Fabrication method of flip-chip ridge waveguide semiconductor laser and semiconductor laser

Abstract

The application discloses a manufacturing method of an inverted ridge waveguide semiconductor laser and the semiconductor laser. The manufacturing method comprises the following steps: providing a substrate, forming a mask layer on the surface of the substrate, etching the mask layer to prepare a strip-shaped window on the mask layer, sequentially growing an n-type cover layer and an n-type limiting layer in the strip-shaped window to form an n-type ridge waveguide, growing an epitaxial structure on the surface of the n-type limiting layer, forming a current spreading layer on the epitaxial structure and forming a p-type electrode on the surface of the current spreading layer, removing the substrate, and forming an n-type electrode on the surface of the n-type cover layer. The manufacturing method of the inverted ridge waveguide semiconductor laser and the semiconductor laser can complete the preparation of the ridge waveguide of the n-type region without etching the n-type region, improve the light emitting performance of the laser, greatly simplify the inverted process of the semiconductor laser, increase the ohmic contact area of the p-type contact layer, and be beneficial to the heat dissipation of the whole device.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a method for fabricating a flip-chip ridge waveguide semiconductor laser and the flip-chip ridge waveguide semiconductor laser itself. Background Technology

[0002] With the development of technology, GaN-based semiconductor laser diodes (LDs) are increasingly being used in laser displays, automotive headlights, visible light communication, industrial processing, and biomedicine. To enhance the lateral optical field confinement and current confinement of lasers, ridge waveguide structures are widely used. Currently, the main technical approach for fabricating laser ridge waveguides, both domestically and internationally, involves photolithography and etching of the p-type confinement layer and p-type contact layer. However, this method causes sidewall damage that is difficult to repair, increasing light absorption loss and easily introducing leakage paths. Furthermore, heat dissipation problems also constrain the development of high-power LDs. LDs have very high peak power during operation, generating a large amount of heat that causes a rapid rise in the active region temperature, leading to optical catastrophic failures or even burnout, severely impacting the reliability and lifespan of the LD. Therefore, exploring new methods for fabricating laser ridge waveguides and solving heat dissipation problems are of great significance for the development of LDs.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a method for fabricating a flip-chip ridge waveguide semiconductor laser and a flip-chip ridge waveguide semiconductor laser. The fabrication of the ridge waveguide in the n-type region can be completed without etching the n-type region (n-type capping layer and n-type confinement layer), which improves the luminescence performance of the laser and greatly simplifies the flip-chip process of the semiconductor laser. It also increases the ohmic contact area of ​​the p-type contact layer, which is beneficial to the heat dissipation of the overall device.

[0005] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0006] A method for fabricating a flip-chip ridge waveguide semiconductor laser includes:

[0007] A substrate is provided, and a mask layer is formed on the surface of the substrate;

[0008] The mask layer is etched to create a strip window on the mask layer;

[0009] An n-type cladding layer and an n-type confinement layer are sequentially grown within the strip window to form an n-type ridge waveguide;

[0010] An epitaxial structure is grown on the surface of the n-type confinement layer;

[0011] A current spreading layer is formed on the epitaxial structure, and a p-type electrode is formed on the surface of the current spreading layer;

[0012] The substrate is removed, and an n-type electrode is formed on the surface of the n-type capping layer to obtain a semiconductor laser epitaxial wafer.

[0013] In one or more embodiments of the present invention, the n-type confinement layer covers the mask layer or the surface of the n-type confinement layer opposite to the n-type cover layer is flush with the surface of the mask layer opposite to the substrate.

[0014] In one or more embodiments of the present invention, strip windows arranged side by side are prepared on the mask layer by photolithography, wet etching, and dry etching processes, and the strip windows expose a portion of the substrate.

[0015] In one or more embodiments of the present invention, the thickness of the mask layer is 1 μm to 2 μm.

[0016] In one or more embodiments of the present invention, the spacing between adjacent strip windows is 1.5 μm to 3 μm.

[0017] In one or more embodiments of the present invention, the n-type capping layer and the n-type confinement layer are epitaxially grown within the strip window using a lateral epitaxial overgrowth technique.

[0018] In one or more embodiments of the present invention, the thickness of the n-type cover layer is less than the thickness of the mask layer, and the sum of the thicknesses of the n-type cover layer and the n-type confinement layer is greater than or equal to the thickness of the mask layer.

[0019] In one or more embodiments of the present invention, the epitaxial structure includes a lower waveguide layer, an active layer, an upper waveguide layer, a p-type electron blocking layer, a p-type confinement layer, a p-type capping layer, and a p-type contact layer sequentially grown on the surface of the n-type confinement layer.

[0020] In one or more embodiments of the present invention, the p-type electrode includes a contact metal and a contact electrode stacked together, wherein the thickness of the contact metal is 1 nm to 300 nm; the material of the contact metal includes one or more of Pd, Ni, Pt, Al, and Ti; the thickness of the contact electrode is greater than or equal to 30 nm; and the material of the contact electrode includes Au.

[0021] In one or more embodiments of the present invention, after the step of forming a p-type electrode on the surface of the current spreading layer, the method further includes:

[0022] The step of bonding a heat sink to the surface of the p-type electrode;

[0023] The heat sink is made of materials including diamond and SiC.

[0024] In one or more embodiments of the present invention, removing the substrate includes: removing the substrate by grinding, thinning, or polishing; or removing the substrate by laser stripping.

[0025] In one or more embodiments of the present invention, the method for fabricating a flip-chip ridge waveguide semiconductor laser further includes: dicing, cleaving, and cavity surface coating of the semiconductor laser epitaxial wafer to obtain a flip-chip ridge waveguide semiconductor laser.

[0026] Another specific embodiment of the present invention provides a flip-chip ridge waveguide semiconductor laser, comprising:

[0027] An n-type electrode has a first surface;

[0028] A mask layer is formed on the first surface, and a strip window is formed within the mask layer, the strip window exposing a portion of the first surface;

[0029] An n-type ridge waveguide is formed within the strip window. The n-type ridge waveguide includes an n-type capping layer formed on the first surface and an n-type confinement layer formed on the surface of the n-type capping layer opposite to the n-type electrode.

[0030] An epitaxial structure is formed on the surface of the n-type confinement layer opposite to the n-type electrode;

[0031] A current spreading layer is formed on the surface of the epitaxial structure opposite to the n-type electrode;

[0032] A p-type electrode is formed on the surface of the current spreading layer opposite to the n-type electrode;

[0033] A heat sink is formed on the surface of the p-type electrode opposite to the n-type electrode.

[0034] Compared with the prior art, the method for fabricating a flip-chip ridge waveguide semiconductor laser and the flip-chip ridge waveguide semiconductor laser of the present invention place the ridge waveguide in the n-type region (n-type capping layer and n-type confinement layer), and the fabrication of the ridge waveguide in the n-type region can be completed without etching the n-type region (n-type capping layer and n-type confinement layer). The n-type region as the ridge waveguide can reduce the differential resistance and threshold voltage, thereby improving the photoelectric conversion efficiency of the semiconductor laser. At the same time, it retains a large ohmic contact area of ​​the p-type contact layer, which is beneficial to the heat dissipation of the overall device, thereby effectively reducing thermal resistance and junction temperature, and improving the performance of the laser.

[0035] The present invention discloses a method for fabricating a flip-chip ridge waveguide semiconductor laser and the flip-chip ridge waveguide semiconductor laser itself. By fabricating a strip-shaped window on a substrate and utilizing lateral epitaxial overgrowth (ELOG) technology, the n-type capping layer and n-type confinement layer are directly formed into a ridge along the strip-shaped window during epitaxial growth. This effectively avoids sidewall damage caused by etching processes in existing technologies, which affects the performance of the semiconductor laser. After fabricating the p-type electrode, the p-type electrode is directly bonded to a heat sink, and then the substrate is removed to fabricate the n-type electrode. This simplifies the flip-chip process of the semiconductor laser, reduces costs, and significantly improves the optical and electrical performance of the semiconductor laser. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a process flow diagram of a method for fabricating a flip-chip ridge waveguide semiconductor laser according to an embodiment of the present invention;

[0038] Figures 2a-2e This is a schematic diagram of the process steps for fabricating a flip-chip ridge waveguide semiconductor laser in one embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of a flip-chip ridge waveguide semiconductor laser in one embodiment of the present invention. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0041] As mentioned in the background section, existing methods for fabricating ridge waveguide semiconductor lasers often involve etching processes. Currently, the main technical approach for fabricating ridge waveguides for lasers, both domestically and internationally, involves photolithography and etching of the p-type confinement layer and the p-type contact layer. However, this traditional method for fabricating ridge waveguides for flip-chip lasers has the following drawbacks:

[0042] 1) The process involves multiple photolithography and etching steps, which increases the complexity of the process and the manufacturing cost;

[0043] 2) The etching process can cause sidewall damage, introduce a large number of non-radiative recombination centers, increase light absorption loss and easily become leakage channels.

[0044] 3) The etching process will damage the surface of the p-type contact layer, and the uneven surface of the p-type contact layer is not conducive to the flip-chip packaging process.

[0045] 4) Most of the p-type contact layer and p-type upper confinement layer are etched away, reducing the ohmic contact area of ​​the p-type contact layer bonded to the heat sink and the conductive channel on the p side, thereby reducing heat dissipation and increasing the operating voltage of the semiconductor laser.

[0046] Furthermore, heat dissipation issues constrain the development of high-power LDs. LDs have very high peak power during operation, which generates a large amount of heat, causing the temperature of the active area to rise rapidly. This can lead to optical catastrophic failures or even burnout of the LD, severely affecting its reliability and lifespan.

[0047] Based on this, the present invention provides a method for fabricating a flip-chip ridge waveguide semiconductor laser and the flip-chip ridge waveguide semiconductor laser itself. By fabricating a strip window on a substrate, and using lateral epitaxial overgrowth (ELOG) technology, the n-type capping layer and the n-type confinement layer are directly formed into a ridge along the strip window during epitaxial growth. By placing the ridge waveguide in the n-type region (n-type capping layer and n-type confinement layer), the fabrication of the n-type ridge waveguide in the n-type region can be completed without etching the n-type region (n-type capping layer and n-type confinement layer). The n-type region as the ridge waveguide can reduce the differential resistance and threshold voltage, thereby improving the photoelectric conversion efficiency of the semiconductor laser. It effectively avoids the sidewall damage caused by the etching process in the prior art, which affects the performance of the semiconductor laser. At the same time, it retains a large ohmic contact area of ​​the p-type contact layer, which is beneficial to the heat dissipation of the overall device, thereby effectively reducing thermal resistance and junction temperature. After the p-type electrode is fabricated, it is directly bonded to the heat sink. Then the substrate is removed and the n-type electrode is fabricated. This simplifies the flip-chip process of semiconductor lasers, reduces costs, and greatly improves the optical and electrical performance of semiconductor lasers.

[0048] like Figure 1 As shown, a method for fabricating a flip-chip ridge waveguide semiconductor laser according to an embodiment of the present invention includes the following steps:

[0049] S1 provides a substrate, and a mask layer is formed on the surface of the substrate;

[0050] S2, Etch the mask layer to create a strip window on the mask layer;

[0051] S3, an n-type cladding layer and an n-type confinement layer are grown sequentially within the strip window to form an n-type ridge waveguide;

[0052] S4, growing an epitaxial structure on the surface of an n-type confinement layer;

[0053] S5, a current spreading layer is formed on the epitaxial structure, and a p-type electrode is formed on the surface of the current spreading layer;

[0054] S6, remove the substrate and form an n-type electrode on the surface of the n-type capping layer to obtain a semiconductor laser epitaxial wafer;

[0055] S7 involves dicing, cleaving, and cavity surface coating of the semiconductor laser epitaxial wafer to obtain a flip-chip ridge waveguide semiconductor laser.

[0056] In step S1, plasma-enhanced chemical vapor deposition (PECVD) is used to grow a mask layer with a thickness of 1 μm-2 μm.

[0057] In step S2, parallel strip windows are formed using photolithography, wet etching, and dry etching processes, with a spacing of 1.5 μm to 3 μm between adjacent strip windows. The cross-section of each strip window is triangular, square, or trapezoidal, and the strip windows expose part of the substrate.

[0058] In step S3, the n-type capping layer and the n-type confinement layer are epitaxially grown using the lateral epitaxial overgrowth (ELOG) technique. Due to the difference in bond energy, the n-type capping layer is deposited much faster on the sidewalls within the strip window than on the mask layer surface. This causes the n-type capping layer to preferentially grow on the sidewalls within the strip window, suppressing its nucleation on the mask layer surface. This allows for lateral epitaxy with a sufficiently large lateral-to-longitudinal growth rate ratio, enabling selective growth of the n-type capping layer. Consequently, the n-type capping layer and the n-type confinement layer directly form a ridge waveguide during the growth process, avoiding the sidewall damage caused by relying on dry etching to form the ridge waveguide in traditional methods.

[0059] In step S3, the thickness of the n-type capping layer is less than the thickness of the mask layer, and the sum of the thicknesses of the n-type capping layer and the n-type confinement layer is greater than or equal to the thickness of the mask layer. That is, the n-type confinement layer grows to cover the mask layer; or the n-type confinement layer grows until its surface away from the n-type capping layer is flush with the surface of the mask layer away from the substrate.

[0060] In step S4, after the n-type confinement layer has grown to cover the mask layer or grown to the point where its surface away from the n-type capping layer is flush with the surface of the mask layer away from the substrate, an epitaxial structure is then grown on the n-type confinement layer. The epitaxial structure may include, sequentially grown on the surface of the n-type confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, a p-type electron blocking layer, a p-type confinement layer, a p-type capping layer, and a p-type contact layer.

[0061] In step S5, a current spreading layer and a p-type electrode are fabricated through photolithography, deposition, and other steps, and a heat sink is directly bonded to the surface of the p-type electrode. The heat sink material can be diamond, SiC, etc. The advantage of this design is that it eliminates the flip-chip process required for existing semiconductor laser flip-chip designs, and because it does not involve etching, it avoids damage to the p-type confinement layer and p-type contact layer, as well as avoiding the reduction of the ohmic contact area of ​​the p-type contact layer, which helps to solve the heat dissipation problem.

[0062] In step S6, the substrate is removed by thinning and polishing. Alternatively, the substrate can be removed by laser lift-off. After substrate removal, an n-type electrode is fabricated on the surface of the n-type capping layer.

[0063] In step S7, the semiconductor laser epitaxial wafer is diced and cleaved, and the resulting bar strips (laser strips formed by multiple semiconductor single tubes arranged side by side) are subjected to cavity surface coating. At this point, the fabrication of the flip-chip ridge waveguide semiconductor laser is complete. The mask layer between each flip-chip ridge waveguide semiconductor laser naturally forms a passivation layer, completing the isolation between the lasers.

[0064] The following detailed description of the fabrication method of the flip-chip ridge waveguide semiconductor laser of this application and the flip-chip ridge waveguide semiconductor laser fabricated by the method is provided through a specific embodiment, so as to further understand the technical solution of this application.

[0065] Please refer to Figure 2a As shown, SiO2 / SiN is first deposited on substrate 10. x Masking materials are used to form a mask layer 20. The mask pattern of strip window 21 is prepared on the mask layer 20 through photolithography, wet etching and other processes, so as to provide a model for subsequent epitaxial growth.

[0066] The substrate 10 is preferably a self-supporting GaN substrate. (SiO2 / SiN) x The mask material is grown using plasma-enhanced chemical vapor deposition (PECVD) to a thickness of 1 μm to 2 μm. Multiple parallel strip windows 21 are fabricated using photolithography, wet etching, and dry etching processes for subsequent epitaxial growth. The spacing between adjacent strip windows 21 is 1.5 μm to 3 μm. The cross-sectional shape of the strip windows 21 can be designed according to the desired ridge shape, and can be any shape such as triangle, square, or trapezoid.

[0067] Please refer to Figure 2b As shown, Figure 2a The substrate 10 with a special shaped mask pattern is placed in the epitaxial equipment chamber, and the n-type capping layer 31 and the n-type confinement layer 32 are epitaxially grown in the strip window 21 using the lateral epitaxial overgrowth (ELOG) technique.

[0068] For example, the n-type capping layer 31 is an n-type GaN capping layer with a thickness of 2 μm and a doping concentration of 5 × 10⁻⁶. 18 cm -3 ~6×10 18 cm -3 The n-type confinement layer 32 is an n-type Al. 0.1 Ga 0.9 The N-confinement layer has a thickness of 1.2 μm and a doping concentration of 3 × 10⁻⁶. 17 cm -3 Epitaxial equipment includes, but is not limited to, metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE).

[0069] Due to the difference in bond energy, GaN capping layers are deposited much faster on strip windows than on the mask surface. This causes the GaN capping layer to preferentially grow on the strip windows, suppressing its nucleation on the mask surface. Lateral epitaxy is then performed with a sufficiently large lateral-to-longitudinal growth rate ratio, enabling selective growth of the GaN capping layer. Consequently, the n-type GaN capping layer and the n-type AlGaN confinement layer directly form ridge waveguides during the growth process, avoiding the sidewall damage caused by relying on dry etching to form ridge waveguides in traditional methods.

[0070] Please refer to Figure 2c As shown, after the n-type AlGaN confinement layer covers the mask layer 20, or the surface of the n-type AlGaN confinement layer facing away from the n-type GaN capping layer is flush with the surface of the mask layer 20 facing away from the substrate 10 so that the strip window 21 is completely filled, the epitaxial structure 40 of the flip-chip ridge waveguide semiconductor laser continues to be grown. The epitaxial structure 40 includes a lower waveguide layer 41, an active layer 42, an upper waveguide layer 43, a p-type electron blocking layer 44, a p-type confinement layer 45, a p-type capping layer 46, and a p-type contact layer 47, which are sequentially grown on the surface of the n-type AlGaN confinement layer.

[0071] For example, undoped In is grown sequentially. 0.07 Ga 0.93 The lower waveguide layer is N-type, with a thickness of 160 nm; undoped In... 0.25 Ga 0.75 The N / GaN active layer has two periods of multiple quantum wells, with the InGaN well width being 3nm–5nm and the GaN barrier width being 8nm–10nm; the undoped In... 0.07 Ga 0.93 N-type waveguide layer, 120 nm thick; p-type Al 0.2 Ga 0.8 An N-electron blocking layer, 15 nm thick, with a doping concentration of 5 × 10⁻⁶. 18 cm -3 p-type Al 0.08 Ga0.92 The N-confinement layer has a thickness of 0.4 μm and a doping concentration of 8 × 10⁻⁶. 18 cm -3 A p-type GaN capping layer, 60 nm thick, with a doping concentration of 1 × 10⁻⁶. 20 cm -3 ; and a p-type InGaN contact layer with a thickness of 5nm to 20nm and a doping concentration of 1×10⁻⁶. 20 cm -3 .

[0072] Please refer to Figure 2d As shown, a current spreading layer 51 and a p-type electrode 52 are fabricated through photolithography, deposition, and other steps, and a heat sink 60 is directly bonded to the surface of the p-type electrode 52. The advantage of this design is that it eliminates the flip-chip process required for existing semiconductor laser flip-chip designs, and because it does not involve etching, it avoids damage to the p-type upper confinement layer and p-type contact layer, as well as avoiding the reduction of the ohmic contact area of ​​the p-type contact layer, which helps to solve the heat dissipation problem.

[0073] For example, the current spreading layer 51 is preferably an ITO layer. The deposition equipment used to deposit the ITO layer and the p-type electrode 52 can be a coating equipment such as electron beam evaporation or magnetron sputtering. An ITO layer of 200 nm is deposited as a partial optical confinement layer using an electron beam evaporation device at a deposition temperature of 300 °C.

[0074] The deposited p-type electrode 52 consists of two layers. The first layer is a contact metal, commonly one or more of Pd, Ni, Pt, Al, and Ti, with a typical thickness of 1 nm to 300 nm. The second layer is the contact electrode, commonly made of Au, with a thickness generally greater than or equal to 30 nm. When the p-type electrode 52 is used in a laser, the preferred electrode material is Ti / Au (100 nm / 500 nm). Commonly used heat sink materials include diamond and SiC.

[0075] Please refer to Figure 2e As shown, the substrate 10 is ground, thinned and polished to remove the substrate 10, and an n-type electrode is prepared on the n-type capping layer 31.

[0076] For example, the substrate 10 is thinned, ground, and polished using a thinning machine, a grinding machine, and a polishing machine to remove the substrate 10, or the substrate 10 is directly removed using laser lift-off. After removing the substrate 10, an n-type electrode 70 is finally deposited on the n-type capping layer 31 using magnetron sputtering. The n-type electrode 70 is preferably a 50nm / 100nm / 50nm / 100nm Ti / Al / Ti / Au electrode.

[0077] The epitaxial wafer of the semiconductor laser is diced and cleaved, and the resulting strips (laser strips formed by multiple semiconductor single tubes arranged side by side) are subjected to cavity surface coating. At this point, the fabrication of the flip-chip ridge waveguide semiconductor laser is complete. The mask layer between each flip-chip ridge waveguide semiconductor laser naturally forms a passivation layer, completing the isolation between the lasers. The structure of a single laser chip is referenced. Figure 3 As shown.

[0078] For example, a laser dicing machine is used to cut the semiconductor laser epitaxial wafer into suitable sizes for cleaving, facilitating subsequent cleaving into strips. The cleaving process uses a Loomis cleaving machine to cut the semiconductor laser epitaxial wafer into single strips, each strip potentially containing multiple semiconductor laser chips. Cavity surface coating is performed using an optical coating machine. The cleaved strips are placed in a fixture, and nine pairs of SiO2 / Ta2O5 are deposited as the back cavity film of the laser, while a single layer of SiO2 is used as the front cavity film. The front cavity surface is coated with a 17% reflective film, and the back cavity surface with a 93% reflective film.

[0079] Compared with the prior art, the method for fabricating a flip-chip ridge waveguide semiconductor laser and the flip-chip ridge waveguide semiconductor laser of the present invention place the ridge waveguide in the n-type region (n-type capping layer and n-type confinement layer), and the fabrication of the ridge waveguide in the n-type region can be completed without etching the n-type region (n-type capping layer and n-type confinement layer). The n-type region as the ridge waveguide can reduce the differential resistance and threshold voltage, thereby improving the photoelectric conversion efficiency of the semiconductor laser. At the same time, it retains a large ohmic contact area of ​​the p-type contact layer, which is beneficial to the heat dissipation of the overall device, thereby effectively reducing thermal resistance and junction temperature, and improving the performance of the laser.

[0080] The present invention discloses a method for fabricating a flip-chip ridge waveguide semiconductor laser and the flip-chip ridge waveguide semiconductor laser itself. By fabricating a strip-shaped window on a substrate and utilizing lateral epitaxial overgrowth (ELOG) technology, the n-type capping layer and n-type confinement layer are directly formed into a ridge along the strip-shaped window during epitaxial growth. This effectively avoids sidewall damage caused by etching processes in existing technologies, which affects the performance of the semiconductor laser. After fabricating the p-type electrode, the p-type electrode is directly bonded to a heat sink, and then the substrate is removed to fabricate the n-type electrode. This simplifies the flip-chip process of the semiconductor laser, reduces costs, and significantly improves the optical and electrical performance of the semiconductor laser.

[0081] refer to Figure 3 As shown, an embodiment of the present invention also provides a flip-chip ridge waveguide semiconductor laser, comprising: a mask layer 20, an n-type ridge waveguide, an epitaxial structure 40, a current spreading layer 51, a p-type electrode 52, a heat sink 60, and an n-type electrode 70.

[0082] The n-type electrode 70 has a first surface, and the n-type electrode 70 is preferably a Ti / Al / Ti / Au electrode with a wavelength of 50nm / 100nm / 50nm / 100nm.

[0083] A mask layer 20 is formed on the first surface. A strip-shaped window 21 is formed within the mask layer 20, exposing a portion of the first surface. The material of the mask layer 20 can be SiO2 / SiN. x The mask material is as follows, and the thickness of the mask layer 20 is 1μm to 2μm. The cross-sectional shape of the strip window 21 can be designed according to the required ridge shape, and can be any shape such as triangle, square, trapezoid, etc.

[0084] An n-type ridge waveguide is formed within the strip window 21. The n-type ridge waveguide includes an n-type capping layer 31 formed on the first surface and an n-type confinement layer 32 formed on the surface of the n-type capping layer 31 facing away from the n-type electrode 70. The thickness of the n-type capping layer 31 is less than the thickness of the mask layer 20, and the sum of the thicknesses of the n-type capping layer 31 and the n-type confinement layer 32 is greater than or equal to the thickness of the mask layer 20.

[0085] For example, the n-type capping layer 31 can be an n-type GaN capping layer with a thickness of 2 μm and a doping concentration of 5 × 10⁻⁶. 18 cm -3 ~6×10 18 cm -3 The n-type confinement layer 32 can be an n-type AlGaN confinement layer with a thickness of 1.2 μm and a doping concentration of 3 × 10⁻⁶. 17 cm -3 .

[0086] The epitaxial structure 40 is formed on the surface of the n-type confinement layer 32 facing away from the n-type electrode 70. The epitaxial structure 40 may include a lower waveguide layer 41, an active layer 42, an upper waveguide layer 43, a p-type electron blocking layer 44, a p-type confinement layer 45, a p-type capping layer 46, and a p-type contact layer 47 sequentially grown on the surface of the n-type confinement layer 32.

[0087] For example, the lower waveguide layer 41 can be undoped In. 0.07 Ga 0.93 The lower waveguide layer is 160 nm thick. The active layer 42 can be undoped In. 0.25 Ga 0.75 The N / GaN active layer has two periods of multiple quantum wells, with the InGaN well width ranging from 3 nm to 5 nm and the GaN barrier width ranging from 8 nm to 10 nm. The upper waveguide layer 43 can be undoped In. 0.07 Ga 0.93 The N-type waveguide layer has a thickness of 120 nm. The p-type electron blocking layer 44 can be a p-type Al. 0.2 Ga0.8 An N-electron blocking layer, 15 nm thick, with a doping concentration of 5 × 10⁻⁶. 18 cm -3 The p-type confinement layer 45 can be a p-type Al 0.08 Ga 0.92 The N-confinement layer has a thickness of 0.4 μm and a doping concentration of 8 × 10⁻⁶. 18 cm -3 The p-type capping layer 46 can be a p-type GaN capping layer with a thickness of 60 nm and a doping concentration of 1 × 10⁻⁶. 20 cm -3 And the p-type contact layer 47 can be a p-type InGaN contact layer with a thickness of 5nm to 20nm and a doping concentration of 1×10⁻⁶. 20 cm -3 .

[0088] A current spreading layer 51 is formed on the surface of the epitaxial structure 40 opposite to the n-type electrode 70. A p-type electrode 52 is formed on the surface of the current spreading layer 51 opposite to the n-type electrode 70. For example, the current spreading layer 51 is preferably an ITO layer. The p-type electrode 52 consists of two layers: the first layer is a contact metal, commonly one or more of Pd, Ni, Pt, Al, Ti, etc., with a common thickness of 1 nm to 300 nm. The second layer is a contact electrode, commonly made of Au, with a thickness generally greater than or equal to 30 nm. When the p-type electrode 52 is used in a laser, the electrode material is preferably Ti / Au (100 nm / 500 nm).

[0089] The heat sink 60 is formed on the surface of the p-type electrode 52 on the side opposite to the n-type electrode 70. Commonly used heat sink materials include diamond and SiC.

[0090] The flip-chip ridge waveguide semiconductor laser of the present invention places the ridge waveguide in the n-type region (n-type capping layer and n-type confinement layer). The n-type region as the ridge waveguide can reduce the differential resistance and threshold voltage, thereby improving the photoelectric conversion efficiency of the semiconductor laser. At the same time, it retains a large ohmic contact area of ​​the p-type contact layer, which is beneficial to the heat dissipation of the overall device, thereby effectively reducing thermal resistance and junction temperature, and improving the performance of the laser.

[0091] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0092] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for fabricating a flip-chip ridge waveguide semiconductor laser, characterized in that, include: A substrate is provided, and a mask layer is formed on the surface of the substrate; The mask layer is etched to create a strip window on the mask layer; An n-type cladding layer and an n-type confinement layer are sequentially grown within the strip window to form an n-type ridge waveguide; An epitaxial structure is grown on the surface of the n-type confinement layer; A current spreading layer is formed on the epitaxial structure, and a p-type electrode is formed on the surface of the current spreading layer; The substrate is removed, and an n-type electrode is formed on the surface of the n-type capping layer to obtain a semiconductor laser epitaxial wafer.

2. The method for fabricating a flip-chip ridge waveguide semiconductor laser according to claim 1, characterized in that, By using photolithography, wet etching, and dry etching processes, parallel strip windows are fabricated on the mask layer, and the strip windows expose a portion of the substrate.

3. The method for fabricating a flip-chip ridge waveguide semiconductor laser according to claim 2, characterized in that, The thickness of the mask layer is 1 μm to 2 μm; and / or, The spacing between adjacent strip windows is 1.5 μm to 3 μm.

4. The method for fabricating a flip-chip ridge waveguide semiconductor laser according to claim 1, characterized in that, Within the strip window, the n-type capping layer and the n-type confinement layer are epitaxially grown using a lateral epitaxial overgrowth technique; and / or, The thickness of the n-type capping layer is less than the thickness of the mask layer, and the sum of the thicknesses of the n-type capping layer and the n-type confinement layer is greater than or equal to the thickness of the mask layer.

5. The method for fabricating a flip-chip ridge waveguide semiconductor laser according to claim 1, characterized in that, The epitaxial structure includes a lower waveguide layer, an active layer, an upper waveguide layer, a p-type electron blocking layer, a p-type confinement layer, a p-type capping layer, and a p-type contact layer, which are sequentially grown on the surface of the n-type confinement layer.

6. The method for fabricating a flip-chip ridge waveguide semiconductor laser according to claim 1, characterized in that, The p-type electrode includes a contact metal and a contact electrode stacked together. The thickness of the contact metal is 1 nm to 300 nm. The material of the contact metal includes one or more of Pd, Ni, Pt, Al, and Ti. The thickness of the contact electrode is greater than or equal to 30 nm. The material of the contact electrode includes Au.

7. The method for fabricating a flip-chip ridge waveguide semiconductor laser according to claim 1, characterized in that, After the step of forming a p-type electrode on the surface of the current spreading layer, the method further includes: The step of bonding a heat sink to the surface of the p-type electrode; The heat sink is made of materials including diamond and SiC.

8. The method for fabricating a flip-chip ridge waveguide semiconductor laser according to claim 1, characterized in that, Removing the substrate includes: The substrate is removed by grinding, thinning, or polishing; or... The substrate is removed by laser.

9. The method for fabricating a flip-chip ridge waveguide semiconductor laser according to claim 1, characterized in that, Also includes: The semiconductor laser epitaxial wafer is diced, cleaved, and subjected to cavity surface coating to obtain a flip-chip ridge waveguide semiconductor laser.

10. A flip-chip ridge waveguide semiconductor laser, characterized in that, include: An n-type electrode has a first surface; A mask layer is formed on the first surface, and a strip window is formed within the mask layer, the strip window exposing a portion of the first surface; An n-type ridge waveguide is formed within the strip window. The n-type ridge waveguide includes an n-type capping layer formed on the first surface and an n-type confinement layer formed on the surface of the n-type capping layer opposite to the n-type electrode. An epitaxial structure is formed on the surface of the n-type confinement layer opposite to the n-type electrode; A current spreading layer is formed on the surface of the epitaxial structure opposite to the n-type electrode; A p-type electrode is formed on the surface of the current spreading layer opposite to the n-type electrode; A heat sink is formed on the surface of the p-type electrode opposite to the n-type electrode.

Images