Echo-wall mode microcavity laser and preparation method thereof

Abstract

The application discloses an echo wall mode microcavity laser and a preparation method thereof. The laser comprises a GaN substrate, a field oxygen isolation layer, a hole transport layer, an insulation layer and a transparent conductive layer from bottom to top. An echo wall mode microcavity is arranged on the upper surface of the GaN substrate. A first electrode and a second electrode are arranged on the upper surface of the transparent conductive layer and the upper surface of the GaN substrate respectively. The first electrode, the transparent conductive layer, the insulation layer and the GaN substrate form a MIS structure. The preparation process and structure are simple. The hole transport layer can improve the injection amount of the minority hole when the device works, thereby significantly reducing the opening voltage of the device. The application can also realize the function of lasing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor optoelectronic devices, and particularly relates to an echo wall mode microcavity laser and a preparation method thereof. BACKGROUND

[0002] Gallium nitride (GaN) based material is a wide band gap semiconductor material with a direct band gap, and the band gap width can be continuously adjusted by forming AlGaN and InGaN ternary alloys, and the corresponding emission wavelength can be continuously adjusted from ultraviolet to near infrared, which is 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 have an irreplaceable role. Among them, the ultraviolet light source is an important application scenario of GaN-based materials. Compared with the common mercury lamp ultraviolet light source, the ultraviolet LED and laser based on GaN-based material have the advantages of non-toxic and environmental protection, easy to carry, low voltage, low power consumption and stable and reliable work, and can be used in polymer curing, sterilization and disinfection, medical diagnosis, biochemical sensing, 3D printing, safety detection and other fields. Moreover, GaN-based semiconductor materials also have a large exciton binding energy and a large phonon strength, and can realize small volume and high efficiency microcavity optoelectronic devices in combination with optical microcavities, which can be used for the study of cavity quantum electrodynamics at room temperature.

[0003] The current popular GaN-based laser structure is basically a p-GaN layer / quantum well layer / n-GaN layer, which generally includes a p-electrode, a contact layer, a p-type optical confinement layer, an electron blocking layer, an upper waveguide, an active region, a lower waveguide, an n-type optical confinement layer, a substrate and an n-electrode, and the like. This structure essentially belongs to a p-n junction electrical injection mode, and the device structure is very complex, the preparation is difficult, and the material, structure and process have high requirements. Another metal-insulator-semiconductor (MIS) electrical injection structure with a simpler manufacturing process and structure can also realize electroluminescence and electrical oscillation, but the working voltage of the device is high, and there is no related report on the realization of oscillation by using the MIS structure in the GaN-based material system. SUMMARY

[0004] The echo wall mode microcavity laser and the preparation method thereof provided by the embodiments of the application can solve the problems of the GaN-based laser structure and preparation process of the p-n junction electrical injection mode and the high working voltage of the GaN-based light emitting device of the MIS structure.

[0005] In a first aspect, the embodiments of the application provide an echo wall mode microcavity laser, comprising:

[0006] A GaN substrate, a back surface of the GaN substrate is provided with a pre-set active region, and a whispering gallery mode microcavity is arranged in the pre-set active region;

[0007] A field oxide isolation layer, the field oxide isolation layer 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, the hole transport layer is arranged on the upper surface of the field oxide 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, on the upper surface of the insulating layer, one side of the pre-set active region is provided with a groove penetrating through the insulating layer, the hole transport layer and the field oxide isolation layer;

[0010] A transparent conductive layer, the transparent conductive layer is arranged in the pre-set active region on the upper surface of the insulating layer;

[0011] A first electrode, the first electrode is arranged on part of the upper surface of the transparent conductive layer and extends to the insulating layer on the other side of the pre-set active region;

[0012] A second electrode, the second electrode is arranged in the groove and extends to the insulating layer.

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

[0014] Etching part of the non-pre-set active region on the upper surface of the GaN substrate to form a whispering gallery mode microcavity in the pre-set active region on the upper surface of the GaN substrate;

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

[0016] Etching the field oxide isolation layer located in the pre-set active region;

[0017] Depositing a hole transport layer on the upper surface of the etched field oxide 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 the pre-set active region on the upper surface of the insulating layer;

[0019] Evaporating or sputtering a metal to form a first electrode in a first electrode region on the upper surface of the transparent conductive layer and the insulating layer, wherein the first electrode region includes part of the upper surface of the transparent conductive layer and extends to the insulating layer located on one side of the pre-set active region;

[0020] Etching a groove penetrating through the insulating layer, the hole transport layer and the field oxide isolation layer on the upper surface of the insulating layer and defining a second electrode region, wherein the second electrode region includes part of the upper surface of the insulating layer located on the other side of the pre-set active region;

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

[0022] Compared with the prior art, the echo-wall mode microcavity laser provided by the embodiment of the present application has the following advantages: the echo-wall mode microcavity laser provided by the present application uses a GaN substrate to provide gain medium material for laser emission, uses a MIS electric injection structure of a first electrode, a transparent conductive layer, an insulating layer and a GaN substrate to provide a pump source for laser emission, and uses an echo-wall mode microcavity provided on the GaN substrate to provide a resonant cavity for laser emission, so that the echo-wall mode microcavity laser provided by the present application can realize the effect of electric excitation by improving the injection amount of minority carriers during the operation of the device and realizing the distribution of particle number inversion; and compared with a laser device of a traditional p-n junction electric injection structure, the echo-wall mode microcavity laser provided by the present application has a relatively simple structure and preparation method; and 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 laser of the p-n junction electric injection structure is greater than or equal to the voltage corresponding to the energy of the material band gap, thereby improving the laser output efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A structure schematic diagram of an echo-wall mode microcavity laser provided by the embodiment of the present application is shown in the figure.

[0024] Figure 2 A structure schematic diagram of an echo-wall mode microcavity laser provided by the embodiment of the present application is shown in the figure.

[0025] Figure 3 An implementation flowchart of a preparation method of an echo-wall mode microcavity laser provided by the embodiment of the present application is shown in the figure.

[0026] Figures 4a-4i A scene schematic diagram of a preparation method of an echo-wall mode microcavity laser provided by the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0027] In the following description, specific details are set forth such as particular system configurations, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, persons skilled in the art should understand that the present application can be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted in order not to obscure the description of the present application with unnecessary detail.

[0028] It should be understood that, when used in the specification and the appended claims of the present application, the term "comprising" indicates the presence of the 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 groups thereof.

[0029] It should also be appreciated that the term "and / or" as used herein is used to associate together alternatively related listing items, and encompasses all possible combinations of one or more of the associated items, and includes all possible combinations.

[0030] As used in the description of the application and the appended claims, the term "if' can be interpreted to mean "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 [a described condition or event] is detected" can be interpreted to mean "upon determining" or "in response to determining" or "upon [the described condition or event] being detected" or "in response to [the described condition or event] being detected," depending on the context.

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

[0032] Reference in the specification to "one embodiment" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in one embodiment" or "in some embodiments" in various places in the specification are not necessarily all referring to the same embodiment, although it can. The terms "including", "containing", "having" and variations thereof are meant to encompass the terms "including but not limited to", unless otherwise expressly specified or limited by context.

[0033] Current GaN-based whispering gallery mode microcavity lasers basically adopt p-n junction electrical injection, and the structure is basically p-GaN layer / quantum well layer / n-GaN layer, which specifically includes 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. Such GaN-based laser has a complex structure, more epitaxial growth steps, and greater difficulty in preparation. 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 such GaN-based laser.

[0034] Compared with the p-n junction structure, the GaN-based electroluminescent device realized by using the MIS electrical injection structure has fewer layers, a simpler structure, can reduce the epitaxial growth steps, simplify the device preparation process, and save the manufacturing cost; in addition, by using the MIS structure, the introduction of p-type doped material can be effectively avoided.

[0035] However, some currently popular MIS structure-based GaN-based electroluminescent devices, such as metal-aluminum nitride-n-type gallium nitride structure ultraviolet light emitting diodes and graphene-silicon dioxide-gallium nitride structure diodes, can only realize electroluminescence, and cannot realize electrical excitation; and the current MIS structure device also has the defect of high turn-on voltage.

[0036] Therefore, the echo wall mode microcavity laser provided by the present application can realize electrical excitation effect; and compared with the traditional p-n junction electrical injection structure laser, the echo wall mode microcavity laser structure and preparation method provided by the present application are relatively simple; 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 p-n junction electrical injection structure laser is greater than or equal to the voltage corresponding to the material band gap width energy, thereby improving the laser output efficiency.

[0037] The present application will be further described in detail below in conjunction with specific embodiments, but the embodiments of the present application are not limited thereto.

[0038] Embodiment 1

[0039] Figure 1 The structure of the echo wall mode microcavity laser provided by the embodiment of the present application is shown. As an example but not limitation, the echo wall mode microcavity laser 100 can include a GaN substrate 1, a field oxide 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, referring to Figure 1 , the upper surface of the GaN substrate 1 is provided with a preset source region (see Figure 2The echo wall mode microcavity 11 can be arranged in the region framed by the rectangle in FIG. 1. The field oxide isolation layer 2 can be arranged on the side surface of the echo wall mode microcavity 11 and the upper surface of the GaN substrate 1. The hole transport layer 3 and the insulating layer 4 can be arranged in sequence on the upper surface of the field oxide isolation layer 2 and the echo wall mode microcavity. The transparent conductive layer 5 can be arranged in the preset source region on the upper surface of the insulating layer 4. The first electrode 6 can cover part of the upper surface of the transparent conductive layer 5 and extend to the insulating layer on the side of the preset source region. The insulating layer 4 is provided with a groove 12 penetrating the insulating layer 4, the hole transport layer 3 and the field oxide isolation layer 2 on the upper surface of the other side of the preset source region. The second electrode 7 is arranged in the groove 12 so that the second electrode 7 realizes ohmic contact with the GaN substrate and covers the insulating layer 4 near the groove 12.

[0041] In a possible implementation, referring to FIG. 2, Figure 1 The GaN substrate 1 can be a multilayer structure including a silicon layer 13, a buffer layer 14 and an epitaxial layer 15 arranged in sequence from bottom to top.

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

[0043] For example, the material of the buffer layer 14 can include an AlN layer, an AlGaN layer and an unintentionally doped u-GaN layer arranged in sequence from bottom to top.

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

[0045] In an example, referring to FIG. 3, Figure 2 The shape of the echo wall mode microcavity 11 can be a disc shape.

[0046] Alternatively, the shape of the echo wall mode microcavity 11 can also be a regular polygon, an oval shape with a notch at the boundary or other shapes.

[0047] For example, the thickness of the echo wall mode microcavity 11 can be 50-1000 nm, and the size of the echo wall mode microcavity 11 can be 0-500 μm.

[0048] In a possible implementation, the material of the field oxide isolation layer 2 can include silicon nitride, and the thickness can include 200-1000 nm.

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

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

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

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

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

[0054] The echo wall mode microcavity laser provided by the application provides a gain medium material for laser emission through the GaN substrate, provides a pump source for laser emission through the MIS structure of the first electrode, the transparent conductive layer, the insulating layer, and the GaN substrate, and provides a resonant cavity for laser emission through the echo wall mode microcavity arranged on the GaN substrate. The hole transport layer improves the minority hole injection amount when the device works, realizes the particle number inversion distribution, so that the echo wall mode microcavity device provided by the application can realize the electric excitation effect. Compared with the traditional p-n junction electric injection structure laser, the echo wall mode microcavity laser structure and the preparation method provided by the application are relatively simple. Due to the introduction of the hole transport layer, the threshold voltage of the GaN-based microcavity laser can also be significantly reduced, and even the inherent limit that the threshold voltage of the p-n junction electric injection structure laser is greater than or equal to the voltage corresponding to the material band gap energy can be broken, and the laser output efficiency is improved.

[0055] The echo wall mode microcavity laser provided by the application can be applied to multiple fields such as ultraviolet curing, sterilization and disinfection, medical diagnosis, and safety detection, has multiple advantages such as small size and low threshold, and can be used as an important light source in a photonic device and a photonic integrated circuit, and can be integrated with other optical elements on a large scale and in a high density, realize photoelectric integration, on-chip communication, optical interconnection, and ultrahigh density storage, and can realize high-efficiency output with low energy loss.

[0056] Embodiment 2

[0057] Figure 3 An implementation flowchart of a preparation method of an echo wall mode microcavity laser provided by an embodiment of the application is shown. As an example but not limitation, the method can be used to prepare the echo wall mode microcavity laser 100 described above, and the method can include steps S301-S308, which are described below.

[0058] S301, etching a part of the upper surface of the GaN substrate other than the pre-set active region to form a whispering gallery mode microcavity in the pre-set 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 an electron beam lithography and an inductively coupled plasma dry etching process can be used to etch a part of the upper surface of the GaN substrate 1 other than the pre-set active region (see 401 in FIG. 4) to form the whispering gallery mode microcavity 11, thereby obtaining a structure as shown in FIG. 5. Figure 4a Figure 4b As an example, before etching, the GaN substrate 1 can be sequentially placed in acetone, stripping solution, acetone and isopropanol solution for ultrasonic cleaning, then rinsed with ultrapure water for two minutes and dried with nitrogen.

[0060] As an example, an electron beam lithography process can be used to define the pre-set active region on the upper surface of the GaN substrate 1, and then a Cl-based dry etching process can be used to etch a part of the non-pre-set active region to form the whispering gallery mode microcavity 11.

[0061] Specifically, the GaN substrate 1 can be first placed on a hot plate at 200°C for baking for 5 minutes; then a spin coater is used to spin 0.9 μm thick electron beam resist on the upper surface of the GaN substrate 1 at a speed of 3500 rpm, and the product after coating is placed on a hot plate at 90°C for baking for 1 minute; then the product is subjected to lithography by an electron beam lithography machine through a mask, and the exposure time can be set to 280 ms. After exposure, the product is placed on a hot plate at 110°C for baking for 1 minute; finally, the product is placed in a developing solution for 90 seconds to remove the photoresist outside the pre-set active region, and then rinsed with ultrapure water and dried with nitrogen, followed by heating for 1 minute for hardening, to complete the definition of the pre-set active region.

[0062] Specifically, BCl3 and Cl2 can be used as etching gas, and an inductively coupled plasma dry etching process is used to dry etch the epitaxial layer 15 outside the pre-set active region to form the whispering gallery mode microcavity 11. Then, the product is sequentially placed in acetone solution, stripping solution, acetone solution and 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 dried with nitrogen.

[0063] As an example, the flow rates of the BCl3 and Cl2 mixed gas in the etching process can be 20 sccm and 8 sccm respectively, and the etching process parameters can be: ICP upper electrode power 50 W, ICP lower electrode power 15 W, pressure 5 mTorr, etching depth 450 nm.

[0064] As an example, the flow rates of the BCl3 and Cl2 mixed gas in the etching process can be 20 sccm and 8 sccm respectively, and the etching process parameters can be: ICP upper electrode power 50 W, ICP lower electrode power 15 W, pressure 5 mTorr, etching depth 450 nm.

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

[0066] In one example, before depositing the field oxide 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 to form the field oxide isolation layer 2 by using a plasma enhanced chemical vapor deposition process, to obtain a structure as shown in Figure 4c .

[0067] Specifically, the GaN substrate 1 including the whispering gallery mode microcavity 11 can be ultrasonically cleaned in an acetone solution for 3 minutes, and then placed in a stripping solution heated in a water bath at a temperature of 60°C for 15 minutes, and then sequentially placed in an acetone solution and an isopropanol solution for ultrasonic cleaning for 3 minutes; finally, the product is rinsed with ultrapure water and dried 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 under the conditions of using ammonia (NH3) and silane (SiH4) as reaction gases, a substrate temperature of 250°C, a reaction chamber pressure of 600 mTorr, and a radio frequency power of 22 W.

[0069] S303, etching the field oxide isolation layer located in the pre-designed active region.

[0070] In one example, the pattern of the pre-designed active region can be photolithographed on the upper surface of the field oxide isolation layer 2, and carbon tetrafluoride (CF4) and oxygen (O2) can be used as etching gases, and a F-based dry etching process can be used to perform opening etching on the upper surface of the whispering gallery mode microcavity 11, to obtain a structure as shown in Figure 4d .

[0071] Specifically, photoresist can be spin-coated on the field oxide isolation layer 2, and then pre-baking is performed, and then the pre-designed active region on the upper surface of the field oxide isolation layer 2 is exposed by using a photolithography machine 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 pre-designed active region on the upper surface of the field oxide isolation layer 2, and the photolithography is completed.

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

[0073] S304, depositing a hole transport layer on the upper surface of the etched field oxide 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 field oxide isolation layer after etching can be cleaned first, and then a hole transport layer 3 is deposited on the upper surface of the field oxide isolation layer after etching and the upper surface of the whispering gallery mode microcavity by using a sputtering process, to obtain a structure as shown in Figure 4e After that, an insulating layer 4 is immediately deposited on the upper surface of the hole transport layer 3 by using an atomic layer deposition process, to obtain a structure as shown in Figure 4f Before depositing the insulating layer 4, the hole transport layer 3 needs to be protected from contacting any liquid such as organic, acid-base solution, and ultrapure water, so as to avoid damaging the prepared metal oxide hole transport layer 3 structure.

[0075] Specifically, the current product (see Figure 4d ) can be sequentially placed in acetone, stripping solution, acetone and isopropanol solution for ultrasonic cleaning, and then the product is rinsed with ultrapure water for two minutes. Further, the product is placed in an aiptasia solution (a mixed solution of concentrated sulfuric acid and hydrogen peroxide) for cleaning for 1 minute, and finally the product is rinsed with ultrapure water for two minutes and dried with nitrogen, to complete the cleaning.

[0076] Specifically, the cleaned structure can be placed in a sputtering equipment chamber, and the chamber is vacuumed to 5x10 - 6 Torr, a molybdenum trioxide target is used, the sputtering power is 100W, the gas used is argon (Ar), the working pressure is 4mTorr, and a molybdenum trioxide film with a thickness of about 5nm is sputtered and grown on the upper surface of the field oxide isolation layer 2 and the upper surface of the whispering gallery mode microcavity to form the hole transport layer 3.

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

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

[0079] In one example, an ultrathin gold layer is deposited on the upper surface of the insulating layer 4 by using an electron beam evaporation process, and then the formed ultrathin gold layer is subjected to photolithography to define a preset source region, and finally the ultrathin gold layer outside the preset source region is subjected to wet etching, and the product as a whole is cleaned, to obtain a structure as shown in Figure 4g .

[0080] Specifically, the current product (see Figure 4f ) can be placed in an electron beam evaporation station, and the reaction chamber of the electron beam evaporation station is vacuumed to 2x10-6 After Torr, a translucent ultrathin gold layer with a thickness of about 10 nm is evaporated on the upper surface of insulating layer 4 at a deposition rate of 0.1 nm / s.

[0081] Specifically, photoresist can be spin-coated onto a translucent ultrathin gold layer, followed by pre-baking. Then, a photolithography machine is used to expose the area outside the preset active area through a mask. After exposure, post-baking is performed. After post-baking, development is performed after the temperature drops to room temperature to remove the photoresist outside the preset active area, thus completing the photolithography.

[0082] Specifically, a gold etching solution can be used to perform wet etching on the ultrathin gold layer outside the preset active area to remove the ultrathin gold layer outside the preset active area exposed after photolithography; after wet etching, rinse with ultrapure water for two minutes.

[0083] Specifically, the product that has undergone wet etching can be ultrasonically cleaned in acetone solution for 3 minutes; then it can be ultrasonically cleaned in acetone solution and isopropanol solution for 3 minutes in sequence; finally, the product is rinsed with ultrapure water and dried with nitrogen.

[0084] S306, a first electrode is formed by evaporating or sputtering metal in the first electrode region on the upper surface of the transparent conductive layer and the insulating layer.

[0085] For example, 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 region.

[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 [reference]). Figure 2 In step 202), the electrode metal is then evaporated on the upper surface of the insulating layer 4 and the transparent conductive layer. Finally, the electrode metal outside the first electrode region is removed to form the first electrode 6, resulting in the following: Figure 4h The structure shown.

[0087] Specifically, the product (see...) Figure 4g The product is placed on a hot plate at 200°C and baked for 5 minutes. Next, a stripper is applied and spun to a thickness of 0.35 μm, and then baked on a hot plate at 200°C for 5 minutes. Then, photoresist is applied and spun to the stripper to a thickness of 0.77 μm, and the product is baked on a hot plate at 90°C for 1 minute. Afterward, the product with the applied and spun photoresist is placed in a lithography machine to expose the photoresist in the first electrode area. Finally, the exposed product is placed in a developing solution to remove the photoresist and stripper in the first electrode area, and then rinsed with ultrapure water and dried with nitrogen to form the first electrode area.

[0088] Specifically, before evaporating the metal, a plasma stripper can be used to remove any remaining residue after exposure and development; then, the currently manufactured product is placed in an electron beam evaporation stage, and the vacuum level in the reaction chamber of the electron beam evaporation stage reaches 2 × 10⁻⁶. -6 After Torr, a gold film with a thickness of approximately 200 nm is evaporated on the product surface to complete the evaporation of the electrode metal.

[0089] Specifically, the product can be soaked in acetone for more than 4 hours, and then ultrasonically cleaned 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; then the product is placed in acetone and isopropanol solutions in sequence and ultrasonically cleaned for 3 minutes; rinsed with ultrapure water for 2 minutes and then dried with nitrogen.

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

[0091] In one example, the area where the groove on the upper surface of the preset active area is located can be started first (see...). Figure 2 Photolithography is performed on 203), and then the groove 12 is etched to form the groove as shown in the figure. Figure 4i The structure shown; then photolithography is performed again to define the second electrode region (see...). Figure 2 (204 in the middle).

[0092] For example, the second electrode region may include a portion of the upper surface of the insulating layer located on the other side of the preset active region.

[0093] Specifically, photoresist can be spin-coated onto the product, followed by pre-baking. Then, the groove area is exposed using a photolithography machine through a mask. After exposure, post-baking is performed. After post-baking, once the product temperature has dropped to room temperature, development is performed to remove the photoresist from the groove area, thus completing the photolithography process.

[0094] Specifically, the insulating layer 4 within the groove location can be removed using BOE solution wet etching, followed by rinsing the product with ultrapure water for two minutes; then, the exposed hole transport layer 3 can be removed with ammonia, and the product can be rinsed with ultrapure water for two minutes and dried with nitrogen; then, the field oxygen isolation layer 2 in the groove area can be etched using F-based dry etching process under the conditions of CF4 and O2 reaction gases, a reaction chamber pressure of 10 mTorr, and RF power of 100 W and 10 W for the upper and lower electrodes, respectively, with an etching depth of approximately 200 nm, until the etching terminates on the upper surface of the epitaxial layer 15; finally, the product is sequentially immersed in acetone solution and isopropanol solution for ultrasonic cleaning to remove the photoresist outside the groove location, and then rinsed with ultrapure water and dried with nitrogen.

[0095] Specifically, the product can be placed on a hot plate at 200 DEG C for baking for 5 minutes; the peeling glue is coated and spun, the spinning thickness is 0.35 microns, and the product is placed on a hot plate at 200 DEG C for baking for 5 minutes; then, the photoresist is coated and spun on the peeling glue, the spinning thickness is 0.77 microns, and the product is placed on a hot plate at 90 DEG C for baking for 1 minute; after that, the product after coating and spinning is placed in a photoetching machine to expose the photoresist in the second electrode area; finally, the product after exposure is placed in a developing solution to remove the photoresist and the peeling glue in the second electrode area, and is subjected to ultrapure water washing and nitrogen blowing dry, to form the second electrode area.

[0096] S308, evaporating the ohmic contact metal in the groove and the second electrode area to form the 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 is peeled off, to form the second electrode 7 in the groove and the second electrode area.

[0098] Specifically, a small amount of residual glue remaining after exposure and development can be removed by using a plasma stripper before evaporation of the metal; then the product is placed in an electron beam evaporation station, and after the reaction chamber of the electron beam evaporation station reaches a vacuum degree of 2x10 - 6 After that, a metal stack composed of four layers of metal from bottom to top, Ti, Al, Ni and Au, is evaporated on the area of the upper surface of the epitaxial layer 15 where the groove is located, the photoresist outside the insulating layer 4 and the second electrode area, the thickness of each layer of metal is Ti (20 nm) / Al (160 nm) / Ni (55 nm) / Au (45 nm).

[0099] Specifically, the product can be soaked in acetone for more than 4 hours, and then ultrasonic cleaning is performed until the metal in the unexposed area is completely removed; the product is placed in a 60 DEG C stripping solution for water bath heating for 15 minutes; then the product is sequentially placed in acetone and isopropyl alcohol for ultrasonic cleaning for 3 minutes, and the product is washed with ultrapure water for 2 minutes and then dried with nitrogen, to complete the fabrication of the whispering gallery mode microcavity laser.

[0100] In the description of the present application, the terms "first", "second" are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically defined.

[0101] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate different embodiments or examples described in the specification.

[0102] Although the present application is described herein in conjunction with various embodiments, it is understood that other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from an inspection of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. A single processor or other unit can fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0103] The above is a further detailed description of the present application in conjunction with specific preferred embodiments, and cannot be deemed to limit the specific implementation of the present application to these descriptions. Modifications made by those skilled in the art without departing from the concept of the present application should be deemed to be within the scope of protection of the present application.

Claims

1. A whispering gallery mode microcavity laser, characterized in that, include: GaN substrate, wherein a whispering-gallery mode microcavity is provided in a preset active region on the upper surface of the GaN substrate; A field oxygen isolation layer is disposed on the upper surface of the GaN substrate and covers the side of the whispering-gallery mode microcavity; Hole transport layer, wherein the hole transport layer is disposed on the upper surface of the field oxygen isolation layer and the upper surface of the whispering gallblade mode microcavity; An insulating layer is disposed 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 provided on one side of the preset active region on the upper surface of the insulating layer. A transparent conductive layer is disposed within a predetermined active region on the upper surface of the insulating layer; The first electrode 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 region; The second electrode is disposed in the groove and extends onto the insulating layer.

2. The laser of claim 1, wherein, The microcavity thickness of the whispering-gallery mode microcavity ranges from 50 to 1000 nm.

3. The laser of claim 1, wherein, The thickness of the field oxygen isolation layer ranges from 200 to 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 ranges from 1 to 15 nm.

6. The laser according to claim 1, characterized in that, The insulating layer is made of materials including: aluminum oxide, silicon dioxide, and aluminum nitride.

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

8. A method for fabricating a whispering-gallery mode microcavity laser, characterized in that, include: Etch a portion of the non-preset active region on the upper surface of the GaN substrate to form a whispering-gallery mode microcavity within the preset active region on the upper surface of the GaN substrate; A field oxygen isolation layer is deposited on the upper surface of the whispering-gallery mode microcavity and the GaN substrate; Etching the field oxygen isolation layer located within the preset active region; A hole transport layer is deposited on the upper surface of the etched field oxygen isolation layer and the upper surface of the whispering galvanic microcavity, and an insulating layer is deposited on the upper surface of the hole transport layer. A transparent conductive layer is deposited in a predetermined active region on the upper surface of the insulating layer; A first electrode is formed by evaporating or sputtering metal in a first electrode region on the upper surface 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; A groove is etched through 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 region of the second electrode to form a second electrode.

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

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