CN111193186A - Vertical cavity surface emitting laser and method of manufacturing the same - Google Patents
Vertical cavity surface emitting laser and method of manufacturing the same Download PDFInfo
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- H—ELECTRICITY
- 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
- H01S5/00—Semiconductor lasers
- 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
- H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
- H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
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- H—ELECTRICITY
- 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
- H01S5/00—Semiconductor lasers
- 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
- H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
- H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
- H01S5/18361—Structure of the reflectors, e.g. hybrid mirrors
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- H—ELECTRICITY
- 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
- H01S5/00—Semiconductor lasers
- 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
- H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
- H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
- H01S5/18361—Structure of the reflectors, e.g. hybrid mirrors
- H01S5/18363—Structure of the reflectors, e.g. hybrid mirrors comprising air layers
- H01S5/18366—Membrane DBR, i.e. a movable DBR on top of the VCSEL
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- H—ELECTRICITY
- 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
- H01S5/00—Semiconductor lasers
- 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
- H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
- H01S5/185—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only horizontal cavities, e.g. horizontal cavity surface-emitting lasers [HCSEL]
- H01S5/187—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only horizontal cavities, e.g. horizontal cavity surface-emitting lasers [HCSEL] using Bragg reflection
Abstract
The embodiment of the invention provides a vertical cavity surface emitting laser and a manufacturing method thereof. The vertical cavity surface emitting laser includes: an N-DBR disposed over a substrate and including a first distributed Bragg reflector disposed in a stack; an active layer disposed on the N-DBR and including a quantum well structure disposed in a stack; a P-DBR disposed on the active layer and including a second distributed Bragg reflector disposed in a stack. According to the vertical cavity surface emitting laser and the manufacturing method thereof provided by the embodiment of the invention, the quantum well structure, the N-DBR and the P-DBR are arranged on the active layer, so that single-mode polarization is realized, the polarization is more sensitive, the threshold current of the VCSEL can be reduced, the photoelectric conversion efficiency is improved, and the quality of an output light beam is higher.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a vertical cavity surface emitting laser and a manufacturing method thereof.
Background
Since the Vertical Cavity Surface Emitting Laser (VCSEL) was commercially available in 1996, although it has been widely used in many fields such as optical communication, information reading, three-dimensional imaging, and Laser radar, it is still at a low power level in the application process, and the power level of the VCSEL material is not greatly improved until the development of the VCSEL material growth and preparation technology in recent years, thereby opening up a broad prospect for the application development of the VCSEL Laser. However, as the laser power of the VCSEL is continuously improved, the threshold current of the conventional vertical cavity surface emitting laser is high, the photoelectric conversion efficiency is low, and the VCSEL is very easy to operate in a dynamic single longitudinal mode due to the short length of the resonant cavity. In order to achieve higher output power, the light extraction size of the VCSEL needs to be very large, so that multiple transverse modes occur, which affects the device performance and limits further development of the VCSEL.
Therefore, it is an important issue to solve in the industry how to provide a vertical cavity surface emitting laser that can reduce the threshold current of the VCSEL, improve the photoelectric conversion efficiency, and achieve a wider tuning range, higher quality of the output beam, and shorter response time.
Disclosure of Invention
Embodiments of the present invention provide a vertical cavity surface emitting laser and a manufacturing method thereof, so as to reduce a threshold current of a VCSEL, improve photoelectric conversion efficiency, achieve a wider tuning range, and improve quality of an output beam.
According to a first aspect of embodiments of the present invention, there is provided a vertical cavity surface emitting laser including: an N-DBR disposed over a substrate and including a first distributed Bragg reflector disposed in a stack; an active layer disposed on the N-DBR and including a quantum well structure disposed in a stack; a P-DBR disposed on the active layer and including a second distributed Bragg reflector disposed in a stack.
According to one embodiment of the present invention, the N-DBR comprises at least 7 first distributed bragg mirrors, each of the first distributed bragg mirrors comprising a Si layer and a SiO2 layer on the Si layer.
According to an embodiment of the present invention, the N-DBR further includes an AlGaAs cladding layer on the first distributed bragg reflector which is stacked, and an air layer on the AlGaAs cladding layer.
According to one embodiment of the invention, the active layer comprises 3 stacked quantum well structures, each comprising a GaAs layer and an AlGaAs layer on the GaAs layer.
According to an embodiment of the present invention, the P-DBR comprises at least 22 of the second distributed bragg mirrors, each of which comprises a GaAs layer and an AlGaAs layer on the GaAs layer, wherein a refractive index of the AlGaAs layer is greater than a refractive index of the GaAs layer.
According to an embodiment of the present invention, the vertical cavity surface emitting laser further includes: an N electrode disposed on a bottom surface of the substrate; a first buffer layer disposed between the top surface of the substrate and the N-DBR; a second buffer layer disposed on the P-DBR; a P electrode disposed on the second buffer layer.
According to an embodiment of the present invention, the N-DBR includes a first top surface covered by the active layer and an exposed second top surface, wherein the second top surface, the sidewall of the active layer, the sidewall of the P-DBR, and the sidewall of the second buffer layer are covered with a mask.
According to a second aspect of embodiments of the present invention, there is provided a method of manufacturing a vertical cavity surface emitting laser, including: forming an N-DBR over a substrate, the N-DBR including a first distributed Bragg reflector arranged in a stack; forming an active layer on the N-DBR, wherein the active layer comprises a quantum well structure which is arranged in a stacked mode; and forming a P-DBR on the active layer, wherein the P-DBR comprises a second distributed Bragg reflector which is arranged in a stacked mode.
According to an embodiment of the invention, the method further comprises: forming a first buffer layer on a top surface of the substrate, and forming the N-DBR on the first buffer layer; forming a second buffer layer on the P-DBR, and forming a P-electrode on the second buffer layer; and thinning the bottom surface of the substrate and forming an N electrode on the bottom surface of the substrate.
According to an embodiment of the invention, the method further comprises: etching the active layer, the P-DBR and the second buffer layer to expose a portion of a top surface of the N-DBR; depositing a mask on a portion of the top surface of the N-DBR, the sidewalls of the active layer, the sidewalls of the P-DBR, and the sidewalls of the second buffer layer.
In the vertical cavity surface emitting laser and the manufacturing method thereof provided by the embodiment of the invention, the quantum well structure is arranged on the active layer, and the multimode structures are arranged on the N-DBR and the P-DBR, so that single-mode polarization is realized, the polarization is more sensitive, the threshold current of the VCSEL can be reduced, the photoelectric conversion efficiency is improved, and the quality of output beams is higher.
Drawings
In order to more clearly illustrate 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, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic cross-sectional structure diagram of a vertical cavity surface emitting laser according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a method for manufacturing a vertical cavity surface emitting laser according to an embodiment of the invention.
Description of reference numerals:
1-N electrode; 2-a substrate;
3-a first buffer layer; 4-N-DBR;
5-an active layer; 6-P-DBR;
7-a second buffer layer; 8-a mask;
a 9-P electrode; 201 to 203-steps.
Detailed Description
In order to make the objects, 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 and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Embodiments of a vertical cavity surface emitting laser and a method of manufacturing the same provided by the present invention will now be described with reference to fig. 1 and 2. It should be understood that the following description is only exemplary embodiments of the present invention and does not constitute any particular limitation of the present invention.
Fig. 1 is a schematic cross-sectional structure diagram of a vertical cavity surface emitting laser according to an embodiment of the present invention. As shown in fig. 1, in one embodiment of the present invention, the vertical cavity surface emitting laser includes an N-DBR (Distributed Bragg Reflector)4, an active layer 5, and a P-DBR 6. Specifically, the N-DBR4 is disposed above the substrate 2 and includes a first distributed bragg reflector which is disposed in a stack. The active layer 5 is disposed on the N-DBR4 and includes a quantum well structure that is stacked. And the P-DBR6 is disposed on the active layer 5 and includes a second distributed bragg reflector which is disposed in a stacked manner.
More specifically, in one embodiment, an embodiment of the present invention provides a vertical cavity surface emitting laser including: a substrate 2, a first buffer layer 3, an N-DBR4, an active layer 5, a P-DBR6, and a second buffer layer 7 are sequentially stacked on an N electrode 1. The N-DBR4 comprises a first top surface covered by the active layer 5 and an exposed second top surface, wherein the second top surface, the sidewalls of the active layer 5, the sidewalls of the P-DBR6 and the sidewalls of the second buffer layer 7 are covered with a mask 8. In addition, the vertical cavity surface emitting laser further includes a P-electrode 9 on the second buffer layer 7.
Specifically, in one embodiment of the present invention, the substrate 2 is made of Si material. In another embodiment, the substrate 2 has a thickness of 500 nanometers.
As shown in fig. 1, in one embodiment of the present invention, a first buffer layer 3 is located on a substrate 2, and optionally, the first buffer layer 3 is a GaAs material.
Further, an N-DBR4 is located on the first buffer layer 3, and the N-DBR4 includes a first distributed Bragg reflector which is arranged in a stacked manner. The active layer 5 is located on the N-DBR4, and the active layer 5 includes a quantum well structure which is stacked. In addition, the P-DBR6 is located on the active layer 5, and the P-DBR6 includes a second distributed Bragg reflector which is stacked. Further, for example, the second buffer layer 7 is located on the P-DBR6, and optionally, the second buffer layer 7 may employ an AlGaAs material.
With continued reference to fig. 1, a P electrode 9 is formed on the second buffer layer 7. In one embodiment, the P electrode 9 is annular and 350nm thick, and adopts a Ti-Pt-Au structure. In the embodiment shown in the figure, an N electrode 1 is formed on the substrate 2 opposite to the first buffer layer 3, the N electrode 1 may adopt Ge, Au or Ni — Au structure, and the light exit hole of the vcsel is etched on the N electrode 1.
In addition, the vertical cavity surface emitting laser provided by the embodiment of the invention further includes a mask 8. For example, the second buffer layer 7, the P-DBR6, and the active layer 5 may be etched to form a cylindrical mesa, and the top surface of the N-DBR4 covered by the cylindrical mesa is a first top surface, and the top surface of the N-DBR4 not covered by the cylindrical mesa is a second top surface. The second top surface is covered with a mask 8 and the sidewalls of the cylindrical mesa formed by the active layer 5, the P-DBR6 and the second buffer layer 7 are also covered with the mask 8. In one embodiment, mask 8 is made of SiO2The material has the thickness of 300nm and is used for improving the overall performance of the laser.
According to the vertical cavity surface emitting laser provided by the embodiment of the invention, the quantum well structure is arranged on the active layer 5, and the N-DBR4 and the P-DBR6 are respectively provided with the multimode structure, so that single-mode polarization is realized, the polarization is more sensitive, the threshold current of a VCSEL (vertical cavity surface emitting laser) can be reduced, the photoelectric conversion efficiency is improved, and the quality of output light beams is higher.
Based on the above description of the embodiments, as an alternative embodiment, the N-DBR4 includes at least 7 distributed bragg reflectors, each of which is composed of a Si layer and SiO on the Si layer2The arrangement of layers, each layer of material having an optical thickness of 1/4 times the center wavelength of the VCSEL. In one embodiment, the VCSEL center wavelength may be 835nm, resulting in a folded N-DBR4The refractive index is more than 99%.
Further, in one embodiment, the N-DBR4 further includes an AlGaAs cladding layer on the at least 7 first distributed bragg mirrors, and an air layer on the AlGaAs cladding layer. Specifically, the N-DBR includes 3 layers: a first layer consisting of at least 7 first distributed Bragg reflectors, a second layer being an AlGaAs cladding layer and a third layer being an air layer. Wherein the content of aluminum contained in the AlGaAs cladding layer is mutated in the growth direction. Specifically, the content of aluminum contained in the AlGaAs cladding layer is abruptly changed from the bottom layer to the top layer, i.e., the bottom layer aluminum content is low and the top layer aluminum content is high, for smoothing out the energy peaks of the conduction band and valence band in the N-DBR 4.
The embodiment of the invention adopts the sub-wavelength grating structure, so that the VCSEL with stable single-mode polarization is formed, the polarization is more sensitive, and the VCSEL has wide application in the aspects of optical interconnection, gas detection, laser ranging, optical sensing and the like.
Based on the above description of the embodiments, as an alternative embodiment, a stacked quantum well structure includes a GaAs layer and an AlGaAs layer on the GaAs layer. In one embodiment, the active layer 5 comprises 3 quantum well structures arranged in a stack, each of which may have a thickness of 14 nm. The quantum well structure is arranged on the active layer 5, so that the gain material is increased in the direction of lasing light resonance, and the optical effect is improved.
Based on the contents of the above-described embodiment, as an alternative embodiment, the P-DBR6 includes at least 22 second distributed bragg mirrors, and each of the second distributed bragg mirrors includes a GaAs layer and an AlGaAs layer on the GaAs layer. Wherein the refractive index of the AlGaAs layer is larger than that of the GaAs layer. In a specific embodiment, the optical thickness of each layer of material is 1/4 of the center wavelength of the VCSEL. In one embodiment, the VCSEL center wavelength may be 835nm, and the refractive index of the P-DBR6 formed is 99% or more. Meanwhile, the P-DBR6 can adopt P-DBR consisting of Al with the valence of 0.12-0.9 and gradually changed components as AlGaAs. That is, the valence state of Al in the AlGaAs layer gradually changes from the bottom layer to the top layer, the valence state of Al in the bottom AlGaAs layer is 0.12, and the valence state of Al in the top AlGaAs layer is 0.9, which can be used to provide the optical gain of the laser.
Fig. 2 is a schematic flow chart of a method for manufacturing a vertical cavity surface emitting laser according to an embodiment of the present invention, for example, the method may include the following steps:
in step 201, an N-DBR4 is formed over a substrate 2, the N-DBR4 including a first distributed Bragg reflector arranged in a stack.
In particular, an N-DBR4 is grown over the substrate 2, the N-DBR4 comprising for example at least 7 first distributed Bragg reflectors arranged one above the other. Wherein each distributed Bragg reflector consists of a Si layer and SiO arranged on the Si layer2The arrangement of layers is such that the optical thickness of each layer of material is, for example, 1/4 times the center wavelength of the VCSEL. In one embodiment, the VCSEL center wavelength may be 835nm, and the refractive index of the N-DBR4 formed is 99% or more. Among them, the substrate 2 may employ a Si-based material, and the thickness of the substrate 2 is 500nm, for example.
The N-DBR4 further comprises AlGaAs cladding layers on the at least 7 first distributed bragg mirrors, and an air layer on the AlGaAs cladding layers. Specifically, the N-DBR4 includes 3 layers: a first layer consisting of at least 7 first distributed Bragg reflectors, a second layer being an AlGaAs cladding layer and a third layer being an air layer. Wherein the content of aluminum contained in the AlGaAs cladding layer is mutated in the growth direction. Specifically, the content of aluminum contained in the AlGaAs cladding layer is abruptly changed from the bottom layer to the top layer, i.e., the bottom layer aluminum content is low and the top layer aluminum content is high, for smoothing out the energy peaks of the conduction band and valence band in the N-DBR 4.
In step 202, an active layer 5 is formed on the N-DBR4, and the active layer 5 includes a quantum well structure stacked.
Specifically, after the N-DBR4 is formed, an active layer 5 is grown on the N-DBR4, the active layer 5 including, for example, 3 quantum well structures stacked. Each quantum well structure comprises a GaAs layer and an arrangement of AlGaAs layers on the GaAs layer. In one embodiment, each quantum well structure is 14nm thick.
In step 203, a P-DBR6 is formed on the active layer 5, and the P-DBR6 includes a second distributed bragg reflector stacked.
Specifically, after the active layer 5 is formed, a P-DBR6 is grown on the active layer 5, the P-DBR6 including, for example, at least 22 second distributed bragg mirrors each including a GaAs layer and an AlGaAs layer on the GaAs layer. Wherein the refractive index of the AlGaAs layer is larger than that of the GaAs layer.
In one embodiment, the optical thickness of each layer of material is 1/4 of the center wavelength of the VCSEL. For example, the VCSEL center wavelength may be 835nm, and the refractive index of the P-DBR6 to be formed is 99% or more. Meanwhile, the P-DBR6 can be a P-DBR6 consisting of AlGaAs and a gradual change component of Al with the valence state of 0.12-0.9. That is, the valence state of Al in the AlGaAs layer gradually changes from the bottom layer to the top layer, the valence state of Al in the bottom AlGaAs layer is 0.12, and the valence state of Al in the top AlGaAs layer is 0.9, which can be used to provide the optical gain of the laser. Then, a second buffer layer 7 is grown on the P-DBR6, for example, the second buffer layer 7 is made of AlGaAs material.
According to the manufacturing method of the vertical cavity surface emitting laser, which is provided by the embodiment of the invention, the quantum well structure is arranged on the active layer 5, and the multimode structures are arranged on the N-DBR4 and the P-DBR6, so that single-mode polarization is realized, the polarization is more sensitive, the threshold current of a VCSEL (vertical cavity surface emitting laser) can be reduced, the photoelectric conversion efficiency is improved, and the quality of output beams is higher.
Based on the content of the above embodiment, as an alternative embodiment, the manufacturing method further includes the steps of:
forming a first buffer layer 3 on the top surface of the substrate 2, and forming the N-DBR4 as described above on the first buffer layer 3;
forming a second buffer layer 7 on the P-DBR 6;
etching the active layer 5, the P-DBR6, and the second buffer layer 7 to expose a portion of the top surface of the N-DBR4, and depositing a mask on the portion of the top surface of the N-DBR4, the sidewalls of the active layer 5, the sidewalls of the P-DBR6, and the sidewalls of the second buffer layer 7;
and forming a P-electrode 9 on the second buffer layer 7; and
the bottom surface of the substrate 2 is thinned and the N-electrode 1 is formed on the bottom surface of the substrate 2.
Specifically, before growing the first buffer layer 3 on the substrate 2, a plasma dry etching process may be used to etch on the Si substrate so that the surface of the substrate 2 on the side facing the first buffer layer 3 is etched smoothly. For example, the root mean square roughness of the surface of the substrate 2 after etching is less than 1 nm. For example, SiCl4/Ar/H2 gas may be used for dry etching.
A first buffer layer 3 is grown on the substrate 2, and the first buffer layer 3 may be made of, for example, GaAs. In one embodiment, the thickness of the first buffer layer 3 is 50 nm. Then, the N-DBR4 is grown on the first buffer layer 3.
In addition, the second buffer layer 7 is grown on the P-DBR6, and for example, AlGaAs material may be used for the second buffer layer 7.
Etching the active layer 5, the P-DBR6, and the second buffer layer 7 to expose a portion of the top surface of the N-DBR 4; a mask 8 is deposited on a portion of the top surface of the N-DBR4, the sidewalls of the active layer 5, the sidewalls of the P-DBR6, and the sidewalls of the second buffer layer 7.
For example, the second buffer layer 7, the P-DBR6, and the active layer 5 are etched to form a cylindrical mesa. The top surface of the N-DBR4 covered by the cylindrical stage body is a first top surface, and the top surface of the N-DBR4 not covered by the cylindrical stage body is a second top surface. A plasma enhanced chemical vapor deposition method is used to deposit SiO2 as a mask 8 on a portion of the top surface of the N-DBR4, the sidewalls of the active layer 5, the sidewalls of the P-DBR6, and the sidewalls of the second buffer layer 7. In one embodiment, the thickness of the mask 8 is 300nm, for improving the overall performance of the laser.
After the mask 8 is completed, a P electrode 9 is formed on the surface of the second buffer layer 7 by sputtering using an electron beam sputtering method. The thickness of the P electrode 9 may be 350nm, for example, and the P electrode 9 may be formed in a ring shape by using a Ti-Pt-Au structure. Further, the thickness of the substrate 2 may be reduced to, for example, 300nm, and the N electrode 1 may be formed after evaporating a Ge/Au/Ni — Au structure on the side of the substrate 2 opposite to the first buffer layer 3 at a temperature of 300 c using a vacuum plating equipment and performing a rapid thermal treatment. After the N electrode 1 is formed, a light exit hole of the vcsel may be etched on the N electrode 1 by using a plasma dry etching process.
The following describes the fabrication process of the vertical cavity surface emitting laser in detail by taking the process of fabricating the vertical cavity surface emitting laser provided by the present invention as an example:
step one, growing a first buffer layer 3 on a substrate 2 made of Si material, and then growing an N-DBR4 on the first buffer layer 3 at the temperature of 1000-1300 ℃, wherein the N-DBR4 comprises 7 first distributed Bragg reflectors, and the 7 first distributed Bragg reflectors comprise an Si layer and an SiO2 layer positioned on the Si layer. During the growth process, the Si layer and the SiO2 layer are bonded together by a metal bonding method, the optical thickness of each layer of material is 1/4 of the central wavelength of the vertical cavity surface emitting laser, and the central wavelength of the vertical cavity surface emitting laser can be 835 nm. The refractive index of the manufactured N-DBR4 is more than 99%.
And step two, growing 3 quantum well structures on the N-DBR4 by adopting a metal organic chemical vapor deposition technology, wherein each quantum well structure comprises a GaAs layer and an AlGaAs layer positioned on the GaAs layer, the thickness of each quantum well structure is 14nm, and the 3 quantum well structures are stacked to form an active layer 5.
And step three, growing a P-DBR6 on the active layer 5, wherein the P-DBR6 comprises 22 second distributed Bragg reflectors, and each second distributed Bragg reflector comprises a GaAs layer and an AlGaAs layer positioned on the GaAs layer. Wherein the refractive index of the AlGaAs layer is larger than that of the GaAs layer. During the growth process, the AlGaAs layer and the GaAs layer are bonded together by a metal bonding method, the optical thickness of each layer of material is 1/4 of the central wavelength of the vertical cavity surface emitting laser, and the central wavelength of the vertical cavity surface emitting laser can be 835 nm. The refractive index of the formed P-DBR6 is more than 99 percent. Then, a second buffer layer 7 is grown on the P-DBR6, and AlGaAs material is used for the second buffer layer 7.
And step four, etching the second buffer layer 7, the P-DBR6 and the active layer 5 by a low-pressure plasma etching method to form a cylindrical table body. A mask 8 is formed for the second top surface not covered by the cylindrical mesa, the sidewall of the active layer 5, the sidewall of the P-DBR6, and the sidewall of the second buffer layer 7.
And step five, depositing SiO2 with the thickness of 300nm as a mask 8 on the second top surface which is not covered by the cylindrical stage body, the side wall of the active layer 5, the side wall of the P-DBR6 and the side wall of the second buffer layer 7 by using a plasma enhanced chemical vapor deposition method so as to improve the overall performance of the laser.
And step six, sputtering a Ti-Pt-Au structure with the thickness of 350nm on the second buffer layer 7 by using an electron beam sputtering method to form a P electrode 9, wherein the P electrode 9 is in a ring shape. Then the thickness of the Si substrate is reduced to 300nm, then a vacuum coating device is utilized to evaporate a Ge/Au/Ni-Au structure on the surface of the Si substrate at the side opposite to the side where the first buffer layer 3 grows at 300 ℃, and after rapid thermal treatment, an N electrode 1 is formed on the Si substrate. And finally, etching the light outlet of the vertical cavity surface emitting laser on the N electrode 1 by using a plasma dry etching technology.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A vertical cavity surface emitting laser, comprising:
an N-DBR disposed over a substrate and including a first distributed Bragg reflector disposed in a stack;
an active layer disposed on the N-DBR and including a quantum well structure disposed in a stack;
a P-DBR disposed on the active layer and including a second distributed Bragg reflector disposed in a stack.
2. A vertical cavity surface emitting laser according to claim 1, wherein said N-DBR comprises at least 7 of said first distributed bragg mirrors, each of said first distributed bragg mirrors comprising a Si layer and a SiO2 layer on said Si layer.
3. A vertical cavity surface emitting laser according to claim 2, wherein said N-DBR further comprises an AlGaAs cladding layer on said first distributed bragg reflector arranged in a stack, and an air layer on said AlGaAs cladding layer.
4. A vertical cavity surface emitting laser according to claim 1, wherein said active layer includes 3 of said quantum well structures arranged in a stack, each of said quantum well structures including a GaAs layer and an AlGaAs layer on said GaAs layer.
5. A vcsel according to claim 1, wherein said P-DBR comprises at least 22 of said second distributed bragg mirrors, each of said second distributed bragg mirrors comprising a GaAs layer and an AlGaAs layer on said GaAs layer, wherein said AlGaAs layer has a refractive index greater than that of said GaAs layer.
6. A vertical cavity surface emitting laser according to claim 1, further comprising:
an N electrode disposed on a bottom surface of the substrate;
a first buffer layer disposed between the top surface of the substrate and the N-DBR;
a second buffer layer disposed on the P-DBR;
a P electrode disposed on the second buffer layer.
7. A vertical cavity surface emitting laser according to claim 6, wherein said N-DBR includes a first top surface covered by said active layer and an exposed second top surface, wherein said second top surface, sidewalls of said active layer, sidewalls of said P-DBR and sidewalls of said second buffer layer are covered with a mask.
8. A method of fabricating a vertical cavity surface emitting laser, comprising:
forming an N-DBR over a substrate, the N-DBR including a first distributed Bragg reflector arranged in a stack;
forming an active layer on the N-DBR, wherein the active layer comprises a quantum well structure which is arranged in a stacked mode;
and forming a P-DBR on the active layer, wherein the P-DBR comprises a second distributed Bragg reflector which is arranged in a stacked mode.
9. The method of claim 8, further comprising:
forming a first buffer layer on a top surface of the substrate, and forming the N-DBR on the first buffer layer;
forming a second buffer layer on the P-DBR, and forming a P-electrode on the second buffer layer;
and thinning the bottom surface of the substrate and forming an N electrode on the bottom surface of the substrate.
10. The method of claim 9, further comprising:
etching the active layer, the P-DBR and the second buffer layer to expose a portion of a top surface of the N-DBR;
depositing a mask on a portion of the top surface of the N-DBR, the sidewalls of the active layer, the sidewalls of the P-DBR, and the sidewalls of the second buffer layer.
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