CN116169560A - Gallium nitride-based photonic crystal surface-emitting laser and preparation method thereof - Google Patents

Gallium nitride-based photonic crystal surface-emitting laser and preparation method thereof Download PDF

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CN116169560A
CN116169560A CN202310441061.0A CN202310441061A CN116169560A CN 116169560 A CN116169560 A CN 116169560A CN 202310441061 A CN202310441061 A CN 202310441061A CN 116169560 A CN116169560 A CN 116169560A
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layer
gan
photonic crystal
algan
refractive index
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刘启发
刘珂
撒同良
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Nanjing University of Posts and Telecommunications
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Nanjing University of Posts and Telecommunications
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    • 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
    • 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
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    • 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
    • H01S5/2004—Confining in the direction perpendicular to the layer structure
    • H01S5/2018—Optical confinement, e.g. absorbing-, reflecting- or waveguide-layers
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    • 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
    • H01S5/2004—Confining in the direction perpendicular to the layer structure
    • H01S5/2018—Optical confinement, e.g. absorbing-, reflecting- or waveguide-layers
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    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
    • H01S5/323—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/32308—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm
    • H01S5/32341—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser emitting light at a wavelength less than 900 nm blue laser based on GaN or GaP
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    • H01S5/00—Semiconductor lasers
    • H01S5/30—Structure or shape of the active region; Materials used for the active region
    • H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
    • H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
    • H01S5/34333—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
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Abstract

The invention discloses a gallium nitride-based photonic crystal surface emitting laser and a preparation method thereof, wherein the gallium nitride-based photonic crystal surface emitting laser comprises a substrate layer, a bottom GaN layer, a DBR layer consisting of porous GaN/GaN, an AlGaN-n layer, a GaN-n layer, an active layer, a p-GaN layer, a TiO2 photonic crystal layer, a p electrode and an n electrode. The invention adopts the DBR and TiO2 photonic crystal layers composed of porous GaN/GaN, and can realize strong constraint and regulation control of light field mode distribution, thereby optimizing and obtaining high limiting factors of light field in the photonic crystal layers and the active layers, and being beneficial to realization of a low-threshold high-efficiency laser.

Description

Gallium nitride-based photonic crystal surface-emitting laser and preparation method thereof
Technical Field
The invention discloses a gallium nitride-based photonic crystal surface-emitting laser and a preparation method thereof, and relates to the field of semiconductor lasers.
Background
Photonic Crystal Surface Emitting Lasers (PCSEL) are focused on solving the problems of traditional semiconductor lasers due to the high quality, extremely narrow divergence and symmetrical beam operation capability supported by wide area band edge resonance in two-dimensional photonic crystals, and are based on two-dimensional (2D) resonance in photonic crystals, capable of realizing laser emission with high power and high beam quality, single-mode operation, low divergence angle, high power output and the like, and are very suitable for applications such as material processing, data communication, laser radar, high-density optical storage, micro-projector light sources, biomedical sensing, laser solid-state lighting and the like. Compared to Vertical Cavity Surface Emitting Lasers (VCSELs) and Edge Emitting Lasers (EELs), PCSEL has its own advantages. The optical fiber has the characteristics of good single longitudinal mode characteristic, high output power, high coupling strength of an active region, low divergence angle, high quality and high symmetry light beam and easy optical fiber coupling. In addition, PCSEL can realize a watt-level single-mode beam by increasing the gain area of the active region due to the unique photon limiting characteristic, and becomes an ideal laser light source in the future.
GaN-based materials are direct band gap luminescent materials, which are used in various electronic devices and optoelectronic devices. GaN-based lasers typically operate in the near ultraviolet, blue, green spectral ranges. However, in addition to the electrical performance bottleneck of p-GaN, the refractive index limitation of AlGaN and the requirement of high-quality epitaxial growth make the optical field confinement layer, which is not efficient and is not effective, not easy to be realized like GaAs and InP-based systems, so that a high-performance blue laser is difficult to break through.
Disclosure of Invention
Aiming at the defects in the background technology, the invention provides a gallium nitride-based photonic crystal surface-emitting laser and a preparation method thereof, which can reduce the laser threshold of the laser, reduce the series resistance of the DBR, improve the emitting power and efficiency and reduce the manufacturing difficulty.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a gallium nitride-based photonic crystal surface emitting laser, comprising:
a substrate layer; the substrate layer is a sapphire substrate or a silicon substrate;
the bottom GaN layer is positioned on the substrate layer;
a DBR layer located over the underlying GaN layer;
an AlGaN-n layer located over the DBR layer;
a GaN-n layer located on the AlGaN-n layer;
a quantum well active layer located over the GaN-n layer;
the AlGaN-p barrier layer is positioned on the quantum well active layer;
a GaN-p layer located on the AlGaN-p barrier layer;
TiO 2 a photonic crystal layer located over the GaN-p layer;
a p electrode located on the surface of the GaN-p layer;
an n-electrode positioned on the surface of the AlGaN-n layer;
the DBR layer is formed by alternately growing 20-60 pairs of porous GaN and GaN-n, wherein the refractive index of the GaN-n is 2.42-2.49, and the refractive index of the porous GaN is 1.6-2.0;
the TiO 2 The thickness of the photonic crystal layer is 100-500 nm, which is TiO 2 The layer is etched to a certain depth to form a periodic hole structure.
Further, the layer thickness of GaN-n in the DBR layer is 40-50 nm, and the layer thickness of GaN is 50-60 nm.
Further, the thickness of the bottom GaN layer is 100-10000 nm, and the refractive index is 2.42-2.49;
the thickness of the AlGaN-n layer is 100-5000 nm, and the refractive index is 2.3-2.4.
Further, the thickness of the GaN-n layer is 500-5000 nm, and the refractive index is 2.42-2.49;
further, the quantum well active layer is a 3-12 quantum well layer composed of InGaN/GaN pairs, and each quantum well layer comprises: the InGaN well layer is 3nm and the GaN barrier layer is 6nm, wherein the refractive index of the InGaN layer is 2.58-2.65, and the refractive index of the GaN barrier layer is 2.42-2.49;
further, the thickness of the AlGaN-p barrier layer is 10-5000 nm, the refractive index is 2.3-2.4, and the Al content is 10-20%;
further, the thickness of the GaN-p layer is 50-1000 nm, and the refractive index is 2.42-2.49;
further, the TiO 2 The photonic crystal layer lattice type is triangular lattice or tetragonal lattice or honeycomb lattice, the etching depth is 30-500 nm, the period is 150-250 nm, and the pore radius is 10-200 nm;
further, the p electrode is an ohmic contact metal electrode or a composite electrode of the metal electrode and ITO; the n electrode is an ohmic contact metal electrode.
The preparation method of the gallium nitride-based photonic crystal surface emitting laser is characterized by comprising the following steps of:
step (1): growing GaN-based III-V materials on a sapphire substrate or a silicon substrate in an epitaxial manner, and sequentially growing a 'quasi DBR layer', an AlGaN-n layer, a GaN-n layer, a quantum well active layer, an AlGaN-p barrier layer and a GaN-p layer, wherein the quasi DBR layer is formed by alternately forming bottom GaN, gaN-n and heavily doped GaN-n, the quantum well active layer, the AlGaN-p barrier layer and the GaN-p layer are formed by alternately forming GaN-n layer, gaN-p layer and GaN-n layer;
step (2): adopting physical vapor deposition or chemical vapor deposition and other methods to deposit a TiO layer with set thickness on the GaN-p layer 2 A film;
step (3): coating TiO by photoresist 2 Exposing and developing the surface of the film through EBL or FIB or UV lithography to form a template of the photonic crystal;
step (4): dry etching to remove TiO in the uncovered area of photoresist 2 Forming a hole structure; the etching time and the etching depth can be adjusted according to actual requirements so as to obtain the required parameters of hole depth, radius, period and the like.
Step (5): removing photoresist residue, cleaning, and oven drying to obtain clean and flat TiO 2 A photonic crystal film;
step (6): performing photoetching, medium protection and electrochemical corrosion processes to change the heavily doped GaN-n layer into a porous GaN layer; obtaining a DBR structure formed by porous GaN/GaN alternately;
step (7): adopting photoetching and lift off technology to prepare a p electrode in a GaN-p surface set area;
step (8): photoetching, namely defining a photoetching window, and carrying out dry etching until the AlGaN-n layer is etched to form a mesa;
step (9): and adopting photoetching and lift off processes to prepare an n electrode in a set area of the AlGaN-n surface.
According to the method, the number of pn junction particles can be inverted by an optical pump or an electric pump, meanwhile, the quantum well active layer spontaneously radiates to emit light in a certain wave band range, when some light frequencies meet the resonance condition of the photonic crystal, the wavelength resonates in the photonic crystal surface to be enhanced, and in the process of interaction with the active layer, electrons at a high energy level of the active layer generate stimulated radiation; in addition, due to the inversion of the particle number, the stimulated radiation is larger than the stimulated absorption; the stimulated radiation emits photons with the same frequency and phase as the resonant wavelength, and the photons are continuously resonated and strengthened, so that the resonance-stimulated radiation is continuously circularly strengthened, laser is generated, and meanwhile, the out-of-plane vertical emission of the laser is realized due to the first-order Bragg diffraction of the photonic crystal;
the principle of DBR operation is based on the principle of bragg reflection: when light waves are incident from one medium interface into another medium, reflection and transmission occur, the ratio of which is determined by the angle of incidence and the refractive index of the medium; when the phase difference is integer times, the reflected wave is amplified, and the DBR is used for restricting the distribution of the resonant light field, so that the light field is distributed in a range above the DBR and below the top air layer, thereby realizing that the resonant light field has higher restriction factors in an active area and a photonic crystal area, and being beneficial to the realization of the laser generation principle;
TiO 2 the refractive index control principle of the layer is based on TiO 2 The optical field is distributed and pulled to the photonic crystal region, so that the photonic crystal region has higher limiting factor.
The beneficial effects are that: 1. the invention adopts the DBR formed by porous GaN/GaN to limit the light field, and the large refractive index difference of the two materials ensures that the DBR has the characteristics of high reflectivity and large bandwidth, so that the light field distribution can be effectively limited, the high limiting factors of an active region and a photonic crystal region are realized, and the high-performance laser irradiation is realized, and in addition, the output power of the front side of the laser can be improved through the reflection of downward laser. In addition, the high refractive index difference between the two materials reduces the number of DBR layers compared with the conventional AlGaN/GaN DBR, and is beneficial to realizing lower series resistance of the laser.
2. The field distribution of the optical field in the surface type photonic crystal region can be further improved by adopting the field regulation and control of the refractive index of the titanium dioxide, so that the limiting factor of the surface type photonic crystal region is large enough, and the possibility is provided for high-performance light excitation.
3. The method adopts the method that titanium dioxide grows on the GaN surface and etches certain thickness to form the photonic crystal, has simple and convenient process and low preparation cost, and is favorable for realizing high-quality photonic crystals; the refractive index of the surface photonic crystal layer can be precisely controlled by the surface etched titanium dioxide through a nano processing technology, so that the morphology and distribution of a field are regulated and controlled, and the flexible optical field limiting factors with different design requirements can be realized.
4. The invention is based on high-efficiency DBR and field regulation, can realize GaN-PCSEL based on the traditional GaN-based active material platform and the traditional epitaxial growth process, overcomes the special requirements of GaN-PCSEL on layer structure parameters, and can also design and realize PCSEL based on the VCSEL, EEL and other chip platforms.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a flow chart of the preparation process of the present invention;
FIG. 3 is a light field distribution diagram of a laser according to an embodiment;
fig. 4 is a light field distribution diagram of a laser of the second embodiment.
Description of the embodiments
The implementation of the technical solution is described in further detail below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.
Examples
As shown in FIG. 1, a GaN-based photonic crystal surface-emitting laser based on porous GaN DBR constraint and titanium dioxide refractive index regulation comprises
The substrate layer is a sapphire substrate or a silicon substrate;
the bottom GaN layer is positioned on the substrate layer;
a DBR layer located over the underlying GaN layer;
an AlGaN-n layer located over the DBR layer;
a GaN-n layer located on the AlGaN-n layer;
a quantum well active layer located over the GaN-n layer;
the AlGaN-p barrier layer is positioned on the quantum well active layer;
a GaN-p layer located on the AlGaN-p barrier layer;
TiO 2 a photonic crystal layer located over the GaN-p layer;
a p electrode located on the surface of the GaN-p layer;
an n-electrode positioned on the surface of the AlGaN-n layer;
the thickness of the bottom GaN layer is 2000nm, and the refractive index is 2.46.
The DBR layer was 30 pairs of alternately grown porous GaN and GaN-n, each pair comprising 45nmGAN-n and 54nm porous GaN. Wherein the refractive index of GaN-n is 2.46, and the refractive index of porous GaN is 1.7.
Forming a square mesa from the GaN-p layer to the AlGaN-p layer from top to bottom;
the AlGaN-n layer had a thickness of 300nm and a refractive index of 2.36.
The GaN-n layer had a thickness of 593nm and a refractive index of 2.46.
The quantum well active layer is a 10-layer quantum well layer formed by pairing InGaN3nm/GaN6nm, wherein the refractive index of the InGaN layer is 2.62, and the content of in is as follows: 10% of GaN barrier layer refractive index is 2.46.
The AlGaN-p barrier layer had a thickness of 20nm and a refractive index of 2.36, with an Al content of 20%.
The GaN-p layer had a thickness of 65nm and a refractive index of 2.46.
TiO 2 The thickness of the photonic crystal layer is 200nm, and the etching depth is 50nm; the lattice type is a triangular lattice, the period is 212nm, and the radius of the hole is 40nm.
As can be seen from the light field profile of figure 3,
under this parameter, a resonance wavelength of 453nm and a quality factor q= 6.1562 ×10 are obtained 4 Photon crystal layer limiting factor gamma PhC Active region restriction factor Γ = 1.7742% act = 6.5005), while achieving a higher optical field confinement factor at the photonic crystal layer and active region.
As shown in fig. 2, the preparation process of this example comprises the following steps:
step 1: growing GaN-based III-V materials on a sapphire substrate or a silicon substrate in an epitaxial manner, and sequentially growing a 'quasi DBR layer', an AlGaN-n layer, a GaN-n layer, a quantum well active layer, an AlGaN-p barrier layer and a GaN-p layer, wherein the quasi DBR layer is formed by alternately forming bottom GaN, gaN-n and heavily doped GaN-n, the quantum well active layer, the AlGaN-p barrier layer and the GaN-p layer are formed by alternately forming GaN-n layer, gaN-p layer and GaN-n layer;
step 2: depositing a TiO layer with 200nm thickness on the GaN-p layer by adopting Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD) and the like 2 A film;
step 3: coating TiO by photoresist 2 Exposing and developing the surface of the film through EBL photoetching to form a template of the photonic crystal, and etching TiO with the depth of 50nm by adopting a dry method 2 Removing residual glue;
step 4: after patterning treatment by adopting a photoetching technology, protecting a non-pattern area of the GaN-n layer by using a medium protection layer; subsequently, an electrochemical etching process is performed to convert the heavily doped GaN-n layer into a porous GaN layer. Thereby obtaining a DBR structure formed by porous GaN/GaN alternation;
step 5: spin-coating a layer of photoresist with the thickness of 5 mu m on the front surface of the wafer; then pre-baking at 90 ℃ for 3min, using a mask plate with a certain pattern as a mask, performing UV exposure and development to expose a specific area of the metal electrode to be deposited of the p-type gallium nitride, and performing baking treatment; then, depositing Ni/Au two layers of metal with a certain thickness by a sputtering technology, stripping photoresist and metal on the photoresist by using a lift-off technology, finally leaving a metal electrode with a thickness of 100nm in a specific area, and finally carrying out drying treatment;
step 6: defining a photoetching window on the front surface of a wafer by adopting a photoetching technology, etching to an AlGaN-n layer by using a dry etching process and slightly etching by 150nm until a mesa with the length and the width of about 300 mu m is formed.
Step 7: and spin-coating 8 mu m thick photoresist on the sample, and performing photoresist baking treatment. Then, using the mask same as the previous photoetching, performing overlay in a specific area to expose the part where the n electrode needs to be deposited; drying the sample, and depositing Ni/Au two-layer metal with a certain thickness by using a sputtering technology; finally, lift-off techniques are used to strip the photoresist and metal, leaving a 100nm thick metal electrode in a specific region of the AlGaN-n layer.
Examples
A manufacturing method of a GaN-based photonic crystal surface emitting laser based on porous gallium nitride DBR constraint and titanium dioxide refractive index regulation comprises the following steps:
the substrate layer is a sapphire substrate or a silicon substrate;
the bottom GaN layer is positioned on the substrate layer;
a DBR layer located over the underlying GaN layer;
an AlGaN-n layer located over the DBR layer;
a GaN-n layer located on the AlGaN-n layer;
a quantum well active layer located over the GaN-n layer;
the AlGaN-p barrier layer is positioned on the quantum well active layer;
a GaN-p layer located on the AlGaN-p barrier layer;
TiO 2 a photonic crystal layer located over the GaN-p layer;
a p electrode located on the surface of the GaN-p layer;
an n-electrode positioned on the surface of the AlGaN-n layer;
the thickness of the bottom GaN layer is 2000nm, and the refractive index is 2.46.
The DBR layer is 30 pairs of alternately grown porous GaN and GaN-n, and each pair of structure comprises 45nmGAN-n and 54nm porous GaN; wherein the refractive index of GaN-n is 2.46, and the refractive index of porous GaN is 1.7.
The AlGaN-n layer had a thickness of 300nm and a refractive index of 2.36.
The GaN-n layer had a thickness of 593nm and a refractive index of 2.46.
The quantum well active layer is a 10-layer quantum well layer formed by pairing InGaN3nm/GaN6nm, wherein the refractive index of the InGaN layer is 2.62, and the content of in is as follows: 10% of GaN barrier layer refractive index is 2.46.
The AlGaN-p barrier layer had a thickness of 20nm and a refractive index of 2.36, with an Al content of 20%.
The GaN-p layer had a thickness of 65nm and a refractive index of 2.46.
TiO 2 The thickness of the photonic crystal layer is 200nm, and the etching depth is 200nm; the lattice type is triangular lattice with period of 212nm, the pore radius is 40nm.
From the light field profile of fig. 4, it can be seen that:
under this parameter, a resonant wavelength of 450nm is obtained, the quality factor being q= 9.12541 ×10 3 Photon crystal layer limiting factor gamma PhC Active region restriction factor Γ = 2.9509% act =5.0781%；
The preparation process steps of this example are as follows:
step 1: growing GaN-based III-V materials on a sapphire substrate or a silicon substrate in an epitaxial manner, and sequentially growing a 'quasi DBR layer', an AlGaN-n layer, a GaN-n layer, a quantum well active layer, an AlGaN-p barrier layer and a GaN-p layer, wherein the quasi DBR layer is formed by alternately forming bottom GaN, gaN-n and heavily doped GaN-n, the quantum well active layer, the AlGaN-p barrier layer and the GaN-p layer are formed by alternately forming GaN-n layer, gaN-p layer and GaN-n layer;
step 2: depositing a TiO layer with 200nm thickness on the GaN-p layer by adopting Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD) and the like 2 A film;
step 3: coating a photoresist protective layer with the thickness of about 1 mu m, manufacturing a photonic crystal mask layer by electron beam lithography, etching a deep hole with the thickness of 200nm by a dry method, and removing the mask layer to obtain the photonic crystal layer;
step 4: after patterning treatment by adopting a photoetching technology, protecting a non-pattern area of the GaN-n layer by using a medium protection layer; then, carrying out electrochemical corrosion treatment to convert the heavily doped GaN-n layer into a porous GaN layer; thereby obtaining a DBR structure formed by porous GaN/GaN alternation;
step 5: and spin-coating a layer of photoresist with the thickness of 8 mu m on the front surface of the gallium nitride substrate. And then performing pre-baking treatment for 4min at 90 ℃, using a mask plate with a certain pattern as a mask, performing UV exposure and development to expose a specific area of the p-type gallium nitride to be deposited with the metal electrode, and performing baking treatment. Then, depositing Ni/Au two layers of metal with a certain thickness by a sputtering technology, stripping photoresist and metal on the photoresist by using a lift-off technology, finally leaving a metal electrode with a thickness of 200nm in a specific area, and finally carrying out drying treatment;
step 6: defining a photoetching window on the front side of a wafer by adopting a photoetching technology, etching to an AlGaN-n layer by using a dry etching process, and slightly etching by 150nm to form a mesa with a diameter of 300 mu m;
step 7: spin-coating 8 mu m thick photoresist on the surface of a sample, manufacturing a mask by using a photoetching technology, developing an n electrode area, and drying; next, a Ti/Al/Ni/Au metal layer was deposited on the exposed areas using a sputtering technique, and the photoresist and metal layer were stripped using a lift-off technique to obtain a 100nm thick metal electrode.
The invention provides a DBR structure formed by alternately laminating porous GaN and GaN, which is used as a light field limiting layer of GaN-PCSEL and passes through high refractive index TiO 2 The photonic crystal layer performs effective light field regulation and control to realize a PCSEL structure with high light field limiting factors together; the large refractive index difference between porous GaN and GaN can realize that the DBR has a high-efficiency wide reflection band exceeding 80nm and fewer DBR layers; meanwhile, the surface etching type photonic crystal reduces the manufacturing difficulty of the photonic crystal and is easy to obtain a high-quality structure. By integrating the design, the laser threshold of the laser can be reduced, the series resistance of the DBR can be reduced, the transmitting power and the efficiency can be improved, and the manufacturing difficulty can be reduced.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.

Claims (10)

1. A gallium nitride-based photonic crystal surface emitting laser, comprising:
a substrate layer;
the bottom GaN layer is positioned on the substrate layer;
a DBR layer located over the underlying GaN layer;
an AlGaN-n layer located over the DBR layer;
a GaN-n layer located on the AlGaN-n layer;
a quantum well active layer located over the GaN-n layer;
the AlGaN-p barrier layer is positioned on the quantum well active layer;
a GaN-p layer located on the AlGaN-p barrier layer;
TiO 2 a photonic crystal layer located over the GaN-p layer;
a p electrode located on the surface of the GaN-p layer;
an n-electrode positioned on the surface of the AlGaN-n layer;
the DBR layer is formed by alternately growing 20-60 pairs of porous GaN and GaN-n, wherein the refractive index of the GaN-n is 2.42-2.49, and the refractive index of the porous GaN is 1.6-2.0;
the TiO 2 The thickness of the photonic crystal layer is 100-500 nm, and TiO is prepared by 2 The layer is etched to a periodic hole structure of a set depth.
2. The gallium nitride-based photonic crystal surface emitting laser according to claim 1, wherein the layer thickness of GaN-n in the DBR layer is 40 to 50nm, and the layer thickness of GaN is 50 to 60nm.
3. The gallium nitride-based photonic crystal surface-emitting laser according to claim 1, wherein the thickness of the underlying GaN layer is 100-10000 nm and the refractive index is 2.42-2.49.
4. The gallium nitride-based photonic crystal surface emitting laser according to claim 1, wherein the AlGaN-n layer has a thickness of 100-5000 nm and a refractive index of 2.3-2.4;
the thickness of the GaN-n layer is 500-5000 nm, and the refractive index is 2.42-2.49.
5. The gallium nitride-based photonic crystal surface emitting laser according to claim 1, wherein the quantum well active layer is a 3-12 quantum well layer composed of InGaN/GaN pairs, each layer comprising: the InGaN well layer is 3nm and the GaN barrier layer is 6nm, wherein the refractive index of the InGaN layer is 2.58-2.65, and the refractive index of the GaN barrier layer is 2.42-2.49.
6. The gan-based photonic crystal surface emitting laser of claim 1, wherein the AlGaN-p blocking layer has a thickness of 10 to 5000nm, a refractive index of 2.3 to 2.4, and an Al content of 10 to 20%.
7. The gallium nitride-based photonic crystal surface emitting laser according to claim 1, wherein the GaN-p layer has a thickness of 50-1000 nm and a refractive index of 2.42-2.49.
8. A gallium nitride-based photonic crystal surface emitting laser according to claim 1, wherein said TiO 2 The photonic crystal layer lattice type is triangular lattice or tetragonal lattice or honeycomb lattice, the etching depth is 30-500 nm, the period is 150-250 nm, and the pore radius is 10-200 nm.
9. A gallium nitride-based photonic crystal surface emitting laser according to claim 1, wherein said p-electrode is an ohmic contact metal electrode or a composite electrode of a metal electrode and ITO; the n electrode is an ohmic contact metal electrode.
10. The preparation method of the gallium nitride-based photonic crystal surface emitting laser is characterized by comprising the following steps of: step (1): growing GaN-based III-V materials on a sapphire substrate or a silicon substrate in an epitaxial manner, and sequentially growing a 'quasi DBR layer', an AlGaN-n layer, a GaN-n layer, a quantum well active layer, an AlGaN-p barrier layer and a GaN-p layer, wherein the quasi DBR layer is formed by alternately forming bottom GaN, gaN-n and heavily doped GaN-n, the quantum well active layer, the AlGaN-p barrier layer and the GaN-p layer are formed by alternately forming GaN-n layer, gaN-p layer and GaN-n layer;
step (2): adopting physical vapor deposition or chemical vapor deposition and other methods to deposit a TiO layer with set thickness on the GaN-p layer 2 A film;
step (3): coating TiO by photoresist 2 Exposing and developing the surface of the film through EBL or FIB or UV lithography to form a template of the photonic crystal;
step (4): dry etching to remove TiO in the uncovered area of photoresist 2 Forming a hole structure;
step (5): removing photoresist residue, cleaning, and oven drying to obtain TiO 2 A photonic crystal film;
step (6): performing photoetching, medium protection and electrochemical corrosion processes to change the heavily doped GaN-n layer into a porous GaN layer; obtaining a DBR structure formed by porous GaN/GaN alternately;
step (7): adopting photoetching and lift off technology to prepare a p electrode in a GaN-p surface set area;
step (8): photoetching, namely defining a photoetching window, and carrying out dry etching until the AlGaN-n layer is etched to form a mesa;
step (9): and adopting photoetching and lift off processes to prepare an n electrode in a set area of the AlGaN-n surface.
CN202310441061.0A 2023-04-23 2023-04-23 Gallium nitride-based photonic crystal surface-emitting laser and preparation method thereof Pending CN116169560A (en)

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