Quantum well laser and method of fabricating the same

Abstract

The present disclosure provides a quantum well laser and a preparation method thereof. The laser comprises a first electrode, a patterned substrate arranged on an upper surface of the first electrode, an upper surface of the patterned substrate being etched with a groove, an epitaxial layer grown in the groove and extending out of the groove to cover a predetermined area of the upper surface of the patterned substrate, an area of the predetermined area being smaller than an area of the patterned substrate, a filling layer filled between a sidewall of the epitaxial layer and the upper surface of the patterned substrate, a height of the filling layer being greater than a height of the epitaxial layer, and a second electrode located on an upper surface of the epitaxial layer and the filling layer.

Description

Technical Field

[0001] This disclosure relates to the field of optoelectronic devices, specifically to a quantum well laser and its fabrication method. Background Technology

[0002] Silicon-based selective epitaxial III-V quantum well lasers have great application potential in silicon-based monolithic integrated light source solutions. Compared with bonding and thick buffer epitaxial solutions, silicon-based selective epitaxial III-V quantum well laser solutions based on high aspect ratio confinement (ART) technology have advantages such as large-scale integration and compatibility with CMOS processes.

[0003] However, due to the severe lattice mismatch between the InP epitaxial substrate, a typical long-wavelength gain material, and silicon, the active region of silicon-based III-V lasers fabricated using the ART method is limited to the vicinity of the silicon oxide mask strip, thus restricting the active region area to the size parameters of the patterned substrate. Furthermore, because the ART technique typically uses trenches less than 1 μm wide to confine epitaxial defects, the active region area of ​​III-V lasers is small, resulting in high optical field mode leakage loss, low injection efficiency, and insufficient gain provided by the active material during electrical injection, preventing the device from achieving electrically pumped lasing. In addition, the monolithic integration of silicon-based lasers and silicon-based modulators fabricated using the ART method is immature, exhibiting complex processes, high coupling losses, and high costs, limiting its application as a commercial silicon-based high-speed device. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] In view of the above problems, this disclosure provides a quantum well laser and its fabrication method, so as to at least partially solve the technical problems of traditional III-V group lasers, such as small active region area, large optical field mode leakage loss, low injection efficiency, poor gain performance, complex process, large coupling loss and high cost.

[0006] (II) Technical Solution

[0007] This disclosure provides a quantum well laser, comprising: a first electrode; a patterned substrate disposed on the upper surface of the first electrode, wherein a trench is etched on the upper surface of the patterned substrate; an epitaxial layer grown within the trench and extending out of the trench to cover a predetermined area of ​​the upper surface of the patterned substrate, wherein the area of ​​the predetermined area is smaller than the area of ​​the patterned substrate; a filling layer filling the space between the sidewall of the epitaxial layer and the upper surface of the patterned substrate, wherein the height of the filling layer is greater than the height of the epitaxial layer; and a second electrode located on the upper surfaces of the epitaxial layer and the filling layer.

[0008] According to an embodiment of this disclosure, the patterned substrate includes a silicon substrate and a mask strip; wherein the trench is formed by etching a selected area on the surface of the silicon substrate; the mask strip is located on the upper surface of the silicon substrate and does not cover the trench.

[0009] According to embodiments of this disclosure, the epitaxial layer comprises, from bottom to top: a bottom conductive layer, a bottom conductive transition layer, an undoped bottom waveguide layer, an undoped multiple quantum well layer, an undoped upper waveguide layer, a first upper conductive layer, a grating structure layer, a second upper conductive layer, and a contact layer.

[0010] According to embodiments of this disclosure, the filling layer comprises, from the inside out, a first inorganic insulating material layer, an organic insulating material layer, and a second inorganic insulating material layer.

[0011] According to embodiments of this disclosure, the material of the epitaxial layer is a III-V group compound.

[0012] According to an embodiment of this disclosure, the first electrode is made of TiAu alloy, the second electrode is made of TiAu, TiPtAu or AuZn alloy, and the pad of the second electrode is circular.

[0013] According to embodiments of this disclosure, the grating structure layer is a first-order or higher-order Bragg grating.

[0014] According to embodiments of this disclosure, the undoped multi-quantum-well layer is made of InGaAsP or AlGaInAs material, with 3 to 8 quantum wells and a quantum well thickness of 3 to 7 nm. The number of barriers is greater than the number of quantum wells, the barrier thickness is 10 to 15 nm, and the bandgap wavelength is 1.1 to 1.3 μm.

[0015] A second aspect of this disclosure provides a method for fabricating a quantum well laser, comprising: etching trenches in a selected area on the surface of a silicon substrate to obtain a patterned substrate with mask strips on its surface; growing an epitaxial layer in a predetermined region on the upper surface of the patterned substrate, extending from and within the trenches of the patterned substrate, wherein the area of ​​the predetermined region is smaller than the area of ​​the patterned substrate; depositing a filler layer between the sidewalls of the epitaxial layer and the upper surface of the patterned substrate, wherein the height of the filler layer is greater than the height of the epitaxial layer; photolithographically etching and depositing a second electrode on the upper surfaces of the epitaxial layer and the filler layer; and obtaining a first electrode on the lower surface of the patterned substrate by thinning and deposition techniques.

[0016] According to embodiments of this disclosure, the step of growing an epitaxial layer in a predetermined region on the upper surface of the patterned substrate within a trench in the patterned substrate and extending from the trench using epitaxial technology includes: obtaining a bottom conductive layer inside the silicon substrate of the trench using low-temperature epitaxy; obtaining a lower conductive transition layer inside the mask strip and on its upper surface using low-temperature and high-temperature epitaxy; obtaining an undoped lower waveguide layer, an undoped multiple quantum well layer, an undoped upper waveguide layer, a first upper conductive layer, and a grating structure layer sequentially from bottom to top on the upper surface of the mask strip and the upper surface of the lower conductive transition layer using high-temperature epitaxy; and obtaining a second upper conductive layer and a contact layer sequentially from bottom to top on the upper surface of the mask strip and the upper surface of the grating structure layer using high-temperature secondary epitaxy.

[0017] (III) Beneficial Effects

[0018] The quantum well laser disclosed herein enhances the optical field confinement factor and reduces mode loss by increasing the gain area of ​​the III-V group quantum well in the epitaxial layer, thereby promoting electrically pumped lasing. Simultaneously, single-mode output is achieved by employing a Bragg grating in the grating structure layer of the epitaxial layer. Furthermore, parasitic capacitance is reduced by using a low-dielectric-constant filling material and a circular pad as the second electrode. Attached Figure Description

[0019] To gain a more complete understanding of this disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which:

[0020] Figure 1 A schematic diagram of a quantum well laser provided according to an embodiment of the present disclosure is shown.

[0021] Figure 2 A schematic diagram of a patterned substrate for a quantum well laser provided according to an embodiment of the present disclosure is shown.

[0022] Figure 3 A schematic diagram of the epitaxial layer of a quantum well laser provided according to an embodiment of the present disclosure is shown.

[0023] Figure 4 This schematically illustrates a structural diagram of the filling layer of a quantum well laser provided according to an embodiment of the present disclosure;

[0024] Figure 5 A top view schematically illustrating a quantum well laser structure provided according to an embodiment of the present disclosure;

[0025] Figure 6 The small-signal response curve of a quantum well laser structure provided according to an embodiment of the present disclosure is schematically shown.

[0026] Figure 7A flowchart illustrating a method for fabricating a quantum well laser according to an embodiment of the present disclosure is shown schematically.

[0027] Explanation of reference numerals in the attached figures:

[0028] 10 - First electrode;

[0029] 11-Patterned substrate;

[0030] 111-Silicon substrate;

[0031] 112 - Mask strip;

[0032] 12-Epipolar layer;

[0033] 121 - Bottom conductive layer;

[0034] 122-lower conductive transition layer;

[0035] 123 - Undoped lower waveguide layer;

[0036] 124-Undoped multiple quantum well layer;

[0037] 125 - Undoped upper waveguide layer;

[0038] 126 - First upper conductive layer;

[0039] 127 - Grating structure layer;

[0040] 128 - Second upper conductive layer;

[0041] 129 - Contact layer;

[0042] 13-Fill layer;

[0043] 131 - First inorganic insulating material layer;

[0044] 132 - Organic insulating material layer;

[0045] 133 - Second inorganic insulating material layer;

[0046] 14 - Second electrode;

[0047] 15-Non-light-emitting end face;

[0048] 16-Light exit end face. Detailed Implementation

[0049] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0050] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0051] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0052] Figure 1 A schematic diagram of the structure of a quantum well laser provided according to an embodiment of the present disclosure is shown.

[0053] like Figure 1 As shown, the quantum well laser includes: a first electrode 10; a patterned substrate 11 disposed on the upper surface of the first electrode 10, wherein a trench is etched on the upper surface of the patterned substrate 11; an epitaxial layer 12 grown in the trench and extending out of the trench, covering a predetermined area on the upper surface of the patterned substrate 11, wherein the area of ​​the predetermined area is smaller than the area of ​​the patterned substrate 11; a filling layer 13 filling the space between the sidewall of the epitaxial layer 12 and the upper surface of the patterned substrate 11, wherein the height of the filling layer 13 is greater than the height of the epitaxial layer 12; and a second electrode 14 located on the upper surfaces of the epitaxial layer 12 and the filling layer 13.

[0054] In embodiments of this disclosure, trenches are formed on the surface of the patterned substrate 11 to guide the growth direction of the epitaxial layer 12 and facilitate the formation of the desired optical cavity structure. The material of the epitaxial layer 12 is a III-V compound, which possesses excellent light-emitting properties and carrier mobility; that is, the quantum well laser in embodiments of this disclosure is a silicon-based III-V quantum well laser. The quantum well structure is achieved by precisely controlling the growth thickness and composition of different materials in the epitaxial layer 12, thereby forming an energy potential well in the energy band to allow electrons and holes to recombine at specific energy states, emitting light of a specific wavelength. The filling layer 13 provides a smooth interface with the epitaxial layer 12.

[0055] It is understood that the quantum well laser provided in this disclosure can increase the gain area of ​​the quantum well by optimizing the growth conditions of the epitaxial layer and the design of the patterned substrate, thereby improving the output power and efficiency of the laser. Simultaneously, by precisely controlling the refractive index difference between the epitaxial layer and the filling layer, the confinement of the light field in the quantum well structure can be enhanced, mode loss reduced, and the performance stability of the laser improved. This allows for the output of high-speed direct modulation signals via electrical pumping, facilitating large-scale integration and compatibility with CMOS processes.

[0056] Figure 2 A schematic diagram of a patterned substrate for a quantum well laser provided according to an embodiment of the present disclosure is shown.

[0057] like Figure 2 As shown, the patterned substrate 11 includes a silicon substrate 111 and a mask strip 112. A trench is etched in a selected area on the surface of the silicon substrate 111, and the mask strip 112 is located on the upper surface of the silicon substrate 111 and does not cover the trench.

[0058] Optionally, the trenches on the upper surface of the silicon substrate 111 are V-shaped trenches with a width of 500~1000 nm. The silicon substrate 111 is an N-type silicon substrate with a doping concentration of 2e17~3e18 cm⁻¹. -3 After thinning, the thickness is 50~100 μm.

[0059] Optionally, the mask strip 112 is a silicon oxide mask strip with a mask height of 1000~1500 nm and a period of 3~10 μm.

[0060] Figure 3 A schematic diagram of the epitaxial layer of a quantum well laser provided according to an embodiment of the present disclosure is shown.

[0061] like Figure 3 As shown, the epitaxial layer 12 includes, from bottom to top, the following layers: bottom conductive layer 121, bottom conductive transition layer 122, undoped bottom waveguide layer 123, undoped multi-quantum well layer 124, undoped top waveguide layer 125, first top conductive layer 126, grating structure layer 127, second top conductive layer 128 and contact layer 129.

[0062] For example, the bottom conductive layer 121 is an N-type GaAs layer disposed within the N-type silicon substrate of the V-shaped trench of the patterned substrate 11, and the doping concentration of the bottom conductive layer 121 is 1e17~1e18 cm⁻¹. -3 The thickness is 300~800 nm, and the upper surface is the {001} plane.

[0063] For example, the lower conductive transition layer 122 is a lower N-type InP layer, disposed within the mask strip 112 and on the upper surface of the patterned substrate 11, with a doping concentration of 1e17~1e18 cm⁻¹. -3 The thickness is 1300~1600 nm, and the upper surface is {110}, {111}, and {001}.

[0064] For example, the undoped lower waveguide layer 123 is disposed on the upper surface of the mask strip 112 of the patterned substrate 11 and the upper surface of the lower conductive transition layer 122. It can be InGaAsP or AlGaInAs material, with a thickness of 20~100 nm and a bandgap wavelength of 1.1~1.3 μm.

[0065] In the embodiments of this disclosure, an undoped multi-quantum-well layer 124 is disposed on the upper surface of the mask strip 112 of the patterned substrate 11 and the upper surface of the undoped lower waveguide layer 123. It is made of InGaAsP or AlGaInAs material, has 3 to 8 quantum wells, a quantum well thickness of 3 to 7 nm, a gain spectrum peak in the C-band or O-band, and a compressive strain of 0 to 1%. The number of barriers is greater than the number of quantum wells, and can be the number of quantum wells plus one. The barrier thickness is 10 to 15 nm, the bandgap wavelength is 1.1 to 1.3 μm, and the tensile strain is 0 to 0.4%.

[0066] For example, an undoped upper waveguide layer 125 is disposed on the upper surface of the mask strip 112 of the patterned substrate 11 and the upper surface of the undoped multiple quantum well layer 124. It can be InGaAsP or AlGaInAs material, with a thickness of 20~100 nm and a bandgap wavelength of 1.1~1.3 μm.

[0067] For example, the first upper conductive layer 126 is a first upper P-type InP layer, disposed on the upper surface of the mask strip 112 of the patterned substrate 11 and the upper surface of the undoped upper waveguide layer 125, with a doping concentration of 5e16~1e17 cm⁻¹. -3 The thickness is 50~100nm, and the upper surface is {110}, {111}, and {001}.

[0068] In the embodiments of this disclosure, the grating structure layer 127 is a first-order or higher-order Bragg grating, made of InGaAsP, with a bandgap wavelength of 1.1~1.2 μm. The grating structure layer 127 can be a P-type grating layer, disposed on the upper surface of the mask strip 112 of the patterned substrate 11 and the upper surface of the first upper conductive layer 126, with a doping concentration of 5e16~1e17 cm⁻¹. -3 The thickness is 50~80 nm, and the upper surface is {110}, {111}, and {001}. The Bragg center wavelength of the grating structure layer 127 is in the C-band or O-band, and the upper surface of the Bragg grating is {111} and {001}.

[0069] Understandably, single-mode output of a laser can be achieved by using a Bragg grating.

[0070] For example, the second upper conductive layer 128 can be a second upper P-type InP layer, disposed on the upper surface of the mask strip 112 of the patterned substrate 11 and the upper surface of the grating structure layer 127, with a doping concentration of 1e17~5e17 cm⁻¹. -3 The thickness is 1000~1200nm, and the upper surface is {110}, {111}, and {001}.

[0071] For example, the contact layer 129 can be a p-type InGaAs contact layer, disposed on the upper surface of the mask strip 112 of the patterned substrate 11 and the upper surface of the second upper conductive layer 128, with a doping concentration of 5e18~1e19 cm⁻¹. -3 The thickness is 100~200nm, and the upper surface is {110}, {111}, and {001}.

[0072] Figure 4 The schematic diagram illustrates the structure of the filling layer of a quantum well laser provided according to an embodiment of the present disclosure.

[0073] like Figure 4 As shown, the filling layer 13 includes, from the inside out, a first inorganic insulating material layer 131, an organic insulating material layer 132, and a second inorganic insulating material layer 133.

[0074] It should be noted that the selection of the filler layer 13 material should take into account its refractive index, dielectric constant, and compatibility with the epitaxial layer. A filler material with a low dielectric constant helps reduce parasitic capacitance and improve laser performance.

[0075] For example, the first inorganic insulating material layer 131 is silicon oxide or silicon nitride, with a thickness of 100~300 nm.

[0076] For example, the organic insulating material layer 132 is polyimide or benzocyclobutene with a thickness of 2000~2400 nm.

[0077] For example, the second inorganic insulating material layer 133 is silicon oxide or silicon nitride, with a thickness of 200~400 nm.

[0078] Figure 5 A top view schematically illustrates a quantum well laser structure provided according to an embodiment of the present disclosure.

[0079] In embodiments of this disclosure, such as Figure 5 As shown, the first electrode 10 is an N-face electrode made of TiAu alloy and is used to provide current input.

[0080] The second electrode 14 is a P-side electrode made of TiAu, TiPtAu, or AuZn alloy, used to provide current input and collect photons generated by the quantum well structure. The electrode pad of the second electrode 14 is circular with a diameter of 70~100 μm.

[0081] Understandably, by using low dielectric constant filling materials and circular electrode pad design, the parasitic capacitance and contact resistance of the laser can be effectively reduced, thereby improving its high-speed modulation capability and stability.

[0082] In some exemplary embodiments, the cavity length of the quantum well laser is 100~300 μm, the non-emitting end face 15 of the laser is coated with a high reflectivity film with a reflectivity of 90~95%, and the emitting end face 16 of the laser is a natural cleavage surface or a cavity surface etched by a focused ion beam.

[0083] Figure 6 The small-signal response curve of a quantum well laser structure provided according to an embodiment of the present disclosure is illustrated schematically.

[0084] like Figure 6 As shown, the 3dB cutoff bandwidth of the quantum well laser provided in this embodiment increases with current injection, and the 3dB bandwidth can exceed 10 GHz.

[0085] Figure 7 A flowchart illustrating a method for fabricating a quantum well laser according to an embodiment of the present disclosure is shown schematically.

[0086] like Figure 7 As shown, this specifically includes operations S1-S5.

[0087] In operation S1, trenches are etched in a selected area on the surface of silicon substrate 111 to obtain a patterned substrate 11 with a mask strip 112 on the surface.

[0088] Specifically, a patterned substrate 11 with silicon oxide mask strips 112 and V-shaped trenches on the surface is obtained on an N-type silicon substrate 111 by deposition (such as plasma-enhanced chemical vapor deposition), photolithography (such as contact photolithography) and etching (such as wet and dry etching).

[0089] In operation S2, an epitaxial layer 12 is grown in a predetermined region on the upper surface of the patterned substrate 11 by means of epitaxial technology, within the trenches of the patterned substrate 11 and extending out of the trenches, wherein the area of ​​the predetermined region is smaller than the area of ​​the patterned substrate 11.

[0090] Specifically, using epitaxial techniques, such as metal-organic chemical vapor deposition, a bottom conductive layer 121, a lower conductive transition layer 122, an undoped lower waveguide layer 123, an undoped multiple quantum well layer 124, an undoped upper waveguide layer 125, a first upper conductive layer 126, and a grating structure layer 127 are formed on a patterned substrate 11. Then, using photolithography and etching methods, such as electron beam lithography, a Bragg grating is formed within the grating structure layer 127. Finally, using epitaxial methods, a second upper conductive layer 128 and a contact layer 129 are formed on the grating structure layer 127.

[0091] In operation S3, a fill layer 13 is deposited between the sidewall of the epitaxial layer 12 and the upper surface of the patterned substrate 11, the height of the fill layer 13 being greater than the height of the epitaxial layer 12.

[0092] Specifically, a filling layer 13 is obtained on both sides of the epitaxial layer 12 through deposition, photolithography and etching techniques. The deposition method may include plasma-enhanced chemical vapor deposition.

[0093] It should be noted that when the filler layer is made of BCB (benzocyclobutene) or PI (polyimide), it is usually applied by spin coating (also known as spin coating) rather than by deposition.

[0094] In operation S4, a second electrode is photolithographically etched and deposited on the upper surface of the epitaxial layer and the filling layer.

[0095] A second electrode (P-side electrode) is obtained on the upper surface of the epitaxial layer 12 and the filling layer 13 using photolithography and deposition (such as sputtering) techniques.

[0096] In operation S5, a first electrode (N-face electrode) is obtained on the lower surface of a patterned substrate through thinning and deposition techniques.

[0097] Finally, silicon-based group III-V quantum well lasers were obtained through alloying, cleavage, and deposition techniques. In this process, alloying methods, such as rapid thermal annealing, were used to adjust the bandgap in the quantum well structure, thereby optimizing the laser's emission wavelength and efficiency. Furthermore, focused ion beam etching was used to guide the cleavage process along specific crystal planes, resulting in high-quality crystal wafers and reducing damage and defects during the cleavage process.

[0098] Based on the above embodiments, in this embodiment, the epitaxial layer 12 is grown in a predetermined region on the upper surface of the patterned substrate 11 within the trenches of the patterned substrate 11 and extending out of the trenches using epitaxial technology. This includes: obtaining a bottom conductive layer 121 inside the silicon substrate 111 of the trench using low-temperature epitaxial technology; obtaining a lower conductive transition layer 122 inside the mask strip 112 and on its upper surface using low-temperature and high-temperature epitaxial technology; obtaining an undoped lower waveguide layer 123, an undoped multiple quantum well layer 124, an undoped upper waveguide layer 125, a first upper conductive layer 126, and a grating structure layer 127 sequentially from bottom to top on the upper surface of the mask strip 112 and the upper surface of the lower conductive transition layer 122 using high-temperature epitaxial technology; and obtaining a second upper conductive layer 128 and a contact layer 129 sequentially from bottom to top on the upper surface of the mask strip 112 and the upper surface of the grating structure layer 127 using high-temperature secondary epitaxial technology.

[0099] Specifically, a bottom conductive layer 121 is obtained within a V-groove N-type silicon substrate 111 using a low-temperature epitaxy method. Then, a lower conductive transition layer 122 is sequentially obtained within and on the upper surface of a mask strip 112 using both low-temperature and high-temperature epitaxy methods. Next, an undoped lower waveguide layer 123, an undoped multiple quantum well layer 124, an undoped upper waveguide layer 125, a first upper conductive layer 126, and a grating structure layer 127 are sequentially obtained on the upper surface of the mask strip 112 and the upper surface of the lower conductive transition layer 122 using a high-temperature secondary epitaxy method. Finally, a second upper conductive layer 128 and a contact layer 129 are obtained on the upper surface of the mask strip 112 and the upper surface of the grating structure layer 127 using a high-temperature secondary epitaxy method.

[0100] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0101] Although this disclosure has been shown and described with reference to specific exemplary embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made to this disclosure without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Therefore, the scope of this disclosure should not be limited to the above embodiments, but should be defined not only by the appended claims, but also by their equivalents.

Claims

1. A quantum well laser, characterized in that, include: First electrode; A patterned substrate is disposed on the upper surface of the first electrode, and a trench is etched on the upper surface of the patterned substrate; An epitaxial layer is grown within the trench and extends out of the trench, covering a predetermined area on the upper surface of the patterned substrate, wherein the area of ​​the predetermined area is smaller than the area of ​​the patterned substrate. The epitaxial layer, from bottom to top, includes: a bottom conductive layer, a bottom conductive transition layer, an undoped bottom waveguide layer, an undoped multiple quantum well layer, an undoped top waveguide layer, a first top conductive layer, a grating structure layer, a second top conductive layer, and a contact layer. A filler layer is provided between the sidewall of the epitaxial layer and the upper surface of the patterned substrate, wherein the height of the filler layer is greater than the height of the epitaxial layer. The second electrode is located on the upper surface of the epitaxial layer and the filling layer.

2. The quantum well laser according to claim 1, characterized in that, The patterned substrate includes: Silicon substrate and mask strip; wherein, The trench is formed by etching within a selected area on the surface of the silicon substrate. The mask strip is located on the upper surface of the silicon substrate and does not cover the trench.

3. The quantum well laser according to claim 1, characterized in that, The filling layer comprises, from the inside out, the following: The material consists of a first inorganic insulating layer, an organic insulating layer, and a second inorganic insulating layer.

4. The quantum well laser according to claim 1, characterized in that, The material of the epitaxial layer is a III-V group compound.

5. The quantum well laser according to claim 1, characterized in that, The first electrode is made of TiAu alloy, the second electrode is made of TiAu, TiPtAu or AuZn alloy, and the pad of the second electrode is circular.

6. The quantum well laser according to claim 3, characterized in that, The grating structure layer is a first-order or higher-order Bragg grating.

7. The quantum well laser according to claim 3, characterized in that, The undoped multi-quantum-well layer is made of InGaAsP or AlGaInAs material, with 3 to 8 quantum wells and a thickness of 3 to 7 nm. The number of barriers is greater than the number of quantum wells, with a barrier thickness of 10 to 15 nm and a bandgap wavelength of 1.1 to 1.3 μm.

8. A method for fabricating a quantum well laser, characterized in that, include: Trenches are etched in a selected area on the surface of a silicon substrate to obtain a patterned substrate with mask strips on the surface; Using epitaxial technology, an epitaxial layer is grown in a predetermined region on the upper surface of the patterned substrate within and extending from the trenches of the patterned substrate, wherein the area of ​​the predetermined region is smaller than the area of ​​the patterned substrate; wherein the epitaxial layer comprises, from bottom to top: a bottom conductive layer, a bottom conductive transition layer, an undoped bottom waveguide layer, an undoped multiple quantum well layer, an undoped upper waveguide layer, a first upper conductive layer, a grating structure layer, a second upper conductive layer, and a contact layer; A filler layer is deposited between the sidewall of the epitaxial layer and the upper surface of the patterned substrate, the height of the filler layer being greater than the height of the epitaxial layer; A second electrode is photolithographically etched and deposited on the upper surface of the epitaxial layer and the filling layer; A first electrode is obtained on the lower surface of the patterned substrate using thinning and deposition techniques.

9. The method for fabricating a quantum well laser according to claim 8, characterized in that, The step of growing an epitaxial layer in a predetermined region on the upper surface of the patterned substrate within and extending from trenches in the patterned substrate using epitaxial technology includes: A bottom conductive layer is obtained inside the silicon substrate of the trench using low-temperature epitaxy technology. A lower conductive transition layer is obtained on the inner side and upper surface of the mask strip using low-temperature and high-temperature epitaxial techniques. Using high-temperature epitaxy, an undoped lower waveguide layer, an undoped multiple quantum well layer, an undoped upper waveguide layer, a first upper conductive layer, and a grating structure layer are sequentially obtained from bottom to top on the upper surface of the mask strip and the upper surface of the lower conductive transition layer. Using high-temperature secondary epitaxy technology, a second upper conductive layer and a contact layer are sequentially obtained from bottom to top on the upper surface of the mask strip and the upper surface of the grating structure layer.

Images