阅读说明：本技术 等离激元回音壁光泵激光器及其制备方法 (Plasmon echo wall optical pump laser and preparation method thereof ) 是由 赵丽霞 林杉 胡天贵 李晓东 于 2020-07-23 设计创作，主要内容包括：一种等离激元回音壁光泵激光器及其制备方法,所述等离激元回音壁光泵激光器包括：衬底；缓冲层,位于所述衬底上；回音壁谐振腔,位于所述缓冲层上；由下至上依次包括：底部多孔DBR层、n型掺杂GaN层、有源层、电子阻挡层、p型掺杂GaN层；金属颗粒层,形成于所述回音壁谐振腔的侧壁上,用于产生等离激元。本发明采用底部多孔DBR层反射镜对回音壁谐振腔的光场有很好的垂直方向的限制作用,因而该发明制备的回音壁光泵激光器阈值功率密度较低；此外,包裹在回音壁谐振腔侧壁的金属颗粒会产生等离激元将回音壁模式的光场更好的限制在谐振腔中,进一步降低了阈值功率密度,本发明有助于实现小尺寸低阈值激光器。(A plasmon echo wall optical pump laser and a preparation method thereof are provided, the plasmon echo wall optical pump laser comprises: a substrate; a buffer layer on the substrate; the echo wall resonant cavity is positioned on the buffer layer; from bottom to top include in proper order: the GaN-based LED comprises a bottom porous DBR layer, an n-type doped GaN layer, an active layer, an electron blocking layer and a p-type doped GaN layer; and the metal particle layer is formed on the side wall of the echo wall resonant cavity and is used for generating plasmons. The invention adopts the bottom porous DBR layer reflector to have good limiting effect in the vertical direction on the optical field of the echo wall resonant cavity, so that the threshold power density of the echo wall optical pump laser prepared by the invention is lower; in addition, the metal particles wrapped on the side wall of the echo wall resonant cavity can generate plasmons to better limit the optical field of the echo wall mode in the resonant cavity, so that the threshold power density is further reduced, and the invention is beneficial to realizing a small-size low-threshold laser.)

1. A plasmon echo wall optical pump laser, comprising:

a substrate;

a buffer layer on the substrate;

the echo wall resonant cavity is positioned on the buffer layer; from bottom to top include in proper order:

a bottom porous DBR layer on the buffer layer;

an n-type doped GaN layer on the bottom porous DBR layer;

an active layer on the n-type doped GaN layer;

an electron blocking layer on the active layer;

the p-type doped GaN layer is positioned on the electron blocking layer;

and the metal particle layer is formed on the side wall of the echo wall resonant cavity and is used for generating plasmons.

2. The plasmonic echo wall optical pump laser of claim 1 further comprising a current spreading layer, said current spreading layer being located between said buffer layer and said bottom porous DBR layer;

the current spreading layer is made of n-type GaN.

3. The plasmon echo wall optical pump laser of claim 1,

the bottom porous DBR layer comprises porous layers and non-porous layers which are alternately stacked and grown; wherein the content of the first and second substances,

the alternate stacking growth period of the bottom porous DBR layer is 5-20;

the porous layer is made of a heavy doped nitride material;

the non-porous layer is made of a light doped nitride material.

4. The plasmonic echo wall optical pump laser of claim 3 wherein said nitride material comprises GaN, A1GaN, or combinations thereof.

5. The plasmon echo wall optical pump laser of claim 1,

the material of the substrate comprises sapphire, silicon, gallium nitride or silicon carbide;

the material of the metal particle layer includes Ag, Al, or Au.

6. The plasmonic echo wall optical pump laser of claim 1 wherein the buffer layer comprises a GaN nucleation layer and an unintentionally doped GaN layer; the buffer layer is formed by adopting the following method: pure ammonia gas is used as a nitrogen source, trimethyl gallium or triethyl gallium is used as a Ga source, a GaN nucleation layer is grown firstly, and an unintentionally doped GaN layer is grown again.

7. The plasmon echo wall optical pump laser of any of claims 1 to 6,

the echo wall resonant cavity is in a cylindrical or circular ring column structure.

8. The plasmonic echo wall optical pump laser of claim 7,

the buffer layer is of a table-board structure and comprises an upper table-board and a lower table-board;

the upper table top is of a cylindrical or circular ring cylindrical structure.

9. A method for preparing a plasmon echo wall optical pump laser is characterized by comprising the following steps:

sequentially epitaxially growing a buffer layer, alternately stacked light and heavy doping layers, an n-type doped GaN layer, an active layer, an electronic barrier layer and a p-type doped GaN layer on a substrate;

performing transverse corrosion on the alternately stacked light and heavy doped layers by adopting an electrochemical corrosion method to form a bottom porous DBR layer;

manufacturing a metal mask on the p-type doped GaN layer;

with the mask as a mask, sequentially etching the p-type doped GaN layer, the electron blocking layer, the active layer, the n-type doped layer, the bottom porous DBR layer and the buffer layer downwards by adopting a plasma enhanced etching technology;

removing the metal mask to obtain a echo wall resonant cavity;

forming a patterned metal film on the side wall of the echo wall resonant cavity;

and (4) thermal annealing, namely converting the metal film into a metal particle layer to generate a plasmon, and finishing the preparation of the plasmon echo wall optical pump laser.

10. The method according to claim 9, wherein the metal thin film has a thickness of 3 to 40 nm.

Technical Field

The invention relates to the field of laser light sources, in particular to a plasmon echo wall optical pump laser and a preparation method thereof.

Background

Due to the characteristics of high speed and large capacity information transfer processing, integrated optoelectronics has attracted extensive attention in the industry and the academia. For the optoelectronic integration technology, the on-chip integrated laser can provide an efficient light source for an optical system to ensure normal transmission of signals, and in order to meet the requirements of high integration level and low power consumption of optoelectronic integration, a small-sized and low-power-consumption on-chip light source is required. The echo wall laser is an ideal light source due to the advantages of small volume, low threshold value, high quality factor, low power consumption and simple preparation.

At present, the GaN-based whispering gallery laser distance becomes an on-chip integrated light source, and a plurality of problems need to be solved, and how to reduce the lasing threshold is one of the most important problems. Because the lasing threshold is directly related to the limiting capability of the device structure of the laser to the optical field of the active region, optimizing the design of the cladding with low refractive index to improve the optical field limiting effect of the cladding contributes to the realization of a low-threshold optical pump and even an electric pump GaN-based echo wall laser. At present, the lower cladding of the GaN-based echo wall laser mainly adopts AlGaN or an air gap, however, for the former scheme, because GaN and AlN have 2.4% lattice mismatch, the epitaxy difficulty is higher, and the problem is more serious under high Al composition. For the echo wall laser adopting the air gap, an InGaN superlattice needs to be additionally designed below the active region, and the design of the superlattice needs to take account of the stress effect brought by corrosion and epitaxy, so that the epitaxy difficulty is increased. Secondly, the contact area between the support material connecting the microdisk and the substrate and the microdisk is very small, and the electrical and thermal contact is poor.

In addition to the optimization of the lower cladding layer, the combination of the surface plasmon further improves the confinement effect of an optical field, and becomes another focus of low-threshold GaN-based echo wall laser. The micro-nano structure metal is modified on the side wall of the echo wall resonant cavity, and the echo wall mode can be better limited in the resonant cavity by means of the plasmon generated by the micro-nano structure metal, so that pumping with a lower threshold value is realized. However, the related research is mainly directed to a single nanowire laid on a metal film or a metal particle, or a microdisk resonator with a single metal rod modified on a sidewall. These are used only for basic research and are difficult to be subsequently converted into electrical devices.

Disclosure of Invention

In view of the above, the main objective of the present invention is to provide a plasmon echo wall optical pump laser and a method for manufacturing the same, so as to at least partially solve at least one of the above mentioned technical problems.

In order to achieve the purpose, the technical scheme of the invention comprises the following steps:

as an aspect of the present invention, there is provided a plasmon echo wall optical pump laser including:

a substrate;

a buffer layer on the substrate;

the echo wall resonant cavity is positioned on the buffer layer; from bottom to top include in proper order:

a bottom porous DBR layer on the buffer layer;

an n-type doped GaN layer on the bottom porous DBR layer;

an active layer on the n-type doped GaN layer;

an electron blocking layer on the active layer;

the p-type doped GaN layer is positioned on the electron blocking layer;

and the metal particle layer is formed on the side wall of the echo wall resonant cavity and is used for generating plasmons.

As another aspect of the present invention, there is also provided a method for manufacturing a plasmon echo wall optical pump laser, including the steps of:

sequentially epitaxially growing a buffer layer, alternately stacked light and heavy doping layers, an n-type doped GaN layer, an active layer, an electronic barrier layer and a p-type doped GaN layer on a substrate;

performing transverse corrosion on the alternately stacked light and heavy doped layers by adopting an electrochemical corrosion method to form a bottom porous DBR layer;

manufacturing a metal mask on the p-type doped GaN layer;

with the mask as a mask, sequentially etching the p-type doped GaN layer, the electron blocking layer, the active layer, the n-type doped layer, the bottom porous DBR layer and the buffer layer downwards by adopting a plasma enhanced etching technology;

removing the metal mask to obtain a echo wall resonant cavity;

forming a patterned metal film on the side wall of the echo wall resonant cavity;

and (4) thermal annealing, namely converting the metal film into metal particles to generate a plasmon, and finishing the preparation of the plasmon echo wall optical pump laser.

Based on the technical scheme, compared with the prior art, the invention has at least one or one part of the following beneficial effects:

(1) different from most GaN-based echo wall lasers, the bottom porous DBR layer reflector adopted by the invention has good limiting effect on the light field of the echo wall resonant cavity in the vertical direction, so that the threshold power density of the echo wall laser prepared by the invention is lower; in addition, the metal particles wrapped on the side wall of the echo wall resonant cavity can generate plasmons to better limit the optical field of the echo wall mode in the resonant cavity, so that the threshold power density is further reduced, and the invention is beneficial to realizing a small-size low-threshold laser;

(2) according to the porous GaN-DBR, the doping concentration of gallium nitride in different epitaxial periods is regulated and controlled, and then the heavily doped region is selectively corroded by an electrochemical method, so that transverse porous GaN is formed, and the refractive index is changed; thus, a larger refractive index difference is formed between the periodic porous GaN-DBR layer and the un-corroded lightly doped GaN layer, so that a bottom porous DBR layer of the periodic porous GaN-DBR structure is obtained, and the high-quality factor GaN-based echo wall resonant cavity is realized.

Drawings

FIG. 1 is a schematic diagram of a plasmon echo wall optical pump laser structure according to an embodiment of the present invention;

FIG. 2 is a flowchart of a method for manufacturing a plasmon echo wall optical pump laser according to an embodiment of the present invention;

fig. 3 is a top view of a plasmon echo wall optical pump laser with a cylindrical echo wall resonant cavity according to an embodiment of the present invention;

fig. 4 is a top view of a plasmon echo wall optical pump laser with an echo wall resonant cavity of a circular ring column structure according to an embodiment of the present invention.

In the above drawings, the reference numerals have the following meanings:

1. a substrate; 2. a buffer layer; 2', a convex part; 3. a bottom porous DBR layer; 4. an n-type doped GaN layer; 5. an active layer; 6. an electron blocking layer; 7. a p-type doped GaN layer; 8. a layer of metal particles.

Detailed Description

The invention aims to provide a low-threshold plasmon echo wall optical pump laser beneficial to photoelectron integration and a preparation method for preparing the device.

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

As an aspect of the present invention, there is provided a plasmon echo wall optical pump laser including:

a substrate;

a buffer layer on the substrate;

the echo wall resonant cavity is positioned on the buffer layer; from bottom to top include in proper order:

a bottom porous DBR layer on the buffer layer;

an n-type doped GaN layer located on the bottom porous DBR layer;

an active layer on the n-type doped GaN layer;

an electron blocking layer on the active layer;

the p-type doped GaN layer is positioned on the electron blocking layer;

and the metal particle layer is formed on the side wall of the echo wall resonant cavity and is used for generating plasmons.

In an embodiment of the invention, the laser further comprises a current spreading layer, the current spreading layer being located between the buffer layer and the bottom porous DBR layer;

the current spreading layer is made of n-type GaN.

In an embodiment of the invention, the bottom porous DBR layer comprises porous layers and non-porous layers grown in alternating stacks; wherein the content of the first and second substances,

the alternate stacking growth period of the bottom porous DBR layer is 5-20;

the porous layer is made of a heavy doped nitride material;

the non-porous layer is made of a light doped nitride material.

In an embodiment of the present invention, the nitride material includes GaN, AlGaN, or a combination thereof.

In an embodiment of the invention, the material of the substrate comprises sapphire, silicon, gallium nitride or silicon carbide;

the material of the metal particle layer includes Ag, Al, or Au.

In an embodiment of the present invention, the buffer layer includes a GaN nucleation layer and an unintentionally doped GaN layer; the buffer layer is formed by the following method: pure ammonia gas is used as a nitrogen source, trimethyl gallium or triethyl gallium is used as a Ga source, a GaN nucleation layer is grown firstly, and an unintentionally doped GaN layer is grown again.

In the embodiment of the invention, the echo wall resonant cavity is in a cylindrical or circular ring cylindrical structure.

In the embodiment of the invention, the buffer layer is of a mesa structure and comprises an upper mesa and a lower mesa;

the upper table-board is in a cylindrical or circular ring cylindrical structure.

As another aspect of the present invention, there is also provided a method for manufacturing a plasmon echo wall optical pump laser, including the steps of:

sequentially epitaxially growing a buffer layer, alternately stacked light and heavy doping layers, an n-type doped GaN layer, an active layer, an electronic barrier layer and a p-type doped GaN layer on a substrate;

performing transverse corrosion on the alternately stacked light and heavy doped layers by adopting an electrochemical corrosion method to form a bottom porous DBR layer;

manufacturing a metal mask on the p-type doped GaN layer;

with the mask as a mask, sequentially etching the p-type doped GaN layer, the electron blocking layer, the active layer, the n-type doped layer, the bottom porous DBR layer and the buffer layer downwards by adopting a plasma enhanced etching technology;

removing the metal mask to obtain a echo wall resonant cavity;

forming a patterned metal film on the side wall of the echo wall resonant cavity;

and (4) thermal annealing, namely converting the metal film into a metal particle layer to generate a plasmon, and finishing the preparation of the plasmon echo wall optical pump laser.

In the embodiment of the invention, the thickness of the metal film is 3-40 nm.

The technical solution of the present invention is further described below with reference to specific examples, but it should be noted that the following examples are only for illustrating the technical solution of the present invention, but the present invention is not limited thereto.

Referring to fig. 1, the present invention provides a plasmon echo wall optical pump laser, including:

a substrate 1, which is a planar or graphic substrate, wherein the substrate 1 is made of sapphire, silicon, gallium nitride or silicon carbide;

the buffer layer 2 is positioned on the upper surface of the substrate 1, the buffer layer 2 is composed of a low-temperature GaN nucleation layer and an unintentionally doped GaN layer, high-purity pure ammonia gas is used as a nitrogen source, trimethyl gallium or triethyl gallium is used as a Ga source, the GaN nucleation layer grows at a low temperature (400-750 ℃) first, and then the unintentionally doped GaN layer grows at a high temperature (750-1000 ℃). The periphery of the buffer layer 2 is etched downwards to form a cylindrical or circular column table surface, the depth of the table surface is smaller than the thickness of the buffer layer 2, and the middle of the buffer layer 2 is provided with a convex part 2' (namely an upper table surface);

a bottom porous DBR layer 3 located on the convex portion 2' of the buffer layer 2, the material of the bottom porous DBR layer 3 is GaN, AlGaN, or the multi-period DBR formed by alternately stacking porous layers and non-porous layers of the nitride material combination;

wherein the bottom porous DBR layer 3 is obtained by electrochemically etching alternately stacked lightly and heavily doped layers, wherein the typical doping concentration of the heavily doped layers is 1 x 10¹⁹cm^-3Typical concentration of lightly doped layer 5 × 10¹⁶cm^-3The period number of the bottom porous DBR layer 3 is 5-20;

an n-type GaN layer is grown between the bottom porous DBR layer 3 and the buffer layer 2 and is used as a current expansion layer specially used for forming the bottom porous DBR layer 3 through electrochemical corrosion;

an n-type doped GaN layer 4, the dopant being silane, typically with a doping concentration of 1 × 10¹⁸cm^-3On the upper surface of the bottom porous DBR layer 3;

an active layer 5, which is manufactured on the upper surface of the n-type doped GaN layer 4, wherein the active layer 5 is of an InGaN/GaN multi-quantum well structure;

an electron blocking layer 6, located on the upper surface of the active layer 5, wherein the electron blocking layer 6 is an A1GaN material and can be doped p-type, and the dopant is magnesium cyclopentadienyl;

a p-type doped GaN layer 7 located on the upper surface of the electron blocking layer 6;

and the metal particle layer 8 is coated on the side wall of the echo wall resonant cavity, wherein the echo wall resonant cavity structure sequentially comprises a p-type doped GaN layer 7, an electron barrier layer 6, an active layer 5, an n-type doped GaN layer 4 and a bottom porous DBR layer 3 from top to bottom.

Referring to fig. 2, and with reference to fig. 1, fig. 3 and fig. 4, the present invention provides a method for manufacturing a plasmon echo wall optical pump laser, including the following steps:

step 1: sequentially growing a buffer layer 2, alternately stacked light and heavy doping layers, an n-type doped GaN layer 4, an active layer 5, an electron blocking layer 6 and a p-type doped GaN layer 7 on a substrate 1;

wherein the substrate 1 is made of sapphire, silicon, gallium nitride or silicon carbide, and an n-type GaN layer is grown between the light and heavy doping layers and the buffer layer 2 which are alternately stacked and is used as a current expansion layer specially used for forming the porous DBR by electrochemical corrosion;

step 2: performing transverse corrosion on the alternately stacked light and heavy doped layers by adopting an electrochemical corrosion method, and converting the light and heavy doped layers into bottom porous DBR layers 3 with alternately stacked porous layers and non-porous layers; the material of the bottom porous DBR layer 3 is a multi-period DBR formed by alternately stacking a nitride porous layer and a non-porous layer, and the forming material is GaN, AlGaN or the combination material of the materials;

and step 3: spin-coating a photoresist on the surface of the porous GaN wafer obtained in the step (2), wherein the photoresist is a negative photoresist, then defining a circular or annular pattern on the spin-coated photoresist layer by adopting a photoetching technology, then evaporating metallic nickel on the wafer spin-coated with the photoresist by utilizing an electron beam evaporation technology, then pasting a blue film on metal, stripping unnecessary metal by utilizing the adhesive force of the blue film and the metal to form a disc or a ring of the metallic nickel, and finally removing the residual photoresist;

and 4, step 4: and (3) etching the porous epitaxial wafer obtained in the step (2) by using the metal pattern prepared in the step (3) as a hard mask by adopting a plasma enhanced etching technology, and sequentially etching the porous epitaxial wafer from the top to the bottom, wherein the porous epitaxial wafer comprises a p-type doped GaN layer 7, an electronic barrier layer 6, an active layer 5, an n-type doped layer 4, a bottom porous DBR layer 3 and a buffer layer 2, and the etching depth of the buffer layer 2 is less than the thickness of the buffer layer 2. After the etching is completed, the pattern defined in step 3 is transferred to other layers above the substrate 1.

And 5: attaching a blue film to the metal-evaporated surface of the wafer obtained in the step (4), forcibly tearing off the blue film, stripping most of the redundant metal except the defined pattern, removing the redundant photoresist by using a film remover, and finally obtaining the GaN-based echo wall resonant cavity, wherein the p-type doped GaN layer 7 and the buffer layer 2 are exposed in the air, and the top view of the resonant cavity is a disc pattern, which is referred to as a picture 3; or a circular ring pattern in top view, see fig. 4.

Step 6: spin-coating a photoresist on the surface of the wafer obtained in the step 5, defining an upper annular pattern on the spin-coated photoresist layer by adopting a photoetching technology, wherein the annular pattern needs to cover the edge of the disc or the ring in the step 5, then evaporating a metal film on the photoresist, wherein the metal can be Ag, Au or Al, stripping the metal by utilizing a blue film to form a metal disc or a ring, and finally removing the residual photoresist;

and 7: and (3) carrying out rapid thermal annealing on the wafer obtained in the step (6) to convert the covered metal film into a metal particle layer 8, wherein the annealing temperature is 300-600 ℃.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.