in the above embodiment.
Specifically, a specific example is given below, and an indium phosphide InP-based DFB laser is produced using the production method provided in the above example, as shown in fig. 2 to 8, and the specific production method is as follows:
providing a substrate 101, selecting an n-type InP material, epitaxially growing an epitaxial structure of the DFB laser on the substrate 101 at one time, specifically including the n-InP material with the thickness of 1.6 μm as a buffer layer 102, the n-InP material with the thickness of 1.2 μm as a lower optical field limiting layer 103, the InAlGaAs material with the thickness of 120nm as a lower waveguide layer 104,3 as an active region 105 for AlGaInAs strained multiple quantum well material with the period of 15nm, the InAlGaAs material with the thickness of 120nm as an upper waveguide layer 106, the InAlGaAs material with the thickness of 200nm as a grating layer 107, the p-InP material with the thickness of 1.6 μm as an upper optical field limiting layer 108, and the p-InGaAs material with the thickness of 50nm as a contact layer 109.
And cleaning the epitaxial structure, and coating or depositing metal In or AuGe on the edge region of the contact layer 109 of the epitaxial structure far away from the first surface of the substrate 101 or on the second surface of the substrate 101 of the epitaxial structure far away from the buffer layer 102 to serve as a first electrode for photoelectrochemical corrosion.
Depositing a light absorption layer 110 on the first surface of the epitaxial structure, selecting a poly-Si material with a thickness of 200nm for the absorption layer 110, coating an adhesive, spin-coating a photoresist 111, and preparing a grating pattern required for preparing the DFB laser on the photoresist 111 by using methods such as electron beam exposure or holographic exposure, as shown in fig. 4.
Reactive ion beam etching RIE is used to transfer the pattern on the photoresist 111 into the light absorbing layer 110 to form the grating pattern in the absorbing layer required for fabricating the DFB laser, as shown in fig. 5.
Placing the epitaxial structure into a photoelectrochemical etching solution NaOH, irradiating the surface of a sample with light with a specific wavelength, controlling the etching rate by controlling the power of the irradiated light and the current in a circuit, and etching the grating layer 107 irradiated by the light into a porous structure or completely etching the grating layer to prepare a grating structure required by the DFB laser, as shown in FIGS. 6 and 7.
Cleaning the surface of the epitaxial structure, removing the polysilicon of the absorption layer 110 by using a BOE solution, then using the photoresist 111 as a mask, and forming a ridge structure by adopting reactive coupled plasma (ICP) etching; a dielectric film of SiO2 is then deposited as an insulating layer 112 on the surface of the ridge structure to a thickness of 300 nm.
And removing the dielectric film 112 in the ridge region of the ridge structure by adopting photoetching and etching technologies, then depositing p-type ohmic contact metal, and carrying out alloy annealing.
And thinning, grinding, polishing and the like are carried out on the epitaxial wafer, and then n-type ohmic contact metal is prepared on the second surface side of the epitaxial structure in a metal coating or depositing mode.
And scribing, cleaving, coating and splitting the epitaxial structure to form a laser tube core, so as to obtain the epitaxial structure required for preparing the DFB laser, as shown in FIG. 8.
The indium phosphide InP-based DFB laser provided by the embodiment of the invention adopts one-time epitaxy to produce an epitaxial structure, and transfers the grating structure on the surface of the epitaxial structure of the laser to the grating layer inside the laser by a photoelectrochemical etching method to obtain the grating structure required by the indium phosphide InP-based DFB laser. The preparation method provided by the embodiment of the invention avoids the pollution problem of a secondary epitaxial growth interface, effectively improves the performance and reliability of the device, has simple preparation process and low cost, and realizes that the DFB laser with the internal grating structure with high coupling efficiency can be prepared by only one-time epitaxial growth. Based on the same preparation method, the grating with a specific period can be prepared for adjustment according to the needs, so that various DFB lasers can be prepared, the wide applicability is realized, and the large-scale production of companies is facilitated.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will appreciate that the present invention is not limited to the specific embodiments described herein, but rather, features of the various embodiments of the invention may be partially or fully coupled or combined with each other and yet still cooperate with each other and be technically driven in various ways. Numerous variations, rearrangements, combinations, and substitutions will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (9)
1. A preparation method of a distributed feedback laser is characterized by comprising the following steps:
preparing an epitaxial structure of a distributed feedback laser, wherein the epitaxial structure comprises a grating layer; the epitaxial structure comprises a first surface and a second surface which are oppositely arranged;
preparing a photoelectrochemical etching first electrode;
preparing an absorption layer on the first surface and patterning the absorption layer to form a grating pattern in the absorption layer;
arranging the epitaxial structure in a photoelectrochemical etching solution, wherein a photoelectrochemical etching second electrode is arranged in the photoelectrochemical etching solution;
providing a power supply which is respectively and electrically connected with the photoelectrochemical corrosion first electrode and the photoelectrochemical corrosion second electrode to form a loop;
providing a light source to illuminate the epitaxial structure on the first surface side to form the grating pattern in the grating layer; wherein the grating pattern is disposed inside the epitaxial structure;
etching a part of the epitaxial structure on one side of the first surface to form a ridge structure;
preparing a first type of ohmic contact metal on the surface of the ridge structure, and preparing a second type of ohmic contact metal on one side of the second surface;
and carrying out scribing, cleavage, coating and splitting processes on the epitaxial structure to form the distributed feedback laser.
2. The method of claim 1, wherein preparing an absorption layer on the first surface and patterning the absorption layer to form a grating pattern in the absorption layer comprises:
depositing an absorption layer on one side of the first surface;
coating an adhesive on one side of the absorption layer far away from the epitaxial structure;
spin-coating a photoresist on one side of the adhesive, which is far away from the epitaxial structure;
forming a grating pattern in the photoresist by adopting an electron beam exposure or holographic exposure mode;
and transferring the grating pattern into the absorption layer by reactive ion beam etching.
3. The method according to claim 1, wherein after etching a portion of the epitaxial structure on the first surface side to form a ridge structure, the method further comprises:
depositing an insulating layer on the first surface, wherein the insulating layer covers the ridge structure;
removing the insulating layer on the surface of the ridge structure by adopting photoetching and etching technologies;
preparing a first type of ohmic contact metal on the surface of the ridge structure, comprising:
and preparing a first type of ohmic contact metal on the surface of the ridge structure exposed by the insulating layer.
4. A method according to claim 1, wherein the step of fabricating an epitaxial structure of a distributed feedback laser comprises:
providing a substrate;
preparing a buffer layer on one side of the substrate;
preparing a lower optical field limiting layer on one side of the buffer layer far away from the substrate;
preparing a lower waveguide layer on one side of the lower optical field limiting layer far away from the substrate;
preparing an active region on one side of the lower waveguide layer far away from the substrate;
preparing an upper waveguide layer on one side of the active region far away from the substrate;
preparing the grating layer on one side of the upper waveguide layer far away from the substrate;
preparing an upper optical field limiting layer on one side of the grating layer far away from the substrate;
a contact layer is prepared on the side of the upper optical field limiting layer away from the substrate.
5. The method of claim 4, wherein preparing the photoelectrochemically etched first electrode comprises:
preparing the photoelectrochemical etching first electrode at the edge area of the first surface;
or preparing the photoelectrochemical corrosion first electrode on the second surface;
before the second-type ohmic contact metal is prepared on the second surface side, the method further comprises the following steps:
thinning the substrate; when the photoelectrochemical etching first electrode is prepared on the second surface, the substrate is thinned, and the photoelectrochemical etching first electrode is removed.
6. The manufacturing method according to claim 4, wherein photon energy of emergent light of the light source is larger than forbidden band widths of the grating layer and the absorption layer and smaller than forbidden band widths of the contact layer and the upper optical field limiting layer.
7. The method of claim 4, wherein a forbidden bandwidth of the grating layer is greater than a forbidden bandwidth of the active region.
8. The method according to claim 1, wherein the absorbing layer material includes at least one of silicon, germanium, black phosphorus, lead antimonide, lead sulfide, indium antimonide, and gallium antimonide.
9. A distributed feedback laser, characterized by being prepared by the preparation method of any one of claims 1 to 8.
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