InAs Quantum Dot Lasers and Their Preparation Methods

Abstract

The present application discloses an InAs quantum dot laser and a preparation method thereof. The InAs quantum dot laser includes a GaAs substrate, a lower cladding layer, a plurality of InAs quantum dot active regions, and an upper cladding layer stacked in sequence; each InAs quantum dot active region includes a first InGaAs quantum well layer, a quantum dot layer, a second InGaAs quantum well layer, and a GaAs spacer layer stacked in sequence; wherein, there is no doping source in the quantum dot layer, and the average thickness of the GaAs spacer layer of each InAs quantum dot active region is 10 - 50 nm. In the present application, there is no doping source in the quantum dot layer. By reasonably controlling the average thickness of each GaAs spacer layer, the uniformity of the quantum dots is gradually improved, the linewidth enhancement factor is reduced, and the antireflection performance of the laser is stronger. Among them, the antireflection performance can be increased to at least above -10 dB, so that the isolator in the optical module can be removed to solve the technical problems of large volume, high cost, and low integration degree caused by the optical module with an isolator.

Description

Technical Field

[0001] This application relates to the field of communication technologies, and particularly to an InAs quantum dot laser and a method for preparing the same. Background Art

[0002] Semiconductor lasers, as signal light emission sources, are widely used in scenarios such as data centers, access networks, and optical fiber transmission networks. They have the characteristics of small size, high efficiency, long life, and easy modulation. However, traditional lasers are very sensitive to external reflected light. Relatively strong external reflected light will affect parameters such as the optical field, carrier concentration, and effective refractive index of the laser, resulting in an increase in the relative intensity noise (RIN) of the laser, linewidth broadening, and further leading to problems such as jitter in the small-signal frequency response of communication devices using this laser, eye diagram degradation, and an increase in the bit error rate. In various application scenarios, especially in optical modules, the light emitted by the laser will be reflected multiple times after passing through various components and connectors. The anti-reflection stability of the laser directly affects the high-speed performance of the optical module and the system. To solve the influence of reflection on the performance of the laser, isolators are usually required in optical modules. However, existing isolators have problems such as large volume, high cost, and difficulty in integration. Summary of the Invention

[0003] The purpose of this application is to provide an InAs quantum dot laser and a method for preparing the same to solve the technical problems of large volume, high cost, and low integration of existing optical modules using isolators.

[0004] To achieve the above purpose, this application provides an InAs quantum dot laser, including a GaAs substrate, a lower cladding layer, a plurality of InAs quantum dot active regions, and an upper cladding layer stacked in sequence; each InAs quantum dot active region includes a first InGaAs quantum well layer, a quantum dot layer, a second InGaAs quantum well layer, and a GaAs spacer layer stacked in sequence; among them, there is no doping source in the quantum dot layer, and the average thickness of the GaAs spacer layer of each InAs quantum dot active region is 10 - 50 nm.

[0005] In some embodiments, in the direction away from the GaAs substrate, the thickness of each GaAs spacer layer gradually increases.

[0006] In some embodiments, the thickness of the first InGaAs quantum well layer is 1 - 3 nm, the thickness of the quantum dot layer is 2.5 - 3.5 nm, and the thickness of the second InGaAs quantum well layer is 3 - 10 nm.

[0007] In some embodiments, the lower cladding layer includes:

[0008] An N-type GaAs contact layer and an N-type Al x Ga （1-x）As / GaAs doped strained layer, N-type Al x Ga （1-x） As confinement layer, undoped GaAs confinement transition layer, Al x Ga （1-x） As / GaAs undoped strained layer and GaAs undoped strained layer;

[0009] The upper cladding layer includes a GaAs undoped upper strained layer, Al x Ga （1-x） As / GaAs undoped upper strained layer, P-type Al x Ga （1-x） As confinement layer, P-type Al x Ga （1-x） As / GaAs doped strained layer and P-type GaAs contact layer; where Al x Ga （1-x） In Al

[0010] In some embodiments, the thickness of the N-type GaAs contact layer is 150 - 300 nm;

[0011] N-type Al x Ga （1-x） The thickness of the As / GaAs doped strained layer is 40 - 80 nm;

[0012] N-type Al x Ga （1-x） The thickness of the As confinement layer is 1200 - 1500 nm;

[0013] The thickness of the undoped GaAs confinement transition layer is 30 - 50 nm;

[0014] Al x Ga （1-x） The thickness of the Al

[0015] The thickness of the GaAs undoped strained layer is 40 - 150 nm.

[0016] In some embodiments, the thickness of the GaAs undoped upper strained layer is 40 - 150 nm;

[0017] Al x Ga （1-x） The thickness of the As / GaAs undoped upper strained layer is 10 - 50 nm;

[0018] P-type Al x Ga （1-x） The thickness of the As confinement layer is 1200 - 1500 nm;

[0019] P-type Alx Ga （1-x） The thickness of the As / GaAs doped strained layer is 40 - 80 nm;

[0020] The thickness of the P-type GaAs contact layer is 150 - 300 nm.

[0021] To achieve the above object, the present application also provides a method for preparing an InAs quantum dot laser, including the following steps:

[0022] Send the GaAs substrate into the molecular beam epitaxy chamber of GaAs material to remove the surface oxide layer;

[0023] Grow a lower cladding layer on the GaAs substrate;

[0024] Grow a plurality of InAs quantum dot active regions on the lower cladding layer. Each InAs quantum dot active region includes a first InGaAs quantum well layer, a quantum dot layer, a second InGaAs quantum well layer, and a GaAs spacer layer stacked in sequence. Among them, the average thickness of the GaAs spacer layer is 10 - 50 nm;

[0025] Grow an upper cladding layer on the InAs quantum dot active region.

[0026] In some embodiments, the step of growing the InAs quantum dot active region on the lower cladding layer includes:

[0027] Grow the first InGaAs quantum well layer on the lower cladding layer. The temperature of the first InGaAs quantum well layer is 450 - 500 °C, and the thickness of the first InGaAs quantum well layer is 1 - 3 nm;

[0028] Grow the quantum dot layer on the first InGaAs quantum well layer. The temperature of the quantum dot layer is 450 - 500 °C, and the thickness of the quantum dot layer is 2.5 - 3.5 nm;

[0029] Grow the second InGaAs quantum well layer on the quantum dot layer. The thickness of the second InGaAs quantum well layer is 3 - 10 nm, and the temperature of the second InGaAs quantum well layer is 450 - 500 °C;

[0030] Grow the GaAs spacer layer on the second InGaAs quantum well layer. The temperature of the GaAs spacer layer is 550 - 650 °C.

[0031] In some embodiments, the step of growing the lower cladding layer on the GaAs substrate includes:

[0032] Grow an N-type GaAs contact layer on the GaAs substrate. The doping concentration of the N-type GaAs contact layer is 1 - 10×10 18 / cm3 The temperature of the N-type GaAs contact layer is 500 - 600 °C, and the thickness of the N-type GaAs contact layer is 150 - 300 nm;

[0033] On the N-type GaAs contact layer, the growth of the N-type Al x Ga （1-x） As / GaAs doped strained layer is carried out. The doping concentration of the N-type Al x Ga （1-x） As / GaAs doped strained layer is 1 - 10×10 18 / cm 3 The temperature of the N-type Al x Ga （1-x） As / GaAs doped strained layer is 500 - 650 °C, and the thickness of the N-type Al x Ga （1-x） As / GaAs doped strained layer is 40 - 80 nm;

[0034] On the N-type Al x Ga （1-x） As / GaAs doped strained layer, the growth of the N-type Al x Ga （1-x） As confinement layer is carried out. The doping concentration of the N-type Al x Ga （1-x） As confinement layer is 5×10 18 / cm 3 The temperature of the N-type Al x Ga （1-x） As confinement layer is 500 - 650 °C, and the thickness of the N-type Al x Ga （1-x） As confinement layer is 1200 - 1500 nm;

[0035] On the N-type Al x Ga （1-x） As confinement layer, the growth of the undoped GaAs confinement transition layer is carried out. The temperature of the undoped GaAs confinement transition layer is 500 - 600 °C, and the thickness of the undoped GaAs confinement transition layer is 30 - 50 nm;

[0036] On the undoped GaAs confinement transition layer, the growth of the Al x Ga （1-x） As / GaAs undoped strained layer is carried out. The temperature of the Al x Ga （1-x） As / GaAs undoped strained layer is 500 - 650 °C, and the thickness of the Al x Ga （1-x） As / GaAs undoped strained layer is 10 - 50 nm;

[0037] On Al x Ga （1-x） The growth of a strain layer of GaAs without doping is carried out on a strain layer without doping of AlGaAs / GaAs. The temperature of the strain layer of GaAs without doping is 400 - 600 °C, and the thickness of the strain layer of GaAs without doping is 40 - 150 nm;

[0038] Among them, in Al x Ga （1-x） In As, x is from 20% to 80%.

[0039] In some embodiments, the steps of growing an upper cladding layer on an InAs quantum dot active region include:

[0040] The growth of a strain layer of GaAs without doping is carried out on a GaAs spacer layer. The temperature of the strain layer of GaAs without doping is 400 - 600 °C, and the thickness of the strain layer of GaAs without doping is 40 - 150 nm;

[0041] On the strain layer of GaAs without doping, the growth of a strain layer of AlGaAs / GaAs without doping is carried out. The temperature of the strain layer of AlGaAs / GaAs without doping is 500 - 650 °C, and the thickness of the strain layer of AlGaAs / GaAs without doping is 10 - 50 nm; x Ga （1-x） As / GaAs without doping upper strain layer growth, Al x Ga （1-x） As / GaAs without doping upper strain layer temperature is 500 - 650 °C, Al x Ga （1-x） As / GaAs without doping upper strain layer thickness is 10 - 50 nm;

[0042] On the strain layer of AlGaAs / GaAs without doping, the growth of a P-type AlGaAs confinement layer is carried out. The doping concentration of the P-type AlGaAs confinement layer is 1×10 x Ga （1-x） As / GaAs without doping upper strain layer, P-type Al x Ga （1-x） As confinement layer growth, P-type Al x Ga （1-x） As confinement layer doping concentration is 1×10 17 ~5×10 18 / cm 3 The temperature of the P-type AlGaAs confinement layer is 500 - 650 °C, and the thickness of the P-type AlGaAs confinement layer is 1200 - 1500 nm; x Ga （1-x） As confinement layer temperature is 500 - 650 °C, P-type Al x Ga （1-x） As confinement layer thickness is 1200 - 1500 nm;

[0043] On the P-type AlGaAs confinement layer, the growth of a P-type AlGaAs / GaAs doped strain layer is carried out, P-type Al x Ga （1-x） As confinement layer, P-type Al x Ga （1-x） As / GaAs doped strain layer growth, P-type Al x Ga（1-x） The doping concentration of the As / GaAs doped strained layer is 1 to 10×10 18 / cm 3 , and the P-type Al x Ga （1-x） The temperature of the As / GaAs doped strained layer is 500 to 650 °C, and the P-type Al x Ga （1-x） The thickness of the As / GaAs doped strained layer is 50 to 100 nm;

[0044] On the P-type Al x Ga （1-x） The P-type GaAs contact layer is grown on the As / GaAs doped strained layer. The doping concentration of the P-type GaAs contact layer is 5×10 18 ~5×10 19 / cm 3 , the temperature of the P-type GaAs contact layer is 500 to 600 °C, and the thickness of the P-type GaAs contact layer is 150 to 300 nm;

[0045] Among them, x in Al x Ga （1-x） As is 20% to 80%.

[0046] In some embodiments, in the step of sending the GaAs substrate into the molecular beam epitaxy chamber of the GaAs material to remove the surface oxide layer, the temperature is 500 to 650 °C.

[0047] The technical effect of this application is to provide an InAs quantum dot laser and a preparation method thereof. There is no doping source in the quantum dot layer of the InAs quantum dot active region, and the average thickness of the GaAs spacer layer of each InAs quantum dot active region is 10 to 50 nm. In this way, by reasonably controlling the average thickness of each GaAs spacer layer, the uniformity of the quantum dots is gradually improved, and the linewidth broadening factor is reduced. The antireflection performance of the InAs quantum dot laser in this application is stronger. Among them, the antireflection performance of the InAs quantum dot laser in this application is improved, which is beneficial to removing the design of the isolator to solve the technical problems such as the large volume, high cost, and low integration of the optical module using the isolator. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The following will clearly show the technical solutions and other beneficial effects of this application by describing the specific embodiments of this application in detail with reference to the drawings.

[0049] Figure 1 It is a schematic structural diagram of the InAs quantum dot laser provided by the embodiment of this application.

[0050] Figure 2 It is a stacked schematic diagram of the light-emitting structure provided by the embodiment of this application.

[0051] Figure 3 It is a stacked schematic diagram of the active layer provided by the embodiment of the present application.

[0052] Figure 4 It is a stacked schematic diagram of the single-layer InAs quantum dot active region provided by the embodiment of the present application.

[0053] Figure 5 It is a schematic diagram of the photoluminescence intensity of the InAs quantum dot laser provided by the embodiment of the present application.

[0054] The identification of the attached drawing components is as follows:

[0055] 1-GaAs substrate; 2-undercladding layer; 3-active layer; 4-overcladding layer;

[0056] 21-N-type GaAs contact layer; 22-N-type Al x Ga （1-x） As / GaAs doped strained layer; 23-N-type Al x Ga （1-x） As confinement layer; 24-undoped GaAs confinement transition layer, 25-Al x Ga （1-x） As / GaAs undoped lower strained layer; 26-GaAs undoped lower strained layer;

[0057] 3a-InAs quantum dot active region; 31-first InGaAs quantum well layer; 32-quantum dot layer; 33-second InGaAs quantum well layer; 34-GaAs spacer layer;

[0058] 341-first GaAs spacer layer; 342-second GaAs spacer layer; 343-third GaAs spacer layer; 344-fourth GaAs spacer layer; 345-fifth GaAs spacer layer;

[0059] 41-GaAs undoped upper strained layer; 42-Al x Ga （1-x） As / GaAs undoped upper strained layer; 43-P-type Al x Ga （1-x） As confinement layer; 44-P-type Al x Ga （1-x） As / GaAs doped strained layer; 45-P-type GaAs contact layer;

[0060] 101-epitaxial wafer; 102-first waveguide layer; 103-second waveguide layer; 104-first cladding layer; 105-second cladding layer; 106-high reflection film; 107-low reflection film. Detailed implementation manners

[0061] In the following, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0062] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchases or can be prepared by existing methods.

[0063] Existing antireflection lasers are usually designed based on traditional bulk materials or quantum well structures, and their preparation processes are relatively complex. These methods usually require multiple etching and regrowth steps, and also require the preparation of antireflection films with high requirements, which increases the cost and production difficulty of the lasers. However, due to their unique physical properties, quantum dots have a linewidth factor close to zero and a high damping coefficient. Theoretically, they have a strong feedback critical coefficient. Therefore, quantum dots can be used as candidate materials for preparing lasers with stable antireflection capabilities.

[0064] Specifically, a laser using quantum dots as the emission medium can achieve antireflection capabilities by regulating its energy band structure and energy band edge energy levels. This means that in the design and preparation process of quantum dot materials, the antireflection characteristics can be optimized by reasonably selecting material and structural parameters. This design concept can avoid the complex etching and regrowth steps in traditional methods, thereby reducing costs and production difficulties.

[0065] In view of this, the embodiments of the present application provide an InAs quantum dot laser, and the average thickness of the GaAs spacer layer of each InAs quantum dot active region is set to be 10 - 50 nm. Thus, by reasonably controlling the average thickness of each GaAs spacer layer, the uniformity of the quantum dots is gradually improved, the line broadening factor is reduced, and the antireflection performance of the InAs quantum dot laser is stronger. This will be elaborated in detail below.

[0066] Please refer to Figure 1 , Figure 1 , which is a schematic structural diagram of the InAs quantum dot laser provided by the embodiments of the present application.

[0067] In one embodiment, the InAs quantum dot laser includes a light-emitting structure 101, a first waveguide layer 102, a second waveguide layer 103, a first cladding layer 104, a second cladding layer 105, a high-reflection film 106, and a low-reflection film 107. The first waveguide layer 102 and the first cladding layer 104 are sequentially disposed on the lower surface of the light-emitting structure 101, and the first waveguide layer 102 is closer to the light-emitting structure 101 than the first cladding layer 104. The second waveguide layer 103 and the second cladding layer 105 are sequentially disposed on the upper surface of the light-emitting structure 101, and the second waveguide layer 103 is closer to the light-emitting structure 101 than the second cladding layer 105. The high-reflection film 106 and the low-reflection film 107 are respectively disposed on opposite sides of the light-emitting structure 101 (i.e., Figure 1 the left and right sides in the figure). Among them, the position where the high-reflection film 106 is located represents the far end of the InAs quantum dot laser, and the position where the low-reflection film 107 is located represents the light-emitting surface (also called the proximal end) of the InAs quantum dot laser.

[0068] The first waveguide layer 102 and the second waveguide layer 103 cooperate to guide the laser to propagate in the relative direction of the high-reflection film 106 and the low-reflection film 107 (i.e., Figure 1 the left and right directions in the figure), and restrict the laser from propagating in the Figure 1 up and down directions in the figure. The high-reflection film 106 is used to reflect the laser reaching the far end of the InAs quantum dot laser, so that the laser continuously propagates in the optical cavity of the InAs quantum dot laser, and the laser is output through the low-reflection film 107. Optionally, the reflectivity of the low-reflection film 107 can be 30% or the like, and the reflectivity of the far-end high-reflection film 106 can be 90% or the like.

[0069] The light-emitting structure 101 of the embodiment of the present application will be described below.

[0070] Please refer to Figure 2 together, Figure 2 which is a stacked schematic diagram of the light-emitting structure provided by the embodiment of the present application. The light-emitting structure 101 includes a GaAs substrate 1, a lower cladding layer 2, an active layer 3, and an upper cladding layer 4 stacked in sequence. The active layer 3 includes a plurality of stacked InAs quantum dot active regions 3a.

[0071] The lower cladding layer includes an N-type GaAs contact layer 21, an N-type Al x Ga （1-x） As / GaAs doped strain layer 22, an N-type Al x Ga （1-x） As confinement layer 23, an undoped GaAs confinement transition layer 24, an Al x Ga （1-x） As / GaAs undoped lower strain layer 25, and a GaAs undoped lower strain layer 26.

[0072] In some embodiments, the thickness of the N-type GaAs contact layer 21 is 150 - 300 nm. It can be understood that the thickness (unit: nm) of the N-type GaAs contact layer 21 can be any value among 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300 or a value between any two of them. The N-type GaAs contact layer 21 achieves ohmic contact through high doping.

[0073] In some embodiments, N-type Al x Ga （1-x） As / GaAs doped strain layer 22 has a thickness of 40 - 80 nm, where x is from 20% to 80%. It can be understood that the thickness (unit: nm) of the N-type Al x Ga （1-x） As / GaAs doped strain layer 22 can be any value among 40, 50, 60, 70, 80 or a value between any two of them. The N-type Al x Ga （1-x） As / GaAs doped strain layer 22 can confine light within the InAs quantum dot active region 3a.

[0074] In some embodiments, N-type Al x Ga （1-x） As confinement layer 23 has a thickness of 1200 - 1500 nm, where x is from 20% to 80%. It can be understood that the thickness (unit: nm) of the N-type Al x Ga （1-x） As confinement layer 23 can be any value among 1200, 1300, 1400, 1500 or a value between any two of them. The N-type Al x Ga （1-x） As confinement layer 23 can be used to confine the transmission of light and electrons.

[0075] In some embodiments, the thickness of the undoped GaAs confinement transition layer 24 is 30 - 50 nm. It can be understood that the thickness (unit: nm) of the undoped GaAs confinement transition layer 24 can be any value among 30, 40, 50 or a value between any two of them. The undoped GaAs confinement transition layer 24 can be used to confine the transmission of electrons.

[0076] In some embodiments, Al x Ga （1-x） As / GaAs undoped lower strain layer 25 has a thickness of 10 - 50 nm, where x is from 20% to 80%. It can be understood that Al x Ga （1-x）The thickness (unit: nm) of the strain layer 25 under non-doped As / GaAs can be any value among 10, 20, 30, 40, 50 or a value between any two of them.

[0077] In some embodiments, the thickness of the strain layer 26 under non-doped GaAs is 40 - 150 nm. It can be understood that the thickness (unit: nm) of the strain layer 26 under non-doped GaAs can be any value among 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 or a value between any two of them.

[0078] In some embodiments, each layer of InAs quantum dot active region 3a is disposed on the strain layer 26 under non-doped GaAs. As Figure 4 shown, each layer of InAs quantum dot active region 3a includes a first InGaAs quantum well layer 31, a quantum dot layer 32, a second InGaAs quantum well layer 33, and a GaAs spacer layer 34 stacked in sequence.

[0079] In some embodiments, the thickness of the first InGaAs quantum well layer 31 is 1 - 3 nm. It can be understood that the thickness (unit: nm) of the first InGaAs quantum well layer 31 can be any value among 1, 1.5, 2, 2.5, 3 or a value between any two of them.

[0080] In some embodiments, there is no doping source in the quantum dot layer 32. In this way, the uniformity of the quantum dots can be improved, the line broadening factor can be reduced, and thus the antireflection ability of the laser is stronger. The thickness (unit: nm) of the quantum dot layer 32 is 2.5 - 3.5. It can be understood that the thickness of the quantum dot layer 32 can be any value among 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5 or a value between any two of them. The quantum dot (monolayer) growth method is based on Stranski-Krastanov growth (abbreviated as S-K growth). The thickness of the quantum dot layer 32 can satisfy the 2D-3D growth structure, and the size of the generated quantum dots corresponds to the wavelength of 1310 nm (oband) in the O band. To ensure the uniformity of the quantum dot size, the thickness of the quantum dot layer 32 can be adjusted within the range of 2.5 - 3.5.

[0081] In some embodiments, the thickness of the second InGaAs quantum well layer 33 is 3 - 10 nm. It can be understood that the thickness (unit: nm) of the second InGaAs quantum well layer 33 can be any value among 3, 4, 5, 6, 7, 8, 9, 10 or a value between any two of them.

[0082] In some embodiments, the thickness of the GaAs spacer layer 34 is 10 to 50 nm. It can be understood that the thickness of the GaAs spacer layer 34 (unit: nm) can be any value among 10, 15, 20, 25, 30, 35, 40, 45, 50 or a value between any two of them. Thus, by reasonably setting the thickness of the GaAs spacer layer 34 in this embodiment, it is possible to avoid the problem that the GaAs spacer layer 34 is too thin to release enough stress and cannot return to the same quantum dot growth conditions, and it is also possible to avoid the problem that the GaAs spacer layer 34 is too thick, resulting in too long growth time, affecting heat dissipation and the spot shape. Moreover, setting the average thickness of the GaAs spacer layer 34 in each InAs quantum dot active region 3a will not have a great impact on antireflection.

[0083] In the prior art, for the growth of multi-layer quantum dots, if the thickness of the GaAs spacer layer 34 in each InAs quantum dot active region 3a remains the same, such as 10 nm, since the InAs quantum dot laser is grown on the GaAs substrate 1 in sequence, as the number of grown layers increases, the stress confinement of the quantum dots will become smaller and the volume of the quantum dots will become larger, so it is impossible to ensure the uniformity between each layer of quantum dots. Therefore, in the embodiment of the present application, by setting the thickness of the GaAs spacer layer 34 in each InAs quantum dot active region 3a to gradually increase in the direction away from the GaAs substrate 1, the cumulative stress of the first InGaAs quantum well layer 31, the quantum dot layer 32 and the second InGaAs quantum well layer 33 can be released, and the original growth conditions of the first InGaAs quantum well layer 31 in each period can be kept the same, so as to improve the uniformity of the quantum dots, reduce the linewidth enhancement factor, and make the antireflection performance of the InAs quantum dot laser stronger. Among them, the antireflection performance can be increased to at least above -10 dB. Thus, due to the improvement of the antireflection performance of the InAs quantum dot laser, the isolator in the optical module can be removed to solve the technical problems of large volume, high cost and low integration degree caused by the optical module with an isolator.

[0084] As Figures 2 to 4 shown, since multiple InAs quantum dot active regions 3a are stacked, the luminous intensity of the quantum dots can be improved. Each InAs quantum dot active region 3a includes a first InGaAs quantum well layer 31, a quantum dot layer 32, a second InGaAs quantum well layer 33 and a GaAs spacer layer 34 which are stacked. In the direction away from the GaAs substrate 1, the thickness of the GaAs spacer layer 34 in each InAs quantum dot active region 3a gradually increases, that is, the farther away from the GaAs substrate 1, the greater the thickness of the GaAs spacer layer 34, and the closer to the GaAs substrate 1, the smaller the thickness of the GaAs spacer layer 34. For example, as Figure 3As shown, the InAs quantum dot laser can include five or more InAs quantum dot active regions 3a. For example, the InAs quantum dot laser can include five GaAs spacer layers. In the direction away from the GaAs substrate 1, the InAs quantum dot laser includes a first GaAs spacer layer 341, a second GaAs spacer layer 342, a third GaAs spacer layer 343, a fourth GaAs spacer layer 344, and a fifth GaAs spacer layer 345 that are sequentially stacked, and the thicknesses of the first GaAs spacer layer 341 to the fifth GaAs spacer layer 345 are 17nm, 18nm, 19nm, 20nm, 21nm, and 22nm respectively. Among them, the average thickness of the GaAs spacer layer 34 of each InAs quantum dot active region 3a is the average value of the total thickness of the first GaAs spacer layer 341 to the fifth GaAs spacer layer 345.

[0085] Combined with Figure 5 , curve a is the photoluminescence intensity curve when the average thickness of the GaAs spacer layer 34 of each InAs quantum dot active region 3a is 5nm, curve b is the photoluminescence intensity curve when the average thickness of the GaAs spacer layer 34 of each InAs quantum dot active region 3a is 10nm, and curve c is the photoluminescence intensity curve when the average thickness of the GaAs spacer layer 34 of each InAs quantum dot active region 3a is 30nm. It can be seen from this that according to curve a, curve b, and curve c, as the average thickness of the GaAs spacer layer 34 of each InAs quantum dot active region 3a changes, the uniformity of the quantum dots gradually improves and the linewidth enhancement factor decreases.

[0086] As Figure 2 shown, the upper cladding layer 4 includes a GaAs undoped upper strained layer 41, an Al x Ga （1-x） As / GaAs undoped upper strained layer 42, a p-type Al x Ga （1-x） As confinement layer 43, a p-type Al x Ga （1-x） As / GaAs doped strained layer 44, and a p-type GaAs contact layer 45.

[0087] In some embodiments, the thickness of the GaAs undoped upper strained layer 41 is 40 - 150nm. It can be understood that the thickness (unit: nm) of the GaAs undoped upper strained layer 41 can be any value among 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 or a value between any two of them.

[0088] In some embodiments, Al x Ga （1-x）The thickness of the undoped upper strained layer 42 of Al x Ga （1-x） As is 10 to 50 nm, where x in Al x Ga （1-x） As is from 20% to 80%. It is understood that the thickness (unit: nm) of the undoped upper strained layer 42 of Al x Ga （1-x） As / GaAs can be any value among 10, 20, 30, 40, 50 or a value between any two of them. x Ga （1-x） In Al x Ga （1-x） As, x is from 20% to 80%. It is understood that x Ga （1-x） The thickness (unit: nm) of the undoped upper strained layer 42 of Al x Ga （1-x） As / GaAs can be any value among 10, 20, 30, 40, 50 or a value between any two of them.

[0089] In some embodiments, the thickness of the p-type Al x Ga （1-x） As confinement layer 43 is 1200 to 1500 nm, where x in Al x Ga （1-x） As is from 20% to 80%. It is understood that the thickness (unit: nm) of the p-type Al x Ga （1-x） As confinement layer 43 can be any value among 1200, 1300, 1400, 1500 or a value between any two of them. x Ga （1-x） In some embodiments, the thickness of the p-type Al x Ga （1-x） As confinement layer 43 is 1200 to 1500 nm, where x in Al x Ga （1-x） As is from 20% to 80%. It is understood that the thickness (unit: nm) of the p-type Al x Ga （1-x） As confinement layer 43 can be any value among 1200, 1300, 1400, 1500 or a value between any two of them. x Ga （1-x） In Al x Ga （1-x） As, x is from 20% to 80%. It is understood that x Ga （1-x） The thickness (unit: nm) of the p-type Al x Ga （1-x） As confinement layer 43 can be any value among 1200, 1300, 1400, 1500 or a value between any two of them.

[0090] In some embodiments, the thickness of the p-type Al x Ga （1-x） As / GaAs doped strained layer 44 is 40 to 80 nm, where x in Al x Ga （1-x） As is from 20% to 80%. It is understood that the thickness (unit: nm) of the p-type Al x Ga （1-x） As / GaAs doped strained layer 44 can be any value among 40, 50, 60, 70, 80 or a value between any two of them. x Ga （1-x） In some embodiments, the thickness of the p-type Al x Ga （1-x） As / GaAs doped strained layer 44 is 40 to 80 nm, where x in Al x Ga （1-x） As is from 20% to 80%. It is understood that the thickness (unit: nm) of the p-type Al x Ga （1-x） As / GaAs doped strained layer 44 can be any value among 40, 50, 60, 70, 80 or a value between any two of them. x Ga （1-x） In Al x Ga （1-x） As, x is from 20% to 80%. It is understood that x Ga （1-x） The thickness (unit: nm) of the p-type Al x Ga （1-x） As / GaAs doped strained layer 44 can be any value among 40, 50, 60, 70, 80 or a value between any two of them.

[0091] In some embodiments, the thickness of the p-type GaAs contact layer 45 is 150 to 300 nm. It is understood that the thickness (unit: nm) of the p-type GaAs contact layer 45 can be any value among 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300 or a value between any two of them.

[0092] An embodiment of the present application further provides a method for manufacturing an InAs quantum dot laser, including the following steps:

[0093] Send the GaAs substrate into the GaAs material molecular beam epitaxy chamber to remove the surface oxide layer;

[0094] Grow the lower cladding layer on the GaAs substrate;

[0095] The InAs quantum dot active region is grown on the lower cladding layer. The InAs quantum dot active region includes a first InGaAs quantum well layer, a quantum dot layer, a second InGaAs quantum well layer, and a GaAs spacer layer stacked in sequence. Among them, the thickness of the GaAs spacer layer is 10 - 50 nm;

[0096] The upper cladding layer is grown on the InAs quantum dot active region.

[0097] In some embodiments, in the step of feeding the GaAs substrate into the molecular beam epitaxy chamber of GaAs material to remove the surface oxide layer, the temperature is 500 - 650 °C.

[0098] In some embodiments, the step of growing the InAs quantum dot active region on the lower cladding layer includes:

[0099] The first InGaAs quantum well layer is grown on the lower cladding layer, with a temperature of 450 - 500 °C and a thickness of 1 - 3 nm;

[0100] The quantum dot layer is grown on the first InGaAs quantum well layer, with a temperature of the quantum dot layer being 450 - 500 °C and a thickness of the quantum dot layer being 2.5 - 3.5 atomic layer thicknesses;

[0101] The second InGaAs quantum well layer is grown on the quantum dot layer, with a temperature of 450 - 500 °C and a thickness of 3 - 10 nm;

[0102] The GaAs spacer layer is grown on the second InGaAs quantum well layer, with a temperature of 550 - 650 °C and a thickness of the GaAs spacer layer being 10 - 50 nm.

[0103] In some embodiments, the step of growing the lower cladding layer on the GaAs substrate includes:

[0104] An N-type GaAs contact layer is grown on the GaAs substrate. The doping concentration of the N-type GaAs contact layer is 1 - 10×10 18 / cm 3 , the temperature of the N-type GaAs contact layer is 500 - 600 °C, and the thickness of the N-type GaAs contact layer is 150 - 300 nm;

[0105] An N-type Al x Ga （1-x） As / GaAs doped strained layer is grown on the N-type GaAs contact layer. The doping concentration of the N-type Al x Ga （1-x） As / GaAs doped strained layer is 1 - 10×10 18 / cm 3 , N-type Al x Ga（1-x） The temperature of the As / GaAs doped strained layer is 500 - 650 °C, N-type Al x Ga （1-x） The thickness of the As / GaAs doped strained layer is 40 - 80 nm, N-type Al x Ga （1-x） The period of the As / GaAs doped strained layer is 10 - 20, it can be understood that N-type Al x Ga （1-x） The As / GaAs doped strained layer includes multiple Al x Ga （1-x） As layers and multiple GaAs layers, Al x Ga （1-x） The As layer and the GaAs layer are alternately stacked, where two adjacent Al x Ga （1-x） The As layer and the GaAs layer form a period. N-type Al x Ga （1-x） The As / GaAs doped strained layer is cycled 10 - 20 times according to the period formed by two adjacent Al x Ga （1-x） The As layer and the GaAs layer. Among them, in Al x Ga （1-x） As, x is 20% to 80%;

[0106] On the N-type Al x Ga （1-x） As / GaAs doped strained layer, the growth of the N-type Al x Ga （1-x） As confinement layer is carried out. The doping concentration of the N-type Al x Ga （1-x） As confinement layer is 5 × 10 18 / cm 3 The temperature of the N-type Al x Ga （1-x） As confinement layer is 500 - 650 °C, the thickness of the N-type Al x Ga （1-x） As confinement layer is 1200 - 1500 nm, among which, in Al x Ga （1-x） As, x is 20% to 80%;

[0107] On the N-type Al x Ga （1-x） As confinement layer, the growth of the undoped GaAs confinement transition layer is carried out. The temperature of the undoped GaAs confinement transition layer is 500 - 600 °C, and the thickness of the undoped GaAs confinement transition layer is 30 - 50 nm;

[0108] Perform the growth of an Al x Ga （1-x） As / GaAs strained layer under non-doping on a non-doped GaAs confinement transition layer. The temperature of the Al x Ga （1-x） As / GaAs strained layer under non-doping is 500 - 650 °C. The thickness of the Al x Ga （1-x） As / GaAs strained layer under non-doping is 10 - 50 nm. The period of the Al x Ga （1-x） As / GaAs strained layer under non-doping is 10 - 50 periods. Among them, in Al x Ga （1-x） As, x is 20% to 80%;

[0109] Perform the growth of a GaAs strained layer under non-doping on the Al x Ga （1-x） As / GaAs strained layer under non-doping. The temperature of the GaAs strained layer under non-doping is 400 - 600 °C. The thickness of the GaAs strained layer under non-doping is 40 - 150 nm. Among them, in Al x Ga （1-x） As, x is 20% to 80%;

[0110] In some embodiments, the steps of growing an upper cladding layer on an InAs quantum dot active region include:

[0111] Perform the growth of a GaAs strained layer under non-doping on a GaAs spacer layer. The temperature of the GaAs strained layer under non-doping is 400 - 600 °C. The thickness of the GaAs strained layer under non-doping is 40 - 150 nm;

[0112] Perform the growth of an Al x Ga （1-x） As / GaAs strained layer under non-doping on the GaAs strained layer under non-doping. The temperature of the Al x Ga （1-x） As / GaAs strained layer under non-doping is 500 - 650 °C. The thickness of the Al x Ga （1-x） As / GaAs strained layer under non-doping is 10 - 50 nm. The period of the Al x Ga （1-x） As / GaAs strained layer under non-doping is 10 - 50 periods. Among them, in Al x Ga （1-x） As, x is 20% to 80%;

[0113] Perform the growth of a P-type Al x Ga （1-x） As / GaAs strained layer under non-doping on the Alx Ga （1-x） Growth of the P-type Al x Ga （1-x） As confinement layer is limited, and the doping concentration of the P-type Al 17 ~5×10 18 / cm 3 ; the temperature of the P-type Al x Ga （1-x） As confinement layer is 500 - 650 °C, and the thickness of the P-type Al x Ga （1-x） As confinement layer is 1200 - 1500 nm. Among them, x in Al x Ga （1-x） As is 20% to 80%;

[0114] On the P-type Al x Ga （1-x） As confinement layer, the growth of the P-type Al x Ga （1-x） As / GaAs doped strain layer is carried out. The doping concentration of the P-type Al x Ga （1-x） As / GaAs doped strain layer is 1 - 10×10 18 / cm 3 ; the temperature of the P-type Al x Ga （1-x） As / GaAs doped strain layer is 500 - 650 °C, and the thickness of the P-type Al x Ga （1-x） As / GaAs doped strain layer is 50 - 100 nm. The period of the P-type Al x Ga （1-x） As / GaAs doped strain layer is 10 - 20. Among them, x in Al x Ga （1-x） As is 20% to 80%;

[0115] On the P-type Al x Ga （1-x） As / GaAs doped strain layer, the growth of the P-type GaAs contact layer is carried out. The doping concentration of the P-type GaAs contact layer is 5×10 18 ~5×10 19 / cm 3 ; the temperature of the P-type GaAs contact layer is 500 - 600 °C, and the thickness of the P-type GaAs contact layer is 150 - 300 nm. Among them, x in Al x Ga （1-x） As is 20% to 80%.

[0116] Test Example 1

[0117] Specifically, the preparation method of the InAs quantum dot laser is as follows:

[0118] S1. Feed the GaAs substrate into the GaAs material molecular beam epitaxy chamber to perform high-temperature deoxidation to remove the surface oxide layer at a temperature of 500 °C;

[0119] S2. Grow the lower cladding layer on the GaAs substrate;

[0120] Among them, the preparation method of the lower cladding layer includes:

[0121] S21. Grow an N-type GaAs contact layer on the GaAs substrate. The doping concentration of the N-type GaAs contact layer is 1×10 18 cm -3 , the temperature of the N-type GaAs contact layer is 500 °C, and the thickness of the N-type GaAs contact layer is 150 nm;

[0122] S22. Grow an N-type AlGaAs / GaAs doped strained layer on the N-type GaAs contact layer. The doping concentration of the N-type AlGaAs / GaAs doped strained layer is 1×10 18 / cm 3 , the temperature of the N-type AlGaAs / GaAs doped strained layer is 500 °C, the thickness of the N-type AlGaAs / GaAs doped strained layer is 40 nm, and the period of the N-type AlGaAs / GaAs doped strained layer is 10;

[0123] S23. Grow an N-type AlGaAs confinement layer on the N-type AlGaAs / GaAs doped strained layer. The doping concentration of the N-type AlGaAs confinement layer is 5×10 18 / cm 3 , the temperature of the N-type AlGaAs confinement layer is 500 °C, and the thickness of the N-type AlGaAs confinement layer is 1200 nm;

[0124] S24. Grow an undoped GaAs confinement transition layer on the N-type AlGaAs confinement layer. The temperature of the undoped GaAs confinement transition layer is 500 °C, and the thickness of the undoped GaAs confinement transition layer is 30 nm;

[0125] S25. Grow an AlGaAs / GaAs undoped lower strained layer on the undoped GaAs confinement transition layer. The temperature of the AlGaAs / GaAs undoped lower strained layer is 500 °C, the thickness of the AlGaAs / GaAs undoped lower strained layer is 10 nm, and the period of the AlGaAs / GaAs undoped lower strained layer is 10;

[0126] S26. Grow a strained layer of GaAs without doping on a strained layer of AlGaAs / GaAs without doping. The temperature of the strained layer of GaAs without doping is 400 °C, and the thickness of the strained layer of GaAs without doping is 40 nm.

[0127] S3. Grow a plurality of InAs quantum dot active regions on the lower cladding layer. The InAs quantum dot active region includes a first InGaAs quantum well layer, a quantum dot layer, a second InGaAs quantum well layer, and a GaAs spacer layer stacked in sequence.

[0128] Among them, the preparation method of each InAs quantum dot active region includes:

[0129] S31. Grow a first InGaAs quantum well layer on the lower cladding layer. The temperature of the first InGaAs quantum well layer is 450 °C, and the thickness of the first InGaAs quantum well layer is 1 nm.

[0130] S32. Grow a quantum dot layer on the first InGaAs quantum well layer. The temperature of the quantum dot layer is 450 °C, and the thickness of the quantum dot layer is 2.5.

[0131] S33. Grow a second InGaAs quantum well layer on the quantum dot layer with a thickness of 3 nm. The temperature of the second InGaAs quantum well layer is 450 °C, and the thickness of the second InGaAs quantum well layer is 3 nm.

[0132] S34. Grow a GaAs spacer layer on the second InGaAs quantum well layer. The temperature of the GaAs spacer layer is 550 °C.

[0133] Repeat the above steps S31 - S34 five times, and obtain five InAs quantum dot active regions, namely the first InAs quantum dot active region, the second InAs quantum dot active region, the third InAs quantum dot active region, the fourth InAs quantum dot active region, and the fifth InAs quantum dot active region. Among them, the GaAs spacer layer in the first InAs quantum dot active region is the first GaAs spacer layer, and the thickness of the first GaAs spacer layer is 7 nm. The GaAs spacer layer in the second InAs quantum dot active region is the second GaAs spacer layer, and the thickness of the second GaAs spacer is 8 nm. The GaAs spacer layer in the third InAs quantum dot active region is the third GaAs spacer layer, and the thickness of the third GaAs spacer layer is 10 nm. The GaAs spacer layer in the fourth InAs quantum dot active region is the fourth GaAs spacer layer, and the thickness of the fourth GaAs spacer layer is 12 nm. The GaAs spacer layer in the fifth InAs quantum dot active region is the fifth GaAs spacer layer, and the thickness of the fifth GaAs spacer layer is 13 nm. Therefore, the average thickness of the five-layer GaAs spacer layer is 10 nm.

[0134] S4. Grow an upper cladding layer on the InAs quantum dot active region;

[0135] Among them, the preparation method of the upper cladding layer includes:

[0136] S41. Grow a GaAs undoped upper strained layer on the GaAs spacer layer. The temperature of the GaAs undoped upper strained layer is 400 °C, the thickness of the GaAs undoped upper strained layer is 40 nm, and the period of the GaAs undoped upper strained layer is 10;

[0137] S42. Grow an AlGaAs / GaAs undoped upper strained layer on the GaAs undoped upper strained layer. The temperature of the AlGaAs / GaAs undoped upper strained layer is 500 °C, and the thickness of the AlGaAs / GaAs undoped upper strained layer is 10 nm;

[0138] S43. Grow a P-type AlGaAs confinement layer on the AlGaAs / GaAs undoped upper strained layer. The doping concentration of the P-type AlGaAs confinement layer is 1×10 17 / cm 3 , the temperature of the P-type AlGaAs confinement layer is 500 °C, and the thickness of the P-type AlGaAs confinement layer is 1200 nm;

[0139] S44. Grow a P-type AlGaAs / GaAs doped strained layer on the P-type AlGaAs confinement layer. The doping concentration is 1×10 18 / cm 3 , the temperature is 500 °C, the thickness is 40 nm, and the period is 10;

[0140] S45. Grow a P-type GaAs contact layer on the P-type AlGaAs / GaAs doped strained layer. The doping concentration of the P-type GaAs contact layer is 5×10 18 / cm 3 , the temperature of the P-type GaAs contact layer is 500 °C, and the thickness of the P-type GaAs contact layer is 150 nm.

[0141] Through the above steps, a quantum dot material is obtained.

[0142] S5. Process the grown quantum dot material to form the structure of a laser. Specifically, etch the ohmic contact layer and the upper cladding layer 4 to form two trenches and a ridge waveguide located between the two trenches, Figure 1 where the first waveguide layer 102 and the second waveguide layer 103 in

[0143] S6. Thinning the lower cladding layer and evaporating and depositing the metal materials for the positive and negative electrodes of the laser. Specifically, first thin the lower cladding layer to 100 um, and then use sputtering or electron beam method to evaporate and deposit metal materials such as gold. Among them, the front gold can be TiPtAu, and the back gold can be Ni / GeAu / Ni / Au;

[0144] S7. Cleave the light-emitting structure to form a bar with the required cavity length, deposit an anti-reflection film 107 on the light-emitting surface of the InAs quantum dot laser, and deposit a high-reflection film 106 on the far end.

[0145] Test Example 2

[0146] The preparation method of this test example is the same as that of Test Example 1, the difference is that the average thickness of the multi-layer (for example, five-layer) GaAs spacer layer in this test example is 30 nm.

[0147] Test Example 3

[0148] The preparation method of this test example is the same as that of Test Example 1, the difference is that the average thickness of the multi-layer (for example, five-layer) GaAs spacer layer in this test example is 50 nm.

[0149] Comparative Example 1

[0150] The preparation method of this comparative example is the same as that of Test Example 1, the difference is that the average thickness of the multi-layer (for example, five-layer) GaAs spacer layer in this comparative example is 5 nm.

[0151] Comparative Example 2

[0152] The preparation method of this comparative example is the same as that of Test Example 1, the difference is that the average thickness of the multi-layer (for example, five-layer) GaAs spacer layer in this comparative example is 60 nm.

[0153] Combined Figure 5 , Figure 5 where a is the curve with an average thickness of 10 nm of the multi-layer (for example, five-layer) GaAs spacer layer in Test Example 1; b is the curve with an average thickness of 30 nm of the multi-layer (for example, five-layer) GaAs spacer layer in Test Example 2; c is the curve with an average thickness of 50 nm of the multi-layer (for example, five-layer) GaAs spacer layer in Test Example 3, d is the curve with an average thickness of 5 nm of the multi-layer (for example, five-layer) GaAs spacer layer in Comparative Example 1; e is the curve with an average thickness of 60 nm of the multi-layer (for example, five-layer) GaAs spacer layer in Comparative Example 2.

[0154] Photoluminescence (PL) reflects the quality of quantum dots. It can be used to analyze the structure, composition, and environmental atomic arrangement information of quantum dots in the quantum dot layer, and is a non-destructive and highly sensitive analysis method. Among them, the photoluminescence intensity reflects the density of quantum dots, and the photoluminescence spectral width reflects the uniformity of quantum dots.

[0155] Therefore, combined with Figure 5 , in Test Examples 1-3 of this application, there is no doping source in the quantum dot layer of the InAs quantum dot active region, and the average thickness of the GaAs spacer layer in each InAs quantum dot active region is 10-50 nm. As the photoluminescence intensity increases, the gain also increases, and the quantum dot density reflected is better. Thus, the photoluminescence (PL) spectral line is narrower, the uniformity of quantum dots is improved, the line broadening factor is reduced, and the anti-reflection performance of the laser is stronger. In Comparative Example 1, as the photoluminescence intensity increases, the gain is small, the quantum dot density is uneven, and the line broadening factor is large. Comparing Test Example 3 with Comparative Example 2, although the average thickness of the multi-layer GaAs spacer layer in Comparative Example 2 is 60 nm, it can also improve the uniformity of quantum dots and the effect of reducing the line broadening factor. However, the effect brought by Comparative Example 2 is not significant enough.

[0156] Therefore, when the thickness of the GaAs spacer layer in the embodiment of this application is 10-50 nm, the uniformity of quantum dots can be gradually improved, the line broadening factor can be reduced, and the anti-reflection performance of the laser is stronger. The anti-reflection performance can be increased to at least above -10 dB, which is beneficial to removing the isolator in the optical module to solve the technical problems of large volume, high cost, and low integration degree caused by the optical module with an isolator.

[0157] In the above embodiments, the descriptions of each embodiment have their own focuses. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0158] The above has introduced in detail an InAs quantum dot laser and its preparation method provided by the embodiments of this application. Specific examples are used in this article to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the technical solution and its core idea of this application; those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An InAs quantum dot laser, characterized in that: It includes a GaAs substrate, a lower cladding layer, a plurality of InAs quantum dot active regions and an upper cladding layer stacked in sequence; The multiple InAs quantum dot active regions are stacked, and each of the InAs quantum dot active regions includes a first InGaAs quantum well layer, a quantum dot layer, a second InGaAs quantum well layer, and a GaAs spacer layer stacked in sequence; There is no doping source in the quantum dot layer, and the average thickness of the GaAs spacer layer in the active region of each InAs quantum dot is 10-50 nm; In a direction away from the GaAs substrate, the thickness of each GaAs spacer layer gradually increases; The thickness of the first InGaAs quantum well layer is 1-3 nm, the thickness of the quantum dot layer is 2.5-3.5 nm, and the thickness of the second InGaAs quantum well layer is 3-10 nm.

2. The InAs quantum dot laser according to claim 1, characterized in that: The lower cladding layer comprises: The N-type GaAs contact layer and N-type Al x Ga （1-x） As / GaAs doped strained layer, N-type Al x Ga （1-x） As confinement layer, non-doped GaAs confinement transition layer, Al x Ga （1-x） As / GaAs undoped lower strained layer and GaAs undoped lower strained layer; The upper cladding layer includes a GaAs non-doped upper strain layer, an Al x Ga （1-x） As / GaAs undoped upper strained layer, P-type Al x Ga （1-x） As confinement layer, P-type Al x Ga （1-x） As / GaAs doped strained layer and P-type GaAs contact layer; x Ga （1-x） In As, x is 20% to 80%.

3. The InAs quantum dot laser according to claim 2, characterized in that: The thickness of the N-type GaAs contact layer is 150-300 nm; The N-type Al x Ga （1-x） The thickness of the As / GaAs doped strained layer is 40~80nm; The N-type Al x Ga （1-x） The thickness of the As confinement layer is 1200~1500nm; The thickness of the non-doped GaAs limiting transition layer is 30-50 nm; The Al x Ga （1-x） The thickness of the As / GaAs undoped lower strain layer is 10~50nm; The thickness of the GaAs non-doped lower strain layer is 40-150 nm.

4. The InAs quantum dot laser according to claim 2, characterized in that: The thickness of the GaAs undoped upper strained layer is 40-150 nm; The Al x Ga （1-x） The thickness of the As / GaAs undoped upper strained layer is 10~50nm; The P-type Al x Ga （1-x） The thickness of the As confinement layer is 1200~1500nm; The P-type Al x Ga （1-x） The thickness of the As / GaAs doped strained layer is 40~80nm; The thickness of the P-type GaAs contact layer is 150~300nm.

5. A method for preparing an InAs quantum dot laser, characterized in that: The following steps are involved: The GaAs substrate is placed into a GaAs material molecular beam epitaxy cavity to remove the surface oxide layer; Growing a lower cladding layer on the GaAs substrate; Growing a plurality of InAs quantum dot active regions on the lower cladding layer, the plurality of InAs quantum dot active regions are stacked, each of the InAs quantum dot active regions comprises a first InGaAs quantum well layer, a quantum dot layer, a second InGaAs quantum well layer and a GaAs spacer layer stacked in sequence, wherein the average thickness of the GaAs spacer layer is 10-50 nm; in a direction away from the GaAs substrate, the thickness of each of the GaAs spacer layers gradually increases; the thickness of the first InGaAs quantum well layer is 1-3 nm, the thickness of the quantum dot layer is 2.5-3.5 nm, and the thickness of the second InGaAs quantum well layer is 3-10 nm; An upper cladding layer is grown on the InAs quantum dot active region.

6. The method for preparing an InAs quantum dot laser according to claim 5, characterized in that: The step of growing an InAs quantum dot active region on the lower cladding layer comprises: Growing the first InGaAs quantum well layer on the lower cladding layer, wherein the temperature of the first InGaAs quantum well layer is 450-500° C.; Growing the quantum dot layer on the first InGaAs quantum well layer, wherein the temperature of the quantum dot layer is 450-500° C.; Growing the second InGaAs quantum well layer on the quantum dot layer, wherein the temperature of the second InGaAs quantum well layer is 450-500° C.; The GaAs spacer layer is grown on the second InGaAs quantum well layer, and the temperature of the GaAs spacer layer is 550-650°C.

7. The method for preparing an InAs quantum dot laser according to claim 5, characterized in that: The step of growing a lower cladding layer on the GaAs substrate comprises: An N-type GaAs contact layer is grown on the GaAs substrate, wherein the doping concentration of the N-type GaAs contact layer is 1-10×10 18 / cm 3 , the temperature of the N-type GaAs contact layer is 500-600° C., and the thickness of the N-type GaAs contact layer is 150-300 nm; N-type Al x Ga （1-x） The growth of As / GaAs doped strained layer, the N-type Al x Ga （1-x） The doping concentration of As / GaAs doped strained layer is 1~10×10 18 / cm 3 , the N-type Al x Ga （1-x） The temperature of the As / GaAs doped strained layer is 500-650°C. x Ga （1-x） The thickness of the As / GaAs doped strained layer is 40~80nm; In the N-type Al x Ga （1-x） N-type Al x Ga （1-x） As restricts the growth of the layer, the N-type Al x Ga （1-x） The doping concentration of the As confinement layer is 5×10 18 / cm 3 , the N-type Al x Ga （1-x） The temperature of the As limiting layer is 500~650℃, and the N-type Al x Ga （1-x） The thickness of the As confinement layer is 1200~1500nm; In the N-type Al x Ga （1-x） Growing a non-doped GaAs limiting transition layer on the As limiting layer, wherein the temperature of the non-doped GaAs limiting transition layer is 500-600° C., and the thickness of the non-doped GaAs limiting transition layer is 30-50 nm; Al is formed on the non-doped GaAs confinement transition layer. x Ga （1-x） Growth of As / GaAs undoped lower strained layer, the Al x Ga （1-x） The temperature of the As / GaAs undoped lower strained layer is 500-650°C. x Ga （1-x） The thickness of the As / GaAs undoped lower strain layer is 10~50nm; In the Al x Ga （1-x） Growing a GaAs non-doped lower strained layer on the As / GaAs non-doped lower strained layer, wherein the temperature of the GaAs non-doped lower strained layer is 400-600° C., and the thickness of the GaAs non-doped lower strained layer is 40-150 nm; Among them, Al x Ga （1-x） In As, x is 20% to 80%.

8. The method for preparing an InAs quantum dot laser according to claim 5, characterized in that: The step of growing an upper cladding layer on the InAs quantum dot active region comprises: Growing a GaAs non-doped upper strained layer on the GaAs spacer layer, wherein the temperature of the GaAs non-doped upper strained layer is 400-600° C., and the thickness of the GaAs non-doped upper strained layer is 40-150 nm; The GaAs undoped upper strained layer is Al x Ga （1-x） The growth of As / GaAs undoped upper strained layer, the Al x Ga （1-x） The temperature of the As / GaAs undoped upper strained layer is 500-650°C. x Ga （1-x） The thickness of the As / GaAs undoped upper strained layer is 10~50nm; In the Al x Ga （1-x） P-type Al x Ga （1-x） As restricts the growth of the layer, the P-type Al x Ga （1-x） The doping concentration of the As confinement layer is 1×10 17 ~5×10 18 / cm 3 , the P-type Al x Ga （1-x） The temperature of the As limiting layer is 500~650℃, and the P-type Al x Ga （1-x） The thickness of the As confinement layer is 1200~1500nm; In the P-type Al x Ga （1-x） P-type Al x Ga （1-x） The growth of As / GaAs doped strained layer, the P-type Al x Ga （1-x） The doping concentration of As / GaAs doped strained layer is 1~10×10 18 / cm 3 , the P-type Al x Ga （1-x） The temperature of the As / GaAs doped strained layer is 500-650°C. x Ga （1-x） The thickness of the As / GaAs doped strained layer is 50~100nm; In the P-type Al x Ga （1-x） A P-type GaAs contact layer is grown on the As / GaAs doped strained layer, and the doping concentration of the P-type GaAs contact layer is 5×10 18 ~5×10 19 / cm 3 , the temperature of the P-type GaAs contact layer is 500-600° C., and the thickness of the P-type GaAs contact layer is 150-300 nm; Among them, Al x Ga （1-x） In As, x is 20% to 80%.

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