Fabrication Method of Active Feedback Laser and Active Feedback Laser

Abstract

The present application provides a method for fabricating an active feedback laser and an active feedback laser. The method includes: sequentially growing a buffer layer and an active region structure on a deoxidized substrate to obtain a laser growth structure; dividing the laser growth structure into a DFB region and an IFB region, and performing bandgap blue shift on the quantum dot active region in the IFB region through regional annealing to obtain a first-stage laser structure, then sequentially performing ridge waveguide etching and coplanar N-type electrode region etching, and performing sidewall grating etching on the ridge waveguide corresponding to the DFB region; and performing electrical isolation etching at the adjacent position of the DFB region and the IFB region to obtain an active feedback laser. By integrating a quantum dot DFB laser and a quantum dot IFB region with bandgap blue shift, the problem that it is difficult to meet its application in low-cost high-speed direct modulation due to the low modulation bandwidth of the quantum dot gain medium laser is solved, and the low-cost requirement of high-speed direct modulation quantum dot lasers is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor lasers, and particularly to a manufacturing method of an active feedback laser and an active feedback laser. Background Art

[0002] Semiconductor distributed feedback (DFB) lasers have become important light sources for optical fiber communication and free-space optical communication due to their excellent single-mode characteristics, modulation characteristics, and mass production advantages. Currently, commercial lasers in optical communication networks are mainly InP-based quantum well DFB lasers. However, due to the limitations of the materials themselves, their output power varies significantly with temperature and often requires external temperature control, making it difficult to meet the requirements of low cost and low power consumption. In addition, quantum well lasers are extremely sensitive to optical feedback. As the feedback light increases, it will cause an increase in the relative intensity noise (RIN) of the laser, broadening of the laser linewidth, and the occurrence of coherent collapse. Therefore, an optical isolator needs to be introduced to reduce optical feedback, which further increases the cost and complexity of the optical communication system.

[0003] In recent years, with the development of 5G technology, data center, and access network technology, the system requires a large number of low-cost optical transceiver devices. High-speed directly modulated DFB lasers have become the core devices in these application scenarios.

[0004] No refrigeration, no isolator, wide-temperature operation, and high modulation rate are the technical requirements for such applications and also an important development direction for major manufacturers at home and abroad. Quantum dot gain media have strong three-dimensional quantum confinement effects, material differential gain, and low linewidth enhancement factors. In particular, 1.3μm InAs / GaAs quantum dot DFB lasers have shown many advantages such as low threshold current, high temperature stability, low linewidth enhancement factor, and high anti-reflection. It can work without temperature control and isolator, thereby greatly reducing cost expenditure, energy consumption, and device size, and is expected to become an important light source for next-generation optical communication and optical interconnection systems.

[0005] However, due to the limitations of the quantum dot gain material, such as a large damping factor and a long carrier capture time in the active region, the modulation bandwidth of lasers based on quantum dot gain media is relatively low, making it difficult to meet their applications in low-cost high-speed direct modulation. Summary of the Invention

[0006] The present application aims to solve at least one of the technical problems in the related art to some extent.

[0007] To this end, the first object of the present application is to propose a manufacturing method of an active feedback laser to realize an active feedback laser with low cost and high-speed direct modulation, and to solve the problem in the related art that it is difficult to meet its application in low-cost high-speed direct modulation due to the low modulation bandwidth of the quantum dot gain medium laser.

[0008] The second object of the present application is to propose an active feedback laser.

[0009] To achieve the above object, an embodiment of the first aspect of the present application proposes a manufacturing method of an active feedback laser, including:

[0010] A manufacturing method of an active feedback laser, characterized by including the following steps:

[0011] Performing high-temperature deoxidation treatment on the substrate to obtain a deoxidized substrate with the surface oxide layer removed;

[0012] Sequentially growing a buffer layer and the active region structure of the active feedback laser on the deoxidized substrate to obtain a laser growth structure;

[0013] Dividing the laser growth structure into a distributed feedback (DFB) region and an integrated feedback (IFB) region, and performing bandgap blue shift on the quantum dot active region of the IFB region through regional annealing technology to obtain a first-stage laser structure with increased bandwidth;

[0014] Performing ridge waveguide etching and coplanar N-type electrode region etching on the surface of the first-stage laser structure in sequence to obtain a second-stage laser structure with a ridge waveguide and a coplanar N-type electrode region;

[0015] Performing sidewall grating etching on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure; and performing electrical isolation etching at the adjacent position of the DFB region and the IFB region to obtain a third-stage laser structure;

[0016] Coating a protective layer and an insulating layer on different regions of the third-stage laser structure respectively, and evaporating positive and negative electrodes at corresponding positions of the DFB region and the IFB region to obtain a fourth-stage laser structure;

[0017] Performing coating treatment on the fourth-stage laser structure to obtain an active feedback laser.

[0018] In some implementation manners, the sequentially growing a buffer layer and the active region structure of the active feedback laser on the deoxidized substrate to obtain a laser growth structure; includes:

[0019] Growing a GaAs N-type contact layer on the deoxidized substrate;

[0020] Above the GaAs N-type contact layer, a superlattice of N-type doped AlxGa1-xAs / GaAs is grown;

[0021] Above the superlattice of N-type doped AlxGa1-xAs / GaAs, a confinement layer of N-type AlxGa1-xAs is grown;

[0022] Above the confinement layer, a superlattice of undoped AlxGa1-xAs / GaAs is grown;

[0023] Above the superlattice of undoped AlxGa1-xAs / GaAs, a layer of GaAs is grown, and a layer of AlGaAs is grown on the GaAs, and taking AlGaAs / GaAs as one period, the first 12 periods of AlGaAs / GaAs are continuously grown;

[0024] Above the first 12 periods of 1nm AlGaAs / 1nm GaAs, an undoped GaAs lower waveguide layer is grown;

[0025] Above the GaAs lower waveguide layer, a quantum dot active region based on the DWELL structure in the well is grown;

[0026] Above the quantum dot active region, an undoped GaAs upper waveguide layer is grown;

[0027] Above the GaAs upper waveguide layer, the second 12 periods of 1nm AlGaAs / 1nm GaAs are continuously grown;

[0028] Above the second 12 periods of 1nm AlGaAs / 1nm GaAs, a strained superlattice of undoped AlxGa1-xAs / GaAs is grown;

[0029] Above the strained superlattice, a confinement layer of p-type AlxGa1-xAs is grown;

[0030] Above the p-type AlxGa1-xAs confinement layer, a strained superlattice of p-type doped AlxGa1-xAs / GaAs is grown;

[0031] Above the strained superlattice of p-type doped AlxGa1-xAs / GaAs, a GaAs P-type metal contact layer is grown.

[0032] In some implementations, the total thickness of the GaAs lower waveguide layer, the quantum dot active region based on the DWELL structure, and the GaAs upper waveguide layer is less than 300nm.

[0033] In some implementations, above the GaAs lower waveguide layer, a quantum dot active region based on a quantum dot DWELL structure in a well is grown; including:

[0034] Above the GaAs lower waveguide layer, an In0. 15 Ga0. 85 As quantum well and multiple layers of InAs quantum dots are grown in sequence;

[0035] Above the multiple layers of InAs quantum dots, an In0. 15 Ga0. 85 As quantum well and GaAs are deposited; and high-temperature annealing is performed;

[0036] Above the deposited In0. 15 Ga0. 85 As quantum well and GaAs, a GaAs spacer layer is grown; wherein, the GaAs spacer layer sequentially includes an undoped GaAs layer, a p-type doped GaAs layer, and an undoped GaAs layer from bottom to top.

[0037] In some implementations, when the quantum dot active region in the IFB region is subjected to bandgap blue shift through area annealing technology, the blue shift value is greater than 20 meV.

[0038] In some implementations, on the surface of the first-stage laser structure, ridge waveguide etching and coplanar N-type electrode region etching are sequentially performed; including:

[0039] Ridge waveguide etching is performed on the surface of the first-stage laser structure;

[0040] A pattern window is prepared in a preset region on the side of the ridge waveguide, and a preset pattern is etched in the preset region to expose the N-type contact layer, and the corresponding region of the exposed N-type contact layer is used as the coplanar N-type electrode region.

[0041] In some implementations, on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure, sidewall grating etching is performed; and electrical isolation etching is performed at the adjacent position of the DFB region and the IFB region; including:

[0042] The grating period is set by laser detuning technology, and based on the grating period, sidewall grating etching is performed on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure; wherein, the middle of the grating has a phase shift of λ / 4, and the λ is the wavelength of the laser;

[0043] Perform an electrical isolation etch at the adjacent position of the DFB region and the IFB region to disconnect the P-type metal contact layer between the DFB region and the IFB region.

[0044] In some implementations, depositing a protective layer and an insulating layer on different regions of the third-stage laser structure respectively, and evaporating positive and negative electrodes at corresponding positions of the DFB region and the IFB region; includes:

[0045] Deposit a protective layer on the exposed DFB region to the air;

[0046] Deposit an insulating layer on the third-stage laser structure;

[0047] Perform graphic processing and top-layer windowing on the protective layer and the insulating layer to obtain a laser sample exposing the P-type metal contact layer of the ridge waveguide;

[0048] Spin-coat a planarizing material and perform planarizing etching on the laser sample to obtain a planarized laser sample;

[0049] For the DFB region and the IFB region, evaporate a positive electrode on the P-type metal contact layer and evaporate a negative electrode on the coplanar N-type electrode region.

[0050] In some implementations, performing a high-temperature deoxidation treatment on the substrate to obtain a deoxidized substrate with the surface oxide layer removed; includes:

[0051] Thin the substrate to obtain a laser sample after thinning treatment;

[0052] Perform bar cleavage on the laser sample after thinning treatment;

[0053] Deposit a high-reflection film on the end face of the IFB region and deposit an antireflection film on the end face of the DFB region.

[0054] To achieve the above object, an active feedback laser is proposed in the second aspect embodiment of the present application, which is characterized in that it includes a substrate and a buffer layer and an active region structure of the active feedback laser formed on the substrate in sequence; the active region structure is divided into a distributed feedback DFB region and an integrated feedback IFB region, and the IFB region is a region where the bandgap blue shift is achieved through the region annealing technology; the surfaces of the DFB region and the IFB region are both provided with a ridge waveguide and a coplanar N-type electrode region; a grating structure is provided on the side wall of the ridge waveguide in the DFB region; a groove for electrical isolation is provided at the adjacent position of the DFB region and the IFB region; positive and negative electrodes are provided at corresponding positions of the DFB region and the IFB region.

[0055] The manufacturing method of the active feedback laser provided by this application and the manufactured active feedback laser integrate a quantum dot DFB laser and a quantum dot IFB region with a blue-shifted bandgap to obtain the active feedback laser, solving the problem that it is difficult to meet its application in low-cost high-speed direct modulation due to the low modulation bandwidth of the quantum dot gain medium laser, and realizing the low-cost requirement of high-speed direct modulation quantum dot lasers.

[0056] Additional aspects and advantages of this application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The above and / or additional aspects and advantages of this application will become apparent and be readily understood from the following description of the embodiments in conjunction with the drawings, where:

[0058] Figure 1 is a schematic flow chart of a manufacturing method of an active feedback laser provided by an embodiment of this application;

[0059] Figure 2 is a schematic diagram of the material structure of each layer of an InAs quantum dot laser provided by an embodiment of this application;

[0060] Figure 3 is a schematic diagram of the material structure of each layer of the active region structure provided by an embodiment of this application;

[0061] Figure 4 is a three-dimensional schematic diagram of the active feedback laser provided by an embodiment of this application;

[0062] Figure 5 is a side schematic diagram of the active feedback laser provided by an embodiment of this application;

[0063] Figure 6 is a front schematic diagram of the active feedback laser provided by an embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] The embodiments of this application will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain this application and should not be construed as limiting this application.

[0065] The manufacturing method of the active feedback laser of the embodiments of this application and the active feedback laser manufactured by this manufacturing method of the active feedback laser will be described below with reference to the drawings.

[0066] Figure 1Schematic flow chart of a method for fabricating an active feedback laser provided by an embodiment of the present application. As Figure 1 shown, the method for fabricating the active feedback laser includes the following steps:

[0067] Step 101, subject the substrate to high-temperature deoxidation treatment to obtain a deoxidized substrate with the surface oxide layer removed.

[0068] It should be noted that the substrate of the present invention is not limited to a silicon substrate, and can be a group III-V or group IV substrate, such as GaAs, InP, silicon, germanium substrate, etc., which is not limited herein. Also, the substrate in the embodiment of the present application can be a substrate of different doping types, which can be N-type and P-type doping, depending on specific requirements, and is not limited herein.

[0069] In some implementation manners, the silicon substrate is sent into a molecular beam epitaxy chamber (Molecular beam epitaxy, MBE) for high-temperature deoxidation treatment to remove the surface oxide layer of the substrate, and a deoxidized substrate with the surface oxide layer removed is obtained.

[0070] Exemplarily, the silicon substrate is sent into the MBE chamber for high-temperature deoxidation treatment, the deoxidation temperature is 1000 °C, and the deoxidation time is 30 minutes to remove the surface oxide layer of the substrate.

[0071] It should be noted that the molecular beam epitaxy chamber as an epitaxial preparation tool can be replaced by the metalorganic chemical vapor deposition (MOCVD) method.

[0072] Step 102, grow a buffer layer and an active region structure of the active feedback laser on the deoxidized substrate in sequence to obtain a laser growth structure.

[0073] In some embodiments, the buffer layer is a GaAs buffer layer.

[0074] That is to say, grow a GaAs buffer layer on the substrate with the surface oxide layer removed, and grow the active region structure of the active feedback laser on the GaAs buffer layer.

[0075] In some embodiments, the implementation method of growing a GaAs buffer layer on the substrate with the surface oxide layer removed includes: growing a layer of GaAs N-type contact layer on the deoxidized substrate in the molecular beam epitaxy chamber.

[0076] Exemplarily, adjust the temperature in the molecular beam epitaxy chamber to 500 °C - 700 °C, grow a layer of GaAs N-type contact layer with a thickness of 1 μm - 2 μm on the silicon substrate with the surface oxide layer removed, and the doping concentration is 1×10 18 cm- 3 – 5×10 18 cm-3 , realize the growth of the GaAs buffer layer on the substrate with the surface oxide layer removed.

[0077] In some embodiments, the implementation method for growing the active region structure of the active feedback laser on the GaAs buffer layer includes:

[0078] Grow a superlattice of N-doped AlxGa1-xAs / GaAs on top of the GaAs N-type contact layer;

[0079] Grow a confinement layer of N-type AlxGa1-xAs on top of the superlattice of N-doped AlxGa1-xAs / GaAs;

[0080] Grow a superlattice of undoped AlxGa1-xAs / GaAs on top of the confinement layer;

[0081] Grow a layer of GaAs on top of the superlattice of undoped AlxGa1-xAs / GaAs, grow a layer of AlGaAs on the GaAs, and continuously grow the first 12 periods of AlGaAs / GaAs with AlGaAs / GaAs as one period;

[0082] Grow an undoped GaAs lower waveguide layer on top of the first 12 periods of 1nm AlGaAs / 1nm GaAs;

[0083] Grow a quantum dot active region based on the DWELL structure of quantum dots in the well on top of the GaAs lower waveguide layer;

[0084] Grow an undoped GaAs upper waveguide layer on top of the quantum dot active region;

[0085] Continuously grow the second 12 periods of 1nm AlGaAs / 1nm GaAs on top of the GaAs upper waveguide layer;

[0086] Grow a strained superlattice of undoped AlxGa1-xAs / GaAs on top of the second 12 periods of 1nm AlGaAs / 1nm GaAs;

[0087] Grow a confinement layer of p-type AlxGa1-xAs on top of the strained superlattice;

[0088] Grow a strained superlattice of p-doped AlxGa1-xAs / GaAs on top of the confinement layer of p-type AlxGa1-xAs;

[0089] Grow a GaAs P-type metal contact layer on top of the strained superlattice of p-doped AlxGa1-xAs / GaAs.

[0090] In one embodiment, the implementation of growing the active region structure of an active feedback laser on a GaAs buffer layer includes:

[0091] Above the GaAs N-type contact layer, first grow an N-type doped superlattice of AlxGa1-xAs / GaAs with a thickness of 50 nm - 100 nm, and the doping concentration is 1×10 18 cm- 3 – 5×10 18 cm- 3 , the temperature of the MBE chamber is 500 °C - 650 °C, and x is 20% to 90%;

[0092] Subsequently, grow a confinement layer of N-type AlxGa1-xAs with a thickness of 1200 nm - 1800 nm, and the doping concentration is 1×10 18 cm- 3 –5×10 18 cm- 3 , the temperature of the MBE chamber is 500 °C - 650 °C;

[0093] Subsequently, grow an undoped AlxGa1-xAs / GaAs superlattice with a thickness of 10 nm - 50 nm, the temperature of the MBE chamber is 500 °C - 650 °C, and x is 20% to 90%;

[0094] Subsequently, grow a 1-nm-thick GaAs, and grow a 1-nm-thick AlGaAs on the 1-nm-thick GaAs. Taking 1-nm AlGaAs / 1-nm GaAs as one cycle, continuously grow 12 cycles of 1-nm AlGaAs / 1-nm GaAs;

[0095] Then grow an undoped GaAs lower waveguide layer, and the temperature of the MBE chamber drops to 400 °C - 600 °C;

[0096] Above the GaAs lower waveguide layer, grow a quantum dot active region based on the DWELL structure;

[0097] After the growth of the DWELL quantum dot active region is completed, grow an undoped GaAs upper waveguide layer; wherein, the thickness of the GaAs upper waveguide layer is the same as that of the GaAs lower waveguide layer, and the temperature of the MBE chamber drops to 400 - 600 °C;

[0098] Then continuously grow 12 cycles of 1-nm AlGaAs / 1-nm GaAs;

[0099] Subsequently, a non-doped strained superlattice of AlxGa1-xAs / GaAs with a thickness of 10 nm - 50 nm is grown, the temperature of the MBE chamber is 500 °C - 650 °C, and x is from 20% to 90%; then a p-type AlxGa1-xAs confinement layer with a thickness of 1200 nm - 1800 nm is grown, and the doping concentration is 1×10 18 cm- 3 – 5×10 18 cm- 3 , the temperature of the MBE chamber is 500 °C - 650 °C, and x is from 20% to 90%;

[0100] Then, a p-type doped strained superlattice of AlxGa1-xAs / GaAs with a thickness of 50 nm - 100 nm is grown, and the doping concentration is 2 ×10 17 cm- 3 – 50×10 17 cm- 3 , the temperature of the MBE chamber is 500 °C - 650 °C, and x is from 20% to 90%;

[0101] Finally, a GaAs p-type contact layer with a thickness of 150 nm–300 nm is grown, and the doping concentration is 5×10 18 cm- 3 –15×10 18 cm- 3 , the temperature of the MBE chamber is 400 °C - 500 °C.

[0102] In some embodiments, the total thickness of the GaAs lower waveguide layer, the quantum dot active region based on the DWELL structure, and the GaAs upper waveguide layer is less than 300 nm.

[0103] That is to say, during the growth process, the total thickness L of the GaAs lower waveguide layer, the quantum dot active region, and the GaAs upper waveguide layer is controlled to be below 300 nm.

[0104] It can be understood that in order to achieve high-speed modulation, it is necessary to minimize the total thickness of the GaAs waveguide layer and the active region while satisfying the gain of the active feedback laser to reduce the carrier capture time. Therefore, the total thickness L of the GaAs waveguide layer and the active region should be controlled below 300 nm.

[0105] Exemplarily, as Figure 2 shown, above the GaAs N-type contact layer (corresponding to Figure 2 the second layer in Figure 2The third layer), with a thickness of 50 - 100 nm and a doping concentration of 1–5×10 18 cm- 3 , the temperature of the MBE chamber is 500℃ - 650 ℃, and x is from 20% to 90%;

[0106] Subsequently, a confinement layer of N-type AlxGa1-xAs is grown (corresponding to Figure 2 the fourth layer), with a thickness of 1200 nm - 1800 nm and a doping concentration of 1–5×10 18 cm- 3 , and the temperature is 500℃ - 650 ℃;

[0107] Subsequently, an undoped AlxGa1-xAs / GaAs superlattice is grown (corresponding to Figure 2 the fifth layer), with a thickness of 10 nm - 50 nm, a temperature of 500℃ - 650 ℃, and x is from 20% to 90%;

[0108] Subsequently, a 1-nm-thick GaAs layer is grown, and a 1-nm-thick AlGaAs layer is grown on the 1-nm GaAs layer. Taking 1-nm AlGaAs / 1-nm GaAs as one cycle, 12 cycles of 1-nm AlGaAs / 1-nm GaAs are continuously grown; (corresponding to Figure 2 the sixth layer)

[0109] Then, an undoped GaAs lower waveguide layer is grown (corresponding to Figure 2 the seventh layer), and the temperature is 400℃ - 600 ℃;

[0110] Above the lower waveguide layer, a quantum dot active region based on the DWELL structure is grown (corresponding to Figure 2 the eighth layer), and the specific structural schematic diagram is as Figure 3 shown.

[0111] In some embodiments, 10 nm of GaAs in the GaAs spacer layer in the quantum dots is p-type doped with a doping concentration of 1×10 17 cm- 3 –20×10 17 cm- 3 , aiming to improve the high-temperature characteristics of the device.

[0112] After the growth of the DWELL active region is completed, an undoped GaAs upper waveguide layer is grown (corresponding to Figure 2 the ninth layer) to make its thickness the same as that of the lower waveguide layer;

[0113] Then, 12 cycles of 1-nm AlGaAs / 1-nm GaAs are continuously grown; (corresponding to Figure 2(in the 10th layer)

[0114] Subsequently, a strained superlattice of undoped AlxGa1-xAs / GaAs with a growth thickness of 10 nm - 50 nm is grown (corresponding to Figure 2 the 11th layer in

[0115] Above it is a confinement layer of p-type AlxGa1-xAs (corresponding to Figure 2 the 12th layer in 18 cm- 3 –5×10 18 cm- 3 , at a temperature of 500 °C - 650 °C, and x is from 20% to 90%;

[0116] Then, a p-type doped strained superlattice of AlxGa1-xAs / GaAs is regrown (corresponding to Figure 2 the 13th layer in 17 cm- 3 –50 ×10 17 cm- 3 , at a temperature of 500 °C - 650 °C, and x is from 20% to 90%;

[0117] Finally, a GaAs p-type contact layer is grown (corresponding to Figure 2 the 14th layer in 18 cm- 3 –15×10 18 cm- 3 , at a temperature of 400 °C - 500 °C.

[0118] It should be noted that the strained superlattice eliminates the defect problem caused by lattice mismatch by generating strain. It is somewhat similar to a transitional role and can further confine the light in the active region.

[0119] In some embodiments, above the GaAs lower waveguide layer, a quantum dot active region based on the quantum dot DWELL structure in the well is grown; including: above the GaAs lower waveguide layer, In0. 15 Ga0. 85 As quantum wells and multiple layers of InAs quantum dots are grown in sequence; above the multiple layers of InAs quantum dots, In0. 15 Ga0. 85 As quantum wells and GaAs are deposited; and high-temperature annealing is performed; on the deposited In0. 15 Ga0. 85On the quantum well and GaAs, a GaAs spacer layer is grown; wherein, the GaAs spacer layer sequentially includes an undoped GaAs layer, a p-type doped GaAs layer, and an undoped GaAs layer from bottom to top.

[0120] Exemplarily, as Figure 3 shown, the growth of the quantum dot active region structure based on the DWELL structure includes:

[0121] Growing an In0. 15 Ga0. 85 As quantum well with a thickness of 2 nm at a low temperature of 510 °C, and then growing 8 - 10 layers of InAs quantum dots with a thickness of 3 ML each;

[0122] Depositing 4.5 nm of In 0.15 Ga 0.85 As quantum well and 4 nm of GaAs on the surface of the last layer of quantum dots, then performing high-temperature annealing to 600 °C, and finally growing a 30 nm - 50 nm GaAs spacer layer to complete the growth of the quantum dots in this layer; wherein, 10 nm of GaAs in the GaAs spacer layer is p-type doped, and the doping concentration of the p-type doped quantum dot layer is 5×10 17 cm -3 .

[0123] It should be noted that using a III-V substrate is different from using a silicon substrate. When using a silicon substrate, only a defect filtering layer or a Ge buffer layer needs to be added during the growth process to reduce the dislocation density, so as to realize a high-performance 1.3 μm band InAs quantum dot laser on the silicon substrate.

[0124] Step 103: Divide the laser growth structure into a distributed feedback DFB region and an integrated feedback IFB region, and perform bandgap blue shift on the quantum dot active region of the IFB region through the zone annealing technique to obtain the first-stage laser structure with increased bandwidth.

[0125] As an implementation method, perform selective area annealing on the active region structure of the active feedback laser, and use different dielectric materials as the capping layer.

[0126] It should be noted that using different dielectric materials as the capping layer means growing dielectric layers with different thermal expansion coefficients. After rapid annealing, the composition of the laser material can be changed, thereby affecting the energy bandgap and achieving the purpose of changing the wavelength. Here, the dielectric layer material generally refers to SiO2 or TiO2, and this technology is also called intermixing.

[0127] In some embodiments, when performing bandgap blue shift on the quantum dot active region of the IFB region through the zone annealing technique, the blue shift value is greater than 20 meV.

[0128] It should be noted that although the DFB region and the IFB region are of the same quantum dot heterostructure, in practical applications, the energy band gap of the active region required for the IFB region is different from that of the DFB region. The energy band gap of the IFB region should be slightly larger than that of the DFB region to achieve low-loss transmission. Therefore, the selective area annealing technology is used to blue-shift the energy band gap of the quantum dot active region in the IFB region, and the blue-shift value is greater than 20 meV.

[0129] Step 104: Sequentially perform ridge waveguide etching and coplanar N-type electrode region etching on the surface of the first-stage laser structure to obtain a second-stage laser structure with a ridge waveguide and a coplanar N-type electrode region.

[0130] This step realizes the ridge waveguide etching of the DFB region of the active feedback laser and the etching of the coplanar N-type electrode region.

[0131] In one implementation, sequentially perform ridge waveguide etching and coplanar N-type electrode region etching on the surface of the first-stage laser structure, including: performing ridge waveguide etching on the surface of the first-stage laser structure; preparing a pattern window in a preset region on the side of the ridge waveguide, etching a preset pattern in the preset region to expose the N-type contact layer, and using the corresponding region of the exposed N-type contact layer as the coplanar N-type electrode region.

[0132] In some embodiments, the ridge waveguide etching of the active feedback laser includes: using holographic exposure technology or electron beam exposure technology and inductively coupled plasma (ICP) etching technology to perform ridge waveguide etching, and the etching depth is 1.6 μm - 1.7 μm.

[0133] In some embodiments, the etching of the coplanar N-type electrode region includes: at a position 500 - 1000 nm on the side of the ridge waveguide, first use photolithography technology to prepare a pattern window in the preset region, and then use ICP technology or wet etching technology to etch a preset pattern in the preset region, and the etching depth is 3.4 μm - 3.7 μm. The purpose is to expose the N-type metal contact layer to prepare for the N-type coplanar electrode in the next step.

[0134] Step 105: Perform sidewall grating etching on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure; and perform electrical isolation etching at the adjacent position of the DFB region and the IFB region to obtain a third-stage laser structure.

[0135] As an implementation, on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure, sidewall grating etching is performed; and electrical isolation etching is performed at the adjacent position between the DFB region and the IFB region; including: setting the grating period through laser detuning technology, and based on the grating period, performing sidewall grating etching on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure; wherein, there is a phase shift of λ / 4 in the exact middle of the grating, and λ is the wavelength of the laser; performing electrical isolation etching at the adjacent position between the DFB region and the IFB region to disconnect the P-type metal contact layer between the DFB region and the IFB region.

[0136] This step is to perform surface grating selective etching on the DFB region in the active feedback laser and perform electrical isolation etching on the DFB region and the IFB region.

[0137] In one embodiment, performing surface grating selective etching on the DFB region in the active feedback laser includes: performing sidewall grating etching on the ridge waveguide in the DFB region through electron beam lithography technology and ICP technology, and the ridge waveguide region where grating etching is not performed is the IFB region. Among them, the laser detuning technology is used to set the grating period, and a phase shift of λ / 4 is designed in the exact middle of the DFB grating.

[0138] That is to say, when setting the grating period, the laser detuning technology will be adopted, that is, the detuning amount between the Bragg wavelength of the directly modulated laser (DML) and the gain peak wavelength is directly modulated through the grating period. The operating wavelength of the laser is slightly shorter than the gain peak wavelength to enable the laser to obtain higher differential gain, thereby improving the relaxation of the laser. In addition, through the design of a λ / 4 phase shift in the exact middle of the grating in the DFB region, the generation of stable single transverse mode laser is ensured.

[0139] For electrical isolation etching between the DFB region and the IFB region, for example, dry etching or wet etching can be used to remove the highly doped metal contact layer to disconnect the P-type metal contact layer between the DFB region and the IFB region, and the etching depth is 300 nanometers - 400 nanometers.

[0140] Exemplarily, the three-dimensional diagram of the fabricated active feedback laser is as Figure 4 shown, including the DFB region 1 and the IFB region 3, with electrical isolation 2 provided between the DFB region 1 and the IFB region 3 (electrical isolation 2 is perpendicular to Figure 4 the optical signal direction therein), and a grating 12 is provided on the surface of the DFB region; it also includes the GSG (Ground Signal Ground) pins (pads) 11 corresponding to the DFB region and the GSG pins 31 corresponding to the IFB region.

[0141] It should also be noted that the quantum dot DFB region can also adopt the technical route of buried grating to achieve single-mode output. However, this technical solution involves secondary epitaxy, with high costs and low yield rates.

[0142] Step 106: Deposit a protective layer and an insulating layer on different regions of the third-stage laser structure respectively, and deposit positive and negative electrodes on corresponding positions of the DFB region and the IFB region to obtain the fourth-stage laser structure.

[0143] That is to say, in this step, a protective layer and an insulating layer are deposited on different regions of the active feedback laser respectively. Subsequently, after performing graphic processing and top windowing on the protective layer and the insulating layer, a planarization process is carried out, and positive and negative electrodes are deposited on the DFB region and the IFB region.

[0144] In some embodiments, depositing a protective layer and an insulating layer on different regions of the third-stage laser structure respectively, and depositing positive and negative electrodes on corresponding positions of the DFB region and the IFB region includes:

[0145] Deposit a protective layer on the DFB region exposed to the air; deposit an insulating layer on the third-stage laser structure; perform graphic processing and top windowing on the protective layer and the insulating layer to obtain a laser sample with the P-type metal contact layer of the ridge waveguide exposed; perform planarization material spin coating and planarization etching on the laser sample to obtain a planarized laser sample; for the DFB region and the IFB region, deposit a positive electrode on the P-type metal contact layer and deposit a negative electrode on the coplanar N-type electrode region.

[0146] In one embodiment, depositing a protective layer and an insulating layer on different regions of the active feedback laser respectively, and then performing graphic processing and top windowing on the protective layer and the insulating layer and then performing a planarization process includes:

[0147] Use PVD technology to deposit aluminum oxide with a thickness of 10 nanometers to 20 nanometers on the DFB region exposed to the air as the protective layer;

[0148] Subsequently, use PECVD technology to deposit an insulating layer with a thickness of 200 nanometers to 500 nanometers on the laser sample obtained after forming the protective layer;

[0149] Subsequently, perform graphic processing and top windowing on the protective layer and the insulating layer to expose the P-type contact layer of the ridge waveguide, and then perform planarization material spin coating and planarization etching.

[0150] In some embodiments, depositing positive and negative electrodes on the DFB region and the IFB region includes:

[0151] Using photolithography, electron beam sputtering or magnetron sputtering techniques, deposit positive and negative electrodes on the P-type contact layer and N-type coplanar electrode contact layer in the DFB region and the IFB region, and then perform rapid thermal annealing (RTP) treatment to form low-resistance ohmic contacts.

[0152] Exemplarily, use physical vapor deposition (PVD) to deposit aluminum oxide on the exposed DFB region in air as a protective layer with a thickness of about 10 to 20 nanometers. Subsequently, use plasma-enhanced chemical vapor deposition (PECVD) to deposit an insulating layer on the sample, such as a material of silicon dioxide or nitrogen dioxide, with a thickness of 200 to 500 nanometers. Subsequently, perform patterning on the protective layer and the insulating layer and open a window on the top layer to expose the P-type contact layer of the ridge waveguide. After that, perform spin coating and etching of the planarization material to ensure that there is no material residue on the III-V ridge waveguide.

[0153] Using photolithography, electron beam sputtering or magnetron sputtering, deposit positive and negative electrodes on the P-type contact layer and N-type coplanar electrode contact layer in each region of the DFB region and the IFB region respectively, and then perform RTP treatment to form low-resistance ohmic contacts.

[0154] Step 107: Coat the laser structure in the fourth stage to obtain an actively feedback laser.

[0155] As an implementation method, perform high-temperature deoxidation treatment on the substrate to obtain a deoxidized substrate with the surface oxide layer removed, including: thinning the substrate to obtain a thinned laser sample; cleaving the bar of the thinned laser sample; depositing a high-reflection film on the end face of the IFB region and an anti-reflection film on the end face of the DFB region.

[0156] This step mainly performs post-processing such as thinning, cutting, and coating on the laser sample obtained in step 106.

[0157] In one embodiment, the implementation method for obtaining an actively feedback laser includes: performing post-processing on the current sample of the actively feedback laser: thinning GaAs to 200 to 120 micrometers through a grinding machine, then performing bar cleavage, and finally depositing a high-reflection film HR on the end face of the IFB region and an anti-reflection film AR on the DFB end.

[0158] Exemplarily, thin the silicon substrate to 200 to 120 micrometers through a grinding machine to reduce the influence of thermal effects on the device. Then perform bar cleavage, and finally perform end-face coating. When performing end-face coating, it is necessary to deposit a high-reflection film HR on the end face of the passive region to increase the feedback amount, and deposit an anti-reflection film AR on the DFB region to ensure low-loss output of light from the DFB end.

[0159] Such as Figure 5 and Figure 6As shown, the entire device is an AFL, i.e., an active feedback laser (AFL). That is, the active feedback laser fabricated in the embodiments of the present application consists of two parts. One part is a DFB laser formed by the DFB region, and the other part is formed by the IFB region. Through the photon-photon resonance (PPR) effect, the overall structure of the obtained active feedback laser is such that the DFB laser part is powered to generate light, and then the IFB part affects the refractive index of the material through the additionally applied current to further generate a phase change until the IFB region of the DFB laser reaches the condition of photon-photon resonance. The modulation bandwidth of the device is extended through the principle of optical-optical oscillation, thereby achieving the effect of high-speed direct modulation.

[0160] The embodiments of the present application implement a new method for fabricating a low-cost high-speed direct modulation 1.3 μm InAs / GaAs quantum dot DFB laser. For the first time, it is proposed to use the photon-photon resonance effect to break through the relaxation bandwidth limitation of the quantum dot laser by adding a response peak outside the relaxation oscillation peak of the quantum dot laser. This additional response peak is mainly achieved by the active feedback laser (AFL) introducing a new feedback mechanism by integrating the IFB region processed by bandgap blue shift.

[0161] The quantum dot active feedback laser obtained by the manufacturing method of the active feedback laser in the embodiments of the present application consists of a quantum dot DFB laser region (i.e., the DFB region) and a quantum dot IFB region. Among them, the DFB laser region generates light with a single wavelength by applying a first current source externally; while the IFB region changes the material reflection coefficient of this region by applying a second current source externally, thereby achieving the effect of phase modulation on the light in the cavity. At the same time, since there is also a quantum dot active region structure in the IFB region, the IFB region will also amplify the light, that is, when the light propagates from the DFB region to the IFB region, not only will the phase be modulated, but the light intensity will also be amplified.

[0162] The manufacturing method of the active feedback laser in the embodiments of the present application realizes the on-chip integration of the surface grating quantum dot DFB laser region and the active feedback laser by integrating the DFB laser formed by the DFB region and the IFB region. Both the DFB laser based on the surface grating structure and the AFL laser use the same epitaxial heterojunction and are grown simultaneously using an MBE device. The entire device does not involve secondary epitaxial growth during the manufacturing process, providing a low-cost and mass-producible solution for realizing high-speed direct modulation quantum dot lasers, with a simple process flow, controllable cost, and high yield.

[0163] Based on the above method embodiments, an embodiment of the present application further provides an active feedback laser, including a substrate and a GaAs buffer layer and an active region structure of the active feedback laser formed on the substrate in sequence; the active region structure is divided into a distributed feedback (DFB) region and an integrated feedback (IFB) region, and the IFB region is a region where bandgap blue shift is achieved through the region annealing technique; ridge waveguides and coplanar N-type electrode regions are provided on the surfaces of both the DFB region and the IFB region; a grating structure is provided on the sidewall of the ridge waveguide in the DFB region; a groove for achieving electrical isolation is provided at the adjacent position between the DFB region and the IFB region; positive and negative electrodes are provided at corresponding positions of the DFB region and the IFB region.

[0164] It should be noted that since the active feedback laser of the present application is obtained through the manufacturing method of the active feedback laser of the present application, thus, the foregoing explanation of the embodiments of the manufacturing method of the active feedback laser is also applicable to the active feedback laser of the embodiments of the present application, and will not be elaborated herein.

[0165] In the description of the foregoing embodiments, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" 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 this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0166] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0167] Any process or method description shown in the flowchart or described in other ways herein can be understood as representing a module, segment, or part of code including one or more executable instructions for implementing a customized logic function or process, and the scope of the preferred embodiments of the present application includes additional implementations, where the functions may be executed in a substantially simultaneous manner or in a reverse order according to the involved functions, rather than in the order shown or discussed, which should be understood by those skilled in the art of the embodiments of the present application.

[0168] Those of ordinary skill in the art can understand that all or part of the steps carried out in implementing the above-described embodiment methods can be completed by instructing relevant hardware through a program. The program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiment.

[0169] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A method for manufacturing an active feedback laser, characterized in that: The following steps are involved: The substrate is subjected to high temperature deoxidation treatment to obtain a deoxidized substrate with a surface oxide layer removed; Growing a buffer layer and an active region structure of the active feedback laser in sequence on the deoxidized substrate to obtain a laser growth structure; Performing bandgap blue shift on a part of the active region structure by regional annealing technology, so that the active region structure is divided into a distributed feedback DFB region and an IFB region subjected to bandgap blue shift treatment, thereby obtaining a first-stage laser structure with increased bandwidth; Sequentially performing ridge waveguide etching and coplanar N-type electrode region etching on the surface of the first-stage laser structure to obtain a second-stage laser structure having a ridge waveguide and a coplanar N-type electrode region; Performing sidewall grating etching on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure; and performing electrical isolation etching at the adjacent portions of the DFB region and the IFB region to obtain a third-stage laser structure; Separately depositing protective layers and insulating layers on different regions of the third-stage laser structure, and evaporating positive and negative electrodes on corresponding positions of the DFB region and the IFB region to obtain a fourth-stage laser structure; wherein, separately depositing protective layers and insulating layers on different regions of the third-stage laser structure comprises: depositing a protective layer on the DFB region exposed to air, and depositing an insulating layer on the laser sample obtained after forming the protective layer; The fourth-stage laser structure is subjected to film coating treatment to obtain an active feedback laser.

2. The method according to claim 1, characterized in that The buffer layer and the active feedback laser active region structure are sequentially grown on the deoxidized substrate to obtain a laser growth structure; comprising: Growing a GaAs N-type contact layer on the deoxidized substrate; On top of the GaAs N-type contact layer, grow an N-type doped Al x Ga 1-x As / GaAs superlattice; In the N-type doped Al x Ga 1-x A layer of N-type Al is grown on the As / GaAs superlattice. x Ga 1-x As restriction layer; On top of the confinement layer, a layer of undoped Al is grown. x Ga 1-x As / GaAs superlattice; In the non-doped Al x Ga 1-x A layer of GaAs is grown on the As / GaAs superlattice, and a layer of AlGaAs is grown on the GaAs, and the first 12 periods of AlGaAs / GaAs are grown continuously, with AlGaAs / GaAs being one period; Growing a non-doped GaAs lower waveguide layer on the first 12 periods of 1nm AlGaAs / 1nm GaAs; Growing a quantum dot active region based on a quantum dot-in-well DWELL structure on the GaAs lower waveguide layer; Growing a non-doped GaAs upper waveguide layer on the quantum dot active region; On the GaAs upper waveguide layer, continuously growing a second 12-period 1nm AlGaAs / 1nm GaAs; On top of the second 12 periods of 1nm AlGaAs / 1nm GaAs, a layer of non-doped Al x Ga 1-x As / GaAs strained superlattice; A layer of p-type Al is grown on the strained superlattice. x Ga 1-x As restriction layer; In the p-type Al x Ga 1-x A layer of p-type doped Al is grown on top of the As confinement layer. x Ga 1-x As / GaAs strained superlattice; In the p-doped Al x Ga 1-x A GaAs P-type metal contact layer is grown on the As / GaAs strained superlattice.

3. The method according to claim 2, characterized in that The total thickness of the GaAs lower waveguide layer, the quantum dot active region based on the quantum dot-in-well DWELL structure and the GaAs upper waveguide layer is less than 300 nm.

4. The method according to claim 2, characterized in that: The method comprises growing a quantum dot active region based on a quantum dot in well DWELL structure on the GaAs lower waveguide layer; comprising: On the GaAs lower waveguide layer, In 0 .15 Ga 0 .85 As quantum wells and multilayer InAs quantum dots; On top of the multilayer InAs quantum dots, In 0 .15 Ga 0 .85 As quantum well and GaAs; and high temperature annealing; In the deposited 0 .15 Ga 0 .85 A GaAs spacer layer is grown on the As quantum well and GaAs; wherein the GaAs spacer layer includes, from bottom to top, a non-doped GaAs layer, a p-type doped GaAs layer and a non-doped GaAs layer.

5. The method according to claim 2, characterized in that: When the band gap of the quantum dot active region of the IFB region is blue-shifted by regional annealing technology, the blue-shift value is greater than 20 millielectron volts.

6. The method according to claim 2, characterized in that The ridge waveguide etching and the coplanar N-type electrode region etching are sequentially performed on the surface of the laser structure in the first stage; comprising: Performing ridge waveguide etching on the surface of the laser structure in the first stage; A pattern window is prepared in a preset area on the side of the ridge waveguide, and a preset pattern is etched in the preset area to expose the N-type contact layer, and the corresponding area of ​​the exposed N-type contact layer is used as a coplanar N-type electrode area.

7. The method according to claim 2, characterized in that performing sidewall grating etching on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure; and performing electrical isolation etching at the adjacent portions of the DFB region and the IFB region; comprising: The grating period is set by laser detuning technology, and based on the grating period, sidewall grating etching is performed on the ridge waveguide corresponding to the DFB region on the surface of the second-stage laser structure; wherein the middle of the grating has a phase shift of λ / 4, and λ is the emission wavelength of the laser; Electrical isolation etching is performed at adjacent portions of the DFB region and the IFB region to disconnect the P-type metal contact layer between the DFB region and the IFB region.

8. The method according to claim 2, characterized in that: The protective layer and the insulating layer are respectively applied to different regions of the third-stage laser structure, and positive and negative electrodes are evaporated at corresponding positions of the DFB region and the IFB region; comprising: A protective layer is provided for the DFB area exposed to air; Applying an insulating layer to the third-stage laser structure; Performing pattern processing and top-layer window opening processing on the protection layer and the insulating layer to obtain a laser sample exposing the P-type metal contact layer of the ridge waveguide; Performing spin coating of a flattening material and flattening etching on the laser sample to obtain a flattened laser sample; For the DFB region and the IFB region, a positive electrode is evaporated on the P-type metal contact layer, and a negative electrode is evaporated on the coplanar N-type electrode region.

9. The method according to claim 2, characterized in that: The method comprises: performing high-temperature deoxidation treatment on the substrate to obtain a deoxidized substrate with the surface oxide layer removed; Performing a thinning process on the substrate to obtain a thinned laser sample; performing bar cleavage on the thinned laser sample; A high-reflection film is plated on the end face of the IFB region, and an anti-reflection film is plated on the end face of the DFB region.

10. An active feedback laser, characterized in that: It comprises a substrate, a buffer layer formed on the substrate in sequence, and an active region structure of the active feedback laser; a part of the active region structure is subjected to bandgap blue shift by regional annealing technology, so that the active region structure is divided into a distributed feedback DFB region and an IFB region subjected to bandgap blue shift treatment; a ridge waveguide and a coplanar N-type electrode region are provided on the surface of the DFB region and the IFB region; a grating structure is provided on the side wall of the ridge waveguide of the DFB region; grooves for achieving electrical isolation are provided at adjacent portions of the DFB region and the IFB region; and positive and negative electrodes are provided at corresponding positions of the DFB region and the IFB region.

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