Echo wall mode microcavity laser and preparation method thereof

Abstract

The invention discloses an echo wall mode microcavity laser and a preparation method thereof, and the laser sequentially comprises a GaN substrate, a field oxygen isolation layer, a hole transport layer, an insulating layer and a transparent conductive layer from bottom to top, and the upper surface of the GaN substrate is provided with an echo wall mode microcavity. The upper surface of the transparent conductive layer and the upper surface of the GaN substrate are respectively provided with a first electrode and a second electrode. The MIS structure of the first electrode and the transparent conducting layer-insulating layer-GaN substrate is adopted, the preparation process and the structure are simple, the hole transport layer can improve the minority carrier hole injection amount when the device works, and therefore the turn-on voltage of the device is remarkably reduced; and the laser device can also realize a lasing function.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor optoelectronic devices, and in particular relates to a whispering gallery mode microcavity laser and a preparation method thereof. Background Art

[0002] Gallium nitride (GaN)-based materials are wide bandgap semiconductor materials with direct band gaps. By forming AlGaN and InGaN ternary alloys, the band gap width can be continuously adjusted, and the corresponding emission wavelength can be continuously adjusted from ultraviolet to near-infrared, making it an ideal material for making solid-state light sources. In the field of optoelectronic devices, such as solar cells, detectors, light-emitting diodes (LEDs) and laser diodes (LDs), GaN-based materials play an irreplaceable role. Among them, ultraviolet light sources are an important application scenario for GaN-based materials. Compared with the common mercury lamp ultraviolet light source, ultraviolet LEDs and lasers based on GaN-based materials have the advantages of non-toxic and environmentally friendly, easy to carry, low voltage, low power consumption, and stable and reliable operation. They can be used in polymer curing, sterilization, medical diagnosis, biochemical sensing, 3D printing, safety testing and other fields. In addition, GaN-based semiconductor materials also have large exciton binding energy and oscillator strength. Combined with optical microcavities, small-volume, high-efficiency microcavity optoelectronic devices can be realized, which can be used for the study of cavity quantum electrodynamics at room temperature.

[0003] The current popular GaN-based laser structure is basically p-GaN layer / quantum well layer / n-GaN layer, generally including p-electrode, contact layer, p-type optical confinement layer, electron blocking layer, upper waveguide, active region, lower waveguide, n-type optical confinement layer, substrate and n-electrode and other multilayer structures. This structure is essentially a pn junction electric injection method. The device structure is very complex and difficult to prepare. It has very high requirements for materials, structures and processes. Another metal-insulator-semiconductor (MIS) electric injection structure with a simpler manufacturing process and structure can also achieve electroluminescence and electro-lasing, but the operating voltage of the device is relatively high, and there is no report on the use of MIS structure to achieve lasing in GaN-based material systems. Summary of the invention

[0004] The embodiment of the present invention provides a whispering gallery mode microcavity laser and a preparation method thereof, which can solve the problems of complex structure and preparation process of GaN-based lasers using pn junction electrical injection and high operating voltage of GaN-based light-emitting devices with MIS structure.

[0005] In a first aspect, an embodiment of the present invention provides a whispering gallery mode microcavity laser, comprising:

[0006] A GaN substrate, wherein a whispering gallery mode microcavity is arranged in a preset active region on an upper surface of the GaN substrate;

[0007] A field oxygen isolation layer, which is arranged on the upper surface of the GaN substrate and covers the side surface of the whispering gallery mode microcavity;

[0008] A hole transport layer, wherein the hole transport layer is arranged on the upper surface of the field oxygen isolation layer and the upper surface of the whispering gallery mode microcavity;

[0009] An insulating layer, the insulating layer is arranged on the upper surface of the hole transport layer, wherein a groove penetrating the insulating layer, the hole transport layer and the field oxygen isolation layer is arranged on one side of the upper surface of the insulating layer where the active area is preset;

[0010] A transparent conductive layer, wherein the transparent conductive layer is disposed in a preset active area on the upper surface of the insulating layer;

[0011] A first electrode, which is disposed on a portion of the upper surface of the transparent conductive layer and extends to the insulating layer on the other side of the preset active area;

[0012] The second electrode is arranged in the groove and extends onto the insulating layer.

[0013] In a second aspect, an embodiment of the present invention provides a method for preparing a whispering gallery mode microcavity laser, comprising:

[0014] Etching a portion of the upper surface of the GaN substrate that is not in the preset active region to form a whispering gallery mode microcavity in the preset active region on the upper surface of the GaN substrate;

[0015] Depositing a field oxygen isolation layer on the upper surface of the whispering gallery mode microcavity and the GaN substrate;

[0016] Etching a field oxygen isolation layer located in a preset active area;

[0017] Depositing a hole transport layer on the upper surface of the etched field oxygen isolation layer and the upper surface of the whispering gallery mode microcavity, and depositing an insulating layer on the upper surface of the hole transport layer;

[0018] Depositing a transparent conductive layer in a preset active area on the upper surface of the insulating layer;

[0019] Forming a first electrode by evaporating or sputtering metal in a first electrode region on the upper surfaces of the transparent conductive layer and the insulating layer, wherein the first electrode region includes a portion of the upper surface of the transparent conductive layer and extends to the insulating layer located on one side of the preset active region;

[0020] Etching a groove penetrating the insulating layer, the hole transport layer and the field oxygen isolation layer on the upper surface of the insulating layer and defining a second electrode region, wherein the second electrode region includes a portion of the upper surface of the insulating layer located on the other side of the preset active region;

[0021] An ohmic contact metal is evaporated in the groove and the second electrode region to form a second electrode.

[0022] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: according to the whispering gallery mode microcavity laser provided by the present invention, a gain medium material is provided for laser emission through a GaN substrate, a pump source is provided for laser emission through a MIS electrical injection structure such as a first electrode and a transparent conductive layer-insulating layer-GaN substrate, a whispering gallery mode microcavity arranged on the GaN substrate provides a resonant cavity for laser emission, and a hole transport layer is used to increase the amount of minority hole injection during device operation to achieve a population inversion distribution, so that the whispering gallery mode microcavity device provided by the present invention can achieve an electro-lasing effect; and compared with a laser device with a traditional pn junction electrical injection structure, the structure and preparation method of the whispering gallery mode microcavity laser provided by the present invention are relatively simple; due to the introduction of the hole transport layer, the threshold voltage of the GaN-based microcavity laser can be significantly reduced, and even the inherent limit that the threshold voltage of the pn junction electrical injection structure laser is greater than or equal to the voltage corresponding to the energy of the material bandgap width can be broken through, thereby improving the laser output efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a whispering gallery mode microcavity laser provided in an embodiment of the present invention;

[0024] Figure 2 A schematic structural diagram of a whispering gallery mode microcavity laser from another perspective provided by an embodiment of the present invention;

[0025] Figure 3 A flowchart of a method for preparing a whispering gallery mode microcavity laser provided in an embodiment of the present invention;

[0026] Figure 4a-Figure 4i A schematic diagram of a scenario for preparing a whispering gallery mode microcavity laser provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0028] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0029] It should also be understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0030] As used in the present specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]", depending on the context.

[0031] In addition, in the description of the present specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0032] References to "one embodiment" or "some embodiments" etc. described in the present specification mean that one or more embodiments of the present invention include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0033] The current GaN-based whispering gallery mode microcavity lasers basically adopt the pn junction electrical injection method, and the structure is basically p-GaN layer / quantum well layer / n-GaN layer, including p-electrode, contact layer, p-type optical confinement layer, electron blocking layer, upper waveguide, active region, lower waveguide, n-type optical confinement layer, substrate and n-electrode, etc. This GaN-based laser has a complex structure, many epitaxial growth steps and is difficult to prepare. At the same time, the current laser preparation technology has difficulties in obtaining high-quality and high-efficiency p-type doped GaN and AlGaN materials, which further increases the difficulty of preparing this GaN-based laser.

[0034] Compared with the pn junction structure, the GaN-based electroluminescent device realized by the MIS electrical injection structure requires fewer layers and has a simpler structure, which can reduce the epitaxial growth steps, simplify the device preparation process, and save manufacturing costs; in addition, the MIS structure can effectively avoid the introduction of p-type doping materials.

[0035] However, some of the currently popular GaN-based electroluminescent devices based on the MIS structure, such as the metal-aluminum nitride-n-type gallium nitride structured ultraviolet light-emitting diodes and the graphene-silicon dioxide-gallium nitride structured diodes, can only achieve electroluminescence but not electrolasing; and the current MIS structured devices also have the disadvantage of a relatively high turn-on voltage.

[0036] In view of this, the present invention provides a whispering gallery mode microcavity laser, which provides a gain medium material for laser emission through a GaN substrate, provides a pump source for laser emission through a MIS electrical injection structure such as a first electrode and a transparent conductive layer-insulating layer-GaN substrate, and a whispering gallery mode microcavity arranged on the GaN substrate provides a resonant cavity for laser emission. The hole transport layer increases the amount of minority hole injection during device operation to achieve a population inversion distribution, so that the whispering gallery mode microcavity device provided by the present invention can achieve an electro-lasing effect; and compared with a conventional pn junction electrical injection structure laser, the whispering gallery mode microcavity laser provided by the present invention has a simpler structure and a simpler preparation method; the introduction of the hole transport layer can also significantly reduce the threshold voltage of the GaN-based microcavity laser, and even break through the inherent limit that the threshold voltage of the pn junction electrical injection structure laser is greater than or equal to the voltage corresponding to the material bandgap width energy, thereby improving the laser output efficiency.

[0037] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0038] Example 1

[0039] Figure 1 The structure diagram of a whispering gallery mode microcavity laser provided by an embodiment of the present invention is shown. As an example but not limitation, the whispering gallery mode microcavity laser 100 may include a GaN substrate 1, a field oxygen isolation layer 2, a hole transport layer 3, an insulating layer 4, a transparent conductive layer 5, a first electrode 6 and a second electrode 7.

[0040] Specifically, see Figure 1 , the preset active area on the upper surface of the GaN substrate 1 (see Figure 2A whispering gallery mode microcavity 11 may be provided in the region selected by the frame 201 in the figure, a field oxygen isolation layer 2 may be provided on the side of the whispering gallery mode microcavity 11 and the upper surface of the GaN substrate 1, and a hole transport layer 3 and an insulating layer 4 stacked in sequence may be provided on the field oxygen isolation layer 2 and the upper surface of the whispering gallery mode microcavity. The transparent conductive layer 5 may be provided in a preset active region on the upper surface of the insulating layer 4. The first electrode 6 may cover a portion of the upper surface of the transparent conductive layer 5 and extend to the insulating layer on one side of the preset active region. The insulating layer 4 is provided with a groove 12 on the upper surface on the other side of the preset active region, which penetrates the insulating layer 4, the hole transport layer 3, and the field oxygen isolation layer 2. The second electrode 7 is provided in the groove 12 so that the second electrode 7 is in ohmic contact with the GaN substrate and covers the insulating layer 4 near the groove 12.

[0041] In one possible implementation, see Figure 1 The GaN substrate 1 may be a multi-layer structure, which may include a stacked silicon layer 13, a buffer layer 14 and an epitaxial layer 15 from bottom to top.

[0042] Exemplarily, the material of the silicon layer 13 may include silicon, and the thickness may be less than or equal to 1 mm.

[0043] Exemplarily, the material of the buffer layer 14 may include an AlN layer, an AlGaN layer, and an unintentionally doped u-GaN layer stacked sequentially from bottom to top.

[0044] For example, the epitaxial layer 15 may be made of n-type doped GaN, with a thickness of 100-5000 nm and a doping concentration of 1×10 19 cm -3 .

[0045] In one example, see Figure 2 The shape of the whispering gallery mode microcavity 11 can be a disk.

[0046] Optionally, the shape of the whispering gallery mode microcavity 11 may also be a regular polygon, an ellipse with a notch at the boundary, or other shapes.

[0047] Exemplarily, the thickness of the whispering gallery mode microcavity 11 may be 50-1000 nm, and the size of the whispering gallery mode microcavity 11 may be between 0-500 μm.

[0048] In a possible implementation, the field oxygen isolation layer 2 may be made of silicon nitride and may have a thickness of 200-1000 nm.

[0049] In a possible implementation, the material of the hole transport layer 3 may include a semiconductor material with a low conduction band, such as molybdenum trioxide (MoO3) or tungsten oxide (WO3), and the thickness may be 1-15 nm.

[0050] In a possible implementation, the material of the insulating layer 4 may include thin film materials such as aluminum oxide, silicon dioxide, aluminum nitride, and other dielectric materials with high dielectric constants, and the thickness thereof may be 1-100 nm.

[0051] In a possible implementation, the material of the transparent conductive layer 5 may include gold, and the thickness thereof may be 0-30 nm.

[0052] In a possible implementation manner, the material of the first electrode 6 may also include gold, and the thickness thereof may be less than or equal to 1000 nm.

[0053] In a possible implementation, the material of the second electrode 7 may be a laminated metal composed of four layers of metals: Ti, Al, Ni, and Au, and the thickness of each layer may be 20 nm, 160 nm, 55 nm, and 45 nm, respectively.

[0054] According to the whispering gallery mode microcavity laser provided by the present invention, a gain medium material is provided for laser emission through a GaN substrate, a pump source is provided for laser emission through a MIS structure such as a first electrode and a transparent conductive layer-insulating layer-GaN substrate, a whispering gallery mode microcavity arranged on the GaN substrate provides a resonant cavity for laser emission, and a hole transport layer is used to increase the amount of minority hole injection during device operation to achieve a population inversion distribution, so that the whispering gallery mode microcavity device provided by the present invention can achieve an electro-lasing effect; and compared with a conventional pn junction electric injection structure laser, the whispering gallery mode microcavity laser provided by the present invention has a simpler structure and a simpler preparation method; due to the introduction of the hole transport layer, the threshold voltage of the GaN-based microcavity laser can be significantly reduced, and even the inherent limit that the threshold voltage of the pn junction electric injection structure laser is greater than or equal to the voltage corresponding to the material bandgap width energy is broken, thereby improving the laser output efficiency.

[0055] The whispering gallery mode microcavity laser provided by the present invention can be applied to multiple fields such as ultraviolet curing, sterilization and disinfection, medical diagnosis, safety detection, etc. It has multiple advantages such as small size and low threshold, and can be used as an important light source in photonic devices and photonic integrated circuits, and can be integrated with other optical elements on a large scale and with high density to achieve optoelectronic integration, on-chip communication, optical interconnection and ultra-high density storage, and can achieve high-efficiency output with low energy loss.

[0056] Example 2

[0057] Figure 3 The flowchart of a method for preparing a whispering gallery mode microcavity laser according to an embodiment of the present invention is shown. As an example but not a limitation, the method can be used to prepare the whispering gallery mode microcavity laser 100, and the method can include steps S301-S308, each of which is described below.

[0058] S301, etching a portion of the upper surface of the GaN substrate that is not in the preset active region to form a whispering gallery mode microcavity in the preset active region on the upper surface of the GaN substrate.

[0059] In one example, a silicon-based gallium nitride epitaxial wafer can be selected as the GaN substrate 1, and the non-preset active area on the upper surface of the GaN substrate 1 can be etched by electron beam lithography and inductively coupled plasma dry etching (see Figure 4a The part 401) in the middle forms a whispering gallery mode microcavity 11, and the result is as follows: Figure 4b The structure shown.

[0060] For example, before etching, the GaN substrate 1 may be sequentially placed in acetone, stripping solution, acetone and isopropanol solution for ultrasonic cleaning, then rinsed with ultrapure water for two minutes and then blown dry with nitrogen.

[0061] Exemplarily, an electron beam lithography process may be used to define a preset active region on the upper surface of the GaN substrate 1 , and then a Cl-based dry etching process may be used to etch a portion other than the preset active region to form the whispering gallery mode microcavity 11 .

[0062] Specifically, the GaN substrate 1 can be placed on a hot plate at 200°C and baked for 5 minutes; then, a 0.9μm thick electron beam photoresist is spin-coated on the upper surface of the GaN substrate 1 using a spinner at a rotation speed of 3500 rpm, and the coated product is placed on a hot plate at 90°C and baked for 1 minute; then, an electron beam lithography machine is used to photolithography the product through a mask, and the exposure time can be set to 280ms. After the exposure is completed, the product is placed on a hot plate at 110°C and baked for 1 minute; finally, the product is placed in a developer for 90 seconds to remove the photoresist outside the preset active area, rinsed with ultrapure water, blown dry with nitrogen, and then heated for 1 minute to harden the film to complete the definition of the preset active area.

[0063] Specifically, first, BCl3 and Cl2 can be used as etching gases, and an inductively coupled plasma dry etching process can be used to dry-etch the epitaxial layer 15 outside the preset active area to form the whispering gallery mode microcavity 11. Then, the product is sequentially placed in an acetone solution, a stripping solution, an acetone solution, and an isopropanol solution for ultrasonic cleaning to remove the photoresist on the upper surface of the whispering gallery mode microcavity 11, and then the product is rinsed with ultrapure water and blown dry with nitrogen.

[0064] Exemplarily, the flow rates of the BCl3 and Cl2 mixed gases during etching may be 20 sccm and 8 sccm respectively, and the etching process parameters may be: ICP upper electrode power of 50 W, ICP lower electrode power of 15 W, pressure of 5 mTorr, and etching depth of 450 nm.

[0065] S302, depositing a field oxygen isolation layer on the upper surface of the whispering gallery mode microcavity and the GaN substrate.

[0066] In one example, before depositing the field oxygen isolation layer 2, the GaN substrate 1 including the whispering gallery mode microcavity 11 can be cleaned first, and then a silicon nitride film is grown by plasma enhanced chemical vapor deposition process to form the field oxygen isolation layer 2, so as to obtain Figure 4c The structure shown.

[0067] Specifically, the GaN substrate 1 including the whispering gallery mode microcavity 11 can be ultrasonically cleaned in an acetone solution for 3 minutes, then placed in a stripping solution at 60° C. in a water bath for 15 minutes, and then placed in an acetone solution and an isopropanol solution for ultrasonic cleaning for 3 minutes in turn; finally, the product is rinsed with ultrapure water and blown dry with nitrogen to complete the cleaning.

[0068] Specifically, a silicon nitride film with a thickness of about 200 nm can be grown based on a plasma enhanced chemical vapor deposition process using ammonia (NH3) and silane (SiH4) as reaction gases, at a substrate temperature of 250°C, a reaction chamber pressure of 600mTorr, and an RF power of 22W.

[0069] S303, etching the field oxygen isolation layer located in the preset active area.

[0070] In one example, the pattern of the active region can be preset by photolithography on the upper surface of the field oxygen isolation layer 2, and carbon tetrafluoride (CF4) and oxygen (O2) are used as etching gases, and an F-based dry etching process is used to perform hole etching on the upper surface of the whispering gallery mode microcavity 11 to obtain the following: Figure 4d The structure shown.

[0071] Specifically, photoresist can be spin-coated on the field oxygen isolation layer 2, and then pre-baked, and then a photolithography machine is used to expose the preset active area on the upper surface of the field oxygen isolation layer 2 through a mask; after the exposure is completed, post-baking is performed; after the post-baking is completed and the product temperature drops to room temperature, development is performed to remove the photoresist in the preset active area on the upper surface of the field oxygen isolation layer 2, and the lithography is completed.

[0072] Specifically, before the hole etching, the product can be baked on a hot plate to enhance the etching resistance of the photoresist. Then, dry etching is performed by an inductively coupled plasma etching process, using CF4 and O2 as etching gases, under the conditions of a reaction chamber pressure of 10mTorr, and RF powers of the upper electrode and the lower electrode of 100W and 10W respectively, to remove the field oxygen isolation layer 2 exposed after photolithography until the epitaxial layer 15.

[0073] S304 , depositing a hole transport layer on the upper surface of the etched field oxygen isolation layer and the upper surface of the whispering gallery mode microcavity, and depositing an insulating layer on the upper surface of the hole transport layer.

[0074] In one example, the etched field oxygen isolation layer can be cleaned first, and then the hole transport layer 3 is deposited on the upper surface of the etched field oxygen isolation layer and the upper surface of the whispering gallery mode microcavity by a sputtering process to obtain Figure 4e Then, an insulating layer 4 is immediately deposited on the upper surface of the hole transport layer 3 by an atomic layer deposition process to obtain a structure as shown in FIG. Figure 4f Before depositing the insulating layer 4, the hole transport layer 3 needs to be protected from contact with any organic, acidic or alkaline solution, ultrapure water or other liquids to avoid damage to the prepared metal oxide hole transport layer 3 structure.

[0075] Specifically, the current manufactured product (see Figure 4d ) are sequentially placed in acetone, stripping solution, acetone and isopropanol solutions for ultrasonic cleaning, and then the product is rinsed with ultrapure water for two minutes, and further placed in piranha solution (a mixed solution of concentrated sulfuric acid and hydrogen peroxide) for cleaning for 1 minute, and finally rinsed with ultrapure water for two minutes and blown dry with nitrogen to complete the cleaning.

[0076] Specifically, the cleaned structure can be placed in a sputtering equipment chamber, and the chamber vacuum is drawn to 5×10 - 6 Torr, using molybdenum trioxide target material, the sputtering power is 100 W, the gas passed is argon (Ar), and the working pressure is 4 mTorr. A molybdenum trioxide film with a thickness of about 5 nm is sputtered and grown on the upper surface of the field oxygen isolation layer 2 and the upper surface of the whispering gallery mode microcavity to form a hole transport layer 3.

[0077] Specifically, after the hole transport layer 3 is deposited, the product can be immediately placed in the chamber of the atomic layer deposition equipment. With trimethylaluminum (TMA) as the Al source and ozone (O3) as the O source, an atomic layer deposition process is used to grow an aluminum oxide film as the insulating layer 4 on the hole transport layer 3 at a deposition temperature of 300°C.

[0078] S305 , depositing a transparent conductive layer in a preset active area on the upper surface of the insulating layer.

[0079] In one example, an ultra-thin gold layer can be deposited on the upper surface of the insulating layer 4 by electron beam evaporation process, and then the ultra-thin gold layer formed is photolithographically processed to define a preset active area, and finally the ultra-thin gold layer outside the preset active area is wet-etched, and the entire product is cleaned to obtain the following: Figure 4g The structure shown.

[0080] Specifically, the current manufactured product (see Figure 4f ) was placed in the electron beam evaporation table and the vacuum degree of the reaction chamber of the electron beam evaporation table reached 2×10-6 After 0.5 0.04 0.08 0.06 ...

[0081] Specifically, photoresist can be spin-coated on a translucent ultra-thin gold layer, and then pre-baked. After that, a photolithography machine is used to expose the area outside the preset active area through a mask; after the exposure is completed, post-baking is performed; after the post-baking is completed, the temperature is lowered to room temperature, and then development is performed to remove the photoresist in the area outside the preset active area, thereby completing the lithography.

[0082] Specifically, a gold etching solution may be used to wet-etch the ultra-thin gold layer outside the preset active area to remove the ultra-thin gold layer outside the preset active area exposed after photolithography; after the wet etching is completed, ultrapure water is used for rinsing for two minutes.

[0083] Specifically, the wet-etched product can be placed in an acetone solution for ultrasonic cleaning for 3 minutes; then placed in an acetone solution and an isopropanol solution for ultrasonic cleaning for 3 minutes in sequence; finally, the product can be rinsed with ultrapure water and blown dry with nitrogen.

[0084] S306, evaporating or sputtering metal in the first electrode region on the upper surfaces of the transparent conductive layer and the insulating layer to form a first electrode.

[0085] Exemplarily, the first electrode region (see Figure 2 202) includes a portion of the upper surface of the transparent conductive layer 5 and extends to the insulating layer 4 located on one side of the preset active area.

[0086] In one example, photolithography can be performed on the upper surfaces of the insulating layer 4 and the transparent conductive layer 5 to define the first electrode region (see Figure 2 202), then evaporate electrode metal on the upper surface of the insulating layer 4 and the transparent conductive layer, and finally remove the electrode metal outside the first electrode region to form the first electrode 6, so as to obtain Figure 4h The structure shown.

[0087] Specifically, the product (see Figure 4g ) is placed on a hot plate at 200°C and baked for 5 minutes; the stripping glue is coated and spun with a thickness of 0.35μm, and it is placed on a hot plate at 200°C and baked for 5 minutes; then, photoresist is coated and spun on the stripping glue with a thickness of 0.77μm, and the product is placed on a hot plate at 90°C and baked for 1 minute; thereafter, the product that has been coated and spun is placed in a photolithography machine to expose the photoresist in the first electrode area; finally, the exposed product is placed in a developer to remove the photoresist and stripping glue in the first electrode area, and is rinsed with ultrapure water and blown dry with nitrogen to form a first electrode area.

[0088] Specifically, before evaporating the metal, a plasma degumming machine can be used to remove the small amount of residual glue remaining after exposure and development; then the currently manufactured product is placed in the electron beam evaporation table, and the vacuum degree of the reaction chamber of the electron beam evaporation table reaches 2×10 -6 After 3000 Å, a gold film with a thickness of about 200 nm is evaporated on the surface of the product to complete the evaporation of the electrode metal.

[0089] Specifically, the product can be immersed in acetone for more than 4 hours, and then ultrasonically treated until the metal in the unexposed area is completely removed to form the first electrode 6; then the product is placed in a 60°C stripping solution and heated in a water bath for 15 minutes; the product is then placed in acetone and isopropanol solutions for ultrasonic cleaning for 3 minutes in turn; the product is rinsed with ultrapure water for 2 minutes and then dried with nitrogen.

[0090] S307, etching a groove penetrating the insulating layer, the hole transport layer and the field oxygen isolation layer on the upper surface of the insulating layer to define a second electrode region.

[0091] In one example, the region where the upper surface groove is located on the other side of the preset active region (see Figure 2 203) is photolithographically processed, and then the groove 12 is etched to form Figure 4i The structure shown; then the second electrode region is defined again by photolithography (see Figure 2 204).

[0092] Exemplarily, the second electrode region may include a portion of an upper surface of the insulating layer located on the other side of the predetermined active region.

[0093] Specifically, photoresist can be spin-coated on the product, and then pre-baked, and then the groove area can be exposed through a mask using a photolithography machine; after the exposure is completed, post-baking is performed; after the post-baking is completed, the product temperature drops to room temperature and then developed to remove the photoresist in the groove area, and the lithography is completed.

[0094] Specifically, the insulating layer 4 in the groove position can be removed by wet etching with a BOE solution, and then the product can be cleaned with ultrapure water for two minutes; the exposed hole transport layer 3 is then removed with ammonia water, and the product is cleaned with ultrapure water for two minutes and blown dry with nitrogen; then, the field oxygen isolation layer 2 in the groove area is etched away by a F-based dry etching process under the conditions that the reaction gases are CF4 and O2, the reaction chamber pressure is 10mTorr, and the RF powers of the upper electrode and the lower electrode are 100W and 10W respectively, and the etching depth is about 200nm, until the etching is terminated on the upper surface of the epitaxial layer 15; finally, the product is placed in an acetone solution and an isopropanol solution in turn for ultrasonic cleaning to remove the photoresist outside the groove position, and then the product is rinsed with ultrapure water and blown dry with nitrogen.

[0095] Specifically, the product can be placed on a hot plate at 200°C and baked for 5 minutes; the stripping glue is coated and spun with a thickness of 0.35μm, and the product is placed on a hot plate at 200°C and baked for 5 minutes; then, photoresist is coated and spun on the stripping glue with a thickness of 0.77μm, and the product is placed on a hot plate at 90°C and baked for 1 minute; thereafter, the product that has been coated and spun is placed in a photolithography machine to expose the photoresist in the second electrode area; finally, the exposed product is placed in a developer to remove the photoresist and stripping glue in the second electrode area, and is rinsed with ultrapure water and blown dry with nitrogen to form the second electrode area.

[0096] S308 , evaporating an ohmic contact metal in the groove and the second electrode region to form a second electrode.

[0097] In one example, an electron beam evaporation process can be used to deposit a Ti / Al / Ni / Au metal stack in the groove on the other side of the preset active area and on the upper surface of the insulating layer, and then the metal stack outside the groove and the second electrode area can be stripped to form a second electrode 7 in the groove and the second electrode area.

[0098] Specifically, before evaporating the metal, a plasma degumming machine can be used to remove the small amount of residual glue left after exposure and development; then the product is placed in the electron beam evaporation table, and the vacuum degree of the reaction chamber of the electron beam evaporation table reaches 2×10 - 6 After 300 Torr, a metal stack consisting of four layers of metal, Ti, Al, Ni, and Au, is evaporated from bottom to top on the photoresist in the area where the groove is located on the upper surface of the epitaxial layer 15, the insulating layer 4, and the second electrode area. The thickness of each metal layer is Ti (20nm) / Al (160nm) / Ni (55nm) / Au (45nm) respectively.

[0099] Specifically, the product can be immersed in acetone for more than 4 hours, and then ultrasonicated until the metal in the unexposed area is completely removed; the product can be placed in a 60°C stripping solution and heated in a water bath for 15 minutes; the product can then be ultrasonically cleaned in acetone and isopropanol for 3 minutes in turn, rinsed with ultrapure water for 2 minutes, and then blown dry with nitrogen to complete the production of the whispering gallery mode microcavity laser.

[0100] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0101] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0102] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0103] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, any modifications made without departing from the concept of the present invention should be deemed to belong to the protection scope of the present invention.

Claims

1. A whispering gallery mode microcavity laser, characterized in that: include: A GaN substrate, wherein a whispering gallery mode microcavity is arranged in a preset active area on the upper surface of the GaN substrate; A field oxygen isolation layer, wherein the field oxygen isolation layer is disposed on the upper surface of the GaN substrate and covers the side surface of the whispering gallery mode microcavity; A hole transport layer, wherein the hole transport layer is disposed on an upper surface of the field oxygen isolation layer and an upper surface of the whispering gallery mode microcavity; An insulating layer, the insulating layer being arranged on an upper surface of the hole transport layer, wherein a groove penetrating the insulating layer, the hole transport layer and the field oxygen isolation layer is arranged on one side of the preset active area on the upper surface of the insulating layer; A transparent conductive layer, wherein the transparent conductive layer is disposed in a preset active area on the upper surface of the insulating layer; A first electrode, which is disposed on a portion of the upper surface of the transparent conductive layer and extends to the insulating layer on the other side of the preset active area; A second electrode is disposed in the groove and extends onto the insulating layer.

2. The laser according to claim 1, characterized in that The microcavity thickness of the whispering gallery mode microcavity is 50-1000 nm.

3. The laser according to claim 1, characterized in that The thickness of the field oxygen isolation layer is 200-1000 nm.

4. The laser according to claim 1, characterized in that The hole transport layer is made of materials including molybdenum trioxide and tungsten oxide.

5. The laser according to claim 1, characterized in that The thickness of the hole transport layer is comprised between 1 and 15 nm.

6. The laser according to claim 1, characterized in that The material of the insulating layer includes: aluminum oxide, silicon dioxide, and aluminum nitride.

7. The laser according to claim 1, characterized in that The thickness of the insulating layer is 1-100 nm.

8. A method for preparing a whispering gallery mode microcavity laser, characterized in that: include: Etching a portion of the upper surface of the GaN substrate that is not in the preset active region to form a whispering gallery mode microcavity in the preset active region on the upper surface of the GaN substrate; Depositing a field oxygen isolation layer on the upper surface of the whispering gallery mode microcavity and the GaN substrate; Etching the field oxygen isolation layer located in the preset active area; Depositing a hole transport layer on the upper surface of the etched field oxygen isolation layer and the upper surface of the whispering gallery mode microcavity, and depositing an insulating layer on the upper surface of the hole transport layer; Depositing a transparent conductive layer in a preset active area on the upper surface of the insulating layer; Forming a first electrode by evaporating or sputtering metal in a first electrode region on the upper surfaces of the transparent conductive layer and the insulating layer, wherein the first electrode region includes a portion of the upper surface of the transparent conductive layer and extends to the insulating layer located on one side of the preset active area; Etching a groove penetrating the insulating layer, the hole transport layer and the field oxygen isolation layer on the upper surface of the insulating layer to define a second electrode region, wherein the second electrode region includes a portion of the upper surface of the insulating layer located on the other side of the preset active region; An ohmic contact metal is evaporated in the groove and the second electrode region to form a second electrode.

9. The method according to claim 8, characterized in that The step of depositing a hole transport layer on the upper surface of the etched field oxygen isolation layer and the upper surface of the whispering gallery mode microcavity, and depositing an insulating layer on the upper surface of the hole transport layer comprises: Depositing the hole transport layer on the upper surface of the etched field oxygen isolation layer and the upper surface of the whispering gallery mode microcavity by using a sputtering process; The insulating layer is deposited on the upper surface of the hole transport layer by using an atomic layer deposition process, and before depositing the insulating layer, the hole transport layer is protected from contact with liquid.

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